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Sample records for dental wear caused

  1. DENTAL WEAR CAUSED BY ASSOCIATION BETWEEN BRUXISM AND GASTROESOPHAGEAL REFLUX DISEASE: A REHABILITATION REPORT

    PubMed Central

    Machado, Naila Aparecida de Godoi; Fonseca, Rodrigo Borges; Branco, Carolina Assaf; Barbosa, Gustavo Augusto Seabra; Fernandes, Alfredo Júlio; Soares, Carlos José

    2007-01-01

    Bruxism is a pathological activity of the stomatognathic system that involves tooth grinding and clenching during parafunctional jaw movements. Clinical signs of bruxism are mostly related to dental wear and muscular and joint discomforts, but a large number of etiological factors can be listed, as local, systemic, psychological and hereditary factors. The association between bruxism, feeding and smoking habits and digestive disorders may lead to serious consequences to dental and related structures, involving dental alterations (wear, fractures and cracks), periodontal signs (gingival recession and tooth mobility) and muscle-joint sensivity, demanding a multidisciplinary treatment plan. This paper presents a case report in which bruxism associated with acid feeding, smoking habit and episodes of gastric reflow caused severe tooth wear and great muscular discomfort with daily headache episodes. From the diagnosis, a multidisciplinary treatment plan was established. The initial treatment approach consisted of medical follow up with counseling on diet and smoking habits and management of the gastric disorders. This was followed by the installation of an interocclusal acrylic device in centric relation of occlusion (CRO) for reestablishment of the occlusal stability, vertical dimension of occlusion, anterior guides and return to normal muscle activity (90-day use approximately). After remission of initial symptoms, oral rehabilitation was implemented in CRO by means of full resin composite restorations and new interocclusal device for protection of restorations. Satisfactory esthetics, improved function and occlusal stability were obtained after oral rehabilitation. The patient has attended annual follow-ups for the past 2 years. The multidisciplinary treatment seems to be the key for a successful rehabilitation of severe cases of dental wear involving the association of different health disorders. PMID:19089153

  2. Comparison of methods for quantifying dental wear caused by erosion and abrasion.

    PubMed

    Passos, Vanara F; Melo, Mary A S; Vasconcellos, Andréa Araújo; Rodrigues, Lidiany K A; Santiago, Sérgio L

    2013-02-01

    Various methods have been applied to evaluate the effect of erosion and abrasion. So, the aim of this study was to check the applicability of stylus profilometry (SP), surface hardness (SH) and focus-variation 3D microscopy (FVM) to the analysis of human enamel and dentin subjected to erosion/abrasion. The samples were randomly allocated into four groups (n = 10): G1-enamel/erosion, G2-enamel/erosion plus abrasion, G3-dentin/erosion, and G4-dentin/erosion plus abrasion. The specimens were selected by their surface hardness, and they were subjected to cycles of demineralization (Coca-Cola®-60 s) and remineralization (artificial saliva-60 min). For groups G2 and G4, the remineralization procedures were followed by toothbrushing (150 strokes). The above cycle was repeated 3×/day during 5 days. The samples were assessed using SH, SP, and FVM. For each substrate, the groups were compared using an unpaired t-test, and Pearson correlation coefficients were calculated (α = 5%). For enamel, both profilometry technique showed greater surface loss when the erosion and abrasion processes were combined (P <0.05). The correlation analysis did not reveal any relationships among SH, SP, and FVM to G2 and G4. There were significant correlation coefficients (-0.70 and -0.67) for the comparisons between the FVM and SH methods in enamel and dentin, respectively, in G1 and G3. Choosing the ideal technique for the analysis of erosion depends on the type of dental substrate. SP was not sufficiently sensitive to measure the effects on dentin of erosion or erosion/abrasion. However, SP, FVM and SH were adequate for the detection of tissue loss and demineralization in enamel. Copyright © 2012 Wiley Periodicals, Inc.

  3. Internal corrosion in dental composite wear.

    PubMed

    Sarkar, N K

    2000-01-01

    The internal corrosion of dental resin composites is associated with water-sorption and leads to (1) interfacial debonding, (2) filler dissolution, (3) matrix cracking, and (4) subsurface damage. The last factor creates a condition for "corrosive-wear" in which the damaged layer is worn with ease exposing a new surface and perpetuating the cycle of corrosion and wear. Central to the simulation of in vivo corrosive-wear is the recreation of the subsurface damage layer. To produce this layer in water, artificial saliva, and in media of low pH is time-consuming, because the degradation process in these environments is extremely slow. In laboratory wear tests using aqueous environments, the contact time of resin composites with water is too short to cause significant internal degradation. Thus, data obtained from such tests represent abrasive and not corrosive-wear, and do not correlate well with in vivo wear data. In considering this limitation of the above media for accelerated wear tests, an alkaline medium has been used in this study to simulate corrosive-wear of eleven commercial composites. The procedure consists of exposing each material to 0.1 N NaOH at 60 degrees C for 2 weeks followed by abrasion in a tooth brushing machine. The medium choice is based on the rationale that in vivo degradation arises from reaction with the OH(-), and this reaction can be enhanced by raising the pH and the temperature of the medium. The warm NaOH solution satisfies both these conditions. Parameters examined to evaluate the resistance of each composite to corrosion and wear were (1) mass loss, (2) Si-loss, (3) degradation depth, and (4) wear depth, respectively. A highly significant correlation has been observed among various corrosion and wear parameters. SEM examination indicated degradation to be associated with interfacial separation, filler dissolution, matrix cracking, and subsurface damage. These features are characteristics of in vivo worn composite restorations. Time is

  4. Diagnosis and management of dental wear.

    PubMed

    Harpenau, Lisa A; Noble, Warden H; Kao, Richard T

    2011-04-01

    Dental wear is loss of tooth structure resulting from erosion, attrition, abrasion, and, possibly, abfraction. Clinical/experimental data suggest no single damaging mechanism but rather simultaneous interaction of these destructive processes. The most important interaction is abrasion/attrition potentiated by dental erosion. Awareness of this pathosis is not well-appreciated by the public and dental professionals because the signs may be subtle. This article focuses on the recognition, diagnosis, and management of dental wear.

  5. Diagnosis and management of dental wear.

    PubMed

    Harpenau, Lisa A; Noble, Warden H; Kao, Richard T

    2012-01-01

    Dental wear is loss of tooth structure resulting from erosion, attrition, abrasion and, possibly, abfraction. Clinical/experimental data suggest no single damaging mechanism, but rather simultaneous interaction of these destructive processes. The most important interaction is abrasion/attrition potentiated by dental erosion. Awareness of this pathosis is not well-appreciated by the public and dental professionals because the signs may be subtle. This article focuses on recognizing, diagnosing and managing dental wear. Dental wear is a challenging problem for clinicians because of the subtlety of early changes; confusion about the etiology of the problem; and the dilemma of when or how to manage the etiology. Unfortunately, failure to recognize and manage the process often results in inaction until the breakdown is severe. At that point, the structural breakdown is so advanced that major rehabilitative treatment often is needed. This introductory article discusses diagnosing and managing dental wear.

  6. Dental Wear: A Scanning Electron Microscope Study

    PubMed Central

    Levrini, Luca; Di Benedetto, Giulia

    2014-01-01

    Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction. PMID:25548769

  7. Dental wear: a scanning electron microscope study.

    PubMed

    Levrini, Luca; Di Benedetto, Giulia; Raspanti, Mario

    2014-01-01

    Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction.

  8. Dental adaptations of Bronze Age Harappans: Occlusal wear, crown size, and dental pathology.

    PubMed

    Lukacs, John R

    2017-09-01

    Systematic study of dental attributes yields insights regarding diet and subsistence that cannot be gained from the archaeological record alone. This analysis documents occlusal tooth wear, tooth crown dimensions and dental pathology of an expanded dental sample from Harappa (2550-2030cal BC; Pakistan). New floral and faunal evidence of subsistence indicates a mix of agriculture and pastoralism that can be integrated with evidence of dental attributes and disease to reveal the impact of Harappan diet on oral health. An enlarged dental sample (58 specimens, 910 teeth) from mature phase Harappa was analyzed using Scott's quadrant wear system, measures of crown size, and prevalence of seven pathological dental lesions. All data were collected by the author using standard methods. Sex differences were found in wear, tooth size and prevalence of dental diseases. Females exhibit greater caries prevalence and antemortem tooth loss than men, an attribute associated with higher rates of pulp exposure and abscesses in women. At Harappa antemortem tooth loss results from penetrating caries, while in foragers the cause is severe occlusal wear. In contrast to early Holocene foragers of north India (Damdama, 8800-8600 BP), Harappans have greater occlusal wear, smaller teeth, and a distinct dental pathology profile. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Interaction of dental erosion and bruxism: the amplification of tooth wear.

    PubMed

    Pettengill, Craig A

    2011-04-01

    Bruxism and erosion are important to identify during a dental examination. By understanding the etiologies of both processes, a management strategy can be implemented to decrease their effects. Management for bruxism, clenching, and parafunction can include medications, cognitive behavioral therapy, and dental appliances. Bruxism, clenching, and parafunction combined with dental erosion can cause dental wear to increase faster than any component alone.

  10. [Wear resistance of tooth hard tissue opposing dental alloy material in an adjustable wear simulator].

    PubMed

    Xiang, Nan; Ma, Zheng; Wei, Bin

    2013-04-01

    To evaluate wear resistance of human enamel by a customized adjustable wear simulator. Enamel specimens were prepared as experiment one which were divided into group A and B. The specimens were wear against soft Co-Cr alloy styli. Vertical loss were tested. The data was analyzed statistically by paired sample t test using SAS14.0 software package. The vertical substance loss of two groups were not significantly different (P=0.7464). The adjustable wear simulator works well. The coefficient of the wear test is adjustable, and the result is reliable. The simulator can be used in wear test of tooth and dental material.

  11. Extramasticatory dental wear reflecting habitual behavior and health in past populations.

    PubMed

    Molnar, Petra

    2011-10-01

    In skeletal remains, teeth are valuable sources of information regarding age, diet, and health. Dental wear is especially helpful in reconstructions of dietary patterns in populations of varying subsistence. In past societies, teeth have also been used as "a third hand" or as a "tool." The present article examines this type of dental wear and traits attributed to habitual behavior during prehistoric and historic times. Terminology and classification of habitual dental wear are described mainly by appearance, for instance, notching, grooving, cuts, scrapes, and polished surfaces, and their characteristics are illuminated by different case studies. Secondary health effects caused by the extramasticatory use of teeth, such as periapical lesions, tilting, skeletal changes at the temporomandibular joint, chipping, and antemortem tooth loss are also examined. During the examination of extramasticatory dental wear, information should be recorded on morphology, size, frequency, intensity, and location within the dental arch, as well as descriptions and detailed photographic documentation. The advantage of using a low- to medium-resolution microscope in all dental examination is emphasized. By categorizing the wear marks, characteristics are emphasized rather than an exact causing agent. In this way, tentative analogies for the origin of different extramasticatory wear, and consequently for human behavior in the past, can be avoided.

  12. Clinical assessment of enamel wear caused by monolithic zirconia crowns.

    PubMed

    Stober, T; Bermejo, J L; Schwindling, F S; Schmitter, M

    2016-08-01

    The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6-, 12-, and 24-month follow-up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser-scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two-sided paired Student's t-tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19-26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75-115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia-opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified.

  13. Abrasive wear and surface roughness of contemporary dental composite resin.

    PubMed

    Han, Jian-min; Zhang, Hongyu; Choe, Hyo-Sun; Lin, Hong; Zheng, Gang; Hong, Guang

    2014-01-01

    The purpose of this study was to evaluate the abrasive wear and surface roughness of 20 currently available commercial dental composite resins, including nanofilled, supra-nanofilled, nanohybrid and microhybrid composite resins. The volume loss, maximum vertical loss, surface roughness (R(a)) and surface morphology [Scanning electron microscopy (SEM)] were determined after wear. The inorganic filler content was determined by thermogravimetric analysis. The result showed that the volume loss and vertical loss varied among the materials. The coefficients of determination (R(2)) of wear volume loss and filler content (wt%) was 0.283. SEM micrographs revealed nanofilled composites displayed a relatively uniform wear surfaces with nanoclusters protrusion, while the performance of nanohybrid composites varied. The abrasive wear resistance of contemporary dental composite resins is material-dependent and cannot be deduced from its category, filler loading and composite matrix; The abrasive wear resistance of some flowable composites is comparable to the universal/posterior composite resins.

  14. Complications caused by contact lens wearing.

    PubMed

    Beljan, Jasna; Beljan, Kristina; Beljan, Zdravko

    2013-04-01

    Complications in wearing contact lenses are very rare and caused by poor maintenance, over-extended wear and wearing of contact lenses in a polluted environment. Regular control by a professional person can efficiently reduce the number of complications. This paper describes the most common risks factors for complications, and complications of wearing contact lenses with the classification according to the anatomic parts of the eye: eyelids, tear film, limbus, corneal epithelium, corneal stroma and corneal endothelium. Every complication has been described by the characteristic signs and symptoms, etiology and pathology, as well as therapy and prognosis. The paper describes how to select adequate customers as contact lens users, with proper education in order to ensure minimal incidence of complications due to contact lens wear, thus attracting a lot of satisfied and healthy customers.

  15. Dental wear and age grading at Roonka, South Australia.

    PubMed

    Littleton, Judith

    2017-07-01

    In many hunter-gatherer populations, the teeth are used as a third hand or a tool. Much attention has been paid to wear and its relationship to gendered division of labor, but age is also a significant organizing factor in many societies. In this article, I analyze whether the pattern of wear at Roonka, Australia, reflects the age-graded acquisition of tasks. The remains analyzed come from Roonka and date from c6000 BP to 150 BP. In total 126 adults and juveniles were analyzed. Wear gradients were calculated for each tooth relative to wear on the first molar. Data were compared using nonparametric statistics and cluster analysis to assess the degree of patterning within the sample. Dental wear proceeded rapidly. There is no evidence of sex differences in the pattern of wear. Age differences do occur. While disproportionate anterior wear occurs among juveniles and young adults, by middle adulthood the pattern is less variable and involves the premolars. Old adults have a much flatter pattern of wear. The pattern of wear is consistent with ethnographic observations, which suggest a degree of latitude in the activities of juveniles and young adults. By middle age variability between individuals declines reflecting shared tasks and more intensive use of the teeth. The pattern of wear amongst old adults, however, is much flatter presumably due to changes in occlusion. While dental wear is informative about the organization of labor there is a need to take into account both patterns of activity and occlusion. © 2017 Wiley Periodicals, Inc.

  16. Agave Chewing and Dental Wear: Evidence from Quids

    PubMed Central

    Hammerl, Emily E.; Baier, Melissa A.; Reinhard, Karl J.

    2015-01-01

    Agave quid chewing is examined as a potential contributing behavior to hunter-gatherer dental wear. It has previously been hypothesized that the contribution of Agave quid chewing to dental wear would be observed in communities wherever phytolith-rich desert succulents were part of subsistence. Previous analysis of coprolites from a prehistoric agricultural site, La Cueva de los Muertos Chiquitos in Durango, Mexico, showed that Agave was a consistent part of a diverse diet. Therefore, quids recovered at this site ought to be useful materials to test the hypothesis that dental wear was related to desert succulent consumption. The quids recovered from the site were found to be largely derived from chewing Agave. In this study, the quids were found to be especially rich in phytoliths, and analysis of dental casts made from impressions left in the quids revealed flat wear and dental attrition similar to that of Agave-reliant hunter-gatherers. Based on evidence obtained from the analysis of quids, taken in combination with results from previous studies, it is determined that Agave quid chewing was a likely contributing factor to dental wear in this population. As such, our method provides an additional avenue of dental research in areas where quids are present. PMID:26230855

  17. Agave Chewing and Dental Wear: Evidence from Quids.

    PubMed

    Hammerl, Emily E; Baier, Melissa A; Reinhard, Karl J

    2015-01-01

    Agave quid chewing is examined as a potential contributing behavior to hunter-gatherer dental wear. It has previously been hypothesized that the contribution of Agave quid chewing to dental wear would be observed in communities wherever phytolith-rich desert succulents were part of subsistence. Previous analysis of coprolites from a prehistoric agricultural site, La Cueva de los Muertos Chiquitos in Durango, Mexico, showed that Agave was a consistent part of a diverse diet. Therefore, quids recovered at this site ought to be useful materials to test the hypothesis that dental wear was related to desert succulent consumption. The quids recovered from the site were found to be largely derived from chewing Agave. In this study, the quids were found to be especially rich in phytoliths, and analysis of dental casts made from impressions left in the quids revealed flat wear and dental attrition similar to that of Agave-reliant hunter-gatherers. Based on evidence obtained from the analysis of quids, taken in combination with results from previous studies, it is determined that Agave quid chewing was a likely contributing factor to dental wear in this population. As such, our method provides an additional avenue of dental research in areas where quids are present.

  18. Wear resistance of a pressable low-fusing ceramic opposed by dental alloys.

    PubMed

    Faria, Adriana Cláudia Lapria; de Oliveira, André Almeida; Alves Gomes, Erica; Silveira Rodrigues, Renata Cristina; Faria Ribeiro, Ricardo

    2014-04-01

    Dental alloys have increasingly replaced by dental ceramics in dentistry because of aesthetics. As both dental alloys and ceramics can be present in the oral cavity, the evaluation of the wear resistance of ceramics opposed by dental alloys is important. The aim of the present study was to evaluate wear resistance of a pressable low-fusing ceramic opposed by dental alloys as well as the microhardness of the alloys and the possible correlation of wear and antagonist microhardness. Fifteen stylus tips samples of pressable low-fusing ceramic were obtained, polished and glazed. Samples were divided into three groups according to the disk of alloy/metal to be used as antagonist: Nickel-Chromium (Ni-Cr), Cobalt-Chromium (Co-Cr) and commercially pure titanium (cp Ti). Vickers microhardness of antagonist disks was evaluated before wear tests. Then, antagonist disks were sandblasted until surface roughness was adjusted to 0.75μm. Wear tests were performed at a speed of 60 cycles/min and distance of 10mm, in a total of 300,000 cycles. Before and after wear tests, samples were weighted and had their profile designed in an optical comparator to evaluate weight and height loss, respectively. Ni-Cr and cp Ti caused greater wear than Co-Cr, presenting greater weight (p=.009) and height (p=.002) loss. Cp Ti microhardness was lower than Ni-Cr and Co-Cr (p<.05). There is a positive correlation between weight and height loss (p<.05), but weight (p=.204) and height (p=.05) loss are not correlated to microhardness. The results suggest that pressable low-fusing ceramic presents different wear according to the dental alloy used as antagonist and the wear is not affected by antagonist microhardness.

  19. Surface texture measurement for dental wear applications

    NASA Astrophysics Data System (ADS)

    Austin, R. S.; Mullen, F.; Bartlett, D. W.

    2015-06-01

    The application of surface topography measurement and characterization within dental materials science is highly active and rapidly developing, in line with many modern industries. Surface measurement and structuring is used extensively within oral and dental science to optimize the optical, tribological and biological performance of natural and biomimetic dental materials. Although there has historically been little standardization in the use and reporting of surface metrology instrumentation and software, the dental industry is beginning to adopt modern areal measurement and characterization techniques, especially as the dental industry is increasingly adopting digital impressioning techniques in order to leverage CAD/CAM technologies for the design and construction of dental restorations. As dental treatment becomes increasingly digitized and reliant on advanced technologies such as dental implants, wider adoption of standardized surface topography and characterization techniques will become evermore essential. The dental research community welcomes the advances that are being made in surface topography measurement science towards realizing this ultimate goal.

  20. Casing wear caused by tooljoint hardfacing

    SciTech Connect

    Best, B.

    1986-02-01

    Casing wear caused by new tooljoint hardfacings, such as fine-mesh tungsten-carbide hardfacing and a hardfacing covered with a layer of relatively soft material, has been investigated in the laboratory. The tests were performed on a full-scale test facility with field conditions-forces, motions, and fluids-simulated as closely as possible. It was found that the major mechanisms responsible for casing wear by tooljoints are adhesive wear, abrasive wear, and ploughing. Wear mechanisms can be classified as mild, normal, and severe. A thorough understanding of these mechanisms could lead to measures for lessening casing wear. This can be achieved with (1) tooljoints that have a sufficiently large, smooth, round, and uniform surface and (2) an appropriate mud that has a sufficiently high content of soft solid particles, such as barites, to form a layer in the tooljoint/casing contact area so that metal-to-metal contact is avoided and small, hard mud particles are embedded.

  1. Wear performance of monolithic dental ceramics with different surface treatments.

    PubMed

    Preis, Verena; Weiser, Felix; Handel, Gerhard; Rosentritt, Martin

    2013-05-01

    To investigate the two-body wear performance of monolithic dental ceramics with different surface treatments. Standardized specimens (n = 8/ series) were fabricated from three monolithic dental ceramics (experimental translucent zirconia, experimental shaded zirconia, lithium disilicate). Four groups of each material were defined according to clinically relevant surface treatments: polished, polishedground, polished-ground-repolished, glazed. Two-body wear tests with steatite antagonists were performed in a chewing simulator. Surface roughness (R(a)) was controlled, and wear depths of specimens and antagonistic wear areas were calculated in relation to human enamel as reference. Statistical analysis of wear data was carried out using one-way ANOVA and Bonferroni multiple comparison test for post hoc analysis (α = .05). Scanning electron microscopy was applied for evaluating wear performance of ceramics and antagonists. Polished, ground, and repolished zirconia showed no wear, while glaze was abraded. Irrespective of the surface treatment, wear depth of lithium disilicate was significantly (P wear areas of steatite antagonists (enamel reference: 1.25 mm2) ranged between 0.86 and 1.57 for zirconia, and between 1.79 and 2.28 for lithium disilicate, with the highest values found after grinding and glazing. Steatite surfaces were smooth when opposed to polished/ground/repolished zirconia, and ploughed when opposed to glaze and lithium disilicate. Translucent and shaded experimental zirconia yielded superior wear behavior and lower antagonistic wear compared to lithium disilicate. A trend to higher ceramic and antagonistic wear was shown after grinding and glazing.

  2. An Anthropological Perspective: Another Dimension to Modern Dental Wear Concepts

    PubMed Central

    Kaidonis, John A.; Ranjitkar, Sarbin; Lekkas, Dimitra; Townsend, Grant C.

    2012-01-01

    For many years, research on tooth wear by dental academics has been diametrically opposite to that of anthropological research, with each discipline having a different understanding as to the nature of the wear processes. Dental focus revolved around preventive and restorative considerations while the anthropological focus was a biological understanding related to human evolution, diet, environment, form, and function and included all the craniofacial structures. Introducing the anthropological perspective into modern dentistry gives an insight into the “bigger picture” of the nature and extent of tooth wear. By combining anthropological evidence with clinical knowledge and experience, it is most likely to provide the best-informed and biologically based approach to the management of tooth wear in modern societies. PMID:23304146

  3. Friction and Wear Behavior of Selected Dental Ceramics

    NASA Astrophysics Data System (ADS)

    Park, Jongee; Pekkan, Gurel; Ozturk, Abdullah

    The purpose of this study was to determine the friction coefficients and wear rates of six commercially available dental ceramics including IPS Empress 2 (E2), Cergo Pressable Ceramic (CPC), Cercon Ceram (CCS) and Super porcelain EX-3 (SPE). Bovine enamel (BE) was also tested as a reference material for comparison purposes. Samples of the dental ceramics were prepared according to the instructions described by the manufacturers in disk-shape with nominal dimensions of 12 mm × 2 mm. The wear tests were performed by means of a pin-on-disk type tribometer. The friction coefficients and specific wear rates of the materials were determined at a load of 10 N and rotating speed of 0.25 cm/s without lubrication. Surface morphology of the wear tracks was examined using a scanning electron microscope. Statistical analyses were made using one-way ANOVA and Turkey's HSD (P < 0.05).

  4. Wear evaluation of the human enamel opposing different Y-TZP dental ceramics and other porcelains.

    PubMed

    Kim, Mi-Jin; Oh, Sun-Hee; Kim, Ji-Hwan; Ju, Sung-Won; Seo, Deog-Gyu; Jun, Sang-Ho; Ahn, Jin-Soo; Ryu, Jae-Jun

    2012-11-01

    This study examined the wear resistance of human enamel and feldspathic porcelain after simulated mastication against 3 zirconia ceramics, heat-pressed ceramic and conventional feldspathic porcelain. Human teeth and feldspathic porcelain cusp were tested against ceramic discs. 5 brands were tested - 3 monolithic zirconia, Prettau, Lava, and Rainbow, one lithium disilicate, IPS e.max Press, and one feldspathic porcelain, Vita-Omega 900. The surface was polished using a 600 grit and 1200 grit SiC paper. Each group was loaded for 300,000 cycles in a chewing simulator. The wear resistance was analyzed by measuring the volume of substance lost. The wear surfaces were observed by scanning electron microscopy to determine the wear characteristics. Vita-Omega 900 led to the greatest amount of enamel wears followed by IPS e.max Press, Prettau, Lava and Rainbow. There was a significant difference between Vita-Omega 900 and IPS e.max Press (p<0.05). The wear values for human enamel were significantly greater than those for feldspathic porcelain, regardless of the surface roughness of the ceramic specimens (p<0.05). The wear behaviour of human enamel and feldspathic porcelain varies according to the type of substrate materials. On the other hand, 3 zirconia ceramics caused less wear in the abrader than the conventional ceramic. Dental professionals should be aware of the wear effect of dental restorations on the opposing teeth or restorations. The amount of enamel wear was highest in feldspathic porcelains whereas zirconia ceramics caused less wear on the opposing teeth. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Wear of nanofilled dental composites in a newly-developed in vitro testing device

    NASA Astrophysics Data System (ADS)

    Lawson, Nathaniel C.

    Purpose. In vivo wear of dental composites can lead to loss of individual tooth function and the need to replace a composite restoration. To evaluate the wear performance of new and existing dental composites, we developed a novel system for measuring in vitro wear and we used this system to analyze the mechanisms of wear of nanofilled composite materials. Methods. A modified wear testing device was designed based on the Alabama wear testing machine. The new device consists of: (1) an antagonist which is lowered to and raised from the composite specimen by weight loading, (2) a motorized stage to cause the antagonist to slide 2mm on the composite surface, and (3) pumps for applying lubricant to the specimens. Various testing parameters of the device were examined before testing, including the impulse force, the third-body medium, the lubricant and antagonist. The parameters chosen for this study were 20N at 1Hz with a 33% glycerine lubricant and stainless steel antagonist. Three nano-composites were fabricated with a BisGMA polymer matrix and 40nm SiO2 filler particles at three filler loads (25%, 50% and 65%). The mechanical properties of the composites were measured. The materials were then tested in the modified wear testing device under impact wear, sliding wear and a combination of impact and sliding wear. The worn surfaces were then analyzed with a non-contact profilometer and SEM. Results. The volumetric wear data indicated that increasing filler content beyond 25% decreased the wear resistance of the composites. Increasing filler content increased hardness and decreased toughness. SEM evaluation of the worn specimens indicated that the 25% filled materials failed by fatigue and the 50% and 65% filled materials failed by abrasive wear. Impact wear produced fretting in this device and sliding wear is more aggressive than impact wear. Conclusion. Based on the results of this study and previous studies on this topic, manufacturers are recommended to use a filler

  6. Enamel formation genes associated with dental erosive wear.

    PubMed

    Søvik, Jenny B; Vieira, Alexandre R; Tveit, A B; Mulic, Aida

    2015-01-01

    Dental erosive wear is a multifactorial condition that is greatly affected by environmental factors. So far, no study has investigated how dental erosive wear is influenced by variations in enamel formation genes. The aim of the present study was to investigate polymorphisms in genes involved in enamel formation and their influence on enamel susceptibility to dental erosion. DNA samples were collected from 795 Norwegian adolescents aged 16-18 years. Five single-nucleotide polymorphism markers were genotyped in selected candidate genes (ameloblastin, amelogenin, enamelin, tuftelin 1 and tuftelin interacting protein 11), reported to influence enamel formation. Allele and genotype frequencies were compared within two patient groups with dental erosions; all participants with dental erosion and only those with severe dental erosion (erosion extending into dentine). Overrepresentation of the G allele of the enamelin marker was seen in the erosion group compared to the unaffected group (p = 0.047). When erosion severity was considered, statistical significant difference in allele frequency was observed for amelogenin, with the C allele suggesting a protective role (p = 0.02). A suggestive overrepresentation of the TT genotype of the amelogenin marker was also seen in cases with severe erosion (p = 0.049) when compared to cases with no dentine erosion. Amelogenin was also associated with severe erosion in the recessive model; the TT genotype was significantly more frequent in the affected group than in the unaffected group (p = 0.01). The present study suggests that polymorphisms in enamel formation genes are statistically associated with an individual's susceptibility to dental erosive wear.

  7. Changes in food processing and occlusal dental wear during the early agricultural period in northwest Mexico.

    PubMed

    Watson, James T

    2008-01-01

    Crown dimensions and occlusal surface wear rate and wear plane were evaluated using paired first and second mandibular molars from a sample of 84 Early Agricultural period (1600 B.C.-A.D. 200) skeletons from northwest Mexico. Although this period represents a major shift in subsistence strategies in the Sonoran Desert, from food-foraging to agriculture, archaeological and dental pathology studies have identified this period as one of relative dietary stability. It was therefore predicted that very little variation in occlusal wear would have occurred between the early phase (San Pedro: 1600-800 B.C.) and late phase (Cienega: 800 B.C.-A.D. 200). Comparison of crown diameters identified some phenotypic differences between sexes but not between archaeological phases. Molar occlusal surfaces were then divided into four quadrants, and wear scores recorded for each quadrant. Principle axis analysis was performed between total wear scores of paired, adjacent first and second mandibular molars to assess rate and occlusal wear plane over time. The analysis demonstrated that both wear rate and wear plane increased from the early to the late phase of the Early Agricultural period. These results indicate that although diet may have indeed remained stable during this period in the Sonoran Desert increases in the rate of wear and wear plane may reflect changes in food-processing techniques. It is suggested that more intensive processing of agricultural products during the Cienega phase simultaneously softened the diet to create more tooth-contact wear and introduced more grit to cause faster and more angled wear on the molar occlusal surfaces.

  8. Wear performance of dental ceramics after grinding and polishing treatments.

    PubMed

    Preis, Verena; Behr, Michael; Handel, Gerhard; Schneider-Feyrer, Sibylle; Hahnel, Sebastian; Rosentritt, Martin

    2012-06-01

    The aim of this in vitro study was to determine the two-body wear resistance of different dental ceramics after grinding and polishing treatments. Standardized specimens were prepared from three zirconia and two veneering ceramics and were subjected to different surface treatments. Zirconia ceramics were polished, ground and repolished, veneering ceramics were ground and repolished. One zirconia ceramic was investigated with a superficial glaze. Human enamel was used for reference. Surface roughness R(a) was determined using a profilometric contact surface measurement device. Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists, respectively. Specimens were loaded pneumatically in a pin-on-block design for 1.2x10(5) mastication cycles (50 N, 1.2 Hz, lateral movement: 1 mm, mouth opening: 2 mm) under simultaneous thermal cycling (600 cycles, 5/55 °C). Wear depths of specimens were determined using a 3D laser scanning device, wear areas of steatite antagonists were measured by means of light-optical micrographs. Means and standard deviations were calculated, and statistical analysis was performed using one-way analysis of variance (ANOVA) and the Bonferroni multiple comparison test for post hoc analysis (α=0.05). Scanning electron microscopy was applied for evaluating the wear performance of ceramics and antagonists. No wear was found for polished, ground and repolished zirconia. Compared to the wear depths of the enamel reference with 274.1±187.4 μm versus steatite and 123.3±131.0 μm versus enamel, relative wear depths of porcelains ranged between 0.54±0.07 and 0.62±0.09 with steatite antagonists and between 0.66±0.26 and 1.04±0.27 with enamel antagonists. Relative wear areas of steatite antagonists (enamel reference: 1.25 mm(2)) varied between 0.84±0.13 and 1.90±0.29 for zirconia and between 1.97±0.38 and 2.47±0.40 for porcelains. Enamel antagonists generally showed wear, cracks or even fractures, but revealed

  9. Prevention and Management of Tooth Wear: The Role of Dental Technology.

    PubMed

    Green, James Ij

    2016-08-01

    Tooth wear is a multifactorial condition and the term is used to describe all types of non-carious tooth substance loss: abrasion (produced by interaction between the teeth and other substances), attrition (produced during tooth-to-tooth contact), erosion (produced by a chemical process) and abfraction (produced through abnormal occlusal loading that predisposes tooth substance to mechanical and chemical wear). Dental technology has an important role in preventing, managing and monitoring tooth wear in a variety of ways. Hard poly(methyl methacrylate) or soft ethylene-vinyl acetate splints can be prescribed to alleviate bruxism, the most common cause of attrition. Thermoformed appliances can be used for the application of products that reduce dental erosion such as fluoride gel. Patients with significant tooth surface loss may require laboratory-made restorations, as well as removable appliances with bite planes that generate inter-occlusal space to facilitate restorations, or surgical templates to provide guidance in preparing restorations for those requiring surgical crown lengthening. Dental study models and digitised models can also prove valuable in terms of monitoring the condition. This paper presents a review of the role that dental technology plays in tooth wear prevention, management and monitoring.

  10. Wear of nanofilled dental composites at varying filler concentrations.

    PubMed

    Lawson, Nathaniel C; Burgess, John O

    2015-02-01

    The aim of this study is to examine the effects of nanofiller concentration on the mechanisms of wear of a dental composite. Nanofilled composites were fabricated with a bisphenol A glycidyl methacrylate polymer and 40 nm SiO2 filler particles at three filler loads (25, 50, and 65 wt %). The elastic modulus, flexural strength, and hardness of the composites and the unfilled resin were measured. The materials (n = 8) were tested in the modified wear testing device at 50,000, 100,000, and 200,000 cycles with 20N force at 1 Hz. A 33% glycerine lubricant and stainless steel antagonist were used. The worn composite and antagonist surfaces were analyzed with noncontact profilometry and SEM. The volumetric wear data indicated that there are significant differences between filler concentrations and cycles (p < 0.05). A trend was noted that increasing filler content beyond 25% decreased the wear resistance of the composites. Increasing filler content increased hardness and modulus and increased flexural strength up to 50% fill. SEM evaluation of the worn specimens indicated that the resin and 25% filled materials exhibited cracking and failed by fatigue and the 50 and 65% filled materials exhibited microcutting and failed by abrasive wear. Based on the results of this study, composite manufacturers are recommended to use a filler concentration between 25 and 50% when using nanosized filler particles.

  11. Prevalence, severity and etiology of dental wear in patients with eating disorders

    PubMed Central

    de Carvalho Sales-Peres, Sílvia Helena; Araújo, Juliana J.; Marsicano, Juliane A.; Santos, José E.; Bastos, José R. M.

    2014-01-01

    Objective: The purpose of this study was to evaluate the prevalence, distribution and associated factors of dental wear among patients with eating disorders (EDs). Materials and Methods: An epidemiological cross-sectional survey was conducted by trained, calibrated examiners, using the dental wear index. The sample was composed of 30 patients with EDs (experimental group – G1) and 30 control patients without current or previous history of EDs (G2). A questionnaire was used to assess the etiological factors of dental wear. The univariate analyses using the Chi-square (χ2) test were used to compare the tooth wear prevalence between groups according to the surface and tooth (P > 0.05). Results: The dental wear was similar for both group; however, the G1 presented more moderate wear in molars when compared with G2 (P = 0.048). The majority of EDs patients related have one or more oral habits (n = 26; 86.6%) and only 13.4% (n = 4) affirmed did not have oral habits. The etiological factors of tooth wear related with dental wear were biting objects (P = 0.04) and pain in temporomandibular disorders (P = 0.03). Conclusion: The highest prevalence of dental wear was observed in the molars teeth. Differences in the extent and pattern of dental wear were found in an individual, emphasized the relevance of clinical parameter. PMID:24966749

  12. Casing wear caused by tooljoint hardfacing

    SciTech Connect

    Best, B.

    1983-10-01

    Casing wear due to new tooljoint hardfacings such as fine-mesh tungsten-carbide hardfacing and a hardfacing covered with a layer of relatively soft material have been tested in the laboratory. The tests have been performed on a full-scale test facility simulating field conditions in terms of forces, motions and fluids as closely as possible. The test equipment and procedure are described. The major casing wear mechanisms by tooljoints are given. Wear mechanisms can be classified in terms of mild, normal and severe. In this paper it is shown that proper understanding of these mechanisms could lead to measures to achieve mild casing wear. These mechanisms are illustrated with test results.

  13. Prevalence of dental wear among 12-year-old Brazilian adolescents using a modification of the tooth wear index.

    PubMed

    de Carvalho Sales-Peres, S H; Goya, S; de Araújo, J J; Sales-Peres, A; Lauris, J R P; Buzalaf, M A R

    2008-09-01

    This study investigated the prevalence of dental wear in 12-year-old adolescents using a modification of the tooth wear index (TWI). The modifications were proposed in order to fit with the World Health Organization standard, thus allowing application of the index in broad epidemiological surveys. An epidemiological cross-sectional survey was performed by trained, calibrated examiners, using a modified version of the TWI. Urban elementary schools were chosen because they provide a fair representation of the city's population in terms of socio-economic status. The sample included 295 adolescents, selected randomly and systematically. Dental wear was assessed by calibrated examiners (kappa>0.85), using a modified version of the TWI. This modified version includes a code for teeth restored due to wear, and another code for teeth that cannot be assessed. In addition, it does not differentiate the depth of dentine involvement. Proportions and confidence intervals were used to describe the prevalence of dental wear. Mann-Whitney test was used to detect differences in the degree of dental wear between males and females. The level of statistical significance was set at 5%. In total, 24,780 dental surfaces were evaluated. Among these surfaces, 73.10% did not present dental wear, 24.10% had incipient lesions, 2.46% had moderate lesions and 0.34% had been restored. No severe lesions were detected. Tooth wear was mainly seen on the occlusal/incisal surfaces (26.55%), involving enamel or enamel-dentine, but not the secondary dentine or pulp. The prevalence of dental wear was 26.90%. Considering the different teeth, wear was present in 53.22% of incisors, 50.51% of canines, 10.17% of premolars and 10.85% of molars. The prevalence of the different degrees of dental wear was similar in males and females (P>0.05). The modified TWI seems to be an effective tool for use in broad epidemiological surveys, due to easier calibration and high reproducibility rates.

  14. Patterns of dental wear in the Lengua Indians of Paraguay.

    PubMed

    Kieser, J A; Groeneveld, H T; Preston, C B

    1985-01-01

    Wear patterns were examined on dental casts of 202 living Lengua Indians from the Chaco area of Paraguay. Consideration was given to the development of the molar helicoidal plane, age-related changes in occlusal attrition, coalescence of dentine exposures, interproximal attrition, and erupted crown height. This study lends support to Osborn's theory of the helicoidal plane development by showing that attrition enhances rather than modifies posteruption molar occlusal planes. The rate of interproximal attrition was found to slow down with the eruption and functional initiation of the third molars. Sinuous and cavo-convex interproximal contact areas that are generated with age, however, appeared to be less abrasion resistant than straight surfaces, hence leading to an increase in interproximal attrition rates with advanced age. Maximum crown height reduction occurred between the ages of 20 and 40 years in central incisors, canines, and first molars. Kruskal-Wallis tests and log linera models failed to demonstrate significant sexually dimorphic or antimeric differences in wear patterns of Lengua teeth.

  15. Dental Surface Texture Characterization Based on Erosive Tooth Wear Processes.

    PubMed

    Hara, A T; Livengood, S V; Lippert, F; Eckert, G J; Ungar, P S

    2016-05-01

    The differential diagnosis of dental wear lesions affects their clinical management. We hypothesized that surface texture parameters can differentiate simulated erosion, abrasion, and erosion-abrasion lesions on human enamel and dentin. This in vitro study comprised 2 parts (both factorial 4 × 2), with 4 lesion types (erosion, abrasion, erosion-abrasion, and sound [no lesion; control]) and 2 substrates (enamel and dentin). Flattened/polished dental specimens were used in part 1, whereas natural dental surfaces were used in part 2. Testing surfaces were evaluated in blind conditions, using average surface roughness (Sa) and the following scale-sensitive fractal analysis parameters: area-scale fractal complexity (Asfc), exact proportion length-scale anisotropy of relief (eplsar), scale of maximum complexity (Smc), and textural fill volume (Tfv). Two-way analyses of variance, followed by Fisher's protected least significant difference tests (α = 0.05), were used to evaluate the effects of lesion and substrate. Classification trees were constructed to verify the strength of potential associations of the tested parameters. In part 1,Asfc, Sa, and Tfv were able to differentiate erosion and erosion-abrasion lesions from the sound (no lesion) control in both substrates; only Asfc differentiated erosion and erosion-abrasion enamel lesions (allP< 0.05). The best association of parameters correctly classified up to 84% and 94% of the lesions on enamel and dentin, respectively. In part 2, only Asfc differentiated erosion and erosion-abrasion lesions from the sound (no lesion) control in both substrates, whereas eplsar was able to differentiate erosion from erosion-abrasion (allP< 0.05). The association of parameters correctly classified up to 81% and 91% of the lesions in enamel and dentin, respectively.Asfc, Sa, and Tfv were able to differentiate erosion and erosion-abrasion lesions, despite their complicated surface textures. The association of parameters improved the

  16. Dental wear quantity and direction in Chalcolithic and Medieval populations from southwest France.

    PubMed

    Grimoud, Anne-Marie; Gibbon, Victoria E

    2017-01-01

    The aim of this study was to verify if dental wear changed due to the dietary shift between the Chalcolithic and Middle Ages from relatively hard and fibrous foods to soft cooked cereals. This was accomplished by comparing dental wear quantity and direction between people from two archaeological sites, Les Treilles during the Chalcolithic (mixed subsistence farmers) and Marsan from the Middle Ages (agriculturalists) in southwest France. The materials studied include 65 mandibles, 32 from Les Treilles and 33 from Marsan; 549 teeth were studied. The results show statistically significant difference in wear quantity and direction, the Chalcolithic population (Les Treilles) had the greatest levels of wear in a mainly oblique direction, with the anterior teeth heavily affected by wear. Comparatively, the Medieval sample (Marsan) had lesser levels of wear in a mainly horizontal direction, and the most heavily worn teeth were the molars and incisors. The quantity of wear seems to correlate well with changes in diet, the high level of wear on the anterior teeth in the Chalcolithic sample corresponds with the consumption of a mixed diet of fibrous and tough foods. At Marsan, the lower wear quantity was likely due to a diet of soft boiled cereals, requiring less mastication. However, wear direction appears dependent on several factors and may correlate with more mixed subsistence practices. This study demonstrates the need for additional research into the complex actions of mastication and its effect on dental wear, as well as standardised methodology for the examination of dental wear in archaeological samples. Copyright © 2016 Elsevier GmbH. All rights reserved.

  17. Mechanisms and causes of wear in tooth enamel: implications for hominin diets

    PubMed Central

    Lucas, Peter W.; Omar, Ridwaan; Al-Fadhalah, Khaled; Almusallam, Abdulwahab S.; Henry, Amanda G.; Michael, Shaji; Thai, Lidia Arockia; Watzke, Jörg; Strait, David S.; Atkins, Anthony G.

    2013-01-01

    The wear of teeth is a major factor limiting mammalian lifespans in the wild. One method of describing worn surfaces, dental microwear texture analysis, has proved powerful for reconstructing the diets of extinct vertebrates, but has yielded unexpected results in early hominins. In particular, although australopiths exhibit derived craniodental features interpreted as adaptations for eating hard foods, most do not exhibit microwear signals indicative of this diet. However, no experiments have yet demonstrated the fundamental mechanisms and causes of this wear. Here, we report nanowear experiments where individual dust particles, phytoliths and enamel chips were slid across a flat enamel surface. Microwear features produced were influenced strongly by interacting mechanical properties and particle geometry. Quartz dust was a rigid abrasive, capable of fracturing and removing enamel pieces. By contrast, phytoliths and enamel chips deformed during sliding, forming U-shaped grooves or flat troughs in enamel, without tissue loss. Other plant tissues seem too soft to mark enamel, acting as particle transporters. We conclude that dust has overwhelming importance as a wear agent and that dietary signals preserved in dental microwear are indirect. Nanowear studies should resolve controversies over adaptive trends in mammals like enamel thickening or hypsodonty that delay functional dental loss. PMID:23303220

  18. Frequency of obstructive sleep apnea syndrome in dental patients with tooth wear.

    PubMed

    Durán-Cantolla, Joaquín; Alkhraisat, Mohammad Hamdan; Martínez-Null, Cristina; Aguirre, Jose Javier; Guinea, Elena Rubio; Anitua, Eduardo

    2015-04-15

    To estimate the frequency of obstructive sleep apnea syndrome (OSAS) in dental patients with tooth wear, and to assess the role of dentists in the identification of patients at risk of OSAS. Dental patients with tooth wear and treated with occlusal splint were prospectively recruited to perform sleep study. The severity of tooth wear was established by the treating dentist before patient referral to sleep disorders unit. Sleep questionnaires, anthropometric measurements, and validated respiratory polygraphy were performed. All patients with dental wear were offered a sleepiness analysis. Of 31 recruited patients, 30 (77% males) participated in this study. Patients' mean age was 58.5 ± 10.7 years (range: 35-90 years) and the body mass index was 27.9 ± 3.4 kg/m(2). Tooth wear was mild in 13 patients, moderate in 8 and severe in 9. The mean apnea-hypopnea index (AHI) was 32.4 ± 24.9. AHI < 5 was reported in 2 patients, AHI of 5-29 in 17, and AHI ≥ 30 in 11. A statistically significant association was found between AHI severity and tooth wear severity (Spearman R = 0.505; p = 0.004). Tooth wear could be a tool to identify those patients at risk of having OSAS. This highlights the importance of dental professionals to identify and refer patients with OSAS. © 2015 American Academy of Sleep Medicine.

  19. Wear and flexural strength comparisons of alumina/feldspar resin infiltrated dental composites.

    PubMed

    Le Roux, A R; Lachman, N; Walker, M; Botha, T

    2008-11-01

    Incorporating a feldspar chemical bond between alumina filler particles is expected to increase the wear-resistant and flexural strength properties. An investigation was carried out to evaluate the influence of the feldspar chemical bonding between alumina filler particles on wear and flexural strength of experimental alumina/feldspar dental composites. It was hypothesized that wear resistance and flexural strength would be significantly increased with increased feldspar mass. Alumina was chemically sintered and bonded with 30% and 60% feldspar mass, silanized and infiltrated with UDMA resin to prepare the dental restorative composite material. Higher wear-resistant characteristics resulted with increased feldspar mass of up to 60% (p < 0.05). Higher flexural strength characteristics resulted as the feldspar mass was increased up to 60% (p > 0.05). Feldspar chemical bonding between the alumina particles may improve on the wear-resistance and flexural strength of alumina/feldspar composites.

  20. On the wear mechanism of human dental enamel.

    PubMed

    Arsecularatne, J A; Hoffman, M

    2010-05-01

    The mechanisms and controlling factors in human enamel wear are not fully understood yet. To address this problem, we have used focused ion beam (FIB) milling and field emission scanning electron microscopy (FESEM) to investigate the processes taking place below the wear surface of enamel specimens from in vitro wear tests. These reveal the generation of subsurface cracks during wear of enamel. An analysis of published qualitative and quantitative experimental wear results for enamel as well as for ceramics shows the similarities of the wear processes taking place under similar contact conditions, despite the differences that exist between these two materials. It is shown that, for the considered conditions, fracture under elastic contact is responsible for enamel wear.

  1. Dental wear patterns in early modern humans from Skhul and Qafzeh: A response to Sarig and Tillier.

    PubMed

    Fiorenza, Luca; Kullmer, Ottmar

    2015-10-01

    The use of teeth as tools for manipulating objects and simple food-processing methods was common among prehistoric and modern hunter-gatherer human populations. Paramasticatory uses of teeth frequently produce enamel chipping and distinctive types of dental wear that can readily be related to specific tool functions. In particular, the presence of unusual occlusal wear areas (named para-facets) on maxillary teeth of prehistoric, historic and modern hunter-gatherers has been associated with cultural habits involving extensive use of teeth (Fiorenza et al., 2011; Fiorenza and Kullmer, 2013). However, Sarig and Tillier (2014) believe that this wear had been caused by pathological occlusal relationships rather than by the use of teeth as tools. In this contribution, we show how occlusal contacts are created and how it is possible to distinguish between masticatory and non-masticatory wear facets by using an innovative digital approach called Occlusal Fingerprint Analysis. Statistical results from the analysis of comparative modern samples clearly demonstrate that described para-facets in Skhul and Qafzeh could not have been produced by dental occlusal anomalies such as malocclusions and crossbites. Moreover, dental pathologies in prehistoric humans were extremely rare. Only with the adoption of the modern lifestyle between 18th and 19th centuries, did the emergence of malocclusions become significantly more common. Because more than 50% of the Skhul and Qafzeh individuals analysed in our study are characterised by this distinctive type of wear, it is highly unlikely that their para-facets occurred as a result of dental pathologies.

  2. Ceramic-like wear behaviour of human dental enamel.

    PubMed

    Arsecularatne, J A; Hoffman, M

    2012-04-01

    This paper reports a transmission electron microscopy (TEM) analysis of subsurfaces of enamel specimens following in vitro reciprocating wear tests with an enamel cusp sliding on a flat enamel specimen under hydrated conditions. The obtained results show that crack formation occurred in the wear scar subsurface. The path followed by these cracks seems to be dictated either by the histological structure of enamel or by the contact stress field. Moreover, the analysis of a set of enamel wear results obtained from the literature and application of fracture-based models, originally developed for ceramics, correlate well, confirming the similar wear processes taking place in these materials. This analysis also reveals a marked influence of coefficient of friction on the enamel wear rate: for a higher coefficient of friction value, enamel wear can be severe even under forces generated during normal operation of teeth.

  3. Dental topography and molar wear in Alouatta palliata from Costa Rica.

    PubMed

    Dennis, John C; Ungar, Peter S; Teaford, Mark F; Glander, Kenneth E

    2004-10-01

    Paleoprimatologists depend on relationships between form and function of teeth to reconstruct the diets of fossil species. Most of this work has been limited to studies of unworn teeth. A new approach, dental topographic analysis, allows the characterization and comparison of worn primate teeth. Variably worn museum specimens have been used to construct species-specific wear sequences so that measurements can be compared by wear stage among taxa with known differences in diet. This assumes that individuals in a species tend to wear their molar teeth in similar ways, a supposition that has yet to be tested. Here we evaluate this assumption with a longitudinal study of changes in tooth form over time in primates. Fourteen individual mantled howling monkeys (Alouatta palliata) were captured and then recaptured after 2, 4, and 7 years when possible at Hacienda La Pacifica in Costa Rica between 1989-1999. Dental impressions were taken each time, and molar casts were produced and analyzed using dental topographic analysis. Results showed consistent decreases in crown slope and occlusal relief. In contrast, crown angularity, a measure of surface jaggedness, remained fairly constant except with extreme wear. There were no evident differences between specimens collected in different microhabitats. These results suggest that different individual mantled howling monkeys wear their teeth down in similar ways, evidently following a species-specific wear sequence. Dental topographic analysis may therefore be used to compare morphology among similarly worn individuals from different species.

  4. Frequency of Obstructive Sleep Apnea Syndrome in Dental Patients with Tooth Wear

    PubMed Central

    Durán-Cantolla, Joaquín; Alkhraisat, Mohammad Hamdan; Martínez-Null, Cristina; Aguirre, Jose Javier; Guinea, Elena Rubio; Anitua, Eduardo

    2015-01-01

    Study Objectives: To estimate the frequency of obstructive sleep apnea syndrome (OSAS) in dental patients with tooth wear, and to assess the role of dentists in the identification of patients at risk of OSAS. Methods: Dental patients with tooth wear and treated with occlusal splint were prospectively recruited to perform sleep study. The severity of tooth wear was established by the treating dentist before patient referral to sleep disorders unit. Sleep questionnaires, anthropometric measurements, and validated respiratory polygraphy were performed. Results: All patients with dental wear were offered a sleepiness analysis. Of 31 recruited patients, 30 (77% males) participated in this study. Patients' mean age was 58.5 ± 10.7 years (range: 35–90 years) and the body mass index was 27.9 ± 3.4 kg/m2. Tooth wear was mild in 13 patients, moderate in 8 and severe in 9. The mean apnea-hypopnea index (AHI) was 32.4 ± 24.9. AHI < 5 was reported in 2 patients, AHI of 5–29 in 17, and AHI ≥ 30 in 11. A statistically significant association was found between AHI severity and tooth wear severity (Spearman R = 0.505; p = 0.004). Conclusions: Tooth wear could be a tool to identify those patients at risk of having OSAS. This highlights the importance of dental professionals to identify and refer patients with OSAS. Citation: Durán-Cantolla J, Alkhraisat MH, Martínez-Null C, Aguirre JJ, Guinea ER, Anitua E. Frequency of obstructive sleep apnea syndrome in dental patients with tooth wear. J Clin Sleep Med 2015;11(4):445–450. PMID:25665693

  5. Two-body wear of dental porcelain and substructure oxide ceramics.

    PubMed

    Rosentritt, Martin; Preis, Verena; Behr, Michael; Hahnel, Sebastian; Handel, Gerhard; Kolbeck, Carola

    2012-06-01

    The aim of this in vitro study was to investigate the two-body wear of different ceramics. Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists, respectively. Specimens were loaded in a pin-on-block design with a vertical load of 50 N for 1.2 × 10(5) cycles; (f = 1.6 Hz; lateral movement, 1 mm; mouth opening: 2 mm). Human enamel was used as a reference. Three zirconia ceramics, three veneering porcelains, two glass-infiltrated and one lithium disilicate ceramic were investigated. Veneering and lithium disilicate ceramics were glazed before testing. Surface roughness Ra (SP6, Perthen-Feinprüf, G) and wear depth were determined using a 3D scanner (Laserscan 3D, Willytec, G). SEM (Quanta FEG 400, FEI, USA) pictures of the worn specimens and antagonists were made for evaluating wear performance. Veneering porcelain provided wear traces between 71.2 and 124.1 μm (enamel antagonist) and 117.4 and 274.1 μm (steatite). Wear of the steatite antagonists varied between 0.618 and 2.85 mm². No wear was found for zirconia and glass-infiltrated substructure ceramics. Also, no wear was found for the corresponding antagonists. Wear of specimens and antagonists was strongly material dependent. No visible wear was found on zirconia and glass-infiltrated ceramics. Porcelain and lithium disilicate ceramic showed a comparable or lower wear than the enamel reference. Antagonist wear was found to be lower when specimens were made of substructure oxide ceramics instead of veneering porcelain. From the point of wear testing, zirconia may be used for the fabrication of fixed dental prosthesis without veneering.

  6. [Dental materials can cause oral allergic reactions].

    PubMed

    Røn Larsen, Kristine; Johansen, Jeanne Duus; Arenholt-Bindslev, Dorthe; Reibel, Jesper; Pedersen, Anne Marie Lynge

    2013-06-17

    A large number of materials used in the diagnosis, treatment and prevention of dental, periodontal and oral mucosal diseases may induce acute or chronic reactions in the oral cavity including allergic reactions. Clinically, it may be difficult to discriminate oral mucosal changes caused by dental materials from changes related to oral mucosal diseases. Diagnosis and management of allergic reactions in the oral mucosa may therefore be a major challenge. The purpose of this paper is to draw attention to commonly used dental materials, which can trigger typical, but also atypical, symptoms and clinical signs of an allergic reaction.

  7. A comparative evaluation of wear of enamel caused by ceramics with different fusion temperatures.

    PubMed

    Khandelwal, Meenakshi; Jain, Deshraj

    2013-12-01

    Dental ceramics are the most used esthetic fixed Prosthodontic restorative material today. However, dentists remain suspicious about their potential abrasivity. Lower-fusing ceramic materials developed, are claimed to be wear friendly. This study was conducted to compare the wear of enamel of extracted teeth against one conventionally used ceramic VMK-95 (fusing temperature 930 °C) and two new lower-fusing ceramics-Omega 900 and Finesse with fusing temperatures 900 and 760 °C respectively, used for metal-ceramic restorations. Metal disks were prepared from ceramic alloy and divided into three groups of 10 disks each on which VMK-95, Omega 900 and Finesse ceramics were applied respectively. Ceramic disks and tooth specimen were mounted on custom-made wear simulator and subjected to predefined masticatory test. Each tooth specimen was profiled by laser triangulation sensor before and after masticatory test. Difference in height was calculated. The results showed that mean loss of height of tooth was least against Finesse (0.3431 + 0.0177 mm) followed by Omega 900 (0.4076 + 0.0135 mm) and VMK-95 (0.6177 + 0.014 mm). Statistical analysis revealed statistically significant difference between VMK-95 & Omega 900 and VMK-95 & Finesse. The difference in loss of height of tooth against Finesse & Omega 900 is statistically insignificant (P < 0.001). The results of this study indicate that lower-fusing dental ceramics cause less wear of opposing enamel.

  8. Wear resistance of experimental titanium alloys for dental applications.

    PubMed

    Faria, Adriana Cláudia Lapria; Rodrigues, Renata Cristina Silveira; Claro, Ana Paula Rosifini Alves; da Gloria Chiarello de Mattos, Maria; Ribeiro, Ricardo Faria

    2011-11-01

    The present study evaluated microstructure, microhardness and wear resistance of experimental titanium alloys containing zirconium and tantalum. Alloys were melted in arc melting furnace according to the following compositions: Ti-5Zr, Ti-5Ta and Ti-5Ta-5Zr (%wt). Hemispheres and disks were obtained from wax patterns that were invested and cast by plasma. Microstructures were evaluated using optical microscopy and X-ray diffraction (XRD) analysis and also Vickers microhardness was measured. Hemispherical samples and disks were used for 2-body wear tests, performed by repeated grinding of the samples. Wear resistance was assessed as height loss after 40,000 cycles. The data were compared using ANOVA and post-hoc Tukey test. Ti-5Zr presented a Widmanstätten structure and the identified phases were α and α' while Ti-5Ta and Ti-5Ta-5Zr presented α, β, α' and α" phases, but the former presented a lamellar structure, and the other, acicular. The microhardness of Ti-5Zr was significantly greater than other materials and cp Ti presented wear resistance significantly lower than experimental alloys. It was concluded that wear resistance was improved when adding Ta and Zr to titanium and Zr increased microhardness of Ti-5Zr alloy. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Wearing complete dental prostheses - Effects on perioral morphology

    PubMed Central

    Eberl, Philipp; Thompson, Geoffrey A.; Güntsch, Arndt; Peisker, Andre; Schultze-Mosgau, Stefan; Gomez-Dammeier, Marta; Djedovic, Gabriel; Rieger, Ulrich M.; Beuer, Florian

    2016-01-01

    Background To adequately perform rehabilitation of edentulous patients by a complete removable dental prosthesis (CRDP) is from basic interest to dentists to understand the morphologic changes caused by re-establishment of a physiologic jaw relationship. Anthropometric analyses of standardized frontal view and profile photographs may help elucidate such changes. Material and Methods Photographs of 31 edentulous patients were compared in relaxed lip closure and after insertion of a CRDP in stable occlusion. 2232 anthropometric distances were raised. Eighteen anthropometric indices reflecting the perioral morphology and its integration in the vertical facial harmony were investigated. Results The intercanthal – mouth width index (p<.001), medial - lateral cutaneous upper lip height index (p=.007), lower vermilion contour index (p=.022), vermilion - total upper lip height index (p=.018), cutaneous - total upper lip height index (p=.023), upper lip - nose height index (p=.001), nose - upper face height index (p=.002), chin - mandible height index (p=.013), upper lip - mandible height index (p=.045), nose - lower face height index (p=.018), and nose - face height index (p=.029) showed significant pre- to post-treatment changes. Conclusions The investigated anthropometric indices presented reproducible results related to an increase in occlusal vertical dimension. Their application may be helpful in assessment, planning, and explanation of morphologic effects of CRDPs on the perioral and overall facial morphology, which may helps to improve the aesthetic outcome. Key words:Dentures, removable dentures, anthropometry, perioral morphology. PMID:27031069

  10. Tooth wear, Neanderthal facial morphology and the anterior dental loading hypothesis.

    PubMed

    Clement, Anna F; Hillson, Simon W; Aiello, Leslie C

    2012-03-01

    The Anterior Dental Loading Hypothesis states that the unique Neanderthal facial and dental anatomy was an adaptive response to the regular application of heavy forces resulting from both the masticatory and cultural use of the anterior teeth. Heavy anterior tooth wear frequently observed in Neanderthal specimens is cited as a main source of evidence for heavy forces being applied to these teeth. From this, it might be predicted that the wear shown on the anterior teeth of Neanderthals would greatly exceed that of the posterior teeth and that this differential would be greater than in other hominins with different facial morphologies. In this paper, a new method of examining tooth wear patterns is used to test these predictions in a large assemblage of Late Pleistocene hominins and a group of recent hunter-gatherers from Igloolik, Canada. The results show that all Late Pleistocene hominins, including Neanderthals, had heavily worn anterior teeth relative to their posterior teeth but, contrary to expectations, this was more pronounced in the modern humans than in the Neanderthals. The Igloolik Inuit showed heavier anterior tooth wear relative to their posterior teeth than any Late Pleistocene hominins. There was, however, a characteristic Neanderthal pattern in which wear was more evenly spread between anterior teeth than in modern humans. Overall, the evidence presented here suggests that all Late Pleistocene hominins habitually applied heavy forces between their anterior teeth and that Neanderthals were not exceptional in this regard. These results therefore does not support the Anterior Dental Loading Hypothesis.

  11. Hardness and modulus of elasticity of primary and permanent teeth after wear against different dental materials

    PubMed Central

    Galo, Rodrigo; Contente, Marta Maria Martins Giamatei; Galafassi, Daniel; Borsatto, Maria Cristina

    2015-01-01

    Objectives: The purpose of this study was to determine the Young's modulus and the hardness of deciduous and permanent teeth following wear challenges using different dental materials. Materials and Methods: Wear challenges were performed against four dental materials: A resin-based fissure sealant (Fluoroshield®), a glass ionomer based fissure sealant (Vitremer®), and two microhybrid composite resins (Filtek Z250 and P90®). Using the pin-on-plate design, a deciduous or a permanent tooth was made into a pin (4 mm × 4 mm × 2 mm) working at a 3 N vertical load, 1 Hz frequency, and 900 cycles (15 min) with Fusayama artificial saliva as a lubricant. Before and after the tribological tests, the hardness and elasticity modulus of the tooth samples were measured by creating a nanoindentation at load forces up to 50 mN and 150 mN. All of the results were statistically analyzed using ANOVA and post-hoc Duncan's tests (P < 0.05). Results: No difference in hardness was encountered between deciduous and permanent teeth (P < 0.05) or modulus of elasticity (P < 0.05) before or after the wear challenges for all of the dental materials tested. Conclusions: Wear challenges against the studied dental materials did not alter the properties of permanent or deciduous teeth after the application of a 3 N load. PMID:26929700

  12. Wear of dental resin composites: insights into underlying processes and assessment methods--a review.

    PubMed

    Turssi, Cecilia Pedroso; De Moraes Purquerio, Benedito; Serra, Mônica Campos

    2003-05-15

    Given the increased aesthetic demands of patients, along with improvements in the formulation of resin composites, the ability of these materials to bond to tooth structures, and concerns about dental amalgam fillings, the applicability of resin composites in dentistry has become increasingly widespread. As resistance to wear represents an important factor in determining the clinical success of resin composite restoratives, the aim of this article was to define what constitutes wear; the major underlying phenomena involved in this process-adhesion, abrasion, fatigue, and corrosion-being described. Discussions were also focused on factors that contribute both to the magnitude and minimization of resin composite wear. Finally, insights were included on both in vivo and laboratory studies used to determine wear resistance. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 280-285, 2003

  13. Effect of Occlusal Splints on the Temporomandibular Disorders, Dental Wear and Anxiety of Bruxist Children

    PubMed Central

    Restrepo, Claudia C.; Medina, Isabel; Patiño, Isabel

    2011-01-01

    Objectives: To evaluate the effectiveness of occlusal splints to reduce the signs and symptoms of temporomandibular disorders (TMD), dental wear and anxiety in a group of bruxist children. Methods: All of the subjects were 3 to 6 years old, had complete primary dentition, class I occlusion and were classified as bruxist according to the minimal criteria of the ICSD for bruxism. For each child, anxiety was evaluated with the Conners’ Parent Rating Scales (CPRS). The TMD were evaluated using the RDC/TMD. The dental wear was processed in digital format with Mat Lab® and Lab view® software to determine its size and form. The children were randomized into an experimental (n=19) and a control (n=17) group. The children in the experimental group used rigid bite plates for a two-year period, until mixed dentition. Afterwards, the CPRS and the RDC/TMD were applied again and dental casts were taken. Comparisons of the variables regarding dental wear, signs and symptoms of TMD and anxiety before and after treatment among the groups were analyzed using the t-test, the Wilcoxon rank sum test and the Mann-Whitney test. Results: The subjects in the experimental group showed no statistically significant difference regarding anxiety levels and dental wear when compared with the control group. The signs and symptoms of TMD were not reduced except for the deviation in mouth opening. Conclusions: The use of rigid occlusal bite plates was not efficient in reducing the signs of bruxism as a whole but did reduce the deviation in mouth opening. PMID:21912500

  14. A new application of dental wear analyses: estimation of duration of hominid occupations in archaeological localities.

    PubMed

    Rivals, Florent; Schulz, Ellen; Kaiser, Thomas M

    2009-04-01

    Characterization of settlement patterns is one of the core concepts in archeological research. The duration of an occupation is usually estimated through zooarchaeology (e.g., density of remains, cementochronology) and is limited by taphonomic processes and sample size. We propose a new application of dental wear methods for estimating the relative duration of hominid settlements in Paleolithic sites. Dental microwear is known to be sensitive to seasonal changes in diet. In this new application we use microwear scratch counts to estimate the variation in the dietary signal of various ungulate species. We propose that this variation is correlated to the duration of site occupation. Each season presents a limited and different set of food resources available in the environment. If animals are sampled only during a specific season (i.e., during a short term occupation) then they would be expected to have a dental wear signal with little variation. On the other hand, a greater diversity of food is available across different seasons. Therefore, if game animals are hunted through various seasons during long occupation periods, then they would be expected to have more variable dental wear. The application of this technique to the Middle Paleolithic site of Arago Cave (France), where various types of occupations occurred, supports this hypothesis. When combined with multidisciplinary studies of archaeological localities (seasonality in particular), this new application of dental wear analysis presents valuable information about hominid settlements and behavior. We contextualize our data with results from lithic and zooarchaeological analyses from Arago. These results reveal the presence of both high and low mobility groups of Homo heidelbergensis throughout the sequence of the Arago Cave.

  15. Advancements in all-ceramics for dental restorations and their effect on the wear of opposing dentition.

    PubMed

    Rashid, Haroon; Sheikh, Zeeshan; Misbahuddin, Syed; Kazmi, Murtaza Raza; Qureshi, Sameer; Uddin, Muhammad Zuhaib

    2016-01-01

    Tooth wear is a process that is usually a result of tooth to tooth and/or tooth and restoration contact. The process of wear essentially becomes accelerated by the introduction of restorations inside the oral cavity, especially in case of opposing ceramic restorations. The newest materials have vastly contributed toward the interest in esthetic dental restorations and have been extensively studied in laboratories. However, despite the recent technological advancements, there has not been a valid in vivo method of evaluation involving clinical wear caused due to ceramics upon restored teeth and natural dentition. The aim of this paper is to review the latest advancements in all-ceramic materials, and their effect on the wear of opposing dentition. The descriptive review has been written after a thorough MEDLINE/PubMed search by the authors. It is imperative that clinicians are aware of recent advancements and that they should always consider the type of ceramic restorative materials used to maintain a stable occlusal relation. The ceramic restorations should be adequately finished and polished after the chair-side adjustment process of occlusal surfaces.

  16. Advancements in all-ceramics for dental restorations and their effect on the wear of opposing dentition

    PubMed Central

    Rashid, Haroon; Sheikh, Zeeshan; Misbahuddin, Syed; Kazmi, Murtaza Raza; Qureshi, Sameer; Uddin, Muhammad Zuhaib

    2016-01-01

    Tooth wear is a process that is usually a result of tooth to tooth and/or tooth and restoration contact. The process of wear essentially becomes accelerated by the introduction of restorations inside the oral cavity, especially in case of opposing ceramic restorations. The newest materials have vastly contributed toward the interest in esthetic dental restorations and have been extensively studied in laboratories. However, despite the recent technological advancements, there has not been a valid in vivo method of evaluation involving clinical wear caused due to ceramics upon restored teeth and natural dentition. The aim of this paper is to review the latest advancements in all-ceramic materials, and their effect on the wear of opposing dentition. The descriptive review has been written after a thorough MEDLINE/PubMed search by the authors. It is imperative that clinicians are aware of recent advancements and that they should always consider the type of ceramic restorative materials used to maintain a stable occlusal relation. The ceramic restorations should be adequately finished and polished after the chair-side adjustment process of occlusal surfaces. PMID:28042280

  17. Enamel wear caused by three different restorative materials.

    PubMed

    Hudson, J D; Goldstein, G R; Georgescu, M

    1995-12-01

    The ideal restorative material should cause minimal wear of opposing enamel. This study compared the effects of gold alloy, glazed porcelain, and a laboratory-processed composite on opposing enamel. Ten samples of a type III gold alloy, a porcelain, and a visible-light, heat, and vacuum-processed composite were abraded against cusps of extracted molars for 10,000 cycles on an abrading machine. Pretest and posttest profilometric measurements of the restorative materials demonstrated no statistical difference. Pretest and posttest tracings of the cusps were made on an optical comparator to determine loss of vertical height and surface area. The porcelain caused significantly more loss of vertical height and surface area than the gold alloy or the composite, which were similar.

  18. Towards using spectral domain optical coherence tomography for dental wear monitoring

    NASA Astrophysics Data System (ADS)

    Mǎrcǎuteanu, Corina; Bradu, Adrian; Sinescu, Cosmin; Topalǎ, Florin I.; Negrutiu, Meda Lavinia; Podoleanu, Adrian G.

    2014-03-01

    In this paper we demonstrate that fast spectral domain optical coherence tomography imaging systems have the potential to monitor the evolution of pathological dental wear. On 10 caries free teeth, four levels of artificially defects similar to those observed in the clinic were created. After every level of induced defect, OCT scanning was performed. B-scans were acquired and 3D reconstructions were generated.

  19. Influence of aging solutions on wear resistance and hardness of selected resin-based dental composites.

    PubMed

    Chladek, Grzegorz; Basa, Katarzyna; Żmudzki, Jarosław; Malara, Piotr; Nowak, Agnieszka J; Kasperski, Jacek

    2016-01-01

    The purpose of this study was to investigate the effect of different plasticizing aging solutions on wear resistance and hardness of selected universal resin-based dental composites. Three light cured (one nanofilled, two microhybride) and one hybride chemical cured composites were aged at 37 °C for 48 h in distillated water, ethyl alcohol solution or Listerine mouthwash. After aging the microhardness tests were carried out and then tribological tests were performed in the presence of aging solution at 37 °C. During wear testing coefficients of friction were determined. The maximal vertical loss in micrometers was determined with profilometer. Aging in all liquids resulted in a significant decrease in hardness of the test materials, with the largest values obtained successively in ethanol solution, mouthwash and water. The effect of the liquid was dependent on the particular material, but not the type of material (interpreted as the size of filler used). Introduction of mouthwash instead of water or ethanol solution resulted in a significant reduction in the coefficient of friction. The lowest wear resistance was registered after aging in ethanol and for the chemical cured hybrid composite, but the vertical loss was strongly material dependent. The effect of different aging solution, including commercial mouthrinse, on hardness and wear was material dependent, and cannot be deduced from their category or filler loading. There is no simple correlation between hardness of resin-based dental composites and their wear resistance, but softening of particular composites materials during aging leads to the reduction of its wear resistance.

  20. Wear properties of dental ceramics and porcelains compared with human enamel.

    PubMed

    D'Arcangelo, Camillo; Vanini, Lorenzo; Rondoni, Giuseppe D; De Angelis, Francesco

    2016-03-01

    Contemporary pressable and computer-aided design/manufacturing (CAD/CAM) ceramics exhibit good mechanical and esthetic properties. Their wear resistance compared with human enamel and traditional gold based alloys needs to be better investigated. The purpose of this in vitro study was to compare the 2-body wear resistance of human enamel, gold alloy, and 5 different dental ceramics, including a recently introduced zirconia-reinforced lithium silicate ceramic (Celtra Duo). Cylindrical specimens were fabricated from a Type III gold alloy (Aurocast8), 2 hot pressed ceramics (Imagine PressX, IPS e.max Press), 2 CAD/CAM ceramics (IPS e.max CAD, Celtra Duo), and a CAD/CAM feldspathic porcelain (Vitablocs Mark II) (n=10). Celtra Duo was tested both soon after grinding and after a subsequent glaze firing cycle. Ten flat human enamel specimens were used as the control group. All specimens were subjected to a 2-body wear test in a dual axis mastication simulator for 120000 loading cycles against yttria stabilized tetragonal zirconia polycrystal cusps. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed with 1-way ANOVA tests (α=.05). The wear depth (0.223 mm) of gold alloy was the closest to that of human enamel (0.217 mm), with no significant difference (P>.05). The greatest wear was recorded on the milled Celtra Duo (wear depth=0.320 mm), which appeared significantly less wear resistant than gold alloy or human enamel (P<.05). The milled and not glazed Celtra Duo showed a small but significantly increased wear depth compared with Aurocast8 and human enamel. Wear depth and volumetric loss for the glaze-fired Celtra Duo and for the other tested ceramics did not statistically differ in comparison with the human enamel. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  1. Dental wear and cultural behavior in Middle Paleolithic humans from the Near East.

    PubMed

    Fiorenza, Luca; Kullmer, Ottmar

    2013-09-01

    Neanderthals and anatomically modern humans (AMHs) may have lived in close proximity in the Near East region during Middle Paleolithic times. Although functional morphological analyses suggest a marked behavioral contrast between these two human groups, new dental micro- and macro-wear studies, together with new archaeological data, have revealed some similarities in ecology and dietary habits. In this study, we analyze the tooth wear patterns of Neanderthals and AMH from Middle Paleolithic sites of Israel and Northern Iraq, using the Occlusal Fingerprint Analysis (OFA) method to virtually reconstruct the jaw movements responsible for the creation of the occlusal wear areas. We particularly focus on para-facets, a distinctive type of wear which has been previously described in the dentition of historic and modern hunter-gatherers. The analysis reveals a similarity in para-facet frequency between early Near Eastern Neanderthals and AMH, and a significant difference with other Pleistocene human groups. The absence of antagonist occlusal contacts in the lower teeth and the occlusal compass analysis suggest that para-facet formation is not related to normal mastication but to nonmasticatory activities. Thus, the identification of these nonmasticatory wear areas on the molars of early Near Eastern Neanderthals and AMH may indicate analogous tooth-tool uses for daily task activities. These may have emerged independently or could be interpreted as indirect evidence of cultural interactions between these two groups. Copyright © 2013 Wiley Periodicals, Inc.

  2. The prevalence, causes, and relativity of dental anxiety in adult patients to irregular dental visits.

    PubMed

    Gaffar, Balgis O; Alagl, Adel S; Al-Ansari, Asim A

    2014-06-01

    To assess the frequency and causes of dental anxiety and their relation to irregular dental visits among adult dental patients. The Dental Anxiety Question (DAQ) included within a self-administered questionnaire was distributed to 1025 patients attending the Interns' Dental Clinics in the Department of Preventive Dental Sciences, College of Dentistry, University of Dammam, Dammam, Kingdom of Saudi Arabia from March 2012 to February 2013. A cross-sectional study design was used. The questionnaire consisted of 22 closed-ended questions divided into 4 sections; 1) demographics, 2) regularity of dental visits, and related causes, 3) DAQ, cancellation of dental appointments, history of previous trauma, dental anxiety provoking factors within dental environment and procedures, and 4) patients' status in dental clinics, preferences of dentists, and perceptions regarding dental anxiety. The prevalence of dental anxiety among the study sample was 27%. Anesthetic injection was the main factor of dental fear (88.2%), while dental surgical procedures (35.7%) and extractions (23%) were the most terrifying dental procedures. Lack of time (79.5%), cost (71.5%), far-situated dental services (62.2%), and fear (57.1%) were causes listed for irregular dental visits; while 31.3% had no specific reason. Irregular dental visits were not related to dental anxiety. Dental anxiety continues to be an obstacle despite the vast improvement in dentistry; and this raises an alert regarding personal and communication factors in the patient-dentist relationship. Factors such as equal distribution of dental services, time, and cost should also be addressed.

  3. Awareness and attitudes related to dental erosive wear among 18-yr-old adolescents in Oslo, Norway.

    PubMed

    Skudutyte-Rysstad, Rasa; Mulic, Aida; Skeie, Marit Slåttelid; Skaare, Anne B

    2013-10-01

    The aim of the present study was to describe awareness and attitudes related to dental erosive wear among 18-yr-old adolescents in Oslo and to explore attitudinal differences between participants with and without the condition. All 18-yr-old subjects scheduled for their routine examination at the Public Dental Service clinics during 2008 (n = 3,206) were invited, and 1,456 agreed to participate (a response rate of 45%). The data were collected using structured questionnaires and by clinical examination of the participants. Dental erosive wear was assessed using a pictorial manual - the Visual Erosion Dental Examination scoring system - as a guide. Overall, 88% of participants had heard about dental erosive wear; however, of participants with erosive lesions only 56% were aware of, and only 47% could recall their dentist mentioning, the condition. Participants with erosive wear were more likely to have low or moderate positive attitudes towards acidic drink consumption and to be reluctant to change. In multivariate analyses controlling for gender and behavioural variables, weak or moderate positive awareness of acidic drinks remained significantly associated with higher erosion risk. This study emphasizes the importance of assessment and understanding of awareness and attitudinal aspects in relation to dental erosive wear. © 2013 Eur J Oral Sci.

  4. On dental wear, dental work, and oral health in the type specimen (LB1) of Homo floresiensis.

    PubMed

    Jungers, William L; Kaifu, Yousuke

    2011-06-01

    The claim that the lower left first mandibular molar of LB1, the type specimen of Homo floresiensis, displays endodontic work, and a filling is assessed by digital radiography and micro-CT scanning. The M(1) tooth crown is heavily worn and exhibits extensive dentine exposure that is stained white, but there is no trace of endodontic treatment or a dental filling in this Indonesian fossil dated to 17.1-19.0 kya. Dental calculus (commonly observed in foragers) is present on the teeth of LB1, but there are no observable caries. The pattern of dental attrition in the mandibles of both LB1/2 and LB6/1 (moderate to extensive flat wear across the entire arch) is consistent with that seen in Plio-Pleistocene Homo fossils and in modern hunter-gatherers, and is not typical of most agriculturalists. We conclude that the dental-work and farming hypotheses are falsified and therefore irrelevant to the debate over the taxonomy and phylogeny of H. floresiensis.

  5. Synergistic interactions between corrosion and wear at titanium-based dental implant connections: A scoping review.

    PubMed

    Apaza-Bedoya, K; Tarce, M; Benfatti, C A M; Henriques, B; Mathew, M T; Teughels, W; Souza, J C M

    2017-06-14

    Two-piece implant systems are mainly used in oral implantology involving an osseointegrated implant connected to an abutment, which supports prosthetic structures. It is well documented that the presence of microgaps, biofilms and oral fluids at the implant-abutment connection can cause mechanical and biological complications. The aim of this review paper was to report the degradation at the implant-abutment connection by wear and corrosion processes taking place in the oral cavity. Most of the retrieved studies evaluated the wear and corrosion (tribocorrosion) of titanium-based materials used for implants and abutments in artificial saliva. Electrochemical and wear tests together with microscopic techniques were applied to validate the tribocorrosion behavior of the surfaces. A few studies inspected the wear on the inner surfaces of the implant connection as a result of fatigue or removal of abutments. The studies reported increased microgaps after fatigue tests. In addition, data suggest that micromovements occurring at the contacting surfaces can increase the wear of the inner surfaces of the connection. Biofilms and/or glycoproteins act as lubricants, although they can also amplify the corrosion of the surfaces. Consequently, loosening of the implant-abutment connection can take place during mastication. In addition, wear and corrosion debris such as ions and micro- and nanoparticles released into the surrounding tissues can stimulate peri-implant inflammation that can lead to pathologic bone resorption. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Tooth wear and dental pathology at the advent of agriculture: new evidence from the Levant.

    PubMed

    Eshed, Vered; Gopher, Avi; Hershkovitz, Israel

    2006-06-01

    Differences in patterns of diet and subsistence through the analysis of dental pathology and tooth wear were studied in skeletal populations of Natufian hunter-gatherers (10,500-8300 BC) and Neolithic populations (8300-5500 BC, noncalibrated) from the southern Levant. 1,160 Natufians and 804 Neolithic teeth were examined for rate of attrition, caries, antemortem tooth loss, calculus, periapical lesions, and periodontal processes. While the Natufian people manifest a higher rate of dental attrition and periodontal disease (36.4% vs. 19%), Neolithic people show a higher rate of calculus. Both populations manifested low and similar rates of caries (6.4% in the Natufian vs. 6.7% in the Neolithic), periapical lesions (not over 1.5%), and antemortem tooth loss (3.7% vs. 4.5%, respectively). Molar wear pattern in the Neolithic is different than in the Natufian. The current study shows that the dental picture obtained from the two populations is multifactorial in nature, and not exclusively of dietary origin, i.e., the higher rate and unique pattern of attrition seen in the Natufian could result from a greater consumption of fibrous plants, the use of pestles and mortars (which introduce large quantities of stone-dust to the food), and/or the use of teeth as a "third hand." The two major conclusions of this study are: 1) The transition from hunting and gathering to a food-producing economy in the Levant did not promote changes in dental health, as previously believed. This generally indicates that the Natufians and Neolithic people of the Levant may have differed in their ecosystem management (i.e., gathering vs. growing grains), but not in the type of food consumed. 2) Changes in food-preparation techniques and nondietary usage of the teeth explain much of the variation in tooth condition in populations before and after the agricultural revolution. (c) 2005 Wiley-Liss, Inc.

  7. Candida albicans, Staphylococcus aureus and Streptococcus mutans colonization in patients wearing dental prosthesis.

    PubMed

    Baena-Monroy, Tania; Moreno-Maldonado, Víctor; Franco-Martínez, Fernando; Aldape-Barrios, Beatriz; Quindós, Guillermo; Sánchez-Vargas, Luis Octavio

    2005-04-01

    Denture stomatitis is associated to Candida albicans, different bacteria and other co-factors such as an acid pH, a carbohydrate ingestion increase, different systemic illnesses and pharmacological treatments. The aim of this study was to determine Candida albicans, Staphylococcus aureus and Streptococcus mutans prevalence in the mucous membrane and prosthesis of patients with and without atrophic denture stomatitis and its relationship with other potential clinical co-factors. Saliva was collected from 105 patients (62 female and 43 male) wearing dental prosthesis in order to measure their pH. Oral samples of the mucous membrane and the internal surface of dental prosthesis were taken with sterile cotton to proceed with the microbiological study. The identification of the isolated microorganisms was performed using conventional microbiological methods. Diabetes and Hypertension were the most frequent systemic illnesses. High carbohydrate ingestion was observed in numerous patients. Atrophic denture stomatitis was reported in 50 patients and the pH average in saliva was of 5.2. The presence of C albicans, S. aureus and S. mutans in the mucous membrane and prosthesis was of 51.4%, 52.4% and 67.6%, respectively. C. albicans was isolated in 66.7% from the prosthesis, whereas S. aureus and S. mutans were isolated in 49.5% of those same prosthesis. C. albicans was isolated in 86% of the patients with atrophic denture stomatitis and S. aureus was isolated in a similar percentage (84% of patients). The isolation of S. mutans was less frequent, and it was observed in 16% of the oral samples of these patients. C. albicans, S. aureus and S. mutans frequently colonize the oral mucous of patients wearing dental prosthesis. This illness-bearing condition is more frequent in patients with denture stomatitis, even though dental prosthesis colonization is lower than in the oral mucous.

  8. A comparative study of sliding wear of nonmetallic dental restorative materials with emphasis on micromechanical wear mechanisms.

    PubMed

    Dupriez, Nataliya Deyneka; von Koeckritz, Ann-Kristin; Kunzelmann, Karl-Heinz

    2015-05-01

    The purpose of this study is to investigate the in vitro tribological behavior of modern nonmetallic restorative materials. Specimen prepared of IPS e.max Press lithium disilicate glass ceramic, IPS Empress Esthetic leucite-reinforced glass ceramic, Everest ZS Blanks yttria-stabilized zirconia and Lava Ultimate composite were subjected to wear using a wear machine designed to simulate occlusal loads. The wear of the investigated materials and antagonists were evaluated by a three-dimensional surface scanner. The quantitative wear test results were used to compare and rank the materials. Specimens were divided into two groups with steatite and alumina antagonists. For each antagonist material an analysis of variance was applied. As a post hoc test of the significant differences, Tukey's honest significant difference test was used. With steatite antagonist: wear of zirconia < wear of leucite-reinforced ceramic < wear of lithium disilicate ceramic < wear of Lava Ultimate composite. No significant wear difference was found for steatite antagonist. The wear of IPS e.max Press and Lava Ultimate against hard alumina was found to be twice lower as compared to their wear when opposing to steatite. The differences were associated with materials mechanical properties (hardness and fracture toughness) and with materials microstructure. Wear mechanisms are discussed. © 2014 Wiley Periodicals, Inc.

  9. Measurement of the rate of wear of dental composite resins by a /sup 90/Sr beta particle transmission gauge

    SciTech Connect

    Moores, G.E.; Glentworth, P.; Harrison, A.

    1983-09-01

    The wear rate of restorative dental composite resins is an important parameter in the assessment of their in vivo performance. The two more widely used methods of quantifying wear are measuring the dimensional change and measuring the change in the mass of the specimen. The former method is complicated by uneven wear of specimens and presents difficulties with samples of irregular shape, and the latter method involves measurements of changes in mass as small as tens of micrograms with specimens of sizes similar to those encountered clinically. A /sup 90/Sr beta particle transmission gauge has been designed and constructed to enable the wear rate of small specimens of dental composite resins to be measured. The /sup 90/Sr beta particle transmission gauge enables indirect measurements of changes in mass to be made and overcomes some of the difficulties inherent in the direct measurement of mass and length. Applications of the /sup 90/Sr beta particle transmission gauge to the measurement of wear rates are given for restorative dental resins having a range of inorganic filler contents and types. The results show that the /sup 90/Sr beta particle transmission gauge is capable of measuring the rate of wear to a degree of precision similar to that of micrometer-derived measurements.

  10. [Study on friction and wear properties of dental zirconia ceramics processed by microwave and conventional sintering methods].

    PubMed

    Guoxin, Hu; Ying, Yang; Yuemei, Jiang; Wenjing, Xia

    2017-04-01

    This study evaluated the wear of an antagonist and friction and wear properties of dental zirconia ceramic that was subjected to microwave and conventional sintering methods. Ten specimens were fabricated from Lava brand zirconia and randomly assigned to microwave and conventional sintering groups. A profile tester for surface roughness was used to measure roughness of the specimens. Wear test was performed, and steatite ceramic was used as antagonist. Friction coefficient curves were recorded, and wear volume were calculated. Finally, optical microscope was used to observe the surface morphology of zirconia and steatite ceramics. Field emission scanning electron microscopy was used to observe the microstructure of zirconia. Wear volumes of microwave and conventionally sintered zirconia were (6.940±1.382)×10⁻², (7.952±1.815) ×10⁻² mm³, respectively. Moreover, wear volumes of antagonist after sintering by the considered methods were (14.189±4.745)×10⁻², (15.813±3.481)×10⁻² mm³, correspondingly. Statistically significant difference was not observed in the wear resistance of zirconia and wear volume of steatite ceramic upon exposure to two kinds of sintering methods. Optical microscopy showed that ploughed surfaces were apparent in zirconia. The wear surface of steatite ceramic against had craze, accompanied by plough. Scanning electron microscopy showed that zirconia was sintered compactly when subjected to both conventional sintering and microwave methods, whereas grains of zirconia sintered by microwave alone were smaller and more uniform. Two kinds of sintering methods are successfully used to produce dental zirconia ceramics with similar friction and wear properties.
.

  11. Wear and fatigue behavior of nano-structured dental resin composites.

    PubMed

    Turssi, Cecilia P; Ferracane, Jack L; Ferracane, Lucas L

    2006-07-01

    Theoretically, nano-structured dental resin composites are purported to have increased wear and fatigue resistance compared with microfill composites and may favor the achievement of restoratives with better long-term performance. This study sought to assess the behavior of nano-structured composites resulting from either abrasion and fatigue loading. Ten specimens (12 x 5 x 2.5 mm) were prepared from each of five composites: Ceram-X mono, Filtek Supreme, Grandio, Premise, and Heliomolar (serving as the microfill control). A surface profile was recorded using a three-dimensional profiling system, and the specimens were subjected to 10(5) cycles of three-body abrasion in the new OHSU oral wear simulator. A second profile was generated and the before and after profiles were fit and analyzed. The volume loss and maximum depth of the wear facet on each specimen were calculated. Another 30 specimens (25 x 2 x 2 mm) were tested for flexural fatigue limit (FFL) in four-point bending via the staircase method. The test was carried out until 10(4) cycles were completed or until fracturing the specimen. One-way ANOVA and Tukey's test demonstrated greater volumetric loss for Grandio and Ceram-X than that observed for the remaining composites. Kruskal-Wallis and the least significant difference test ascertained that Heliomolar, Grandio, and Supreme showed significantly higher FFL than Ceram-X and Premise. In terms of wear and fatigue resistance, nano-structured composites may perform either similarly or comparatively worse than a microfilled composite.

  12. Division of labor by sex and age in Neandertals: an approach through the study of activity-related dental wear.

    PubMed

    Estalrrich, Almudena; Rosas, Antonio

    2015-03-01

    The analysis of activity-related dental wear patterns in prehistoric anatomically modern humans and modern hunter-gatherers has shown sex differences attributable to a gendered division of labor. Neandertals are known to have extensive anterior dental wear related to the use of their front teeth as a tool. In this study we analyze the i) cultural striations (scratches on the labial surface of the anterior teeth with a cut-mark morphology), and ii) dental chipping (ante-mortem microfracture involving enamel or both enamel and dentine) in 19 Neandertal individuals from the l'Hortus (France), Spy (Belgium), and El Sidrón (Spain) sites, and compare the characteristics of those traits with the age and sex estimation for the individuals and among samples. The study reveals that all individuals have cultural striations, but those detected on the adult females are longer than the striations found in adult males. Regarding the distribution of dental chipping, the prevalence of this trait is higher in the maxillary dentition of males whereas females have the majority of dental chipping on their mandibular teeth. The differences detected on the overall activity-related dental wear pattern denote a difference or a division of labor by age and sex in Neandertals while using the mouth as a third hand, i.e., in activities other than the provisioning of food, and provide new evidence for the lifestyle of this Pleistocene fossil human species.

  13. A study on the in-vitro wear of the natural tooth structure by opposing zirconia or dental porcelain

    PubMed Central

    Jung, Yu-Seok; Lee, Jae-Whang; Choi, Yeon-Jo; Ahn, Jin-Soo; Shin, Sang-Wan

    2010-01-01

    PURPOSE This study was conducted to evaluate clinical validity of a zirconia full-coverage crown by comparing zirconia's wear capacity over antagonistic teeth with that of feldspathic dental porcelain. MATERIALS AND METHODS The subject groups were divided into three groups: the polished feldspathic dental porcelain group (Group 1), the polished zirconia group (Group 2), and the polished zirconia with glazing group (Group 3). Twenty specimens were prepared from each group. Each procedure such as plasticity, condensation, and glazing was conducted according to the manufacturer's manual. A wear test was conducted with 240,000 chewing cycles using a dual-axis chewing simulator. The degree of wear of the antagonistic teeth was calculated by measuring the volume loss using a three-dimensional profiling system and ANSUR 3D software. The statistical significance of the measured degree of wear was tested with a significant level of 5% using one-way ANOVA and the Tukey test. RESULTS The degrees of wear of the antagonistic teeth were 0.119 ± 0.059 mm3 in Group 1, 0.078 ± 0.063 mm3 in Group 3, and 0.031 ± 0.033 mm3 in Group 2. Statistical significance was found between Group 1 and Groups 2 and between Group 2 and 3, whereas no statistical significance was found between Group 1 and Group 3. CONCLUSION Despite the limitations of this study on the evaluation of antagonistic teeth wear, the degree of antagonistic tooth wear was less in zirconia than feldspathic dental porcelain, representing that the zirconia may be more beneficial in terms of antagonistic tooth wear. PMID:21165280

  14. Enamel wear caused by monolithic zirconia crowns after 6 months of clinical use.

    PubMed

    Stober, T; Bermejo, J L; Rammelsberg, P; Schmitter, M

    2014-04-01

    The purpose of this study was to evaluate enamel wear caused by monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia crowns were placed in 20 patients requiring full molar crowns. For measurement of wear, impressions of both jaws were made at baseline after crown cementation and at 6-month follow-up. Mean and maximum wear of the occlusal contact areas of the crowns, of their natural antagonists and of the two contralateral natural antagonists were measured by the use of plaster replicas and 3D laser scanning methods. Wear differences were investigated by the use of two-sided paired Student's t-tests and by linear regression analysis. Mean vertical loss (maximum vertical loss in parentheses) was 10 (43) μm for the zirconia crowns, 33 (112) μm for the opposing enamel, 10 (58) μm for the contralateral teeth and 10 (46) μm for the contralateral antagonists. Both mean and maximum enamel wear were significantly different between the antagonists of the zirconia crowns and the contralateral antagonists. Gender and activity of the masseter muscle at night (bruxism) were identified as possible confounders which significantly affected wear. Under clinical conditions, monolithic zirconia crowns seem to be associated with more wear of opposed enamel than are natural teeth. With regard to wear behaviour, clinical application of monolithic zirconia crowns is justifiable because the amount of antagonistic enamel wear after 6 months is comparable with, or even lower than, that caused by other ceramic materials in previous studies.

  15. Cervical Necrotizing Fasciitis Caused by Dental Extraction

    PubMed Central

    Figueiredo, Eugênia; Álvares, Pâmella; Silva, Luciano; Silva, Leorik; Caubi, Antônio; Silveira, Marcia; Sobral, Ana Paula

    2016-01-01

    Cervical necrotizing fasciitis is an unusual infection characterized by necrosis of the subcutaneous tissue and fascial layers. Risk factors for the development of necrotizing fasciitis include diabetes mellitus, chronic renal disease, peripheral vascular disease, malnutrition, advanced age, obesity, alcohol abuse, intravenous drug use, surgery, and ischemic ulcers. This report presents a case of necrotizing fasciitis in the cervical area caused by dental extraction in a 73-year-old woman. Cervical necrotizing fasciitis in geriatric patient is rare, and even when establishing the diagnosis and having it timely treated, the patient can suffer irreversible damage or even death. Clinical manifestations in the head and neck usually have an acute onset characterized by severe pain, swelling, redness, erythema, presence of necrotic tissue, and in severe cases obstruction of the upper airways. Therefore, the presentation of this clinical case can serve as guidance to dentists as a precaution to maintain an aseptic chain and be aware of the clinical condition of older patients and the systemic conditions that may increase the risk of infections. PMID:27375905

  16. Cervical Necrotizing Fasciitis Caused by Dental Extraction.

    PubMed

    Arruda, José Alcides; Figueiredo, Eugênia; Álvares, Pâmella; Silva, Luciano; Silva, Leorik; Caubi, Antônio; Silveira, Marcia; Sobral, Ana Paula

    2016-01-01

    Cervical necrotizing fasciitis is an unusual infection characterized by necrosis of the subcutaneous tissue and fascial layers. Risk factors for the development of necrotizing fasciitis include diabetes mellitus, chronic renal disease, peripheral vascular disease, malnutrition, advanced age, obesity, alcohol abuse, intravenous drug use, surgery, and ischemic ulcers. This report presents a case of necrotizing fasciitis in the cervical area caused by dental extraction in a 73-year-old woman. Cervical necrotizing fasciitis in geriatric patient is rare, and even when establishing the diagnosis and having it timely treated, the patient can suffer irreversible damage or even death. Clinical manifestations in the head and neck usually have an acute onset characterized by severe pain, swelling, redness, erythema, presence of necrotic tissue, and in severe cases obstruction of the upper airways. Therefore, the presentation of this clinical case can serve as guidance to dentists as a precaution to maintain an aseptic chain and be aware of the clinical condition of older patients and the systemic conditions that may increase the risk of infections.

  17. Human tooth wear in the past and the present: tribological mechanisms, scoring systems, dental and skeletal compensations.

    PubMed

    d'Incau, Emmanuel; Couture, Christine; Maureille, Bruno

    2012-03-01

    This review of human tooth wear describes the fundamental mechanisms underlying this process. Using the tribological approach they can be systematised and this in turn aids our understanding of them. In past populations wear was ubiquitous, intense, abrasive and physiological as it was related to their food and their technologies. In these populations, it affected the proximal surfaces, and the occlusal surfaces which modified the occlusal plane profoundly. To categorise this wear many different classification systems are used, from which we can determine diet, cultural changes and the age at death of individuals. They also illustrate the evolution of certain functional dental and skeletal compensations in the masticatory apparatus such as continuous dental eruption, mesial drift of the arches and incisor lingual tipping which can then be monitored. These physiological adaptations related mainly to function and ontogenesis can also be found in present-day populations where wear is moderate, although they are much less obtrusive. Apart from certain pathological cases associated with a specific parafunction, iatrogenic tooth brushing or an eating disorder and encouraged by an acid environment, they are the result of a physiological process that should not be halted. To ensure this, it is essential to prevent lesions related to tooth wear, to detect them early and establish a reliable diagnosis. Types of tooth wear that had remained unchanged since the origin of humanity have undergone profound changes in a very short space of time. Today's tribochemical pathological model has replaced the abrasive physiological model of the past.

  18. Wear Potential of Dental Ceramics and its Relationship with Microhardness and Coefficient of Friction.

    PubMed

    Freddo, Rafael Augusto; Kapczinski, Myriam Pereira; Kinast, Eder Julio; de Souza Junior, Oswaldo Baptista; Rivaldo, Elken Gomes; da Fontoura Frasca, Luis Carlos

    2016-10-01

    To evaluate, by means of pin-on-disk testing, the wear potential of different dental ceramic systems as it relates to friction parameters, surface finish, and microhardness. Three groups of different ceramic systems (Noritake EX3, Eris, Empress II) with 20 disks each (10 glazed, 10 polished) were used. Vickers microhardness (Hv) was determined with a 200-g load for 30 seconds. Friction coefficients (μ) were determined by pin-on-disk testing (5 N load, 600 seconds, and 120 rpm). Wear patterns were assessed by scanning electron microscopy (SEM). The results were analyzed using one-way ANOVA and Tukey's test, with the significance level set at α = 0.05. The coefficients of friction were as follows: Noritake EX3 0.28 ± 0.12 (polished), 0.33 ± 0.08 (glazed); Empress II 0.38 ± 0.08 (polished), 0.45 ± 0.05 (glazed); Eris 0.49 ± 0.05 (polished), 0.49 ± 0.06 (glazed). Microhardness measurements were as follows: Noritake EX3 530.7 ± 8.7 (polished), 525.9 ± 6.2 (glazed); Empress II 534.1 ± 8 (polished), 534.7 ± 4.5 (glazed); Eris, 511.7 ± 6.5 (polished), 519.5 ± 4.1 (glazed). The polished and glazed Noritake EX3 and polished and glazed Eris specimens showed statistically different friction coefficients. SEM image analysis revealed more surface changes, such as small cracks and grains peeling off, in glazed ceramics. Wear potential may be related to the coefficient of friction in Noritake ceramics, which had a lower coefficient than Eris ceramics. Within-group analysis showed no differences in polished or glazed specimens. The differences observed were not associated with microhardness. © 2015 by the American College of Prosthodontists.

  19. Wear pattern, dental function, and jaw mechanism in the Late Cretaceous ankylosaur Hungarosaurus.

    PubMed

    Osi, Attila; Barrett, Paul M; Földes, Tamás; Tokai, Richárd

    2014-07-01

    Feeding in thyreophoran dinosaurs is poorly understood. Although the group existed for over 130 million years, only the Early Jurassic basal thyreophoran Scelidosaurus harrisonii and the Late Cretaceous ankylosaurid Euoplocephalus tutus have been studied from this perspective in detail. In contrast to the earlier, conservative hypothesis of a simple "orthal pulping" feeding mode with no or limited tooth-tooth contact, recent studies have demonstrated precise dental occlusion with differing jaw mechanisms in these two species. Here, we describe the first detailed study of feeding related characters in a nodosaurid ankylosaur, Hungarosaurus tormai, from the Late Cretaceous of Hungary. Dental wear patterns comprising small, apical, and low-angled facets on the maxillary and steep, extended, and bowl-like facets on the dentary teeth reveal sophisticated tooth-tooth contact in this basal nodosaurid. The presence of two different scratch generations (vertical and low-angled) on the dentary teeth unambiguously demonstrate a multiphasic powerstroke, which is further supported by the morphology of the quadrate-articular and mandibular symphyseal joints and by the architecture of the reconstructed jaw adductors. Chewing started with an initial slicing phase associated with orthal movement that was followed by a retractive powerstroke with significant occlusal contact. Because of the curved tooth rows, these movements were probably facilitated by some mediolateral translation and/or axial rotation of the mandibles to produce precise shearing along the whole tooth row. These results demonstrate that complex jaw mechanisms and dental occlusion were more widespread among thyreophorans than thought previously and that palinal movement was present in at least two ankylosaurian lineages.

  20. Cervical Necrotizing Fasciitis Caused by Dental Infection

    PubMed Central

    Song, Chi-Woong; Yoon, Hyun-Joong; Jung, Da-Woon; Lee, Sang-Hwa

    2014-01-01

    Necrotizing fasciitis (NF) is defined as rapidly progressive necrosis of subcutaneous fat and fascia. Although NF of the face is rare, its mortality rate is nearly 30%. It usually originates from dental infection and can lead to involvement of the neck, mediastinum, and chest wall. Complications resulting from pre-existing systemic diseases can increase the mortality rate. Known complication factors for NF include diabetes, malnutrition, advanced age, peripheral vascular disease, renal failure, and obesity. Here, we report a case of NF originating from dental infection in an 88-year-old woman already diagnosed with hypertension, thoracic aortic aneurysm, and renal diseases. Such conditions limited adequate surgical and antibiotic treatment. However, interdisciplinary treatment involving multiple departments was implemented with good results. PMID:27489813

  1. Heat generation and drill wear during dental implant site preparation: systematic review.

    PubMed

    Möhlhenrich, S C; Modabber, A; Steiner, T; Mitchell, D A; Hölzle, F

    2015-10-01

    To identify factors that minimise damage during the drilling of sites for dental implants, we reviewed published papers on the amount of heat that is generated. We systematically searched English language studies published between January 2000 and February 2014 on MEDLINE/PubMed and found 41 articles, of which 27 related to an increase in temperature during preparation of the site. We found only basic research with a low level of evidence. Most of the studies were in vitro, and osteotomies were usually made in non-vital bone from cows or pigs. To measure heat in real time, thermocouples were used in 18 studies and infrared thermographs in 7. Three studies reported the use of immunohistochemical analysis to investigate immediate viability of cells. The highest temperature measured was 64.4°C and the lowest 28.4°C. Drill wear was reported after preparation of 50 sites, and there was a significant increase in temperature and a small change in the physiological balance of the proteins in the bone cells. Differences in the study designs meant that meta-analysis was not appropriate. For future work, we recommend the use of standard variables: an axial load of 2kg, drilling speed of 1500rpm, irrigation, standard artificial bone blocks, and the use of infrared thermography. Copyright © 2015 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  2. Mechanical wear of pacemaker lead insulation. A cause of loss of pacing.

    PubMed

    Kruse, I M; Mark, J; Rydén, L

    1980-03-01

    A pacemaker-treated patient is described in whom lead insulation defect caused sudden loss of capture. The defect was caused by mechanical wear of the posterior leaflet of the tricuspid valve and resulted in shunting of the pulse generator with a current drain exceeding the capacity of the pacemaker. In three further cases a similar explanation to sudden loss of pacing was highly suspected.

  3. Wear-caused deflection evolution of a slide rail, considering linear and non-linear wear models

    NASA Astrophysics Data System (ADS)

    Kim, Dongwook; Quagliato, Luca; Park, Donghwi; Murugesan, Mohanraj; Kim, Naksoo; Hong, Seokmoo

    2017-05-01

    The research presented in this paper details an experimental-numerical approach for the quantitative correlation between wear and end-point deflection in a slide rail. Focusing the attention on slide rail utilized in white-goods applications, the aim is to evaluate the number of cycles the slide rail can operate, under different load conditions, before it should be replaced due to unacceptable end-point deflection. In this paper, two formulations are utilized to describe the wear: Archard model for the linear wear and Lemaitre damage model for the nonlinear wear. The linear wear gradually reduces the surface of the slide rail whereas the nonlinear one accounts for the surface element deletion (i.e. due to pitting). To determine the constants to use in the wear models, simple tension test and sliding wear test, by utilizing a designed and developed experiment machine, have been carried out. A full slide rail model simulation has been implemented in ABAQUS including both linear and non-linear wear models and the results have been compared with those of the real rails under different load condition, provided by the rail manufacturer. The comparison between numerically estimated and real rail results proved the reliability of the developed numerical model, limiting the error in a ±10% range. The proposed approach allows predicting the displacement vs cycle curves, parametrized for different loads and, based on a chosen failure criterion, to predict the lifetime of the rail.

  4. Opportunistic Feeding Strategy for the Earliest Old World Hypsodont Equids: Evidence from Stable Isotope and Dental Wear Proxies

    PubMed Central

    Tütken, Thomas; Kaiser, Thomas M.; Vennemann, Torsten; Merceron, Gildas

    2013-01-01

    Background The equid Hippotherium primigenium, with moderately hypsodont cheek teeth, rapidly dispersed through Eurasia in the early late Miocene. This dispersal of hipparions into the Old World represents a major faunal event during the Neogene. The reasons for this fast dispersal of H. primigenium within Europe are still unclear. Based on its hypsodonty, a high specialization in grazing is assumed although the feeding ecology of the earliest European hipparionines within a pure C3 plant ecosystem remains to be investigated. Methodology/Principal Findings A multi-proxy approach, combining carbon and oxygen isotopes from enamel as well as dental meso- and microwear analyses of cheek teeth, was used to characterize the diet of the earliest European H. primigenium populations from four early Late Miocene localities in Germany (Eppelsheim, Höwenegg), Switzerland (Charmoille), and France (Soblay). Enamel δ13C values indicate a pure C3 plant diet with small (<1.4‰) seasonal variations for all four H. primigenium populations. Dental wear and carbon isotope compositions are compatible with dietary differences. Except for the Höwenegg hipparionines, dental microwear data indicate a browse-dominated diet. By contrast, the tooth mesowear patterns of all populations range from low to high abrasion suggesting a wide spectrum of food resources. Conclusions/Significance Combined dental wear and stable isotope analysis enables refined palaeodietary reconstructions in C3 ecosystems. Different H. primigenium populations in Europe had a large spectrum of feeding habits with a high browsing component. The combination of specialized phenotypes such as hypsodont cheek teeth with a wide spectrum of diet illustrates a new example of the Liem’s paradox. This dietary flexibility associated with the capability to exploit abrasive food such as grasses probably contributed to the rapid dispersal of hipparionines from North America into Eurasia and the fast replacement of the brachydont

  5. Wear of primary teeth caused by opposed all-ceramic or stainless steel crowns

    PubMed Central

    Bae, Ik-Hyun; Noh, Tae-Hwan; Ju, Sung-Won; Lee, Tae-Kyoung; Ahn, Jin-Soo; Jeong, Tae-Sung

    2016-01-01

    PURPOSE This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear. MATERIALS AND METHODS There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey's test (P<.05). RESULTS The Leucite group (2.670±1.471 mm3) showed the greatest amount of antagonist tooth wear, followed by in decreasing order by the Lithium (2.042±0.696 mm3), Zirconia (1.426±0.477 mm3), and Steel groups (0.397±0.192 mm3). Mean volume losses in the Leucite and Lithium groups were significantly greater than in the Steel group (P<.05). No significant difference was observed between mean volume losses in the Zirconia and Steel groups (P>.05). CONCLUSION Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia. PMID:26949487

  6. Dust accumulation in the canopy: a potential cause of dental microwear in primates.

    PubMed

    Ungar, P S; Teaford, M F; Glander, K E; Pastor, R F

    1995-06-01

    Dental microwear researchers consider exogenous grit or dust to be an important cause of microscopic wear on primate teeth. No study to date has examined the accumulation of such abrasives on foods eaten by primates in the forest. This investigation introduces a method to collect dust at various heights in the canopy. Results from dust collection studies conducted at the primate research stations at Ketambe in Indonesia, and Hacienda La Pacifica in Costa Rica indicate that 1) grit collects throughout the canopy in both open country and tropical rain forest environments; and 2) the sizes and concentrations of dust particles accumulated over a fixed period of time differ depending on site location and season of investigation. These results may hold important implications for the interpretation of microwear on primate teeth.

  7. A silver staining technique for investigating wear of restorative dental composites

    SciTech Connect

    Wu, W.; Cobb, E.N.

    1981-05-01

    A silver staining technique was developed to demonstrate microdefects in dental restorative composites. Fine silver particles were preferentially introduced into the damaged region to provide optical contrast between the damaged and the undamaged regions. The amount of silver deposition determined with an electron probe microanalyzer, provided an indication of the extent of damage within the dental composites. Examples to demonstrate this technique were given with one clinically worn dental composite restoration and one in vitro worn composite sample.

  8. Influence of CAD/CAM tool and material on tool wear and roughness of dental prostheses after milling.

    PubMed

    Lebon, Nicolas; Tapie, Laurent; Vennat, Elsa; Mawussi, Bernardin

    2015-08-01

    Computer-aided design/computer-aided manufacturing (CAD/CAM) machining influences the surface roughness of dental restorations and tool wear. Roughness must be suitable to meet clinical requirements, and the tool must last as long as possible. The purpose of this pilot study was to investigate the influence of the CAD/CAM tool-material couple on tool wear and surface roughness after milling. Three tools (Lyra conical tool Ø1 mm; GACD SASU, Lyra conical tool Ø1.05 mm; GACD SASU, and Cerec cylinder pointed tool 12S; Sirona Dental Systems GmbH) and 3 CAD/CAM materials (Lava Ultimate; 3M ESPE, Mark II; VITA Zahnfabrik H. Rauter GmbH, and Enamic; VITA Zahnfabrik H. Rauter GmbH) were tested. The tool wear of 6 tool-material couples at a feed rate of 2 m/min was analyzed before and after 8 minutes of flank and climb milling with optical and scanning electron microscopy (SEM) observations and tool weighing. The surface roughness after milling was observed for 9 tool-material couples for flank and climb milling. Feed rates of 1, 2, 3, and 4.8 m/min were used for each couple. Ra, Rt, Rz, Sa, Sq, and Sz roughness criteria were measured. A paired comparison of tool-material couples was conducted with the Kruskal-Wallis test. The Mark II material led to more severe tool wear. Milling of Lava Ultimate resulted in chip deposits on the tool grit. The Cerec cylinder pointed tool 12S was less worn for each material tested. The Cerec cylinder pointed tool 12S and the Lyra conical tool Ø1.05 mm provided similar roughness measurements for the 3 materials tested. The Lyra conical tool Ø1.05 mm tool provided better roughness than the Lyra conical tool Ø1 mm tool for the Enamic material. Tool lifetime calculated by volume of milled material removed should be the measure provided by CAD/CAM manufacturers instead of a number of blocks. This tool lifetime should be provided for the milling conditions associated with the material milled. Material hardness and tool grit are key factors

  9. The prevalence and associated risk factors for tooth wear and dental erosion in 15- to 16-year-old schoolchildren in Amman, Jordan.

    PubMed

    Abu-Ghazaleh, S B; Burnside, G; Milosevic, A

    2013-02-01

    Tooth wear and acid erosion have not been previously investigated in Jordanian schoolchildren. To determine the prevalence of tooth wear and associations for a range of dietary and behavioural risk factors. A sample of 1,602 children aged between 15 and 16 years were randomly selected from 32 schools in Amman, Jordan. Tooth wear was measured using the modified Tooth Wear Index and dichotomised on the presence or absence of exposed dentine. Analysis of questionnaire items was performed by multiple logistic regression analysis. Dentine was exposed in 51 % of children, and males (59 %) had significantly more tooth wear than females (42 %), OR = 1.9, 95 % CI 1.6, 2.4, p < 0.0001. Over 40 % of children had dentine exposed occlusally, mainly the lower first molars, and less than 1 % of the children had dentine exposed palatally. Daily consumption of oranges, ketchup, olives and sweetened coffee was associated with tooth wear through enamel to expose dentine. Carbonated drinks (fizzy) were on the borderline of significance at p = 0.055. The mean DMFT (5.52) was significantly greater in children without tooth wear compared to children with tooth wear (4.13) (p < 0.001). DMFT, gender, daily consumption of oranges and daily consumption of ketchup were significantly associated with tooth wear in the multiple regression model. In this sample of children resident in Amman, Jordan, males had significantly more tooth wear than females. The acidic dietary items associated with tooth wear and, thus, dental erosion included oranges, olives and tomato ketchup.

  10. Allergic contact dermatitis caused by titanium screws and dental implants.

    PubMed

    Hosoki, Maki; Nishigawa, Keisuke; Miyamoto, Youji; Ohe, Go; Matsuka, Yoshizo

    2016-07-01

    Titanium has been considered to be a non-allergenic material. However, several studies have reported cases of metal allergy caused by titanium-containing materials. We describe a 69-year-old male for whom significant pathologic findings around dental implants had never been observed. He exhibited allergic symptoms (eczema) after orthopedic surgery. The titanium screws used in the orthopedic surgery that he underwent were removed 1 year later, but the eczema remained. After removal of dental implants, the eczema disappeared completely. Titanium is used not only for medical applications such as plastic surgery and/or dental implants, but also for paints, white pigments, photocatalysts, and various types of everyday goods. Most of the usage of titanium is in the form of titanium dioxide. This rapid expansion of titanium-containing products has increased percutaneous and permucosal exposure of titanium to the population. In general, allergic risk of titanium material is smaller than that of other metal materials. However, we suggest that pre-implant patients should be asked about a history of hypersensitivity reactions to metals, and patch testing should be recommended to patients who have experienced such reactions. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  11. Dental changes evaluated with a 3D computer-assisted model analysis after long-term tongue retaining device wear in OSA patients.

    PubMed

    Chen, Hui; Lowe, Alan A; Strauss, Arthur M; de Almeida, Fernanda Riberiro; Ueda, Hiroshi; Fleetham, John A; Wang, Bangkang

    2008-05-01

    Oral appliances (OAs) have been used to treat obstructive sleep apnea (OSA) patients for decades. However, detailed dental side effects in long-term OA cases analyzed with an accurate three-dimensional (3D) measurement tool have seldom been reported. The purpose of this study is to evaluate dental side effects in five OSA patients, who had used a tongue retaining device (TRD) (with occasional other OA wear) for an average of 6 years and 4 months. The baseline and follow-up orthodontic study models were measured with a newly developed MicroScribe-3DX analysis system. High compliance of TRD wear was confirmed in all cases and different patterns and amounts of dental changes were observed. The most common appliance-induced dental changes included anterior and/or unilateral posterior open-bites and reduced anterior overjets. It was hypothesized that there might be two possible mechanisms for the TRD side effects--one is the forward pressure of the tongue upon the anterior dental arch and the other is the lateral pressure of the tongue upon the posterior arch. Considerations to correct the TRD dental side effects should be guided by these different mechanisms of the tongue on the dental arch. Possible solutions to minimize occlusal changes and maximize the benefits for OSA patients are also discussed.

  12. Inferring parrotfish (Teleostei: Scaridae) pharyngeal mill function from dental morphology, wear, and microstructure.

    PubMed

    Carr, Andrew; Tibbetts, Ian R; Kemp, Anne; Truss, Rowan; Drennan, John

    2006-10-01

    Morphology, occlusal surface topography, macrowear, and microwear features of parrotfish pharyngeal teeth were investigated to relate microstructural characteristics to the function of the pharyngeal mill using scanning electron microscopy of whole and sectioned pharyngeal jaws and teeth. Pharyngeal tooth migration is anterior in the lower jaw (fifth ceratobranchial) and posterior in the upper jaw (paired third pharyngobranchials), making the interaction of occlusal surfaces and wear-generating forces complex. The extent of wear can be used to define three regions through which teeth migrate: a region containing newly erupted teeth showing little or no wear; a midregion in which the apical enameloid is swiftly worn; and a region containing teeth with only basal enameloid remaining, which shows low to moderate wear. The shape of the occlusal surface alters as the teeth progress along the pharyngeal jaw, generating conditions that appear suited to the reduction of coral particles. It is likely that the interaction between these particles and algal cells during the process of the rendering of the former is responsible for the rupture of the latter, with the consequent liberation of cell contents from which parrotfish obtain their nutrients.

  13. Variation in dental wear and tooth loss among known-aged, older ring-tailed lemurs (Lemur catta): a comparison between wild and captive individuals.

    PubMed

    Cuozzo, Frank P; Sauther, Michelle L; Gould, Lisa; Sussman, Robert W; Villers, Lynne M; Lent, Cheryl

    2010-11-01

    Tooth wear is generally an age-related phenomenon, often assumed to occur at similar rates within populations of primates and other mammals, and has been suggested as a correlate of reduced offspring survival among wild lemurs. Few long-term wild studies have combined detailed study of primate behavior and ecology with dental analyses. Here, we present data on dental wear and tooth loss in older (>10 years old) wild and captive ring-tailed lemurs (Lemur catta). Among older ring-tailed lemurs at the Beza Mahafaly Special Reserve (BMSR), Madagascar (n=6), the percentage of severe dental wear and tooth loss ranges from 6 to 50%. Among these six individuals, the oldest (19 years old) exhibits the second lowest frequency of tooth loss (14%). The majority of captive lemurs at the Indianapolis Zoo (n=7) are older than the oldest BMSR lemur, yet display significantly less overall tooth wear for 19 of 36 tooth positions, with only two individuals exhibiting antemortem tooth loss. Among the captive lemurs, only one lemur (a nearly 29 year old male) has lost more than one tooth. This individual is only missing anterior teeth, in contrast to lemurs at BMSR, where the majority of lost teeth are postcanine teeth associated with processing specific fallback foods. Postcanine teeth also show significantly more overall wear at BMSR than in the captive sample. At BMSR, degree of severe wear and tooth loss varies in same aged, older individuals, likely reflecting differences in microhabitat, and thus the availability and use of different foods. This pattern becomes apparent before "old age," as seen in individuals as young as 7 years. Among the four "older" female lemurs at BMSR, severe wear and/or tooth loss do not predict offspring survival.

  14. Improved single- and multi-contact life-time testing of dental restorative materials using key characteristics of the human masticatory system and a force/position-controlled robotic dental wear simulator.

    PubMed

    Raabe, D; Harrison, A; Ireland, A; Alemzadeh, K; Sandy, J; Dogramadzi, S; Melhuish, C; Burgess, S

    2012-03-01

    This paper presents a new in vitro wear simulator based on spatial parallel kinematics and a biologically inspired implicit force/position hybrid controller to replicate chewing movements and dental wear formations on dental components, such as crowns, bridges or a full set of teeth. The human mandible, guided by passive structures such as posterior teeth and the two temporomandibular joints, moves with up to 6 degrees of freedom (DOF) in Cartesian space. The currently available wear simulators lack the ability to perform these chewing movements. In many cases, their lack of sufficient DOF enables them only to replicate the sliding motion of a single occlusal contact point by neglecting rotational movements and the motion along one Cartesian axis. The motion and forces of more than one occlusal contact points cannot accurately be replicated by these instruments. Furthermore, the majority of wear simulators are unable to control simultaneously the main wear-affecting parameters, considering abrasive mechanical wear, which are the occlusal sliding motion and bite forces in the constraint contact phase of the human chewing cycle. It has been shown that such discrepancies between the true in vivo and the simulated in vitro condition influence the outcome and the quality of wear studies. This can be improved by implementing biological features of the human masticatory system such as tooth compliance realized through the passive action of the periodontal ligament and active bite force control realized though the central nervous system using feedback from periodontal preceptors. The simulator described in this paper can be used for single- and multi-occlusal contact testing due to its kinematics and ability to exactly replicate human translational and rotational mandibular movements with up to 6 DOF without neglecting movements along or around the three Cartesian axes. Recorded human mandibular motion and occlusal force data are the reference inputs of the simulator

  15. [Noise-induced hearing loss caused by dental turbines].

    PubMed

    Praml, G J; Sonnabend, E

    1980-03-01

    Sound level measurements and third octave analyses were carried out to estimate the risk of hearing impairment caused by working the turbine drills. Idling noise of two turbines equipped with ball-bearings and air-bearings respectively and the effects of different burs under varying load conditions in particular were examined. Finally, the background sound level in a great consulting room of a dental clinic at medium activity was looked at. Without any exception the sound levels were situated below 85 dB (A). The sound level exceeded 80 dB in only a few third octave bands; this was the case only with the antiquated ball-bearing turbine. Working with turbine drills requires only a fraction of the total treatment duration, resulting in a very low equivalent sound level. As a consequence a hearing impairment risk may be excluded within the reach of this investigation.

  16. The comparison of manual lymph drainage and ultrasound therapy on the leg swelling caused by wearing high heels.

    PubMed

    Lee, Dong-Yeop; Han, Ji-Su; Jang, Eun-Ji; Seo, Dong-Kwon; Hong, Ji-Heon; Lee, Sang-Sook; Lee, Dong-Geol; Yu Lee, Jae-Ho

    2014-01-01

    One of the major symptoms when women are wearing high heels for a long time is leg swelling. The purpose of this study was to compare the effect of manual lymph drainage with ultrasound therapy. The forty-five healthy women of twenties were participated in this study and divided randomly into three groups; manual lymph drainage group (n=15), ultrasound therapy group (n=15) and control group (n=15). Swelling was measured before wearing the high heels (10 cm-height), after one-hour of wearing the high heels, wearing the high heels of one-hour after the intervention of 15 minutes. Also swelling was calculated by using a tape measure, volumeter and body composition analyzer. Statistical analysis of the comparison between the three groups was performed by one-way ANOVA. Also comparison to the mean value in swelling according to the time was performed by repeated measure ANOVA. As the result of this study, a significant changes have emerged within each of manual lymph drainage, ultrasound therapy and control group (p< 0.05). However, there were no significant differences between each group (p> 0.05). But the mean value of manual lymph drainage group showed the tendency of fast recovering before causing swelling. Therefore, we consider that the clinical treatment of manual lymph drainage and ongoing studies will be made since manual lymph drainage is very effective in releasing the leg swelling caused by wearing high heels and standing for a long time at work.

  17. Effect of In-Office Carbamide Peroxide-Based Tooth Bleaching System on Wear Resistance of Silorane-Based and Methacrylate-Based Dental Composites

    PubMed Central

    Hasani Tabatabaei, Masoumeh; Sheikhzadeh, Sedigheh; Ghasemi Monfared Rad, Hamidreza; Beygi, Ahmad

    2015-01-01

    Objectives: Several studies have assessed the characteristics and properties of silorane-based composites and adhesive systems. Considering the extensive application of tooth-whitening agents, possible deteriorative effects of tooth bleaching agents on these restorative materials must be studied. The aim of this study was to evaluate the effect of an in-office carbamide peroxide-based tooth bleaching agent on the wear resistance of a silorane-based and a conventional microhybrid dimethyl methacrylate-based dental composite with two different application times. Materials and Methods: Thirty cylindrical specimens were made of Z250 and P90 dental composite resins (n=15 for each composite). Samples made of each composite were divided into three groups (n=5) for immersion in an in-office bleaching agent (Opalescence® Quick 45%) for either three or eight hours or saline solution (control). Wear tests were conducted after bleaching using a pin-on disk apparatus under the load of 40N at a constant sliding speed of 0.5 ms−1 for a sliding distance of 300 m. The samples were weighed before and after the wear test. Repeated measures ANOVA was used to statistically analyze the obtained data (α=0.05). Results: There was a significant decrease in the weight of samples after the wear test (P<0.001). However, no significant difference was found among groups in the mean weight of samples before and after the wear test (P>0.05). Conclusion: Bleaching for three or eight hours using 45% carbamide peroxide had no deteriorative effect on the wear resistance of Z250 and P90 composites. PMID:27123014

  18. A Case Report of Tooth Wear Associated with a Patient's Inappropriate Efforts to Reduce Oral Malodor Caused by Endodontic Lesion

    PubMed Central

    Yoneda, Masahiro; Uchida, Hatsumi; Suzuki, Nao; Mine, Mariko; Iwamoto, Tomoyuki; Masuo, Yosuke; Naito, Toru; Hatano, Yuko; Hirofuji, Takao

    2009-01-01

    Here, we report a case of severe tooth wear associated with a patient's inappropriate efforts to reduce oral malodor. A 72-year-old male patient visited our breath clinic complaining of strong breath odor. Former dentists had performed periodontal treatments including scaling and root planing, but his oral malodor did not decrease. His own subsequent breath odor-reducing efforts included daily use of lemons and vinegar to reduce or mask the odor, eating and chewing hard foods to clean his teeth, and extensive tooth brushing with a hard-bristled toothbrush. Oral malodor was detected in our breath clinic by several tests, including an organoleptic test, portable sulphide monitor, and gas chromatography. Although patient's oral hygiene and periodontal condition were not poor on presentation, his teeth showed heavy wear and hypersensitiving with an unfitted restoration on tooth 16. Radiographic examination of the tooth did not reveal endodontic lesion, but when the metal crown was removed, severe pus discharge and strong malodor were observed. When this was treated, his breath odor was improved. After dental treatment and oral hygiene instruction, no further tooth wear was observed; he was not concerned about breath odor thereafter. PMID:20339568

  19. Assessment of exposures and potential risks to the US adult population from wear (attrition and abrasion) of gold and ceramic dental restorations.

    PubMed

    Richardson, G Mark; Clemow, Scott R; Peters, Rachel E; James, Kyle J; Siciliano, Steven D

    2016-01-01

    Little has been published on the chemical exposures and risks of dental restorative materials other than from dental amalgam and composite resins. Here we provide the first exposure and risk assessment for gold (Au) alloy and ceramic restorative materials. Based on the 2001-2004 US National Health and Nutrition Examination Survey (NHANES), we assessed the exposure of US adults to the components of Au alloy and ceramic dental restorations owing to dental material wear. Silver (Ag) is the most problematic component of Au alloy restorations, owing to a combination of toxicity and proportional composition. It was estimated that adults could possess an average of four tooth surfaces restored with Au alloy before exceeding, on average, the reference exposure level (REL) for Ag. Lithium (Li) is the most problematic component of dental ceramics. It was estimated that adults could possess an average of 15 tooth surfaces restored with ceramics before exceeding the REL for Li. Relative risks of chemical exposures from dental materials decrease in the following order: Amalgam>Au alloys>ceramics>composite resins.

  20. Epidemiological studies of tooth wear and dental erosion in 14-year old children in North West England. Part 2: The association of diet and habits.

    PubMed

    Milosevic, A; Bardsley, P F; Taylor, S

    2004-10-23

    To determine the strength of association (expressed as Odds Ratios) of potential risk factors with erosion and tooth wear in 14-year-old schoolchildren. A random sample of 2,385 children were selected by a stratified two-stage technique based on schools and children. Schools in NW England. Tooth wear was assessed by one examiner on three surfaces of all 12 anterior teeth (labial, incisal and palatal) and the occlusal surface of all four first molars using a four-point scale. Enamel wear was scored 0, dentine exposure <1/3 scored 1, >1/3 scored 2 and secondary dentine or pulpal exposure, scored 3. A questionnaire enquired about general health, dental health, habits and the frequency of intake of a wide range of foods and drinks. The Odds Ratios for tooth wear on any surface for habits, reflux and certain foods were: bruxism, 1.10; stomach upset, 1.45; pickles 1.86; vinegar 1.36; salt and vinegar crisps 1.33; brown/other sauces 1.57. Similarly, the odds ratios for potentially erosive drinks were: fizzy drinks 1.32; sport drinks 1.58; herbal/lemon tea 3.97. The frequency of intake was bi-modal with 397 children drinking a can per day and 207 drinking two cans per day. A significant number drank acidic beverages at bedtime but this was not associated with dental erosion. Although odds ratios greater than unity indicate an association, this was not high for carbonated beverages and many other acidic foods or drinks. Examining at fourteen years may not be ideal, as the determinants of erosion/tooth wear have not acted for long, the indices do not discriminate sufficiently and proportionately few subjects have dentine exposed on smooth surfaces.

  1. Efficacy of Specific Plant Products on Microorganisms Causing Dental Caries

    PubMed Central

    Kanth, M Rajini; Prakash, A Ravi; Sreenath, G; Reddy, Vikram Simha

    2016-01-01

    Introduction Dental caries and periodontal diseases are the most common oral diseases seen globally, both in developed and developing countries. Oral microorganisms that is gram positive and gram negative bacteria are known to be involved in causation of these diseases. Nowadays commercially available dentrifices and mouth rinses are known to contain ingredients that can alter the oral microbial flora and have undesirable side effects such as vomiting, diarrhoea, disarrangement of oral, intestinal flora and tooth staining. Naturally available plant products are known to be less harmful with fewer side effects and also economical for the patient. Aim The aim of this study was to determine the antimicrobial properties of 10 naturally available plant products against oral microorganisms causing caries and to check the efficacy of these products in-vitro and to use these in mouth washes and dentrifices. Materials and Methods Sample of caries material was scrapped out from the extracted teeth and transferred to liquid broth, streaked over the agar media to allow for the growth of microorganisms. Plant products like clove oil, neem, ginger-garlic paste, tea tree oil, ginger, garlic, cinnamon oil, green tea, eucalyptus oil and turmeric were used. Antimicrobial efficacy of these products, was estimated by measuring zones of inhibition in the nutrient agar media. Results Clove oil was the most effective of all products against microorganisms causing caries with zone of inhibition - 30mm followed by ginger-garlic paste - 25mm, Neem - 15mm, tea tree oil - 15mm. Conclusion Based on the above results, it can be inferred that these natural products have the maximum efficacy against microorganisms and can be recommended in dentifrices, mouth rinses, topical gels, etc. PMID:28209019

  2. Efficacy of Specific Plant Products on Microorganisms Causing Dental Caries.

    PubMed

    Kanth, M Rajini; Prakash, A Ravi; Sreenath, G; Reddy, Vikram Simha; Huldah, S

    2016-12-01

    Dental caries and periodontal diseases are the most common oral diseases seen globally, both in developed and developing countries. Oral microorganisms that is gram positive and gram negative bacteria are known to be involved in causation of these diseases. Nowadays commercially available dentrifices and mouth rinses are known to contain ingredients that can alter the oral microbial flora and have undesirable side effects such as vomiting, diarrhoea, disarrangement of oral, intestinal flora and tooth staining. Naturally available plant products are known to be less harmful with fewer side effects and also economical for the patient. The aim of this study was to determine the antimicrobial properties of 10 naturally available plant products against oral microorganisms causing caries and to check the efficacy of these products in-vitro and to use these in mouth washes and dentrifices. Sample of caries material was scrapped out from the extracted teeth and transferred to liquid broth, streaked over the agar media to allow for the growth of microorganisms. Plant products like clove oil, neem, ginger-garlic paste, tea tree oil, ginger, garlic, cinnamon oil, green tea, eucalyptus oil and turmeric were used. Antimicrobial efficacy of these products, was estimated by measuring zones of inhibition in the nutrient agar media. Clove oil was the most effective of all products against microorganisms causing caries with zone of inhibition - 30mm followed by ginger-garlic paste - 25mm, Neem - 15mm, tea tree oil - 15mm. Based on the above results, it can be inferred that these natural products have the maximum efficacy against microorganisms and can be recommended in dentifrices, mouth rinses, topical gels, etc.

  3. Dental Erosion and Medical Conditions: An Overview of Aetiology, Diagnosis and Management.

    PubMed

    Paryag, A; Rafeek, R

    2014-09-01

    Tooth wear or tooth surface loss is a normal physiological process and occurs throughout life but is considered pathological when the degree of destruction is excessive or the rate of loss is rapid, causing functional, aesthetic or sensitivity problems. The importance of tooth wear as a dental problem has been increasingly recognized. The findings of a study in Trinidad indicate that the prevalence of tooth wear in a Trinidadian population is comparable to the United Kingdom (UK) and, indeed, that the level of moderate and severe wear is in fact nearly twice as high. The aetiology of tooth wear is attributed to four causes: erosion, attrition, abrasion and abfraction. Erosion is generally considered to be the most prevalent cause of tooth wear in the UK and Europe. Acids that cause dental erosion originate mainly from the diet or the stomach and to a lesser extent, the environment. Underlying medical problems can contribute to the progress of tooth wear due to erosion and the patient may not be aware of these conditions. Moderate to severe tooth wear poses a significant clinical challenge to dental practitioners and may result in treatment that is more complex and costly to the patient both in terms of finances and time spent in the dental chair. This paper provides an overview of aetiology and diagnosis of tooth wear, in particular tooth wear due to erosion, so that medical and dental practitioners may recognize tooth wear early, institute preventive measures and manage patients appropriately.

  4. Dental Erosion and Medical Conditions An Overview of Aetiology, Diagnosis and Management

    PubMed Central

    Paryag, A; Rafeek, R

    2014-01-01

    ABSTRACT Tooth wear or tooth surface loss is a normal physiological process and occurs throughout life but is considered pathological when the degree of destruction is excessive or the rate of loss is rapid, causing functional, aesthetic or sensitivity problems. The importance of tooth wear as a dental problem has been increasingly recognized. The findings of a study in Trinidad indicate that the prevalence of tooth wear in a Trinidadian population is comparable to the United Kingdom (UK) and, indeed, that the level of moderate and severe wear is nearly twice as high. The aetiology of tooth wear is attributed to four causes: erosion, attrition, abrasion and abfraction. Erosion is generally considered to be the most prevalent cause of tooth wear in the UK and Europe. Acids that cause dental erosion originate mainly from the diet or the stomach and, to a lesser extent, the environment. Underlying medical problems can contribute to influence the progress of tooth wear due to erosion and the patient may not be aware of these conditions. Moderate to severe tooth wear poses a significant clinical challenge to dental practitioners and may result in treatment that is more complex and costly to the patient, both in terms of finances and time spent in the dental chair. This paper provides an overview of aetiology and diagnosis of tooth wear, in particular tooth wear due to erosion, so that medical and dental practitioners may recognize tooth wear early, institute preventive measures and manage patients appropriately. PMID:25781289

  5. Patients' knowledge and understanding of the implications of wearing dentures. Report of a survey conducted at a dental institute in the south of India.

    PubMed

    Shigli, Kamal; Shivappa Angadi, Gangadhar; Hegde, Pradnya; Hebbal, Mamata

    2008-07-01

    The aim of this survey was to assess the knowledge and perceptions of denture treatment among a group of patients who attended the Karnataka Lingayat Education Society's (KLES) Institute of Dental Sciences, Belgaum, Karnataka State, India. A questionnaire with four general questions and 14 statements/questions about denture construction and wearing was developed and piloted. Ethical approval was sought and granted. After some revisions, the questionnaire was given to all patients attending KLES over a two-month period. All 423 patients who attended KLES in the two-month period completed the questionnaire. Five questionnaires were not analysed because of ambiguity in the answers. The final patient sample was 418 (207 females and 211 males, mean age 40 +/- 15.3 years) of whom 140 (33.5%) were dentate and 278 (66.5%) edentulous in either one or both jaws. Among the 278 edentulous patients, 143 (51.4%) had not worn any kind of denture and 135 (48.6%) wore dentures. There was a wide variation in the accuracy of the patients' knowledge of denture treatment. In particular, more than 20% did not know that complete denture treatment requires five or more visits, that denture wearers may experience oral pain, whether or not dentures may cause more problems than natural teeth, or that dentures may make audible clicks and cause problems when speaking. Patient education is an essential element in successful denture treatment. It should begin prior to the treatment, to ensure that the technical capability of the clinician matches the expectations of the patient. The initial appointment needs to be used as an educational tool to raise patients' level of understanding of prosthetic rehabilitation and how the proposed treatment will meet their needs.

  6. Are cleft palate fistulae a cause of dental decay?

    PubMed

    Richards, Helen; van Bommel, Annelotte; Clark, Victoria; Richard, Bruce

    2015-05-01

    To investigate a possible correlation between fistula and dental decay in children at 5 years of age from a single-surgeon series of cleft palate repairs. Retrospective review of data over a 9-year period between 2003 and 2011 of cleft palate repairs performed by the senior author at Birmingham Children's Hospital, U.K. Data collected on age, sex, age at repair, presence of fistula, and number of decayed, missing, or filled primary teeth (i.e., decayed, missing, and filled teeth score) at age 5 years. The overall fistula rate for this patient population was 24.1%. Fistulae were more common in the more severe forms of cleft type, as was frequency of dental decay. Comparison of fistula versus nonfistula groups showed a higher rate of dental decay (40%) in the fistula group, compared with only 20% in the nonfistula group (P = .036). A positive association was established between dental decay and the presence of a fistula. Although not proven as causative, possible reasons for this include nasal mucus retaining sugary food in the mouth and an overall prolonged food-clearance time. The known association between severity of cleft and an increased likelihood of a fistula and severity of cleft and increased dental decay were again demonstrated but were not found to be the exclusive explanation for the new finding of an association between fistulae and higher dental decay rates.

  7. Human dental microwear caused by calcium oxalate phytoliths in prehistoric diet of the lower Pecos region, Texas.

    PubMed

    Danielson, D R; Reinhard, K J

    1998-11-01

    Recent research demonstrates that silica phytoliths of dietary origin are associated with microwear of human teeth. Previous research has shown that severe enamel microwear and dental wear characterizes Archaic hunter-gatherers in the lower Pecos region of west Texas. Calcium oxalate crystals are especially common in Archaic coprolites. The vast majority are derived from prickly pear and agave, which were the dietary staples in west Texas for 6,000 years. The calcium oxalate phytoliths are harder than enamel. Therefore, calcium oxalate crystals are the most likely source of previously documented dental microwear and wear in the lower Pecos region.

  8. Cervicofacial subcutaneous and mediastinal emphysema caused by air cooling spray of dental laser.

    PubMed

    Mitsunaga, Sachiyo; Iwai, Toshinori; Aoki, Noriaki; Yamashita, Yosuke; Omura, Susumu; Matsui, Yoshiro; Maegawa, Jiro; Hirota, Makoto; Mitsudo, Kenji; Tohnai, Iwai

    2013-06-01

    Cervicofacial subcutaneous emphysema is a rare complication of dental procedures with an air turbine or syringe, and dentists and oral surgeons sometimes encounter mediastinal emphysema following the presentation of extensive subcutaneous emphysema. Most emphysema occurs incidentally during tooth extraction, restorative treatment, or endodontic treatment, with only a few cases reported of cervicofacial subcutaneous emphysema associated with dental laser treatment. We report a case of cervicofacial subcutaneous and mediastinal emphysema caused by the air cooling spray of dental laser during dental treatment in a 76-year-old woman. After she underwent dental laser treatment, cervicofacial swelling was noted and she was referred to our department. Computed tomography showed both cervicofacial subcutaneous emphysema and mediastinal emphysema. Antibiotics were administered prophylactically and the emphysema disappeared 5 days after the dental laser treatment, without any complications. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Enhancement of wear and corrosion resistance of low modulus β-type Zr-20Nb-xTi (x=0, 3) dental alloys through thermal oxidation treatment.

    PubMed

    Zhang, Jianfeng; Gan, Xiaxia; Tang, Hongqun; Zhan, Yongzhong

    2017-07-01

    In order to obtain material with low elastic modulus, good abrasion resistance and high corrosion stability as screw for dental implant, the biomedical Zr-20Nb and Zr-20Nb-3Ti alloy with low elastic modulus were thermal oxidized respectively at 700°C for 1h and 600°C for 1.25h to obtain the compact oxidized layer to improve its wear resistance and corrosion resistance. The results show that smooth compact oxidized layer (composed of monoclinic ZrO2, tetragonal ZrO2 and 6ZrO2-Nb2O5) with 22.6μm-43.5μm thickness and 1252-1306HV hardness can be in-situ formed on the surface of the Zr-20Nb-xTi (x=0, 3). The adhesion of oxidized layers to the substrates is determined to be 58.35-66.25N. The oxidized Zr-20Nb-xTi alloys reveal great improvement of the pitting corrosion resistance in comparison with the un-oxidized alloys. In addition, the oxidized Zr-20Nb-3Ti exhibits sharply reduction of the corrosion rates and the oxidized Zr-20Nb shows higher corrosion rates than un-oxidized alloys, which is relevant with the content of the t-ZrO2. Wear test in artificial saliva demonstrates that the wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) are superior to pure Ti. All of the un-oxidized Zr-20Nb-xTi (x=0, 3) alloys suffer from serious adhesive wear due to its high plasticity. Because of the protection from compact oxide layer with high adhesion and high hardness, the coefficients of friction and wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) alloys decrease 50% and 95%, respectively. The defects on the oxidized Zr-20Nb have a negative effect on the friction and wear properties. In addition, after the thermal oxidation, compression test show that elastic modulus and strength of Zr-20Nb-xTi (x=0, 3) increase slightly with plastic deformation after 40% of transformation. Furthermore, stripping of the oxidized layer from the alloy matrix did not occur during the whole experiments. As the surface oxidized Zr-20Nb-3Ti alloy has a combination of excellent performance such as

  10. Esthetic restorative materials and opposing enamel wear.

    PubMed

    Olivera, Anna Belsuzarri; Marques, Márcia Martins

    2008-01-01

    This in vitro study compared the effects of a gold alloy (Degulor M), four dental ceramics (IPS Empress, IPS Empress 2, Duceram Plus, Duceram LFC) and a laboratory-processed composite (Targis) on the wear of human enamel. The amount of wear of the enamel (dental cusps) and restorative materials (disks) were tested in water at 37 degrees C under standard load (20 N), with a chewing rate of 1.3 Hz and was determined after 150,000 and 300,000 cycles. Before the test, the average surface roughness of the restorative materials was analyzed using the Ra parameter. The results of this study indicate that Targis caused enamel wear similar to Degulor M and resulted in significantly less wear than all the ceramics tested. IPS Empress provoked the greatest amount of enamel wear and Degulor M caused less vertical dimension loss. Targis could be an appropriate alternative material to ceramic, because it is esthetic and produces opposing enamel wear comparable to gold alloy.

  11. Structural changes in cuticles on violin bow hair caused by wear.

    PubMed

    Yamamoto, Tomoko; Sugiyama, Shigeru

    2010-01-01

    A bow with horse tail hair is used to play the violin. New and worn-out bow hairs were observed by atomic force microscopy. The cuticles of the new bow hair were already damaged by bleach and delipidation, however the worn-out bow hairs were much more damaged and broken off by force, which relates to wearing out.

  12. Enamel wear opposing polished and aged zirconia.

    PubMed

    Burgess, J O; Janyavula, S; Lawson, N C; Lucas, T J; Cakir, D

    2014-01-01

    Aging of dental zirconia roughens its surface through low temperature degradation. We hypothesized that age-related roughening of zirconia crowns may cause detrimental wear to the enamel of an opposing tooth. To test our hypothesis, we subjected artificially aged zirconia and reference specimens to simulated mastication in a wear device and measured the wear of an opposing enamel cusp. Additionally, the roughness of the pretest surfaces was measured. The zirconia specimens, artificially aged by autoclave, showed no significant increase in roughness compared to the nonaged specimens. Furthermore, no significant difference in material or opposing enamel wear between the aged and nonaged zirconia was seen. All zirconia specimens showed less material and opposing enamel wear than the enamel to enamel control or veneering porcelain specimens. Scanning electron micrographs showed relatively smooth surfaces of aged and nonaged zirconia following wear testing. The micrographs of the veneering ceramic showed sharp fractured edges and fragments of wear debris. Zirconia may be considered a wear-friendly material for restorations opposing enamel, even after simulated aging.

  13. Dental prosthesis aspiration: An uncommon cause of respiratory distress.

    PubMed

    De Wilde, Belphine A L; Malfait, Thomas L; Bonte, Katrien; Malfait, Thomas L A

    2016-12-01

    We present a case of a 66-year-old Caucasian man with acute respiratory distress. The patient had a history of multiple cerebrovascular accidents which resulted in left hemiplegia, swallowing problems, and aphasia. He was tentatively diagnosed with aspiration pneumonia. However, because of clinical deterioration further investigations concluded to the aspiration of a dental prosthesis. After intubation and stabilization, the prosthesis could be manually extracted. However, the patient developed a Staphylococcus epidermidis sepsis and despite adequate antibiotic therapy, he eventually died. Dental prosthesis aspiration is a medical situation associated with a higher morbidity and mortality rate compared to ingested foreign bodies. It requires a high level of suspicion to ensure a timely diagnosis and life-saving treatment. Thorough history taking is of great importance in case of tracheobronchial aspiration, which is in the adult population mostly secondary to an underlying disorder. In impaired adults with missing dental prostheses there should be extra awareness for this problem. This case report illustrates the importance of a detailed history in case of tracheobronchial aspiration and shows the limitations in the diagnostic usefulness of bedside chest radiography.

  14. The effects of three different food acids on the attrition-corrosion wear of human dental enamel

    NASA Astrophysics Data System (ADS)

    Zhang, Yichi; Arsecularatne, Joseph A.; Hoffman, Mark

    2015-07-01

    With increased consumption of acidic drinks and foods, the wear of human teeth due to attrition in acidic environments is an increasingly important issue. Accordingly, the present paper investigates in vitro the wear of human enamel in three different acidic environments. Reciprocating wear tests in which an enamel cusp slides on an enamel flat surface were carried out using acetic, citric and lactic acid lubricants (at pH 3-3.5). Distilled water was also included as a lubricant for comparison. Focused ion beam milling and scanning electron microscopy imaging were then used to investigate the enamel subsurfaces following wear tests. Nanoindentation was used to ascertain the changes in enamel mechanical properties. The study reveals crack generation along the rod boundaries due to the exposure of enamel to the acidic environments. The wear mechanism changes from brittle fracture in distilled water to ploughing or shaving of the softened layer in acidic environments, generating a smooth surface with the progression of wear. Moreover, nanoindentation results of enamel samples which were exposed to the above acids up to a duration of the wear tests show decreasing hardness and Young’s modulus with exposure time.

  15. Strength and wear resistance of a dental glass-ionomer cement with a novel nanofilled resin coating.

    PubMed

    Lohbauer, Ulrich; Krämer, Norbert; Siedschlag, Gustavo; Schubert, Edward W; Lauerer, Brigitte; Müller, Frank A; Petschelt, Anselm; Ebert, Johannes

    2011-04-01

    To evaluate the influence of different resin coating protocols on the fracture strength and wear resistance of a commercial glass-ionomer cement (GIC). A new restorative concept [Equia (GC Europe)] has been introduced as a system application consisting of a condensable GIC (Fuji IX GP Extra) and a novel nanofilled resin coating material (G-Coat Plus). Four-point fracture strength (FS, 2 x 2 x 25 mm, 14-day storage, distilled water, 37 degrees C) were produced and measured from three experimental protocols: no coating GIC (Group 1), GIC coating before water contamination (Group 2), GIC coating after water contamination (Group 3). The strength data were analyzed using Weibull statistics. Three-body wear resistance (Group 1 vs. Group 2) was measured after each 10,000 wear cycles up to a total of 200,000 cycles using the ACTA method. GIC microstructure and interfaces between GIC and coating materials were investigated under SEM and CLSM. The highest FS of 26.1 MPa and the most homogenous behavior (m = 7.7) has been observed in Group 2. The coated and uncoated GIC showed similar wear resistance until 90,000 cycles. After 200,000 wear cycles, the coated version showed significantly higher wear rate (ANOVA, P< 0.05). The coating protocol has been shown to determine the GIC fracture strength. Coating after water contamination and air drying is leading to surface crack formation thus significantly reducing the FS. The resin coating showed a proper sealing of GIC surface porosities and cracks. In terms of wear, the coating did not improve the wear resistance of the underlying cement as similar or higher wear rates have been measured for Group 1 versus Group 2.

  16. Dental wear estimation using a digital intra-oral optical scanner and an automated 3D computer vision method.

    PubMed

    Meireles, Agnes Batista; Vieira, Antonio Wilson; Corpas, Livia; Vandenberghe, Bart; Bastos, Flavia Souza; Lambrechts, Paul; Campos, Mario Montenegro; Las Casas, Estevam Barbosa de

    2016-01-01

    The objective of this work was to propose an automated and direct process to grade tooth wear intra-orally. Eight extracted teeth were etched with acid for different times to produce wear and scanned with an intra-oral optical scanner. Computer vision algorithms were used for alignment and comparison among models. Wear volume was estimated and visual scoring was achieved to determine reliability. Results demonstrated that it is possible to directly detect submillimeter differences in teeth surfaces with an automated method with results similar to those obtained by direct visual inspection. The investigated method proved to be reliable for comparison of measurements over time.

  17. Psychometric properties of the Dutch version of the Orofacial Esthetic Scale (OES-NL) in dental patients with and without self-reported tooth wear.

    PubMed

    Wetselaar, P; Koutris, M; Visscher, C M; Larsson, P; John, M T; Lobbezoo, F

    2015-11-01

    The aim of this study was to test the psychometric properties of the Dutch version of the Orofacial Esthetic Scale (OES) in dental patients with and without self-reported tooth wear. The English version of the OES was translated into Dutch, following established guidelines for cross-cultural adaptation of health-related quality of life measures. The reliability of the resulting OES-NL was tested in a test-retest study on 343 subjects; its validity was tested with the use of convergent validity on 582 subjects. The test-retest reliability of the OES-NL showed intra-class correlation coefficients (ICC) that ranged from 0·76 to 0·82, which can be qualified as excellent. The Cronbach's alpha revealed that the overall internal consistency of the scale was good (α = 0·89). Convergent validity was confirmed by the association between the OES-NL summary scores and three questions of the Dutch version of the Oral Health Impact Profile (OHIP-NL). The calculated Spearman's rank correlation coefficients ranged from -0·43 to -0·54 and were all significant (P < 0·001). The Dutch version of the Orofacial Esthetic Scale (OES-NL) showed good psychometric properties, making it suitable for the assessment of self-perceived aesthetics in Dutch dental patients with and without self-reported tooth wear. © 2015 John Wiley & Sons Ltd.

  18. Comparison between PEEK and Ti6Al4V concerning micro-scale abrasion wear on dental applications.

    PubMed

    Sampaio, M; Buciumeanu, M; Henriques, B; Silva, F S; Souza, J C M; Gomes, J R

    2016-07-01

    In the oral cavity, abrasive wear is predictable at exposed tooth or restorative surfaces, during mastication and tooth brushing. Also, wear can occur at contacting surfaces between the Ti-based prosthetic structures and implants in presence of abrasive compounds from food or toothpaste. Thus, the aim of this work was to compare the abrasive wear resistance of PEEK and Ti6Al4V on three-body abrasion related to different hydrated silica content and loads. Surfaces of Ti6Al4V or PEEK cylinders (8mm diameter and 4mm height) were wet ground on SiC papers and then polished with 1µm diamond paste. After that, surfaces were ultrasonically cleaned in propyl alcohol for 15min and then in distilled water for 10min. Micro-scale abrasion tests were performed at 60rpm and on different normal loads (0.4, 0.8 or 1.2N) after 600 ball revolutions using suspensions with different weight contents of hydrated silica. After abrasive tests, wear scars on flat samples were measured to quantify the wear volume and characterized by scanning electron microscope (SEM) to identify the dominant wear mechanisms. Results showed a higher volume loss rate on PEEK than that recorded on Ti6Al4V,, when subjected to three-body abrasion tests involving hydrated silica suspensions. An increase in volume loss was noted on both tested materials when the abrasive content or load was increased. PEEK was characterized by less wear resistance than that on Ti6Al4V after micro-scale abrasion wear in contact with hydrated silica particles, as commonly found in toothpastes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Dental materials for primary dentition: are they suitable for occlusal restorations? A two-body wear study.

    PubMed

    Lazaridou, D; Belli, R; Krämer, N; Petschelt, A; Lohbauer, U

    2015-04-01

    This was to evaluate the wear resistance of different materials, compomers, resin-modified glass ionomer cements (RMGICs), glass ionomer cements (GICs), used for posterior restorations in primary teeth and to compare the results with the reference material, amalgam. Eight specimens of each material were subjected to two-body wear test, using a chewing simulator. The wear region of each material was examined under a profilometer, measuring the vertical loss (μm) and the volume loss (mm(3)) of the materials. The results showed significant differences of vertical loss and volume loss of the test materials (p < 0.001). Amalgam had the highest wear resistance. Twinky Star (compomer) had the lowest vertical loss and volume loss. There was no significant difference of vertical loss among compomers, Dyract Extra, Dyract Flow and Dyract Posterior. Riva Self Cure (GIC) had no statistically significant difference compared with the compomers (except Twinky Star). No statistically significant difference was found also between Equia (GIC) and Ketac Moral (GIC) with Dyract Extra (Compomer). RMGICs were found to have the lowest wear resistance. For the statistical analysis, the PASW 20.0 (SPSS Statistics, IBM, Chicago) package was used. Means and standard deviations were measured with descriptive statistics and analyzed using one-way ANOVA. Compomers and some GICs, that have moderate wear resistance, may be sufficient for occlusal restorations in primary dentitions.

  20. Artifacts In Magnetic Resonance Imaging and Computed Tomography Caused By Dental Materials

    PubMed Central

    Klinke, Thomas; Daboul, Amro; Maron, Juliane; Gredes, Tomasz; Puls, Ralf; Jaghsi, Ahmad; Biffar, Reiner

    2012-01-01

    Background Artifacts caused by dental restorations, such as dental crowns, dental fillings and orthodontic appliances, are a common problem in MRI and CT scans of the head and neck. The aim of this in-vitro study was to identify and evaluate the artifacts produced by different dental restoration materials in CT and MRI images. Methods Test samples of 44 materials (Metal and Non-Metal) commonly used in dental restorations were fabricated and embedded with reference specimens in gelatin moulds. MRI imaging of 1.5T and CT scan were performed on the samples and evaluated in two dimensions. Artifact size and distortions were measured using a digital image analysis software. Results In MRI, 13 out of 44 materials produced artifacts, while in CT 41 out of 44 materials showed artifacts. Artifacts produced in both MRI and CT images were categorized according to the size of the artifact. Significance Metal based restoration materials had strong influence on CT and less artifacts in MRI images. Rare earth elements such as Ytterbium trifluoride found in composites caused artifacts in both MRI and CT. Recognizing these findings would help dental materials manufacturers and developers to produce materials which can cause less artifacts in MRI and CT images. PMID:22384071

  1. Enamel erosion and mechanical tooth wear in medieval Icelanders.

    PubMed

    Richter, Svend; Eliasson, Sigfus Thor

    2016-01-01

    The Icelandic Sagas are an important source of information on the way of life and diet habits in Iceland and possibly other Nordic countries 1000 years ago. Archaeological human skull material worldwide has revealed extensive tooth wear, with the main cause believed to be coarse diet. From a graveyard near volcano Hekla, 66 skeletons dated from before 1104 were excavated. The purpose of this study was to determine the main causes of tooth wear in Icelanders 1000 years ago. Forty-nine skulls were available for research. Two methods were used to evaluate tooth wear and seven for age estimation. An attempt was made to determine the main causes of tooth wear in the light of likely diet and beverage consumption according to a computer search on food and drink customs described in the Icelandic Sagas. Tooth wear was extensive in all groups, increasing with age. The highest score was on first molars, with no difference between sexes. It had all the similarities seen in wear from coarse diet. In some instances it had similar characteristics to those seen in erosion in modern Icelanders consuming excessive amounts of soft drinks. According to the Sagas, acidic whey was a daily drink and used for preservation of food in Iceland until recently. Since acidic whey has considerably high dental erosive potential, it is postulated that consumption of acidic drinks and food, in addition to a coarse and rough diet, played a significant role in the dental wear of ancient Icelanders.

  2. Dental Amalgam

    MedlinePlus

    ... Pin it Email Print Dental amalgam is a dental filling material which is used to fill cavities caused by ... tooth structure. Dental amalgam is one type of dental filling material used to repair tooth structure that has been ...

  3. Three-body wear potential of dental yttrium-stabilized zirconia ceramic after grinding, polishing, and glazing treatments.

    PubMed

    Amer, Rafat; Kürklü, Duygu; Kateeb, Elham; Seghi, Robert R

    2014-11-01

    Zirconia complete-coverage crowns are being widely used as restorations because of their improved esthetic characteristics. Data about the enamel wear potential of this ceramic after chair side adjustments are sparse. The purpose of this study was to investigate the 3-body wear of enamel opposing 3 types of ceramic (dense sintered yttrium-stabilized zirconia; Crystal Zirconia; DLMS) (Z), a lithium disilicate (IPS e-max CAD; Ivoclar Vivadent) (E), and a conventional low-fusing feldspathic porcelain (VitaVMK-Master; Vita Zahnfabrik) (P), treated to impart a rough, smooth, or glazed surface. Twenty-four specimens of each of the zirconia and the lithium disilicate ceramic were sectioned from computer-aided design and computer-aided manufacturing blocks into rectangular plates (15×12×2 mm). Twenty-four specimens of the feldspathic porcelain were formed into disks (12 mm diameter) from powders compressed in a silicone mold. All specimens (n=72) were prepared according to the manufacturers' recommendations. Specimens of each ceramic group were placed into 1 of 3 groups: group R, rough surface finish; group S, smooth surface finish; and group G, glazed surface finish. A total of 9 groups with 8 specimens each were placed in a 3-body wear simulator, with standardized enamel specimens (n=72) acting as the substrate. The wear of the enamel specimens was evaluated after 50,000 cycles. The data were analyzed with 2-way ANOVA and the Tukey HSD multiple comparison test (α=.05). The data showed that the smooth zirconia group (ZS) was associated with the least amount of enamel wear (1.26 ±0.55 mm(2)). The most antagonistic enamel wear was associated with the glazed groups ZG (5.58 ±0.66 mm(2)), EG (3.29 ±1.29 mm(2)), and PG (4.2 ±1.27 mm(2)). The degree of enamel wear associated with monolithic zirconia was similar to conventional feldspathic porcelain. Smoothly polished ceramic surfaces resulted in less wear of antagonistic enamel than glazing. Copyright © 2014 Editorial

  4. Anthropology, tooth wear, and occlusion ab origine.

    PubMed

    Young, W G

    1998-11-01

    The purpose of this essay is to emphasize that anthropology, the study of man in his environments, is a potent tool for scientific discovery and inspiration in dental science. It attempts to capture flashes of creative anthropological insight which have illuminated studies of tooth wear and occlusion in the past. While it documents contributions, understandings, and misunderstandings from Australian and New Zealand dentists, it is not a hagiography. The real saint of this essay is the Australian aborigine. For when men and women are understood in their environments, much is learned from them which challenges preconceptions of our dental science culture. The essay concludes that new, contemporary Australian culture needs to be studied by anthropological approaches if we are to understand how dental erosion is exacerbating tooth wear and damaging the occlusions of contemporary Australians. Much remains to be discovered about contemporary lifestyles, habits, and diets that lead to dental erosion, the principal cause of contemporary tooth wear in this part of the world.

  5. Topical fluoride as a cause of dental fluorosis in children.

    PubMed

    Wong, May Cm; Glenny, Anne-Marie; Tsang, Boyd Wk; Lo, Edward Cm; Worthington, Helen V; Marinho, Valeria Cc

    2010-01-20

    For many years, topical use of fluorides has gained greater popularity than systemic use of fluorides. A possible adverse effect associated with the use of topical fluoride is the development of dental fluorosis due to the ingestion of excessive fluoride by young children with developing teeth. To describe the relationship between the use of topical fluorides in young children and the risk of developing dental fluorosis. Electronic search of the Cochrane Oral Health Group Trials Register, CENTRAL, MEDLINE, EMBASE, BIOSIS, Dissertation Abstracts and LILACS/BBO. Reference lists from relevant articles were searched. Date of the most recent searches: 9th March 09. Randomised controlled trials (RCTs), quasi-RCTs, cohort studies, case-control studies and cross-sectional surveys, in which fluoride toothpastes, mouthrinses, gels, foams, paint-on solutions, and varnishes were compared to an alternative fluoride treatment, placebo or no intervention group. Children under the age of 6 years at the time topical fluorides were used. Data from all included studies were extracted by two review authors. Risk ratios for controlled, prospective studies and odds ratios for case-control studies or cross-sectional surveys were extracted or calculated. Where both adjusted and unadjusted risk ratios or odds ratios were presented, the adjusted value was included in the meta-analysis. 25 studies were included: 2 RCTs, 1 cohort study, 6 case-control studies and 16 cross-sectional surveys. Only one RCT was judged to be at low risk of bias. The other RCT and all observational studies were judged to be at moderate to high risk of bias. Studies were included in four intervention/exposure comparisons. A statistically significant reduction in fluorosis was found if brushing of a child's teeth with fluoride toothpaste commenced after the age of 12 months odds ratio 0.70 (random-effects: 95% confidence interval 0.57 to 0.88) (data from observational studies). Inconsistent statistically significant

  6. Epigallocatechin-3-Gallate Reduces Cytotoxic Effects Caused by Dental Monomers: A Hypothesis

    PubMed Central

    Jiao, Yang; Ma, Sai; Wang, Yirong; Li, Jing; Shan, Lequn; Chen, Jihua

    2015-01-01

    Resin monomers from dental composite materials leached due to incomplete polymerization or biodegradation may cause contact allergies and damage dental pulp. The cytotoxicity of dental resin monomers is due to a disturbance of intracellular redox equilibrium, characterized by an overproduction of reactive oxygen species (ROS) and depletion of reduced glutathione (GSH). Oxidative stress caused by dental resin monomers leads to the disturbance of vital cell functions and induction of cell apoptosis in affected cells. The nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway plays a key role in the cellular defense system against oxidative and electrophilic stress. Epigallocatechin-3-gallate (EGCG) can activate the Nrf2 pathway and induce expression of a multitude of antioxidants and phase II enzymes that can restore redox homeostasis. Therefore, here, we tested the hypothesis that EGCG-mediated protection against resin monomer cytotoxicity is mediated by activation of the Nrf2 pathway. This study will help to elucidate the mechanism of resin monomer cytotoxicity and provide information that will be helpful in improving the biocompatibility of dental resin materials. PMID:26489899

  7. Self-reported causes for referral to dental treatment under general anaesthesia (DGA): a cross-sectional survey.

    PubMed

    Taskinen, H; Kankaala, T; Rajavaara, P; Pesonen, P; Laitala, M-L; Anttonen, V

    2014-04-01

    To determine causes leading to dental care under general anaesthesia (DGA) in public health care reported by the patients or the parents/caregivers. All the patients referred to DGA at the Municipal Health Centre, Oulu, Finland, during 10 months were invited to participate in the present cross-sectional survey. They were sent a questionnaire on indications for referral to DGA, dental fear, possible reasons for it as well as prior treatment of dental fear. For measuring overall dental fear, the modified Corah dental anxiety scale (MCDAS) and visual analogue scale (VAS) forms were also included in the questionnaire. The most common self-reported indication for referral to DGA was dental fear (63.9%). For children and adolescents (<18 years), need for extensive care was the second most common reported cause. The great majority of the respondents reported having dental fear (90.8%). Dental fear was more common among females than males, but the difference between the genders was not statistically significant. The most common cause for dental fear was earlier negative experiences in dental care (51.9%). The mean MCDAS score was 19.0 (SD 5.7; 5-25) indicating severe dental anxiety. An increasing trend towards older age groups could be seen in VAS scores reporting fear of pain, needles, scaling, scolding by the dentist, extractions, as well as endodontic treatment. Dental fear had been taken into consideration in dental treatment preceding DGA. Dental fear is the most common self-reported indication for referral to DGA and should be taken into consideration.

  8. Novel methods of balancing covariates for the assessment of dental erosion: a contribution to validation of a synthetic scoring system for erosive wear.

    PubMed

    Margaritis, Vasileios; Mamai-Homata, Eleni; Koletsi-Kounari, Haroula

    2011-05-01

    The purpose of the study was to balance several potential erosive covariates, using traditional and novel epidemiological approaches, in order to assess the relative risks of dental erosion more precisely. Traditional (univariate and logistic regression analysis) and novel techniques (propensity scores and Inverse Probability Weighting-IPW) were applied for evaluating the effect of twenty covariates on dental erosion among 502 adolescents. Different approaches gave different estimates of the relative risks of dental erosion. The increased consumption of carbonated soft drinks had the major erosive effect, when traditional analyses were used (unadjusted: OR=3.475 and CI: 1.499-8.052, logistic regression: OR=3.219 and CI: 1.373-7.547). On the other hand, IPW method indicated that the consumption of erosion drinks immediately after intense physical exercise had the highest odds ratio (OR=1.363 and CI: 0.963-1.929), followed by the increased consumption of citrus fruit juice (OR=1.326 and CI: 1.004-1.752). This method also demonstrated a marked improvement in balance, with the 95% CIs for each OR being considerably narrower than those reported in the initial analysis. Standardization of the potential aetiological criteria of erosive wear is a considerably difficult process. Nevertheless, novel methods revealed that the increased consumption of carbonated soft drinks and citrus fruit juices could be included as aetiologic factors in a synthetic scoring system for erosion. Parameters which are related to salivary protective mechanisms (e.g. consumption of erosion drinks immediately after intense physical exercise) could also be a part of such an index. Further research is required in order to achieve the maximum validation of the potential erosive risk factors. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Current concepts on the management of tooth wear: part 1. Assessment, treatment planning and strategies for the prevention and the passive management of tooth wear.

    PubMed

    Mehta, S B; Banerji, S; Millar, B J; Suarez-Feito, J-M

    2012-01-13

    The aim of this series of four articles on tooth wear management is to provide the reader with the necessary information in order to be able to successfully manage cases of tooth wear, regardless of the cause, severity and location of the wear pattern seen. The content will largely focus on contemporary clinical techniques, illustrated where possible by case examples. Emphasis will be placed on 'additive adhesive techniques' utilising fixed prosthodontic protocols; however, cases of tooth wear amongst partially dentate patients involving the use of removable prostheses will also be described. The importance of patient consent and contingency planning will also be discussed. Paper 1 will describe the assessment of the wear patient, including the rationale for the planning of dental care. Also discussed will be the administration of preventative and passive management strategies for cases displaying tooth wear.

  10. Infective endocarditis caused by Veillonella of dental origin.

    PubMed

    Prpić-Mehicić, G; Marsan, T; Miletić, I; Buntak-Kobler, D

    1998-12-01

    The purpose of this investigation was to examine whether Veillonella could cause transitory bacteriemia and endocarditis in both pure and mixed cultures when the port of entrance for infection was made in rats' incisors. Incisors of 54 male Zgr: whistar conventional rats were inoculated with pure culture of Veillonella (18 animals) and with mixed culture of S. mutans and Veillonella (18 animals). Remaining 18 incisors (the control group) were treated with saline solution. The animals were sacrificed after 7, 21 and 52 days respectively. Two positive hemocultures were obtained in mixed infection after 21 days of experimental procedure. Histopatological analysis of endocardial tissue revealed changes in 7 (12.96%) cases. Occurrence of acute endocarditis (one case) and chronical (four cases) ones depended on duration of mixed infections. For chronical endocarditis that appears in two animals with pure Veillonela culture we are at a loss of explanation. In conclusion, on the rats model Veillonella can penetrate into circulation in association with S. mutans via the pulp tissue and could be involved in infective endocarditis.

  11. Can a Tight Saree Wear Cause Cancer? – A Rare Case Report

    PubMed Central

    Balasundaram, Subathira; Ramadas, Rathnadevi; Stumpf, Janos; Hussain, Khader A K

    2014-01-01

    Skin cancer is rare in India with an incidence of about less than 1% of all cancers. Saree Cancer, a kind of skin cancer is rarer entity, which arises from the frequent abrasion over skin caused by tying the rope in inskirts, often tied tightly so that the saree does not slip. This causes hyperpigmented abrasion, ulcer and then may lead to cancer. This report is about a 40-year-old female with non-healing ulcer of six months duration with rapid increase in size over the past one month. The ulcer measured 4x2 cm in size. The patient underwent excision of the tumour and the margins were positive. Re-excision was done for positive margins and re-growth of the tumour. This is one the first few reports on saree cancer. PMID:25478425

  12. [Destructive and protective factors in the development of tooth-wear].

    PubMed

    Máté, Jász; Gábor, Varga; Zsuzsanna, Tóth

    2006-12-01

    The experience of the past decade proves that tooth wear occurs in an increasing number of cases in general dental practice. Tooth wear may have physical (abrasion and attrition) and/or chemical (erosion) origin. The primary physical causes are inadequate dental hygienic activities, bad oral habits or occupational harm. As for dental erosion, it is accelerated by the highly erosive foods and drinks produced and sold in the past decades, and the number of cases is also boosted by the fact that bulimia, anorexia nervosa and gastro-oesophageal reflux disease prevalence have become more common. The most important defensive factor against tooth wear is saliva, which protects teeth from the effect of acids. Tertiary dentin formation plays an important role in the protection of the pulp. Ideally, destructive and protective factors are in balance. Both an increase in the destructive forces, and the insufficiency of defense factors result in the disturbance of the equilibrium. This results in tooth-wear, which means an irreversible loss of dental hard tissue. The rehabilitation of the lost tooth material is often very difficult, irrespectively of whether it is needed because of functional or esthetic causes. For that reason, the dentist should carry out primary and secondary dental care and prevention more often, i.e. dental recall is indispensable every 4-6 months.

  13. Equine dental disease. Part 3: A long-term study of 400 cases: disorders of wear, traumatic damage and idiopathic fractures, tumours and miscellaneous disorders of the cheek teeth.

    PubMed

    Dixon, P M; Tremaine, W H; Pickles, K; Kuhns, L; Hawe, C; McCann, J; McGorum, B C; Railton, D I; Brammer, S

    2000-01-01

    Of 400 horses referred because of dental disorders, 349 cases were diagnosed as suffering from primary disorders of their cheek teeth. Details of 104 of these cases are presented, including 44 cases with abnormalities of wear, 26 cases with traumatic damage, 24 cases with idiopathic fractures and 10 cases with miscellaneous cheek teeth disorders including oral tumours. The long-term response to treatment was excellent in most cases, even in cases with residual secondary periodontal disease.

  14. [Causes of interruption of dental studies and subsequent change in careers].

    PubMed

    Jacobsen, N

    1989-08-01

    During recent years an increasing number of dental students at the University of Oslo used prolonged student time and graduated with mediocre results, or interrupted studies without graduation Jacobsen, Acta Odontol Scand 45:399-408, 1987). The present investigation aimed at clarifying the reasons for interrupted studies and at getting information about subsequent career. Semistructured questionnaires on curricular and socioeconomic causes for drop-out and on subsequent career were mailed to 98 persons who had quit dental studies during a 10-year period. Free comments on circumstances relevant to their drop-out were encouraged. The following findings are based on 68 replies (69 per cent): Sixty-three students (93 per cent) quit dental school for different curricular reasons, a majority of which was "more interest in other subjects". Contributory factors of socioeconomic nature, mostly future unemployment concern, were often mentioned. Forty-five (66 per cent) later graduated with university degrees in medicine, economics, veterinary medicine, science, technology, law etc, and the remainder, except two persons, finished up to 4 years of studies at regional colleges or similar institutions. Free comments focused on curricular, pedagogical, and social shortcomings at the dental faculty. The findings indicated that a large majority of the students who dropped out did so for lack of stimulation by the dental curriculum and not for lack of academic potential. Only a few students quit because, in their own description, they were immature for university studies at the time, or because they had "academic" difficulties with the early science/biology courses or with the preclinical technique courses.

  15. THE PECULIARITIES OF TREATMENT OF UNCOMPLICATED AND COMPLICATED DENTAL INJURIES CAUSED BY TRAUMA.

    PubMed

    Mamaladze, M; Nizharadze, N; Vadachkoria, O

    2017-01-01

    Trauma related injuries of permanent teeth occur frequently and are the most pressing issue the dentists are facing today. In different age groups the same type of trauma affects the teeth with different frequencies. For instance, accident related dental trauma in children and adults affected permanent teeth in 30% and deciduous teeth in 20%, respectively. It should also be noted that front teeth are more susceptible to traumatic injuries compared to the incisors. Upper front teeth were injured in 72% of cases, while lower central, upper lateral incisors, canines and premolars only in 6-8%. The severity of dental injury depends on the type and extent of the trauma. Dental injury can be result of either direct or indirect trauma. A strong, «fast as lightning» impact most often affects the dental crown. A weak and dull impact (thump) extends toward the root apical direction resulting in avulsion of the tooth and root fracture. Dental injury caused by trauma has been always considered as an emergency condition. It requires prompt complex treatment methods from maintaining pulp vitality to tooth extraction option. Treatment plan always depends on the type and severity of the injury and on current clinical condition of tooth. In all cases, the combined treatment includes: care of visible wound, fixation of teeth, performance of surgical manipulations, determining of the need of endodontic treatment, restorations and orthodontic consultation. The recorded clinical cases include descriptions of dental injuries of various types, as well as performed diagnostic and treatment procedures. In both cases root was fractured by impact. In Clinical Case 1 the tooth 2.1 vertical partial displacement of the tooth (extrusion) with root fracture in the apical third was observed; Clinical Case 2 - 1.1 dental root fracture in its middle third and vertical extrusion. Treatment strategy is dictated by pulp condition (Assessment of pulp vitality and status). In both cases, the

  16. Prevalence, causes and correlates of traumatic dental injuries among 13-year-olds in Brazil.

    PubMed

    Nicolau, B; Marcenes, W; Sheiham, A

    2001-10-01

    A cross-sectional survey was carried out. This involved 652 out of a total of 764 (85%) 13-year-old adolescents enrolled in private and public schools located in urban areas in Cianorte, Brazil. They were interviewed and examined for traumatic dental injuries by one trained examiner (B.N.) using validated criteria. Sociodemographic data included sex, family structure (nuclear families, single parents and step-parents) and socio-economic indicators. Anthropometric measures included height and weight. The body mass index (BMI) was calculated (mean=20.1; SD=3.7). Those who had BMI scores equal or above the 85% percentile were considered overweight (BMI >23). The prevalence of traumatic injuries to the permanent incisors was 20.4%. The most common reported cause of injuries to the permanent incisors was falls (24.1%) followed by collisions with people or inanimate objects (15%), traffic accidents (10.5%), misuse of the teeth (6%), sports (2.3%) and violence (1.5%). Unknown causes accounted for 40.6%. Children from non-nuclear families, overweight children and boys were 2.18, 1.93 and 2.19 times respectively more likely to have dental injuries than children from nuclear families, non-overweight children and girls (P<0.01) after adjusting for family structure, BMI, sex, family income and level of education of the parents. The relationship between dental injuries and socioeconomic indicators was not statistically significant. In conclusion, being from a non-nuclear family, overweight and a boy increased the risk of having traumatic dental injury, but the relationship with socio-economic indicators was not statistically significant.

  17. First aid for dental trauma caused by sports activities: state of knowledge, treatment and prevention.

    PubMed

    Emerich, Katarzyna; Kaczmarek, Jan

    2010-05-01

    In view of the widespread lack of knowledge of first aid procedures in cases of dental trauma, this article describes the current state of knowledge and highlights the need for education of those likely to witness or be victims of dental trauma while practising sports. Dental and oral injuries, the commonest type of orofacial injuries, are often sustained by athletes playing contact sports; indeed, they represent the most frequent type of sporting injury. Studies of a large group of children and adults have shown that as many as 31% of all orofacial injuries are caused by sporting activities. Furthermore, current literature on the subject emphasizes that awareness of appropriate triage procedures following dental trauma is unsatisfactory. Delay in treatment is the single most influential factor affecting prognosis. What should we know and, more importantly, what should we do? Immediate replantation of an avulsed tooth is the best treatment option at the site of the accident. If replantation is impossible, milk is the preferred transport medium for the avulsed tooth. There is a general low level of awareness about the need for prompt triage of traumatic dental injuries sustained in sports, despite their relative frequency. When a cohort of Swiss basketball players was interviewed, only half were aware that an avulsed tooth could be replanted. Cheap, commercially available tooth storage devices containing an isotonic transport medium (so-called 'Save-a-Tooth boxes'), can maintain the viability of an avulsed tooth for up to 72 hours, prior to replantation. More readily available storage media such as milk, sterile saline or even saliva may be used, but knowledge of this information is rare among sports participants. For example, just 6.6% of the Swiss basketball players interviewed were aware of the 'Tooth Rescue box' products. Sporting organizations seem to offer very little information about sports-related risks or preventive strategies for orodental trauma. Having

  18. Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

    PubMed

    Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

    2015-02-01

    Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p < 0.05). Highest temperature increase could be observed in the 1-mm thickness group for enamel. Evaluating the 1-mm group for dentine, a significantly lower temperature increase could be measured (p < 0.05) with lowest values in the 3-mm group (p < 0.05). A time delay for temperature increase during the ablation process depending on the material thickness was observed for both hard tissues (p < 0.05). Employing the USPL system to remove dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur.

  19. Modification of depth and distance perception caused by long-term wearing of left-right reversing spectacles.

    PubMed

    Ichikawa, Makoto; Kimura, Takahiko; Egusa, Hiroyuki; Nakatsuka, Makiko; Amano, Jun; Ueda, Tomomi; Tashiro, Takara

    2003-01-01

    For 35 to 39 days, four observers wore continuously left-right reversing spectacles which pseudoscopically reverse the order of binocular disparity and direction of convergence. In three tests, we investigated how the visual system copes with the transformation of depth and distance information due to the reversing spectacles. In stereogram observation, after a few days of wearing the spectacles. the observers sometimes perceived a depth order which was opposite to the depth order that they had perceived in the pre-spectacle-wearing period. Monocular depth cues contributed more to depth perception in the spectacle-wearing period than they did in the pre-spectacle-wearing period. While the perceived distance significantly decreased during the spectacle-wearing period, we found no evidence of adaptive change in distance perception. The results indicate that the visual system adapts itself to the transformed situation by not only changing the processing of disparity but also by changing the relative efficiency of each cue in determining apparent depth.

  20. An unusual infection of cervicofacial area caused by dental pathology: flesh-eating syndrome.

    PubMed

    Ozdinc, Serife; Unlu, Ebru; Oruc, Oya; User, Nese Nur; Karakaya, Zeynep

    2015-10-01

    Necrotizing fasciitis (NF) of the cervicofacial area is highly rare, but physicians should be familiar with the presentation of this situation owing to the suddenness of its beginning, the rapidness of its spread, and ending with high mortality and morbidity. In this article, 5 patients with NF admitted to emergency department with dental pathology history were discussed with a review of the literature. The purpose of this case series is to raise awareness about NF of the cervicofacial area caused by dental pathologies. Five patients admitted to our emergency department between January 2012 and March 2015 and diagnosed as having cervicofacial NF were identified. All patients had dental pathologies. The parameters of the study were patients' age, sex, complaints, self- and family histories, physical examinations' findings, routine laboratory-computed tomographic findings, treatment, and complications. Two of the patients were older than 70 years. One of the patients was healthy but he lost time because of an inappropriate treatment. These 3 patients died. The remaining patients were discharged at the end of the prolonged and intensive treatment. Necrotizing fasciitis should always be remembered in the diagnosis of the infection of the cervicofacial area. Because of difficulty in its diagnosis, a delay in the treatment may result in a horrific outcome.

  1. The Inter-Relationship between Dietary and Environmental Properties and Tooth Wear: Comparisons of Mesowear, Molar Wear Rate, and Hypsodonty Index of Extant Sika Deer Populations

    PubMed Central

    Kubo, Mugino Ozaki; Yamada, Eisuke

    2014-01-01

    In reference to the evolutionary trend of increasing cheek tooth height in herbivorous ungulates, the causes of dental abrasion have long been debated. Interspecific comparisons of extant ungulates have revealed that both phytoliths in grass and external abrasive matter may play important roles. Using analysis of extant sika deer living in various environments and showing continuous latitudinal variation in food habits from northern grazing to southern browsing, we quantitatively evaluated the influence of dietary and environmental properties on three dental variables: mesowear score (MS), molar wear rate, and M3 hypsodonty index. We used 547 skulls and 740 mandibles from 16 populations of sika deer to obtain the dental measurements. We found that only graminoid proportion in diet correlated with MS and the molar wear rate, implying that phytoliths in grass abrade dental tissues. In contrast, annual precipitation in habitat was not correlated with any of the dental variables. We also found a significant correlation between the molar wear rate (selective pressure for high-crowned molars) and the M3 hypsodonty index of extant sika deer, implying an evolutionary increment in molar height corresponding to the molar wear rate. Our intraspecific comparative analyses provide further support for use of mesowear analysis as a paleodiet estimation method; it not only reveals staple food types (graminoids or dicots) but also implies regional or seasonal variation in the diet of the species. PMID:24603896

  2. The inter-relationship between dietary and environmental properties and tooth wear: comparisons of mesowear, molar wear rate, and hypsodonty index of extant Sika deer populations.

    PubMed

    Kubo, Mugino Ozaki; Yamada, Eisuke

    2014-01-01

    In reference to the evolutionary trend of increasing cheek tooth height in herbivorous ungulates, the causes of dental abrasion have long been debated. Interspecific comparisons of extant ungulates have revealed that both phytoliths in grass and external abrasive matter may play important roles. Using analysis of extant sika deer living in various environments and showing continuous latitudinal variation in food habits from northern grazing to southern browsing, we quantitatively evaluated the influence of dietary and environmental properties on three dental variables: mesowear score (MS), molar wear rate, and M3 hypsodonty index. We used 547 skulls and 740 mandibles from 16 populations of sika deer to obtain the dental measurements. We found that only graminoid proportion in diet correlated with MS and the molar wear rate, implying that phytoliths in grass abrade dental tissues. In contrast, annual precipitation in habitat was not correlated with any of the dental variables. We also found a significant correlation between the molar wear rate (selective pressure for high-crowned molars) and the M3 hypsodonty index of extant sika deer, implying an evolutionary increment in molar height corresponding to the molar wear rate. Our intraspecific comparative analyses provide further support for use of mesowear analysis as a paleodiet estimation method; it not only reveals staple food types (graminoids or dicots) but also implies regional or seasonal variation in the diet of the species.

  3. Tooth wear among patients suffering from mental disorders

    PubMed Central

    Piccoli, Luca; Besharat, Laith Konstantinos; Cassetta, Michele; Migliau, Guido; Di Carlo, Stefano; Pompa, Giorgio

    2014-01-01

    Summary Aim Assess oral health, treatment needs and the correlation between tooth wear and medications in patients with psychiatric disease. Methodology 92 patients (40 male and 52 female) admitted in the Department of Neurology and Psychiatry of the Umberto I Hospital of Rome underwent an oral and dental clinical examination in accordance according to World Health Organization Basic Methods Criteria. One dentist performed all clinical examinations, training and calibration was carried out by an experienced clinical examiner. To measure the degree of inter-examiner agreement Kappa statistics was calculated. Level of tooth wear was assessed using the tooth wear classification of Johansson et al. Exact psychiatric pathology and medications of each patient were registrated. The Statistical Package for the Social Sciences (SPSS Inc., Chicago, Ill.) was used to analyze the data. A value of P < 0.05 was considered statistically significant. Results 34.78% of the sample regarding tooth wear demonstrated score 2. Men demonstrated 30% score 2, and 20% score 3 and 4 whereas female patients 38.46% score 2, 7.69% score 3 and none score 4. Conclusions Chronic exposure to neuroleptic drugs can cause phenomena of bruxism. There is a direct correlation between tooth wear, psychiatric disorders and administration of certain drugs. Poor oral hygiene and extensive unmet needs for dental treatment were widespread among psychiatric patients. PMID:25002918

  4. Does impaction of titanium-coated interbody fusion cages into the disc space cause wear debris or delamination?

    PubMed

    Kienle, Annette; Graf, Nicolas; Wilke, Hans-Joachim

    2016-02-01

    A large number of interbody fusion cages are made of polyetheretherketone (PEEK). To improve bone on-growth, some are coated with a thin layer of titanium. This coating may fail when subjected to shear loading. The purpose of this testing was to investigate whether impaction of titanium-coated PEEK cages into the disc space can result in wear or delamination of the coating, and whether titanium cages with subtractive surface etching (no coating) are less susceptible to such failure. A biomechanical study was carried out to simulate the impaction process in clinical practice and to evaluate if wear or delamination may result from impaction. Two groups of posterior lumbar interbody fusion cages with a similar geometry were tested: n=6 titanium-coated PEEK and n=6 surface-etched titanium cages. The cages were impacted into the space in between two vertebral body substitutes (polyurethane foam blocks). The two vertebral body substitutes were fixed in a device, through which a standardized axial preload of 390 N was applied. The anterior tip of the cage was positioned at the posterior border of the space between the two vertebral body substitutes. The cages were then inserted using a drop weight with a mass representative of a surgical hammer. The drop weight impacted the insertion instrument at a maximum speed of about 2.6 m/s, which is in the range of the impaction speed in vivo. This was repeated until the cages were fully inserted. The wear particles were captured and analyzed according to the pertinent standards. The surface-etched titanium cages did not show any signs of wear debris or surface damage. In contrast, the titanium-coated PEEK cages resulted in detached wear particles of different sizes (1-191 µm). Over 50% of these particles had a size <10 µm. In median, on 26% of the implants' teeth, the coating was abraded. Full delamination was not observed. In contrast to the surface-etched implants, the titanium-coated PEEK implants lost some coating material

  5. Saliva and dental erosion

    PubMed Central

    BUZALAF, Marília Afonso Rabelo; HANNAS, Angélicas Reis; KATO, Melissa Thiemi

    2012-01-01

    Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective This review discusses the role of salivary factors on the development of dental erosion. Material and Methods A search was undertaken on MEDLINE website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Results Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Conclusions Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects. PMID:23138733

  6. Numerical modelling of sliding wear caused by pin-on-disk method over copper coated ABS plastic substrate

    NASA Astrophysics Data System (ADS)

    Nigam, S.; Mahapatra, S. S.; Patel, S. K.

    2016-09-01

    The coating of metal increases the face value of the plastic and inhibits other properties like conductivity, hardness and lustre. Thus the combination of plastic and metal coating results in a material that is light in weight because of the presence of plastic as the base material and; electrical and thermal conductive because of the presence of metal on the surface. The requirement of such materials is growing day by day. Copper coated plastic has various applications such as in fabrication of printed circuit boards (PCB's) and various automobile parts and in electromagnetic interference shielding. It is important to analyse the tribological aspect of the same in order to broaden its range of application. The present work contains 3D modelling of thermally sprayed copper on ABS plastic and simulation of sliding wear test by pin-on-disc method. The Johnson cook flow stress model is selected for the coating material. Archard's wear model has provided the best results for calculating the wear rate. The results obtained are in good agreement with the experimental values.

  7. Prevention of microbial contamination of the dental unit caused by suction into the turbine drive air lines.

    PubMed

    Ojajärvi, J

    1996-01-01

    To determine whether a specially designed antisuction device can prevent the bacterial contamination of the drive air lines of the dental turbine that is caused by suction when the turbine is stopped. A dental unit with and without the antisuction device and three different types of sterilized handpieces were used in the tests. Each turbine was operated in air, then submerged into a bacterial suspension of E. coli and enterococci for 3 seconds, removed, and stopped. This procedure was repeated 10 times. Possible bacterial contamination of the drive air lines was examined by submersing the head of a sterilized handpiece with the turbine running into a nutrient broth for 30 seconds. The broth was incubated at 35 degrees C up to 2 days. After use of the conventional dental unit, bacterial growth of drive air lines was found in 10 of 150 broth samples. After the installation of the antisuction device no bacterial growth was found in any of the 138 samples. The difference in the contamination frequencies is statistically significant (p = 0.011, Fisher's two-sided exact test). The drive air lines of the turbine in the dental unit may become contaminated despite the sterilization of handpieces. The antisuction device installed into the dental unit was found to prevent the contamination. With the exception of possibly immunocompromised patients, the transmission of microbes by exhaust air may be too small to cause infections. However, transmission of oral material between patients should be prevented in dental practice.

  8. The dental occlusion as a suspected cause for TMDs: epidemiological and etiological considerations.

    PubMed

    Türp, J C; Schindler, H

    2012-07-01

    The relationship between the dental occlusion and temporomandibular disorders (TMDs) has been one of the most controversial topics in the dental community. In a large epidemiological cross-sectional survey - the Study of Health in Pomerania (Germany) - associations between 15 occlusion-related variables and TMD signs or symptoms were found. In other investigations, additional occlusal variables were identified. However, statistical associations do not prove causality. By using Hill's nine criteria of causation, it becomes apparent that the evidence of a causal relationship is weak. Only bruxism, loss of posterior support and unilateral posterior crossbite show some consistency across studies. On the other hand, several reported occlusal features appear to be the consequence of TMDs, not their cause. Above all, however, biological plausibility for an occlusal aetiology is often difficult to establish, because TMDs are much more common among women than men. Symptom improvement after insertion of an oral splint or after occlusal adjustment does not prove an occlusal aetiology either, because the amelioration may be due to the change of the appliance-induced intermaxillary relationship. In addition, symptoms often abate even in the absence of therapy. Although patients with a TMD history might have a specific risk for developing TMD signs, it appears more rewarding to focus on non-occlusal features that are known to have a potential for the predisposition, initiation or perpetuation of TMDs.

  9. Prevalence and causes of visual impairment and rate of wearing spectacles in schools for children of migrant workers in Shanghai, China.

    PubMed

    He, Jiangnan; Lu, Lina; Zou, Haidong; He, Xiangui; Li, Qiangqiang; Wang, Weijie; Zhu, Jianfeng

    2014-12-22

    To assess the prevalence of visual impairment and rate of wearing spectacles in schools for children of migrant workers in Shanghai, China. Children from grade 1 to 5 in schools for children of migrant workers were randomly chosen for ocular examinations. All children were screened for uncorrected visual acuity and presenting visual acuity. After screening, the children whose uncorrected visual acuity was 20/40 or less received ocular motility evaluation, cycloplegic refraction/non-cycloplegic refraction, and external eye, anterior segment, media, and fundus examinations. A total of 9673 children were enumerated and 9512 (98.34%) participated in this study. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye were 13.33%, 11.26%, and 0.63%, respectively. The rate of wearing spectacles of the children with visual impairment in one or both eyes was 15.50%. Of these, 26.05% were wearing spectacles with inaccurate prescriptions. Refractive error was a major cause of visual impairment, accounting for 89.48% of all the visual impairment causes. Other causes of visual impairment included amblyopia accounting for 10.12%; congenital cataract, 0.1%; congenital nystagmus, 0.1%; ocular prosthesis, 0.1%; macular degeneration, 0.05%; and opaque cornea, 0.05%. This is the first study of the prevalence and causes of visual impairment in schools for children of migrant workers in Shanghai, China. The visual impairment rate in schools for children of migrant workers in suburbs of Shanghai in the best eye before vision correction was lower than those of urban children in mainstream schools in Guangzhou in 2012, and higher than students in rural of Beijing in 1998 and in suburb of Chongqing in 2007. The refractive error was the principal cause of the visual impairment of the children of migrant workers. The rate of wearing spectacles was low and the percentage of inaccurate prescriptions, among those who wore spectacles, was

  10. Mechanical modelling of tooth wear.

    PubMed

    Karme, Aleksis; Rannikko, Janina; Kallonen, Aki; Clauss, Marcus; Fortelius, Mikael

    2016-07-01

    Different diets wear teeth in different ways and generate distinguishable wear and microwear patterns that have long been the basis of palaeodiet reconstructions. Little experimental research has been performed to study them together. Here, we show that an artificial mechanical masticator, a chewing machine, occluding real horse teeth in continuous simulated chewing (of 100 000 chewing cycles) is capable of replicating microscopic wear features and gross wear on teeth that resemble wear in specimens collected from nature. Simulating pure attrition (chewing without food) and four plant material diets of different abrasives content (at n = 5 tooth pairs per group), we detected differences in microscopic wear features by stereomicroscopy of the chewing surface in the number and quality of pits and scratches that were not always as expected. Using computed tomography scanning in one tooth per diet, absolute wear was quantified as the mean height change after the simulated chewing. Absolute wear increased with diet abrasiveness, originating from phytoliths and grit. In combination, our findings highlight that differences in actual dental tissue loss can occur at similar microwear patterns, cautioning against a direct transformation of microwear results into predictions about diet or tooth wear rate. © 2016 The Author(s).

  11. Dental Abrasion of Incisor caused by a Babies' Dummy Clip: A Case Report.

    PubMed

    Doğramacı, Esma J; Rossi-Fedele, Giampiero

    2015-09-01

    Tooth surface loss (TSL), the non-carious loss of tooth tissue, is considered pathological if the teeth involved experience sensitivity and pain, are functionally compromised or they detract from the patient's appearance. TSL is a common clinical finding in many patient groups, although differences between the primary and permanent dentition contribute to TSL occurring at a faster rate and with worse outcomes in the primary dentition. This case report presents localized abrasion and associated apical periodontitis affecting a single primary tooth in a 2-year-old infant following the misuse of a babies' dummy clip whilst teething. Abrasion is rare in the primary dentition. CPD/CLINICAL RELEVANCE: This article highlights an unusual presentation of dental abrasion affecting the primary dentition caused by a previously unreported foreign object; abrasion in this case was a side-effect of soothing the discomfort of teething.

  12. Industrial Noise and Tooth Wear - Experimental Study

    PubMed Central

    Cavacas, Maria Alzira; Tavares, Vitor; Borrecho, Gonçalo; Oliveira, Maria João; Oliveira, Pedro; Brito, José; Águas, Artur; dos Santos, José Martins

    2015-01-01

    Tooth wear is a complex multifactorial process that involves the loss of hard dental tissue. Parafunctional habits have been mentioned as a self-destructive process caused by stress, which results in hyperactivity of masticatory muscles. Stress manifests itself through teeth grinding, leading to progressive teeth wear. The effects of continuous exposure to industrial noise, a “stressor” agent, cannot be ignored and its effects on the teeth must be evaluated. Aims: The aim of this study was to ascertain the effects of industrial noise on dental wear over time, by identifying and quantifying crown area loss. Material and Methods: 39 Wistar rats were used. Thirty rats were divided in 3 experimental groups of 10 animals each. Animals were exposed to industrial noise, rich in LFN components, for 1, 4 and 7 months, with an average weekly exposure of 40 hours (8h/day, 5 days/week with the weekends in silence). The remaining 9 animals were kept in silence. The areas of the three main cusps of the molars were measured under light microscopy. Statistical analysis used: A two-way ANOVA model was applied at significance level of 5%. Results: The average area of the molar cusps was significantly different between exposed and non-exposed animals. The most remarkable differences occurred between month 1 and 4. The total crown loss from month 1 to month 7 was 17.3% in the control group, and 46.5% in the exposed group, and the differences between these variations were significant (p<0.001). Conclusions: Our data suggest that industrial noise is an important factor in the pathogenesis of tooth wear. PMID:25798052

  13. [Wear and different restorative materials--a review].

    PubMed

    Beyth, N; Sharon, E; Lipovetsky, M; Smidt, A

    2006-07-01

    Wear of materials is a complex and unpredictable phenomenon. The variables affecting the mechanism of wear include the properties of the two contacting materials and the surrounding and interfacial media. This paper reviews the dental wear of different restorative materials and their counter effect on the tooth structure. It presents the updated classifications for tooth surface lesions termed dental wear, and discusses the wear behavior of various restorative materials. Some guidelines for restorative material selection are given. Clinical wear bears a multifactorial etiology, understanding the mechanism of action is an important step in an appropriate restoration material selection. Each material selected should meet the individual wear behavior and needs. Individual factors may enhance the wear rates: aggressive tooth brushing, parafunctions, diet, acidic/aqueous environment, surface geometry, and diminished tooth support. Supportive treatment following restoration is important to monitor wear rates.

  14. Dental senescence in a long-lived primate links infant survival to rainfall

    PubMed Central

    King, Stephen J.; Arrigo-Nelson, Summer J.; Pochron, Sharon T.; Semprebon, Gina M.; Godfrey, Laurie R.; Wright, Patricia C.; Jernvall, Jukka

    2005-01-01

    Primates tend to be long-lived, and, except for humans, most primate females are able to reproduce into old age. Although aging in most mammals is accompanied by dental senescence due to advanced wear, primates have low-crowned teeth that wear down before old age. Because tooth wear alters crown features gradually, testing whether early dental senescence causes reproductive senescence has been difficult. To identify whether and when low-crowned teeth compromise reproductive success, we used a 20-year field study of Propithecus edwardsi, a rainforest lemur from Madagascar with a maximum lifespan of >27 years. We analyzed tooth wear in three dimensions with dental topographic analysis by using Geographical Information Systems (GIS) technology. We report that tooth wear exposes compensatory shearing blades that maintain dental function for 18 years. Beyond this age, female fertility remains high; however infants survive only if lactation seasons have elevated rainfall. Therefore, low-crowned teeth accommodate wear to a point, after which reproductive success closely tracks environmental fluctuations. These results suggest a tooth wear-determined, but rainfall-mediated, onset of reproductive senescence. Additionally, our study indicates that even subtle changes in climate may affect reproductive success of rainforest species. PMID:16260727

  15. Dental senescence in a long-lived primate links infant survival to rainfall.

    PubMed

    King, Stephen J; Arrigo-Nelson, Summer J; Pochron, Sharon T; Semprebon, Gina M; Godfrey, Laurie R; Wright, Patricia C; Jernvall, Jukka

    2005-11-15

    Primates tend to be long-lived, and, except for humans, most primate females are able to reproduce into old age. Although aging in most mammals is accompanied by dental senescence due to advanced wear, primates have low-crowned teeth that wear down before old age. Because tooth wear alters crown features gradually, testing whether early dental senescence causes reproductive senescence has been difficult. To identify whether and when low-crowned teeth compromise reproductive success, we used a 20-year field study of Propithecus edwardsi, a rainforest lemur from Madagascar with a maximum lifespan of >27 years. We analyzed tooth wear in three dimensions with dental topographic analysis by using Geographical Information Systems (GIS) technology. We report that tooth wear exposes compensatory shearing blades that maintain dental function for 18 years. Beyond this age, female fertility remains high; however infants survive only if lactation seasons have elevated rainfall. Therefore, low-crowned teeth accommodate wear to a point, after which reproductive success closely tracks environmental fluctuations. These results suggest a tooth wear-determined, but rainfall-mediated, onset of reproductive senescence. Additionally, our study indicates that even subtle changes in climate may affect reproductive success of rainforest species.

  16. Antibiotic resistance in general dental practice--a cause for concern?

    PubMed

    Sweeney, Louise C; Dave, Jayshree; Chambers, Philip A; Heritage, John

    2004-04-01

    This review examines the contribution dental prescribing makes to the selection of antibiotic resistance in bacteria of the oral flora. The antibiotics commonly used in dental prescribing in the UK are discussed, together with the problems of resistance in members of the oral flora. The antibiotic prescribing habits of general dental practitioners are then reviewed with respect to therapeutic prescriptions and those drugs that are prescribed prophylactically. Not all antibiotic prescriptions for dental problems are written by dentists; prescribing outside the dental profession is also considered. The review then considers the support available to dentists from clinical diagnostic microbiology laboratories. It concludes that better use of diagnostic services, surveillance and improvements in dental education are required now to lessen the impact of antibiotic resistance in the future.

  17. Brain abscess caused by Enterococcus faecalis following a dental procedure in a patient with hereditary hemorrhagic telangiectasia.

    PubMed

    Mylona, Eleni; Vadala, Chariklia; Papastamopoulos, Vasilios; Skoutelis, Athanasios

    2012-05-01

    Hereditary hemorrhagic telangiectasia (HHT) is a disease characterized by arteriovenous malformations (AVMs). Brain abscess is a complication of HHT with AVMs. Literature provides evidence that Enterococcus faecalis can cause endodontic infections. We present the case of an HHT patient who developed brain abscess due to E. faecalis after a dental procedure.

  18. Wearing gloves in the hospital

    MedlinePlus

    Infection control - wearing gloves; Patient safety - wearing gloves; Personal protective equipment - wearing gloves; PPE - wearing gloves; Nosocomial infection - wearing gloves; Hospital acquired infection - wearing gloves

  19. An ultrastructural study on indirect injury of dental pulp caused by high-speed missile projectile to mandible in dogs.

    PubMed

    Ren, Changqun; Liu, Ruifeng; Tian, Lei; Chen, Peng; Zhou, Shuxia

    2008-12-01

    The aim of this study was to evaluate the characteristics of indirect injury of dental pulp caused by high-speed missile projectile to mandible in dogs. Eighteen dogs aged 12-13 months were divided equally into six groups (n = 3 in each group) with random allocation, then a high-speed missile projectile (a ball bearing of stainless steel, phi6.0 mm, 0.88 g) was shot at right mandible body (the wound tract was below the fourth premolar, 1 cm or so to the root tips) of each dog, but the teeth were not wounded directly. The dogs were killed 6 h (n = 3), 24 h (n = 3), 3 days (n = 3), 7 days (n = 3), 2 weeks (n = 3) and 4 weeks (n = 3) after the wound, respectively; then ultrastructural change of dental pulp of the fourth premolar and the second premolar of right mandible, and the second premolar of left mandible was observed through transmission electron microscope. The results showed that mean initial velocity of projectiles was 778.0 +/- 33.2 m s(-1) and mean projection energy was 266.1 +/- 19.1 J, which were in conformity with parameters of gunshot wound. On the wound side, dental pulp of the fourth mandibular premolar was injured seriously and irreversible necrosis happened in the end; yet, dental pulp of the second mandibular premolar was injured less seriously, reversibly; on the opposite side, dental pulp of the second mandibular premolar was injured slightly and temporarily. It may be concluded that there are several characteristics in indirect injury of dental pulp caused by high-speed missile projectile to dogs' mandible: the injured area is relatively extensive; traumatic degree decreases progressively and sharply with the distance to the wound tract increasing; ultrastructural change of nerval damage takes place in early stage after wound, etc.

  20. Clinical evaluation of a newly developed method for avoiding artifacts caused by dental fillings on X-ray CT.

    PubMed

    Nakae, Yasuo; Sakamoto, Kiyoshi; Minamoto, Takahiro; Kamakura, Toshiko; Ogata, Yuji; Matsumoto, Mitsuhiro; Johkou, Takeshi

    2008-01-01

    To evaluate the clinical usefulness of gantry tilt scanning as an image reconstruction technique for avoiding artifacts caused by metallic dental fillings. Gantry tilt scanning was used with multidetector-row computed tomography for imaging in patients with dental fillings. Using a novel PC-based program, the oblique images obtained were reconstructed to transverse images using nearest neighbor and bilinear interpolation methodologies in order to avoid metallic streak artifacts. Coronal images were reformatted with the reconstructed transverse images, and the continuity of the reconstructed images was evaluated. Gantry tilt scanning was performed in 12 patients with metal artifacts, and the original and reconstructed images were classified into four grades and assessed by two radiologists. Results of the clinical evaluation indicated that the original images with artifacts, only 4% had good image quality in the region around the medial pterygoid muscle, only 8% depicted areas around the internal carotid artery and internal jugular vein, and only 12% could depict the areas around the parotid gland in the clinical evaluation. These values were improved to 60, 96, and 100%, respectively, in the reconstructed transverse images. Gantry tilt scanning as an image reconstruction technique improves image quality and removes most, if not all, artifacts caused by metallic dental fillings. The resulting images can be used in the evaluation of oropharyngeal lesions in patients with dental fillings.

  1. Childhood dental caries and childhood obesity. Different problems with overlapping causes.

    PubMed

    Spiegel, Kaitlin A; Palmer, Carole A

    2012-02-01

    To review and summarize the current literature on the issues contributing to the increased prevalence of childhood obesity and dental caries and to provide direction and guidelines for dental practitioners as well as other health professionals for interventions that may help stem the tide of both conditions. Through a review of the recent literature, the most recent research on the nutritional issues in common to both childhood caries and childhood obesity are reported, as well as clinical interventions which are considered appropriate in dental practice. Factors contributing to both childhood caries and childhood obesity are psychosocial as well as nutritional. Family patterns, lifestyle issues, and school-based issues all play a role. The literature shows that many of the same issues contribute to both childhood caries and childhood obesity, and that it is within the scope of responsibility of dental practitioners to provide guidance for the prevention and reduction of both.

  2. A study on a dental device for the prevention of mucosal dose enhancement caused by backscatter radiation from dental alloy during external beam radiotherapy

    PubMed Central

    Katsura, Kouji; Utsunomiya, Satoru; Abe, Eisuke; Sakai, Hironori; Kushima, Naotaka; Tanabe, Satoshi; Yamada, Takumi; Hayakawa, Takahide; Yamanoi, Yoshihiko; Kimura, Syuhei; Wada, Shinichi; Aoyama, Hidefumi; Hayashi, Takafumi

    2016-01-01

    The changes in dose distribution caused by backscatter radiation from a common commercial dental alloy (Au–Ag–Pd dental alloy; DA) were investigated to identify the optimal material and thicknesses of a dental device (DD) for effective prevention of mucositis. To this end, 1 cm3 of DA was irradiated with a 6-MV X-ray beam (100 MU) in a field size of 10 × 10 cm2 using a Novalis TX linear accelerator. Ethylene vinyl acetate copolymer, polyolefin elastomer, and polyethylene terephthalate (PET) were selected as DD materials. The depth dose along the central axis was determined with respect to the presence/absence of DA and DDs at thicknesses of 1–10 mm using a parallel-plate ionization chamber. The dose in the absence of DDs showed the lowest value at a distance of 5 mm from the DA surface and gradually increased with distance between the measurement point and the DA surface for distances of ≥5 mm. Except for PET, no significant difference between the DA dose curves for the presence and absence of DDs was observed. In the dose curve, PET showed a slightly higher dose for DA with DD than for DA without DD for thicknesses of ≥4 mm. The findings herein suggest that the optimal DD material for preventing local dose enhancement of the mucosa caused by DA backscatter radiation should have a relatively low atomic number and physical density and that optimal DD thickness should be chosen considering backscatter radiation and percentage depth dose. PMID:27702778

  3. A study on a dental device for the prevention of mucosal dose enhancement caused by backscatter radiation from dental alloy during external beam radiotherapy.

    PubMed

    Katsura, Kouji; Utsunomiya, Satoru; Abe, Eisuke; Sakai, Hironori; Kushima, Naotaka; Tanabe, Satoshi; Yamada, Takumi; Hayakawa, Takahide; Yamanoi, Yoshihiko; Kimura, Syuhei; Wada, Shinichi; Aoyama, Hidefumi; Hayashi, Takafumi

    2016-11-01

    The changes in dose distribution caused by backscatter radiation from a common commercial dental alloy (Au-Ag-Pd dental alloy; DA) were investigated to identify the optimal material and thicknesses of a dental device (DD) for effective prevention of mucositis. To this end, 1 cm(3) of DA was irradiated with a 6-MV X-ray beam (100 MU) in a field size of 10 × 10 cm(2) using a Novalis TX linear accelerator. Ethylene vinyl acetate copolymer, polyolefin elastomer, and polyethylene terephthalate (PET) were selected as DD materials. The depth dose along the central axis was determined with respect to the presence/absence of DA and DDs at thicknesses of 1-10 mm using a parallel-plate ionization chamber. The dose in the absence of DDs showed the lowest value at a distance of 5 mm from the DA surface and gradually increased with distance between the measurement point and the DA surface for distances of ≥5 mm. Except for PET, no significant difference between the DA dose curves for the presence and absence of DDs was observed. In the dose curve, PET showed a slightly higher dose for DA with DD than for DA without DD for thicknesses of ≥4 mm. The findings herein suggest that the optimal DD material for preventing local dose enhancement of the mucosa caused by DA backscatter radiation should have a relatively low atomic number and physical density and that optimal DD thickness should be chosen considering backscatter radiation and percentage depth dose.

  4. Child's dental fear: cause related factors and the influence of audiovisual modeling.

    PubMed

    Mungara, Jayanthi; Injeti, Madhulika; Joseph, Elizabeth; Elangovan, Arun; Sakthivel, Rajendran; Selvaraju, Girija

    2013-01-01

    Delivery of effective dental treatment to a child patient requires thorough knowledge to recognize dental fear and its management by the application of behavioral management techniques. Children's Fear Survey Schedule - Dental Subscale (CFSS-DS) helps in identification of specific stimuli which provoke fear in children with regard to dental situation. Audiovisual modeling can be successfully used in pediatric dental practice. To assess the degree of fear provoked by various stimuli in the dental office and to evaluate the effect of audiovisual modeling on dental fear of children using CFSS-DS. Ninety children were divided equally into experimental (group I) and control (group II) groups and were assessed in two visits for their degree of fear and the effect of audiovisual modeling, with the help of CFSS-DS. The most fear-provoking stimulus for children was injection and the least was to open the mouth and having somebody look at them. There was no statistically significant difference in the overall mean CFSS-DS scores between the two groups during the initial session (P > 0.05). However, in the final session, a statistically significant difference was observed in the overall mean fear scores between the groups (P < 0.01). Significant improvement was seen in group I, while no significant change was noted in case of group II. Audiovisual modeling resulted in a significant reduction of overall fear as well as specific fear in relation to most of the items. A significant reduction of fear toward dentists, doctors in general, injections, being looked at, the sight, sounds, and act of the dentist drilling, and having the nurse clean their teeth was observed.

  5. Sources of tooth wear variation early in life among known-aged wild ring-tailed lemurs (Lemur catta) at the Bezà Mahafaly Special Reserve, Madagascar.

    PubMed

    Cuozzo, Frank P; Head, Brian R; Sauther, Michelle L; Ungar, Peter S; O'Mara, M Teague

    2014-11-01

    Ring-tailed lemurs (Lemur catta) at the Bezà Mahafaly Special Reserve (BMSR), Madagascar display a high frequency of individuals with notable and sometimes extreme tooth wear. Adult lemurs display a range of tooth wear even among individuals of the same age, but we do not know at what age this variation first appears. This study's goal was to determine whether wear variation occurs in younger wild lemurs. Based on the decade-long study of ring-tailed lemur feeding and dental ecology at BMSR, we hypothesized that younger, natal lemurs (under 5 years of age), would display variation in their degree of tooth wear that would correspond to microhabitat differences, given differences in food availability in different troops' home ranges. We also hypothesized that wear would differ between sexes at this young age, given differences in feeding between males and females in this population. Hypotheses were tested using dental topographic analyses using dental impressions collected from known-aged lemurs across 10 years at BMSR. Results illustrate significant differences in wear-related tooth topography (i.e., relief and slope, presented here as "occlusal lift") for microhabitat, sex and troop affiliation among lemurs under 5 years of age in this population. Although, all lemurs in this population consume mechanically challenging tamarind fruit, those in more disturbed habitats eat additional introduced foods, some of which are also mechanically challenging. Thus, dietary variation is the likely cause of variation in tooth wear. The wear variation we show at a young age suggests caution when assigning age based on tooth wear in living and fossil primates. These wear-related tooth shape changes early in life, which reflects sex, habitat variation and levels of anthropogenic disturbance, may potentially impact reproductive fitness later in life. © 2014 Wiley Periodicals, Inc.

  6. Wear resistant valve

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1980-01-01

    A valve which is resistant to wear caused by particles trapped between the valve seat and the valve member or poppet when the valve closes, including an outlet for directing washing fluid at the valve seat and/or sealing face of the poppet and means for supplying pressured fluid to the outlet at the time when the valve is closing.

  7. The interactions between attrition, abrasion and erosion in tooth wear.

    PubMed

    Shellis, R Peter; Addy, Martin

    2014-01-01

    Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Knowledge of these tooth wear processes and their interactions is reviewed. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence is insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear, especially through formation of pellicle, but cannot prevent it. © 2014 S. Karger AG, Basel.

  8. Childhood Obesity & Dental Disease: Common Causes, Common Solutions. Oral Health & Obesity Policy Brief

    ERIC Educational Resources Information Center

    Children Now, 2011

    2011-01-01

    Too many California children suffer from high rates of preventable chronic conditions associated with childhood obesity and dental disease. The state is experiencing a crisis in both areas. Fortunately, common factors that contribute to both conditions--including the rates of breastfeeding, access to healthy food and the consumption of…

  9. Tooth Wear Inclination in Great Ape Molars.

    PubMed

    Knight-Sadler, Jordan; Fiorenza, Luca

    2017-01-01

    Primate dietary diversity is reflected in their dental morphology, with differences in size and shape of teeth. In particular, the tooth wear angle can provide insight into a species' ability to break down certain foods. To examine dietary and masticatory information, digitized polygon models of dental casts provide a basis for quantitative analysis of wear associated with tooth attrition. In this study, we analyze and compare the wear patterns of Pongo pygmaeus, Gorilla gorillagorilla and Pan troglodytes schweinfurthii lower molars, focusing on the degree of inclination of specific wear facets. The variation in wear angles appears to be indicative of jaw movements and the specific stresses imposed on food during mastication, reflecting thus the ecology of these species. Orangutans exhibit flatter wear angles, more typical of a diet consisting of hard and brittle foods, while gorillas show a wear pattern with a high degree of inclination, reflecting thus their more leafy diet. Chimpanzees, on the other hand, show intermediate inclinations, a pattern that could be related to their highly variable diet. This method is demonstrated to be a powerful tool for better understanding the relationship between food, mastication and tooth wear processes in living primates, and can be potentially used to reconstruct the diet of fossil species. © 2017 S. Karger AG, Basel.

  10. Assessing the causes for the dentistry selection as a job by Iranian dental students: A Questionnaire Survey.

    PubMed

    Hamissi, J; Bairami, P; Hamissi, Z

    2015-01-01

    Objective: The purpose of the current research is to discover the causes for the dentistry selection as a profession by senior dental scholars in Iran. Materials & Methods: Surveys are distributed between the first-year to the sixth-year senior dental scholars at the Scholl of Dentistry in Medical Sciences Qazvin University in Iran. The survey presented in a lecture hall at the terminal of the secondary term in the 2011-2012 academic years. The survey included 30 parts, and the pupils asked to measure the significance of any part for choosing dentistry as a profession, on a 10-points scale. In addition, T-test and ANOVA utilized for the data analysis. Results: The answering ratio in the research is 55% (out of 100%) of the pupils delivered. Ninety-six students (93.2%) selected it as an initial selection. Dentistry as a job which is "insurer of financial independence" was gained a most rate via 82.5% of the pupils raised and a comparable amount of the students (75.7%), assigned a highest rate to the parameter "I love to enhance many money". Dentistry as a "science-based job" was also given a score by 80.6% of the pupils. Conclusion: There are no variations in the motivation between men and women students. It obtained that "insurer of financial independence" and "I love to enhance many money" are critical action parameters in the dental pupils population.

  11. Assessing the causes for the dentistry selection as a job by Iranian dental students: A Questionnaire Survey

    PubMed Central

    Hamissi, J; Bairami, P; Hamissi, Z

    2015-01-01

    Objective: The purpose of the current research is to discover the causes for the dentistry selection as a profession by senior dental scholars in Iran. Materials & Methods: Surveys are distributed between the first-year to the sixth-year senior dental scholars at the Scholl of Dentistry in Medical Sciences Qazvin University in Iran. The survey presented in a lecture hall at the terminal of the secondary term in the 2011-2012 academic years. The survey included 30 parts, and the pupils asked to measure the significance of any part for choosing dentistry as a profession, on a 10-points scale. In addition, T-test and ANOVA utilized for the data analysis. Results: The answering ratio in the research is 55% (out of 100%) of the pupils delivered. Ninety-six students (93.2%) selected it as an initial selection. Dentistry as a job which is “insurer of financial independence” was gained a most rate via 82.5% of the pupils raised and a comparable amount of the students (75.7%), assigned a highest rate to the parameter “I love to enhance many money”. Dentistry as a “science-based job” was also given a score by 80.6% of the pupils. Conclusion: There are no variations in the motivation between men and women students. It obtained that “insurer of financial independence” and “I love to enhance many money” are critical action parameters in the dental pupils population. PMID:28316683

  12. A material model for internal stress of dental composites caused by the curing process.

    PubMed

    Koplin, Christof; Jaeger, Raimund; Hahn, Petra

    2009-03-01

    To compare the build-up of internal stresses in four different dental composites (Venus, Tetric Ceram, Ceram X mono and Filtek Supreme) during the curing reaction, based on the results of a former paper on polymerization kinetics, and to characterize the developing mechanical behavior for different modes of activation using experimental methods and simulation tools. A four-parameter viscoelastic model combined with a curing model and a kinetic model was developed to simulate the mechanical behavior in three dimensions using the finite element software ABAQUS. In order to study the influence of slow polymerization behavior on the mechanical properties, the length of the activation period was doubled at half intensity of the curing light. Using a model which describes the complex interplay of stiffness, flowability, curing speed and activation intensity during the curing process gives deeper insight into the spatial and temporal build-up of stresses. An advantageous reaction kinetic or a lower stiffness can compensate for the effect of a higher polymerization shrinkage on the resulting peak stress. The evolution of stress is not directly proportional to the level of shrinkage of the composites. A material model which includes the developing mechanical characteristics of a curing dental composite can be used to develop and optimize dental materials and to assess the effect of different treatment strategies (i.e. mode of photo-polymerization, filling geometries, interfacial strength).

  13. DNA examination of ancient dental pulp incriminates typhoid fever as a probable cause of the Plague of Athens.

    PubMed

    Papagrigorakis, Manolis J; Yapijakis, Christos; Synodinos, Philippos N; Baziotopoulou-Valavani, Effie

    2006-05-01

    Until now, in the absence of direct microbiological evidence, the cause of the Plague of Athens has remained a matter of debate among scientists who have relied exclusively on Thucydides' narrations to introduce several possible diagnoses. A mass burial pit, unearthed in the Kerameikos ancient cemetery of Athens and dated back to the time of the plague outbreak (around 430 BC), has provided the required skeletal material for the investigation of ancient microbial DNA. To determine the probable cause of the Plague of Athens. Dental pulp was our material of choice, since it has been proved to be an ideal DNA source of ancient septicemic microorganisms through its good vascularization, durability and natural sterility. Six DNA amplifications targeted at genomic parts of the agents of plague (Yersinia pestis), typhus (Rickettsia prowazekii), anthrax (Bacillus anthracis), tuberculosis (Mycobacterium tuberculosis), cowpox (cowpox virus) and cat-scratch disease (Bartonella henselae) failed to yield any product in 'suicide' reactions of DNA samples isolated from three ancient teeth. On the seventh such attempt, DNA sequences of Salmonella enterica serovar Typhi were identified providing clear evidence for the presence of that microorganism in the dental pulp of teeth recovered from the Kerameikos mass grave. The results of this study clearly implicate typhoid fever as a probable cause of the Plague of Athens.

  14. Factors affecting enamel and ceramic wear: a literature review.

    PubMed

    Oh, Won-Suck; Delong, Ralph; Anusavice, Kenneth J

    2002-04-01

    Enamel wear by ceramics may adversely affect maintenance of the vertical dimension of occlusion and can increase the potential for thermal sensitivity. In this article, factors related to the abrasion of enamel by dental ceramics are critically reviewed. Concepts of physical, microstructural, chemical, and surface characteristics of dental ceramics on wear are presented based on research published since 1950. A PubMed search for key words (wear of enamel and ceramic) was supplemented with a hand search to identify relevant peer-reviewed articles published in English. Based on the literature, it can be concluded that material factors, their proper handling, and control of the patient's intrinsic risk factors related to wear are critically important to the reduction of enamel wear by dental ceramics.

  15. Interaction between attrition,abrasion and erosion in tooth wear.

    PubMed

    Addy, M; Shellis, R P

    2006-01-01

    Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence seems insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear through formation of pellicle and by remineralisation but cannot prevent it.

  16. Abrasive wear of structural ceramics

    SciTech Connect

    Olsson, M.; Kahlman, L.; Nyberg, B.

    1995-02-01

    The three-body abrasive wear characteristics of four different ceramic materials were investigated. The work focused on the influence of the type of abrasive particles (alumina and silicon carbide) on the wear rate and the dominating wear mechanisms. A solid-state-sintered silicon carbide (SiC), a silicon carbide reinforced with titanium diboride particles (SiC-TiB{sub 2}) and two hot-pressed silicon carbide-whisker-reinforced alumina materials (WRA I and WRAII) were studied. Of the materials investigated, an alumina reinforced with 25 wt% silicon carbide whiskers showed the highest abrasive resistance. This was probably caused by a unique combination of high hardness and high fracture toughness with a dense and homogeneous microstructure. Depending on the test conditions, plastic deformation, intercrystalline and transcrystalline cracking, and fracture were the dominating wear mechanisms of the materials. The silicon carbide abrasive resulted in 5--10 times higher wear rate than the alumina abrasive. This was mainly caused by the higher hardness of silicon carbide (3015 HV) as compared to alumina (2130 HV). The mechanical properties--i.e., hardness and fracture toughness--cannot be used alone to predict the abrasive wear behavior of engineering ceramics. Instead, the microstructural features, of the surface and the near-surface material--including homogeneity, surface porosity, secondary phases, and defect-rich regions--are important in controlling wear.

  17. Cavernous sinus thrombosis caused by a dental infection: a case report

    PubMed Central

    Yeo, Gi-Sung; Kim, Hyun Young; Kwak, Eun-Jung; Jung, Young-Soo; Park, Hyung-Sik

    2014-01-01

    Cavernous sinus thrombosis not only presents with constitutional symptoms including fever, pain and swelling but also with specific findings such as proptosis, chemosis, periorbital swelling, and cranial nerve palsies. It is known to occur secondary to the spread of paranasal sinus infections in the nose, ethmoidal and sphenoidal sinuses. However, paranasal sinus infection of dental origin is rare. The following is a case of cavernous sinus thrombosis due to the spread of an abscess in the buccal and pterygomandibular spaces via buccal mucosal laceration. PMID:25247150

  18. Data acquisition variability using profilometry to produce accurate mean total volumetric wear and mean maximum wear depth measurements for the OHSU oral wear simulator.

    PubMed

    Fleming, Garry J P; Reilly, Edward; Dowling, Adam H; Addison, Owen

    2016-08-01

    To identify the minimum data acquisition variables in the x- and y-planes required when using three-dimensional (3D) profilometry to produce accurate mean total volumetric wear and mean maximum wear depth measurements for a range of wear facets produced by an oral wear simulator. The Oregon Health Science University (OHSU) oral wear simulator was employed to wear an experimental resin-based composite formulation from 25,000 to 400,000 wear cycles. Mean total volumetric wear and mean maximum wear depth were determined using a contact profilometry at a measurement speed of 1mm/s. An area (8mm length and 4mm width) was profiled on each wear facet comprising 8001 horizontal traces (y-axis at 1μm intervals) with 4001 measurement points (x-axis at 1μm intervals) resulting in 32,012,001 measurement points with a z-axis resolution of 40nm. The minimum x- and y-axis spacing data acquisition requirement were assessed using the TalyMap software by reducing the number of measurement points in the original scanned wear facets and normalized data were converted to percentage values. Minimum x- and y-axis spacing to achieve an accuracy of 99, 95 and 90% of the mean total volumetric wear value for the wear facets produced (25,000-400,000 wear cycles) were 20μm×20μm, 100μm×100μm and 200μm×200μm, respectively but for maximum wear depth data normalized with respect to the 'true value or gold standard' the x- and y-axis spacing requirement varied with the size of the wear facet. The study emphasizes the difficulty in employing mean maximum wear depth measurements when assessing the in vitro wear facets produced by an OHSU oral wear simulator and accurate quantification of the mean total volumetric wear of a wear facet is a prerequisite to informing the profession about dental restorative wear performance. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  19. Coal-burning roasted corn and chili as the cause of dental fluorosis for children in southwestern China.

    PubMed

    Luo, Kun-li; Li, Ling; Zhang, Shi-xi

    2011-01-30

    To find the pathologic cause of the children's dental fluorosis in southwestern China, diet structure before the age of 6 and prevalence rate of dental fluorosis (DF) of 405 children were investigated, and the fluorine and arsenic content of several materials were determined. The prevalence rate of DF of children living on roasted corn before the age of 6 is 100% with nearly 95% having the mild to severe DF; while that of children living on non-roasted corn or rice is less than 5% with all having very mild DF. The average fluorine and arsenic concentration are 20.26 mg/kg and 0.249 mg/kg in roasted corn, which are about 16 times and 35 times more than in non-roasted corn, respectively. The average fluorine concentration is 78 mg/kg in coal, 1116 mg/kg in binder clay and 313 mg/kg in briquette (coal mixed with clay). The average arsenic concentration of coal is 5.83 mg/kg, the binder clay is 20.94 mg/kg, with 8.52 mg/kg in the briquette. Living on roasted corn and chili is the main pathologic cause of endemic fluorosis in southwestern China. The main source of fluorine and arsenic pollution of roasted corn and chill is the briquette of coal and binder clay. Copyright © 2010 Elsevier B.V. All rights reserved.

  20. Antimicrobial efficacy of green synthesized drug blended silver nanoparticles against dental caries and periodontal disease causing microorganisms.

    PubMed

    Emmanuel, R; Palanisamy, Selvakumar; Chen, Shen-Ming; Chelladurai, K; Padmavathy, S; Saravanan, M; Prakash, P; Ajmal Ali, M; Al-Hemaid, Fahad M A

    2015-11-01

    Development of biologically inspired green synthesis of silver nanoparticles is evolving into an important branch of nano-biotechnology. In the present investigation, we report the green synthesis of silver nanoparticles (AgNPs) employing the leaf extract of Justicia glauca. Water-soluble organics present in the leaf extract are mainly responsible for the reduction of silver nitrate (AgNO3) solution to AgNPs. The AgNPs are 10-20nm in dimensions as determined by TEM images. The antimicrobial activities of green synthesized AgNPs and drug blended AgNPs have been evaluated against the dental caries and periodontal disease causing microorganisms such as Streptococcus mutans, Staphylococcus aureus, Lactobacillus acidophilus, Micrococcus luteus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. The AgNPs and drug blended AgNPs show a significant antibacterial and antifungal activity. Minimum inhibitory concentration (MIC) value of AgNPs determined against the selected dental caries and periodontal disease causing microorganisms are noticeable between the range of 25-75μg/mL. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Prevalence, causes, and correlates of traumatic dental injuries among seven-to-twelve-year-old school children in Dera Bassi

    PubMed Central

    Dua, Rohini; Sharma, Sunila

    2012-01-01

    Aim: The paper aims to present a study conducted in Dera Bassi, Mohali, India. The purpose of the study was to ascertain the prevalence of traumatic dental injuries (TDI) in children of age group 7-12 years in private schools in Gulabgarh village. Material & Method: Age & sex distribution, etiological factors, risk factors and cause of injury were the parameters taken into consideration. The data collected was processed and analyzed using the SPSS statistical software program. Results: The overall prevalence of dental trauma was 14.5%, amongst the 880 subjects examined, out of which, 63.2% males and 36.4% females were found to be affected. The maxillary central incisor was found to be most commonly affected tooth (43.8%). The most common cause of injury reported was fall during playing (37.5%). Conclusion: Enamel fracture was most prevalent (50%). No risk factor was significantly higher than others; however children with Angle's class II div 1 malocclusion exhibited greater risk factor for traumatic injuries. PMID:22557895

  2. Paleoenvironments and climatic changes in the Italian Peninsula during the Early Pleistocene: evidence from dental wear patterns of the ungulate community of Coste San Giacomo

    NASA Astrophysics Data System (ADS)

    Strani, Flavia; DeMiguel, Daniel; Sardella, Raffaele; Bellucci, Luca

    2015-08-01

    Quaternary glacial/interglacial alternations, influenced by orbital obliquity cycles with a 41-ka long periodicity, started in the northern hemisphere around 2.6 Ma ago. Such alternations affected the terrestrial ecosystems, especially those of the Mediterranean region, with changes in the floristic communities and the dispersal and radiation of a number of large mammal open dwellers. Analyses of tooth wear patterns of ungulates from the Early Pleistocene site of Coste San Giacomo allow for a more objective reconstruction on the paleoenvironments and the climate in the Italian Peninsula during this epoch. Our results show that this area was composed by a mosaic of biomes, in particular by steppe and woodlands/wetlands. Evidence of such heterogeneity is provided by the wide spectrum of feeding behaviours found among the numerous ungulate herbivores here recorded, with cervids (Axis cf. lyra, Croizetoceros cf. ramosus and Eucladoceros sp.) exhibiting browser diets, most of the bovids (Gazella borbonica and Leptobos sp. and Gallogoral meneghinii) being intermediate feeders and the equid Equus stenonis showing a strict grazer behaviour. These results provide new insights for a timing of changing ecosystems in Southern Europe and reveal the environmental legacy of this global climatic shift, which is essential for understanding the early occupation of Homo in Europe. Thus, our data provide new evidence that such an environmental heterogeneity and a wide spectrum of available food resources could have been the main factors favouring the settlement of early species of Homo in this area.

  3. Surface kinetic roughening caused by dental erosion: An atomic force microscopy study

    NASA Astrophysics Data System (ADS)

    Quartarone, Eliana; Mustarelli, Piercarlo; Poggio, Claudio; Lombardini, Marco

    2008-05-01

    Surface kinetic roughening takes place both in case of growth and erosion processes. Teeth surfaces are eroded by contact with acid drinks, such as those used to supplement mineral salts during sporting activities. Calcium-phosphate based (CPP-ACP) pastes are known to reduce the erosion process, and to favour the enamel remineralization. In this study we used atomic force microscopy (AFM) to investigate the surface roughening during dental erosion, and the mechanisms at the basis of the protection role exerted by a commercial CPP-ACP paste. We found a statistically significant difference (p<0.01) in the roughness of surfaces exposed and not exposed to the acid solutions. The treatment with the CPP-ACP paste determined a statistically significant reduction of the roughness values. By interpreting the AFM results in terms of fractal scaling concepts and continuum stochastic equations, we showed that the protection mechanism of the paste depends on the chemical properties of the acid solution.

  4. Dental obturation materials

    NASA Astrophysics Data System (ADS)

    Stockton, Elizabeth; Chudej, Lauren; Bilyeu, Brian; Brostow, Witold

    2006-10-01

    During the last decades, people have tried to develop a better material for use in dental obturation materials. This new material should meet the following requirements: durability, wear resistance, biocompatibility and chemical adhesion to dentin enamel. Wear resistance is very important and it is related with the service life of dental replacements. We have obtained aesthetically promising novel nano composites that can be used as dental replacements. The main objective of this work is to study the scratch and wear resistance of these nano composites. To meet this goal, scratch tests are performed using a micro scratch tester machine (CSEM), where a diamond indenter is used to make the scratch and the penetration of this indenter is measured with high resolution (7nm). We will be looking at the penetration depth (Rp) and the residual (or healing) depth (Rh) to calculate the percent recovery. These measurements represent the scratch resistance of the material.

  5. Wear of human enamel opposing monolithic zirconia, glass ceramic, and composite resin: an in vitro study.

    PubMed

    Sripetchdanond, Jeerapa; Leevailoj, Chalermpol

    2014-11-01

    Demand is increasing for ceramic and composite resin posterior restorations. However, ceramics are recognized for their high abrasiveness to opposing dental structure. The purpose of this study was to investigate the wear of enamel as opposed to dental ceramics and composite resin. Twenty-four test specimens (antagonists), 6 each of monolithic zirconia, glass ceramic, composite resin, and enamel, were prepared into cylindrical rods. Enamel specimens were prepared from 24 extracted human permanent molar teeth. Enamel specimens were abraded against each type of antagonist with a pin-on-disk wear tester under a constant load of 25 N at 20 rpm for 4800 cycles. The maximum depth of wear (Dmax), mean depth of wear (Da), and mean surface roughness (Ra) of the enamel specimens were measured with a profilometer. All data were statistically analyzed by 1-way ANOVA, followed by the Tukey test (α=.05). A paired t test was used to compare the Ra of enamel at baseline and after testing. The wear of both the enamel and antagonists was evaluated qualitatively with scanning electron microscopic images. No significant differences were found in enamel wear depth (Dmax, Da) between monolithic zirconia (2.17 ±0.80, 1.83 ±0.75 μm) and composite resin (1.70 ±0.92, 1.37 ±0.81 μm) or between glass ceramic (8.54 ±2.31, 7.32 ±2.06 μm) and enamel (10.72 ±6.31, 8.81 ±5.16 μm). Significant differences were found when the enamel wear depth caused by monolithic zirconia and composite resin was compared with that of glass ceramic and enamel (P<.001). The Ra of enamel specimens increased significantly after wear tests with monolithic zirconia, glass ceramic, and enamel (P<.05); however, no difference was found among these materials. Within the limitations of this in vitro study, monolithic zirconia and composite resin resulted in less wear depth to human enamel compared with glass ceramic and enamel. All test materials except composite resin similarly increased the enamel

  6. A study on the wear of enamel caused by monolithic zirconia and the subsequent phase transformation compared to two other ceramic systems.

    PubMed

    Rupawala, Amreen; Musani, Smita I; Madanshetty, Pallavi; Dugal, Ramandeep; Shah, Umang D; Sheth, Ektaa J

    2017-01-01

    The purpose of this in vitro research project was to evaluate and compare the wear behavior of human tooth enamel opposing monolithic zirconia and other different ceramic restorative materials and also to observe the tetragonal to monoclinic phase transformation in zirconia-based ceramics that may occur while simulating wear occurring at room temperature in a wet environment. A total of sixty samples were prepared for this study. Fifteen discs of glazed zirconia, 15 discs of polished zirconia without glaze, 15 discs of metal ceramic, and 15 discs of lithium disilicate were fabricated. Sixty extracted premolars were collected and randomly divided into four groups of 15 each. The discs and extracted human premolars were placed onto holders on a two-body wear machine under a constant load of 5 kg to simulate the oral wear cycle. A diffractometer was used to analyze phase transformation. One-way analysis of variance and Tukey's post hoc tests was used. The mean loss of height of tooth samples and its standard deviation for Group I (monolithic zirconia with glaze), Group II (mechanically polished monolithic zirconia without glaze), Group III (porcelain fused to metal), and Group IV (glazed monolithic lithium disilicate) was obtained as 0.2716 ± 0.1409, 0.1240 ± 0.0625, 0.1567 ± 0.0996, and 0.2377 ± 0.1350, respectively. The highest mean loss in height was observed in Group I and the least was observed in Group II. Mechanically polished zirconia showed the least amount of enamel wear followed by porcelain fused to metal and glazed monolithic lithium disilicate, whereas glazed monolithic zirconia showed the highest enamel wear.

  7. [Occupational skin problems among dental personnel].

    PubMed

    Morken, T; Augustson, T; Helland, S

    1999-10-20

    Occupational dermatological problems are common among dental health personnel. We conducted a questionnaire survey to investigate the frequency of occupational dermatological problems among dental health personnel in Hordaland county, Norway. 333 of 394 employees (85%) answered the questionnaire. 148 of 333 respondents (44%) reported skin complaints. The proportion of respondents with skin complaints was lower among those with more than 20 years experience in dental health care. Hands were almost always involved. Use of gloves were reported to be the main cause of skin problems, especially the use of powdered gloves. Other frequently reported causes were soaps and methacrylates. Skin complaints from methacrylates occurred more often among employees wearing gloves most past of the working day. 3% of the respondents reported test-proven rubber allergy and 1% a methacrylate allergy. Our study confirm that occupational dermatological problems among dental health personnel are frequent. Irritant reactions are probably much more common than allergy. The most important allergens causing allergic contact dermatitis are rubber and methacrylates. Dental personnel should use non-powdered non-latex gloves and use non-touch techniques while handling methacrylates.

  8. Wear mechanisms in a nonrotating wire rope

    SciTech Connect

    Schrems, K.K.; Dogan, C.P.; Hawk, J.A.

    1995-04-01

    A nonrotating wire rope used in main hoist operations is being examined by the US Bureau of Mines to determine operative wear mechanisms. Typically, bending and loading the ropes during service cause small, localized movements at interwire contacts, leading to material loss through wear.The cumulative effect of both material loss by wear and wire breakage by fatigue failure accelerates rope retirement. If the macroscopic mechanics of wire rope failure are to be understood, microscopic deformation and degradation processes must be identified and quantified. As a first step in this study, interwire wear and deformation were studied using a combination of scanning electron microscopy and hardness measurements. Both fretting and abrasive wear were identified as wear mechanisms. Preferential sites for fretting and abrasive wear were identified and are discussed regarding rope construction and geometry and the tribo-system.

  9. Clinical measurement of tooth wear: Tooth wear indices

    PubMed Central

    López-Frías, Francisco J.; Castellanos-Cosano, Lizett; Martín-González, Jenifer; Llamas-Carreras, José M.

    2012-01-01

    Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification corresponds to a different process with specific clinical features. Classifications made so far have no accurate prevalence data because the indexes do not necessarily measure a specific etiology, or because the study populations can be diverse in age and characteristics. Tooth wears (attrition, erosion and abrasion) is perceived internationally as a growing problem. However, the interpretation and comparison of clinical and epidemiological studies, it is increasingly difficult because of differences in terminology and the large number of indicators/indices that have been developed for the diagnosis, classification and monitoring of the loss of dental hard tissue. These indices have been designed to identify increasing severity and are usually numerical, none have universal acceptance, complicating the evaluation of the true increase in prevalence reported. This article considers the ideal requirements for an erosion index. A literature review is conducted with the aim of analyzing the evolution of the indices used today and discuss whether they meet the clinical needs and research in dentistry. Key words:Tooth wear, tooth wear indices, attrition, erosion, abrasion, abfraction. PMID:24558525

  10. Clinical measurement of tooth wear: Tooth wear indices.

    PubMed

    López-Frías, Francisco J; Castellanos-Cosano, Lizett; Martín-González, Jenifer; Llamas-Carreras, José M; Segura-Egea, Juan J

    2012-02-01

    Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification corresponds to a different process with specific clinical features. Classifications made so far have no accurate prevalence data because the indexes do not necessarily measure a specific etiology, or because the study populations can be diverse in age and characteristics. Tooth wears (attrition, erosion and abrasion) is perceived internationally as a growing problem. However, the interpretation and comparison of clinical and epidemiological studies, it is increasingly difficult because of differences in terminology and the large number of indicators/indices that have been developed for the diagnosis, classification and monitoring of the loss of dental hard tissue. These indices have been designed to identify increasing severity and are usually numerical, none have universal acceptance, complicating the evaluation of the true increase in prevalence reported. This article considers the ideal requirements for an erosion index. A literature review is conducted with the aim of analyzing the evolution of the indices used today and discuss whether they meet the clinical needs and research in dentistry. Key words:Tooth wear, tooth wear indices, attrition, erosion, abrasion, abfraction.

  11. Distinguishing and diagnosing contemporary and conventional features of dental erosion.

    PubMed

    Bassiouny, Mohamed A

    2014-01-01

    The vast number and variety of erosion lesions encountered today require reconsideration of the traditional definition. Dental erosion associated with modern dietary habits can exhibit unique features that symbolize a departure from the decades-old conventional image known as tooth surface loss. The extent and diversity of contemporary erosion lesions often cause conflicting diagnoses. Specific examples of these features are presented in this article. The etiologies, genesis, course of development, and characteristics of these erosion lesions are discussed. Contemporary and conventional erosion lesions are distinguished from similar defects, such as mechanically induced wear, carious lesions, and dental fluorosis, which affect the human dentition.

  12. Bruxism: its multiple causes and its effects on dental implants - an updated review.

    PubMed

    Lobbezoo, F; Van Der Zaag, J; Naeije, M

    2006-04-01

    There is a growing interest in bruxism, as evidenced by the rapidly increasing number of papers about this subject during the past 5 years. The aim of the present review was to provide an update of two previous reviews from our department (one about the aetiology of bruxism and the other about the possible role of this movement disorder in the failure of dental implants) and to describe the details of the literature search strategies used, thus enabling the readers to judge the completeness of the review. Most studies that were published about the etiology during the past 5 years corroborate the previously drawn conclusions. Similarly, the update of the review about the possible causal relationship between bruxism and implant failure reveals no new points of view. Thus, there is no reason to assume otherwise than that bruxism is mainly regulated centrally, not peripherally, and that there is still insufficient evidence to support or refute a causal relationship between bruxism and implant failure. This illustrates that there is a vast need for well-designed studies to study both the aetiology of bruxism and its purported relationship with implant failure.

  13. Incidence and possible causes of dental pain during simulated high altitude flights.

    PubMed

    Kollmann, W

    1993-03-01

    Of 11,617 personnel participating in simulated high altitude flights up to 43,000 feet, only 30 (0.26%) complained of toothache (barodontalgia). The cause of the barodontalgia in 28 episodes of pain in 25 of these subjects was investigated. Chronic pulpitis was suspected as the cause in 22 cases and maxillary sinusitis in 2. No pathosis was detected in the other four. In 10 cases in which the pulpitis was treated by root filling or replacing a deep filling, subsequent exposure to low pressure caused no pain.

  14. Quantitative evaluation of susceptibility effects caused by dental materials in head magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Strocchi, S.; Ghielmi, M.; Basilico, F.; Macchi, A.; Novario, R.; Ferretti, R.; Binaghi, E.

    2016-03-01

    This work quantitatively evaluates the effects induced by susceptibility characteristics of materials commonly used in dental practice on the quality of head MR images in a clinical 1.5T device. The proposed evaluation procedure measures the image artifacts induced by susceptibility in MR images by providing an index consistent with the global degradation as perceived by the experts. Susceptibility artifacts were evaluated in a near-clinical setup, using a phantom with susceptibility and geometric characteristics similar to that of a human head. We tested different dentist materials, called PAL Keramit, Ti6Al4V-ELI, Keramit NP, ILOR F, Zirconia and used different clinical MR acquisition sequences, such as "classical" SE and fast, gradient, and diffusion sequences. The evaluation is designed as a matching process between reference and artifacts affected images recording the same scene. The extent of the degradation induced by susceptibility is then measured in terms of similarity with the corresponding reference image. The matching process involves a multimodal registration task and the use an adequate similarity index psychophysically validated, based on correlation coefficient. The proposed analyses are integrated within a computer-supported procedure that interactively guides the users in the different phases of the evaluation method. 2-Dimensional and 3-dimensional indexes are used for each material and each acquisition sequence. From these, we drew a ranking of the materials, averaging the results obtained. Zirconia and ILOR F appear to be the best choice from the susceptibility artefacts point of view, followed, in order, by PAL Keramit, Ti6Al4V-ELI and Keramit NP.

  15. Corrosive wear principles

    SciTech Connect

    Schumacher, W.J.

    1993-12-31

    The dual effects of corrosion and wear operate together in such industries as paper and pulp, coal handling, mining, and sugar beet extraction. There is a synergistic effect that causes far greater wastage to carbon steels, alloy steels, and even much more abrasion resistant cast irons. Several laboratory and in situ studies have been conducted to better understand the contributions of corrosion and wear to the wastage process. The environmental conditions are usually set by the process. However, there are a few instances where inhibitors as sodium nitrite, sodium chromate, and sodium metasilicate have been successfully used to reduce metal wastage of carbon steels. Hardness has been found to be an unreliable guide to performance under wet sliding conditions. Heat treated alloy steels and cast irons are inferior to stainless steels. Even distilled water is too severe a corrodent for steels. While the austenitic stainlesses perform the best, cold rolling to increase hardness does not further improve their performance. The surface roughness of stainless steels gets smoother during corrosive wear testing while it gets rougher for the alloy steels. This observation substantiated the reputation of improved slideability for stainless alloys over alloy steels.

  16. What is dental ecology?

    PubMed

    Cuozzo, Frank P; Sauther, Michelle L

    2012-06-01

    Teeth have long been used as indicators of primate ecology. Early work focused on the links between dental morphology, diet, and behavior, with more recent years emphasizing dental wear, microstructure, development, and biogeochemistry, to understand primate ecology. Our study of Lemur catta at the Beza Mahafaly Special Reserve, Madagascar, has revealed an unusual pattern of severe tooth wear and frequent tooth loss, primarily the result of consuming a fallback food for which these primates are not dentally adapted. Interpreting these data was only possible by combining our areas of expertise (dental anatomy [FC] and primate ecology [MS]). By integrating theoretical, methodological, and applied aspects of both areas of research, we adopted the term "dental ecology"-defined as the broad study of how teeth respond to the environment. Specifically, we view dental ecology as an interpretive framework using teeth as a vehicle for understanding an organism's ecology, which builds upon earlier work, but creates a new synthesis of anatomy and ecology that is only possible with detailed knowledge of living primates. This framework includes (1) identifying patterns of dental pathology and tooth use-wear, within the context of feeding ecology, behavior, habitat variation, and anthropogenic change, (2) assessing ways in which dental development and biogeochemical signals can reflect habitat, environmental change and/or stress, and (3) how dental microstructure and macro-morphology are adapted to, and reflect feeding ecology. Here we define dental ecology, provide a short summary of the development of this perspective, and place our new work into this context. Copyright © 2012 Wiley Periodicals, Inc.

  17. Wear of engineering materials

    SciTech Connect

    Hawk, J.A.

    1998-12-31

    Nearly 60 papers discuss fundamental and applied research in the areas of wear, erosion and wear-corrosion of materials. Focus is on ceramics, ceramic and polymer-matrix composites, and coatings; the effect of sliding wear and wear-corrosion of materials in manufacturing processes, automobiles and bearings; and wear and erosion of materials used in fossil-fuel power plants, minerals processing and heavy manufacturing.

  18. Wear Characteristics of Metallic Biomaterials: A Review

    PubMed Central

    Hussein, Mohamed A.; Mohammed, Abdul Samad; Al-Aqeeli, Naser

    2015-01-01

    Metals are extensively used in a variety of applications in the medical field for internal support and biological tissue replacements, such as joint replacements, dental roots, orthopedic fixation, and stents. The metals and alloys that are primarily used in biomedical applications are stainless steels, Co alloys, and Ti alloys. The service period of a metallic biomaterial is determined by its abrasion and wear resistance. A reduction in the wear resistance of the implant results in the release of incompatible metal ions into the body that loosen the implant. In addition, several reactions may occur because of the deposition of wear debris in tissue. Therefore, developing biomaterials with high wear resistance is critical to ensuring a long life for the biomaterial. The aim of this work is to review the current state of knowledge of the wear of metallic biomaterials and how wear is affected by the material properties and conditions in terms of the type of alloys developed and fabrication processes. We also present a brief evaluation of various experimental test techniques and wear characterization techniques that are used to determine the tribological performance of metallic biomaterials.

  19. [Causes of occupational allergy in dental nurses. An analysis based on the material collected at The Institute of Occupational Medicine in Lódź].

    PubMed

    Kieć-Swierczyńska, M; Krecisz, B

    2000-01-01

    The causes of occupational dermatosis were analysed in 27 dental nurses examined at The Nofer Institute of Occupational Medicine during the years 1995-99. Contact sensitisation (at least one positive epidermal test) was found in 18 subjects (66.7%). Occupational allergic dermatitis was induced most frequently by: glutaraldehyde (7 positive patch tests), nickel (7), benzalkonium (4), formaldehyde (4), fragrances (4), chromium compounds (3), glyoxal (3), and thiuram (3). In the authors' opinion, dental nurses are nowadays sensitised to other chemical compounds than it used to be in the past. The present components of disinfectants (aldehydes, quaternary ammonium bases), metals and rubber are the major etiologic agents that induce occupational allergy.

  20. Wear and Tear - Mechanical

    NASA Technical Reports Server (NTRS)

    Swanson, Theodore

    2008-01-01

    The focus of this chapter is on the long term wear and tear, or aging, of the mechanical subsystem of a spacecraft. The mechanical subsystem is herein considered to be the primary support structure (as in a skeleton or exoskeleton) upon which all other spacecraft systems rest, and the associated mechanisms. Mechanisms are devices which have some component that moves at least once, in response to some type of passive or active control system. For the structure, aging may proceed as a gradual degradation of mechanical properties and/or function, possibly leading to complete structural failure over an extended period of time. However, over the 50 years of the Space Age such failures appear to be unusual. In contrast, failures for mechanisms are much more frequent and may have a very serious effect on mission performance. Just as on Earth, all moving devices are subject to normal (and possibly accelerated) degradation from mechanical wear due to loss or breakdown of lubricant, misalignment, temperature cycling effects, improper design/selection of materials, fatigue, and a variety of other effects. In space, such environmental factors as severe temperature swings (possibly 100's of degrees C while going in and out of direct solar exposure), hard vacuum, micrometeoroids, wear from operation in a dusty or contaminated environment, and materials degradation from radiation can be much worse. In addition, there are some ground handling issues such as humidity, long term storage, and ground transport which may be of concern. This chapter addresses the elements of the mechanical subsystem subject to wear, and identifies possible causes. The potential impact of such degradation is addressed, albeit with the recognition that the impact of such wear often depends on when it occurs and on what specific components. Most structural elements of the mechanical system typically are conservatively designed (often to a safety factor of greater than approximately 1.25 on yield for

  1. Friction, wear, transfer, and wear surface morphology of ultrahigh-molecular-weight polyethylene

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1985-01-01

    Tribological studies at 25 C in a 50-percent-relative-humidity air atmosphere were conducted using hemispherically tipped 440 C HT (high temperature) stainless steel pins sliding against ultra-high-molecular-weight polyethylene (UHMWPE) disks. The results indicate that sliding speed, sliding distance, contact stress and specimen geometry can markedly affect friction, UHMWPE wear, UHMWPE transfer and the type of wear mechanisms that occur. Adhesion appears to be the predominant wear mechanism; but after long sliding distances at slow speeds, heavy ridges of transfer result which can induce fatigue-like wear on the UHMWPE disk wear track. In one instance, abrasive wear to the metallic pin was observed. This was caused by a hard particle embedded in the UHMWPE disk wear track.

  2. Friction, wear, transfer and wear surface morphology of ultra-high-molecular-weight polyethylene

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1983-01-01

    Tribological studies at 25 C in a 50-percent-relative-humidity air atmosphere were conducted using hemispherically tipped 440 C HT (high temperature) stainless steel pins sliding against ultra-high-molecular-weight polyethylene (UHMWPE) disks. The results indicate that sliding speed, sliding distance, contact stress and specimen geometry can markedly affect friction, UHMWPE wear, UHMWPE transfer and the type of wear mechanisms that occur. Adhesion appears to be the predominant wear mechanism; but after long sliding distances at slow speeds, heavy ridges of transfer result which can induce fatigue-like wear on the UHMWPE disk wear track. In one instance, abrasive wear to the metallic pin was observed. This was caused by a hard particle embedded in the UHMWPE disk wear track.

  3. Tooth wear in captive giraffes (Giraffa camelopardalis): mesowear analysis classifies free-ranging specimens as browsers but captive ones as grazers.

    PubMed

    Clauss, Marcus; Franz-Odendaal, Tamara A; Brasch, Juliane; Castell, Johanna C; Kaiser, Thomas

    2007-09-01

    Captive giraffe (Giraffa camelopardalis) mostly do not attain the longevity possible for this species and frequently have problems associated with low energy intake and fat storage mobilization. Abnormal tooth wear has been among the causes suggested as an underlying problem. This study utilizes a tooth wear scoring method ("mesowear") primarily used in paleobiology. This scoring method was applied to museum specimens of free-ranging (n=20) and captive (n=41) giraffes. The scoring system allows for the differentiation between attrition--(typical for browsers, as browse contains little abrasive silica) and abrasion--(typical for grazers, as grass contains abrasive silica) dominated tooth wear. The dental wear pattern of the free-ranging population is dominated by attrition, resembles that previously published for free-ranging giraffe, and clusters within browsing herbivores in comparative analysis. In contrast, the wear pattern of the captive population is dominated by abrasion and clusters among grazing herbivores in comparative analyses. A potential explanation for this difference in tooth wear is likely related to the content of abrasive elements in zoo diets. Silica content (measured as acid insoluble ash) is low in browse and alfalfa. However, grass hay and the majority of pelleted compound feeds contain higher amounts of silica. It can be speculated that the abnormal wear pattern in captivity compromises tooth function in captive giraffe, with deleterious long-term consequences.

  4. Diagnosis of erosive tooth wear.

    PubMed

    Ganss, Carolina; Lussi, Adrian

    2014-01-01

    The clinical diagnosis 'erosion' is made from characteristic deviations from the original anatomical tooth morphology, thus distinguishing acid-induced tissue loss from other forms of wear. Primary pathognomonic features are shallow concavities on smooth surfaces occurring coronal from the enamel-cementum junction. Problems from diagnosing occlusal surfaces and exposed dentine are discussed. Indices for recording erosive wear include morphological as well as quantitative criteria. Currently, various indices are used, each having their virtues and flaws, making the comparison of prevalence studies difficult. The Basic Erosive Wear Examination (BEWE) is described, which is intended to provide an easy tool for research as well as for use in general dental practice. The cumulative score of this index is the sum of the most severe scores obtained from all sextants and is linked to suggestions for clinical management. In addition to recording erosive lesions, the assessment of progression is important as the indication of treatment measures depends on erosion activity. A number of evaluated and sensitive methods for in vitro and in situ approaches are available, but the fundamental problem for their clinical use is the lack of reidentifiable reference areas. Tools for clinical monitoring are described. © 2014 S. Karger AG, Basel.

  5. Tooth wear and dentoalveolar remodeling are key factors of morphological variation in the Dmanisi mandibles

    PubMed Central

    Margvelashvili, Ann; Zollikofer, Christoph P. E.; Lordkipanidze, David; Peltomäki, Timo; Ponce de León, Marcia S.

    2013-01-01

    The Plio-Pleistocene hominin sample from Dmanisi (Georgia), dated to 1.77 million years ago, is unique in offering detailed insights into patterns of morphological variation within a paleodeme of early Homo. Cranial and dentoalveolar morphologies exhibit a high degree of diversity, but the causes of variation are still relatively unexplored. Here we show that wear-related dentoalveolar remodeling is one of the principal mechanisms causing mandibular shape variation in fossil Homo and in modern human hunter–gatherer populations. We identify a consistent pattern of mandibular morphological alteration, suggesting that dental wear and compensatory remodeling mechanisms remained fairly constant throughout the evolution of the genus Homo. With increasing occlusal and interproximal tooth wear, the teeth continue to erupt, the posterior dentition tends to drift in a mesial direction, and the front teeth become more upright. The resulting changes in dentognathic size and shape are substantial and need to be taken into account in comparative taxonomic analyses of isolated hominin mandibles. Our data further show that excessive tooth wear eventually leads to a breakdown of the normal remodeling mechanisms, resulting in dentognathic pathologies, tooth loss, and loss of masticatory function. Complete breakdown of dentognathic homeostasis, however, is unlikely to have limited the life span of early Homo because this effect was likely mediated by the preparation of soft foods. PMID:24101504

  6. Wear of materials 1985

    SciTech Connect

    Ludema, K.C.

    1985-01-01

    This book presents the papers given at a conference on wear resistance. Topics considered at the conference included erosion in aluminium oxides, abrasive wear tests, x-ray diffraction, transmission electron microscopy, wear tests of low-cobalt alloys for hardfacing nuclear components, microstructure, the elevated temperature erosion of steels, and steels under cyclic operation in corrosive liquids.

  7. Wear of materials - 1987

    SciTech Connect

    Ludema, K.C.

    1987-01-01

    This book presents the papers given at a conference on materials testing to determine wear resistance. Topics considered at the conference included the wear of metals in a magnetic field, ceramics in advanced heat engine applications, wear tests of silicon carbides, microstructure, hardfacing alloys, sliding friction, coated systems, abrasion, erosion, test methods, tribology, stacking fault energy, and adhesion.

  8. Wear-mechanism modelling

    SciTech Connect

    Ashby, M.F. . Dept. of Engineering)

    1993-03-01

    Goals of the program are to calculate the surface temperatures in dry sliding, develop a soft wear tester for ceramics, survey the wear mechanisms in brittle solids, and couple the temperature calculations with models to give wear maps for brittle solids. (DLC)

  9. The effect of glazed and polished ceramics on human enamel wear.

    PubMed

    Olivera, Anna Belsuzarri; Matson, Edmir; Marques, Márcia Martins

    2006-01-01

    This in vitro study compared the effect of glazed and polished dental ceramic on the wear of human enamel. Five ceramics were tested under standard load after 150,000 and 300,000 simulated chewing cycles. Wear was determined from collected digital data and analyzed before and after loading. Statistical comparisons were analyzed. Polished ceramics produced less enamel wear. The amount of enamel wear for opposing IPS Empress ceramic was significantly higher (P < .001) than wear provoked by the other ceramics. The enamel wear rate was higher at the first 150,000 cycles, and polishing increased ceramic roughness, except for the IPS Empress ceramic. Polishing of dental ceramics at the contact area produces less antagonistic enamel wear.

  10. Wear Behaviour of Pressible Lithium Disilicate Glass Ceramic

    PubMed Central

    Peng, Zhongxiao; Rahman, Muhammad Izzat Abdul; Zhang, Yu; Yin, Ling

    2015-01-01

    This paper reports effects of surface preparation and contact loads on abrasive wear properties of highly aesthetic and high-strength pressible lithium disilicate glass-ceramics (LDGC). Abrasive wear testing was performed using a pin-on-disk device in which LDGC disks prepared with different surface finishes were against alumina pins at different contact loads. Coefficients of friction and wear volumes were measured as functions of initial surface finishes and contact loads. Wear-induced surface morphology changes in both LDGC disks and alumina pins were characterized using 3D laser scanning microscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy. The results show that initial surface finishes of LDGC specimens and contact loads significantly affected the friction coefficients, wear volumes and wear-induced surface roughness changes of the material. Both wear volumes and friction coefficients of LDGC increased as the load increased while surface roughness effects were complicated. For rough LDGC surfaces, three-body wear was dominant while for fine LDGC surfaces, two-body abrasive wear played a key role. Delamination, plastic deformation and brittle fracture were observed on worn LDGC surfaces. The adhesion of LDGC matrix materials to alumina pins was also discovered. This research has advanced our understanding of the abrasive wear behaviour of LDGC and will provide guidelines for better utilisation and preparation of the material for long-term success in dental restorations. PMID:25980530

  11. Wear behavior of pressable lithium disilicate glass ceramic.

    PubMed

    Peng, Zhongxiao; Izzat Abdul Rahman, Muhammad; Zhang, Yu; Yin, Ling

    2016-07-01

    This article reports effects of surface preparation and contact loads on abrasive wear properties of highly aesthetic and high-strength pressable lithium disilicate glass-ceramics (LDGC). Abrasive wear testing was performed using a pin-on-disk device in which LDGC disks prepared with different surface finishes were against alumina pins at different contact loads. Coefficients of friction and wear volumes were measured as functions of initial surface finishes and contact loads. Wear-induced surface morphology changes in both LDGC disks and alumina pins were characterized using three-dimensional laser scanning microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results show that initial surface finishes of LDGC specimens and contact loads significantly affected the friction coefficients, wear volumes and wear-induced surface roughness changes of the material. Both wear volumes and friction coefficients of LDGC increased as the load increased while surface roughness effects were complicated. For rough LDGC surfaces, three-body wear was dominant while for fine LDGC surfaces, two-body abrasive wear played a key role. Delamination, plastic deformation, and brittle fracture were observed on worn LDGC surfaces. The adhesion of LDGC matrix materials to alumina pins was also discovered. This research has advanced our understanding of the abrasive wear behavior of LDGC and will provide guidelines for better utilization and preparation of the material for long-term success in dental restorations. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 968-978, 2016.

  12. Early detection of tooth wear by en-face optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Mărcăuteanu, Corina; Negrutiu, Meda; Sinescu, Cosmin; Demjan, Eniko; Hughes, Mike; Bradu, Adrian; Dobre, George; Podoleanu, Adrian G.

    2009-02-01

    Excessive dental wear (pathological attrition and/or abfractions) is a frequent complication in bruxing patients. The parafunction causes heavy occlusal loads. The aim of this study is the early detection and monitoring of occlusal overload in bruxing patients. En-face optical coherence tomography was used for investigating and imaging of several extracted tooth, with a normal morphology, derived from patients with active bruxism and from subjects without parafunction. We found a characteristic pattern of enamel cracks in patients with first degree bruxism and with a normal tooth morphology. We conclude that the en-face optical coherence tomography is a promising non-invasive alternative technique for the early detection of occlusal overload, before it becomes clinically evident as tooth wear.

  13. Analysis of workplace injuries in a dental school environment.

    PubMed

    McDonald, R I; Walsh, L J; Savage, N W

    1997-04-01

    Workplace injuries at the University of Queensland Dental School during the period 1992-1994 were assessed to determine their incidence, and the associated indirect costs, causal factors, and appropriate preventive strategies. Overall, dental chairside assistants experienced a higher incidence of injuries than students both on a per worker and per time basis. Of the injuries with a low risk of cross-infection, burns and scalds from sterilizing equipment, and eye injuries in laboratories were the most common. This emphasizes the importance of wearing appropriate protective equipment in areas outside the treatment zone, and the need for signage and education. Common causes of sharps injuries were burs left in handpieces, two-handed needle recapping, and cleaning of probes in the sterilizing room. Changes to techniques and equipment would prevent such incidents. A range of factors which contribute to the calculation of indirect costs following injuries in the dental workplace are identified.

  14. Scattering effects of irradiation on surroundings calculated for a small dental implant.

    PubMed

    Friedrich, Reinhard E; Todorovic, Manuel; Heiland, Max; Scheuer, Hanna A; Krüll, Andreas

    2012-05-01

    A fundamental improvement of restorative dentistry is the compensation of missing teeth by insertion of artificial dental roots allowing retention of dental prosthesis. The function of dental implants conserves a permanent perforation of the mucosa and upholds a non-physiological contact of bone with foreign material and oral micro-organisms. Occasionally head and neck cancer patients are scheduled to receive radiotherapy but are wearing dental implants. An earlier study had shown that the distribution of x-rays is noteworthily changed when dental implants are present in the irradiation field. New implants of smaller size are currently being designed that allow sufficient retention for dental prosthesis. The aim of this consecutive study was to calculate alterations in the irradiated bone caused by a foreign body, representing an implant of reduced size and physical qualities equivalent to titanium, using a stochastic (Monte Carlo) simulation. A clinical linear accelerator was simulated using BEAM/EGS4. The calculations showed that the presence of a dimension-reduced implant results in remarkable differences of the dose distribution all around the implant. Titanium dental implants of reduced size located in the field of irradiation were capable of causing significant radiation scattering. Similar to standard implants, the risk for dose enhancement was notably important for the bone in direct contact with the implant. All therapists involved in the therapy of cancer patients undergoing head and neck radiotherapy should consider the impact of dental implants on the radiation beam as a catalyst of osteoradionecrosis.

  15. Mechanical food properties and dental topography differentiate three populations of Lemur catta in southwest Madagascar.

    PubMed

    Yamashita, Nayuta; Cuozzo, Frank P; Sauther, Michelle L; Fitzgerald, Emily; Riemenschneider, Andrea; Ungar, Peter S

    2016-09-01

    Determining the proximate causes of tooth wear remains a major focus of dental study. Here we compare the diets of three ring-tailed lemur (Lemur catta) populations and examine how different dietary components may contribute to patterns of wear-related tooth shape. Casts were made from dental impressions collected between 2003 and 2010 from lemurs in the gallery and spiny/mixed forests of the Bezá Mahafaly Special Reserve (BMSR; Parcels 1 and 2) and the spiny/mixed forests of Tsimanampesotse National Park (TNP), Madagascar. Tooth shape variables (occlusal relief and slope, angularity) were analyzed using dental topographic analysis. Focal observations and food mechanical properties (FMPs: toughness, hardness, elastic modulus) were conducted and tested, respectively, during wet and dry seasons from 2008 to 2012. We found that FMPs correlate with patterns of dental topography in these three populations. Specifically, food toughness and elastic modulus correlate with the dental variables, but hardness does not. Average food toughness and elastic modulus, but not hardness, are highest in BMSR Parcel 2, followed by BMSR Parcel 1 and TNP. Occlusal relief and slope, which serve as proxies for tooth wear, show the greatest wear in Parcel 2 and the least in TNP. Angularity is also more pronounced in TNP. Further, dental topographic patterns correspond to reliance on Tamarindus indica (tamarind) fruit. Both BMSR populations consume tamarind at high frequencies in the dry season, but the fruits are rare at TNP and only occasionally consumed. Thus, high seasonal tamarind consumption and its mechanical values help explain the low dental relief and slope among BMSR lemurs. By investigating the ecology of a single widespread species across a variety of habitats, we have been able to link specific components of diet to patterns of dental topography in this species. This provides a context for interpreting wear-related tooth shape changes more generally, illustrating that

  16. Wear mechanism and wear prevention in coal-fueled diesel engines

    SciTech Connect

    Schwalb, J.A.; Ryan, T.W.

    1991-10-01

    Coal fueled diesel engines present unique wear problems in the piston ring/cylinder liner area because of their tendency to contaminate the lube-oil with high concentrations of highly abrasive particles. This program involved a series of bench-scale wear tests and engine tests designed to investigate various aspects of the ring/liner wear problem and to make specific recommendations to engine manufacturers as to how to alleviate these problems. The program was organized into tasks, designed to accomplish the following objectives: (1) define the predominant wear mechanisms causing accelerated wear in the ring/liner area; (2) investigate the effectiveness of traditional approaches to wear prevention to prevent wear in coal-fueled engines; (3) further refine information on the most promising approaches to wear prevention; (4) present detailed information and recommendations to engine manufacturers on the most promising approach to wear prevention; (5) present a final report covering the entire program; (6)complete engine tests with a coal-derived liquid fuel, and investigate the effects of the fuel on engine wear and emissions.

  17. Wear mechanism and wear prevention in coal-fueled diesel engines. Final report

    SciTech Connect

    Schwalb, J.A.; Ryan, T.W.

    1991-10-01

    Coal fueled diesel engines present unique wear problems in the piston ring/cylinder liner area because of their tendency to contaminate the lube-oil with high concentrations of highly abrasive particles. This program involved a series of bench-scale wear tests and engine tests designed to investigate various aspects of the ring/liner wear problem and to make specific recommendations to engine manufacturers as to how to alleviate these problems. The program was organized into tasks, designed to accomplish the following objectives: (1) define the predominant wear mechanisms causing accelerated wear in the ring/liner area; (2) investigate the effectiveness of traditional approaches to wear prevention to prevent wear in coal-fueled engines; (3) further refine information on the most promising approaches to wear prevention; (4) present detailed information and recommendations to engine manufacturers on the most promising approach to wear prevention; (5) present a final report covering the entire program; (6)complete engine tests with a coal-derived liquid fuel, and investigate the effects of the fuel on engine wear and emissions.

  18. Modeling UHMWPE wear debris generation.

    PubMed

    Baudriller, H; Chabrand, P; Moukoko, D

    2007-02-01

    It is widely recognized that polyethylene wear debris is one of the main causes of long-term prosthesis loosening. The noxious bioreactivity associated with this debris is determined by its size, shape, and quantity. The aim of this study was to develop a numerical tool that can be used to investigate the primary polyethylene wear mechanisms involved. This model illustrates the formation of varying flow of polyethylene debris with various shapes and sizes caused by elementary mechanical processes. Instead of using the classical continuum mechanics formulation for this purpose, we used a divided materials approach to simulate debris production and release. This approach involves complex nonlinear bulk behaviors, frictional adhesive contact, and characterizes material damage as a loss of adhesion. All the associated models were validated with various benchmark tests. The examples given show the ability of the numerical model to generate debris of various shapes and sizes such as those observed in implant retrieval studies. Most of wear mechanisms such as abrasion, adhesion, and the shearing off of micro-asperities can be described using this approach. Furthermore, it could be applied to study the effects of friction couples, macroscopic geometries, and material processing (e.g. irradiation) on wear. (c) 2006 Wiley Periodicals, Inc.

  19. Effect of low temperature annealing on the wear properties of NITINOL

    NASA Astrophysics Data System (ADS)

    Mukunda, Sriram; Nath. S, Narendra; Herbert, Mervin A.; Mukunda, P. G.

    2016-02-01

    NiTi shape memory alloy is a wonder material that is a solution looking for problems. The material finds wide biomedical applications like endodontic files for root canal treatment and cardiovascular stents. This material has rendered the surgical procedure simple compared to that with the existing Stainless Steel (SS) or titanium ones. NiTi as an endodontic file would cause less discomfort to the patients in comparison to that with far stiffer SS or titanium ones. Here nearly equi-atomic 50:50 commercial NiTi rods were subjected to low temperature aging at 300 to 450°C. The wear resistance of the as-received and the heat-treated samples was studied using adhesive wear tests on hardened steel counter face. Abrasive wear tests were run against Alumina disc to simulate the working of endodontic drills and files against dental hard and soft tissues. The abrasive wear resistance is expected to be proportional to the Vickers Hardness of the material and is high for the 450°C heat-treated sample. A correlation between the mechanical properties and microstructures of this material is attempted

  20. New model to explain tooth wear with implications for microwear formation and diet reconstruction.

    PubMed

    Xia, Jing; Zheng, Jing; Huang, Diaodiao; Tian, Z Ryan; Chen, Lei; Zhou, Zhongrong; Ungar, Peter S; Qian, Linmao

    2015-08-25

    Paleoanthropologists and vertebrate paleontologists have for decades debated the etiology of tooth wear and its implications for understanding the diets of human ancestors and other extinct mammals. The debate has recently taken a twist, calling into question the efficacy of dental microwear to reveal diet. Some argue that endogenous abrasives in plants (opal phytoliths) are too soft to abrade enamel, and that tooth wear is caused principally by exogenous quartz grit on food. If so, variation in microwear among fossil species may relate more to habitat than diet. This has important implications for paleobiologists because microwear is a common proxy for diets of fossil species. Here we reexamine the notion that particles softer than enamel (e.g., silica phytoliths) do not wear teeth. We scored human enamel using a microfabrication instrument fitted with soft particles (aluminum and brass spheres) and an atomic force microscope (AFM) fitted with silica particles under fixed normal loads, sliding speeds, and spans. Resulting damage was measured by AFM, and morphology and composition of debris were determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Enamel chips removed from the surface demonstrate that softer particles produce wear under conditions mimicking chewing. Previous models posited that such particles rub enamel and create ridges alongside indentations without tissue removal. We propose that although these models hold for deformable metal surfaces, enamel works differently. Hydroxyapatite crystallites are "glued" together by proteins, and tissue removal requires only that contact pressure be sufficient to break the bonds holding enamel together.

  1. Age-related tooth wear differs between forest and savanna primates.

    PubMed

    Galbany, Jordi; Romero, Alejandro; Mayo-Alesón, Mercedes; Itsoma, Fiacre; Gamarra, Beatriz; Pérez-Pérez, Alejandro; Willaume, Eric; Kappeler, Peter M; Charpentier, Marie J E

    2014-01-01

    Tooth wear in primates is caused by aging and ecological factors. However, comparative data that would allow us to delineate the contribution of each of these factors are lacking. Here, we contrast age-dependent molar tooth wear by scoring percent of dentine exposure (PDE) in two wild African primate populations from Gabonese forest and Kenyan savanna habitats. We found that forest-dwelling mandrills exhibited significantly higher PDE with age than savanna yellow baboons. Mandrills mainly feed on large tough food items, such as hard-shell fruits, and inhabit an ecosystem with a high presence of mineral quartz. By contrast, baboons consume large amounts of exogenous grit that adheres to underground storage organs but the proportion of quartz in the soils where baboons live is low. Our results support the hypothesis that not only age but also physical food properties and soil composition, particularly quartz richness, are factors that significantly impact tooth wear. We further propose that the accelerated dental wear in mandrills resulting in flatter molars with old age may represent an adaptation to process hard food items present in their environment.

  2. Age-Related Tooth Wear Differs between Forest and Savanna Primates

    PubMed Central

    Galbany, Jordi; Romero, Alejandro; Mayo-Alesón, Mercedes; Itsoma, Fiacre; Gamarra, Beatriz; Pérez-Pérez, Alejandro; Willaume, Eric; Kappeler, Peter M.; Charpentier, Marie J. E.

    2014-01-01

    Tooth wear in primates is caused by aging and ecological factors. However, comparative data that would allow us to delineate the contribution of each of these factors are lacking. Here, we contrast age-dependent molar tooth wear by scoring percent of dentine exposure (PDE) in two wild African primate populations from Gabonese forest and Kenyan savanna habitats. We found that forest-dwelling mandrills exhibited significantly higher PDE with age than savanna yellow baboons. Mandrills mainly feed on large tough food items, such as hard-shell fruits, and inhabit an ecosystem with a high presence of mineral quartz. By contrast, baboons consume large amounts of exogenous grit that adheres to underground storage organs but the proportion of quartz in the soils where baboons live is low. Our results support the hypothesis that not only age but also physical food properties and soil composition, particularly quartz richness, are factors that significantly impact tooth wear. We further propose that the accelerated dental wear in mandrills resulting in flatter molars with old age may represent an adaptation to process hard food items present in their environment. PMID:24732967

  3. Antibacterial activity, corrosion resistance and wear behavior of spark plasma sintered Ta-5Cu alloy for biomedical applications.

    PubMed

    Cui, Jing; Zhao, Liang; Zhu, Weiwei; Wang, Bi; Zhao, Cancan; Fang, Liming; Ren, Fuzeng

    2017-10-01

    Tantalum has been widely used in orthopedic and dental implants. However, the major barrier to the extended use of such medical devices is the possibility of bacterial adhesion to the implant surface which will cause implant-associated infections. To solve this problem, bulk Ta-5Cu alloy has been fabricated by a combination of mechanical alloying and spark plasma sintering. The effect of the addition of Cu on the hardness, antibacterial activity, cytocompatibility, corrosion resistance and wear performance was systematically investigated. The sintered Ta-5Cu alloy shows enhanced antibacterial activity against E. Coli due to the sustained release of Cu ions. However, the addition of Cu would produce slight cytotoxicity and decrease corrosion resistance of Ta. Furthermore, pin-on-disk wear tests show that Ta-5Cu alloy has a much lower coefficient of friction but a higher wear rate and shows a distinct wear mode from that of Ta upon sliding against stainless steel 440C. Wear-induced plastic deformation leads to elongation of Ta and Cu grains along the sliding direction and nanolayered structures were observed upon approaching the sliding surface. The presence of hard oxides also shows a profound effect on the plastic flow of the base material and results in localized vortex patterns. The obtained results are expected to provide deep insights into the development of novel Ta-Cu alloy for biomedical applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Investigation on the Tribological Behavior and Wear Mechanism of Five Different Veneering Porcelains

    PubMed Central

    Min, Jie; Zhang, Qianqian; Qiu, Xiaoli; Zhu, Minhao; Yu, Haiyang; Gao, Shanshan

    2015-01-01

    Objectives The primary aim of this research was to investigate the wear behavior and wear mechanism of five different veneering porcelains. Methods Five kinds of veneering porcelains were selected in this research. The surface microhardness of all the samples was measured with a microhardness tester. Wear tests were performed on a ball-on-flat PLINT fretting wear machine, with lubrication of artificial saliva at 37°C. The friction coefficients were recorded by the testing system. The microstructure features, wear volume, and damage morphologies were recorded and analyzed with a confocal laser scanning microscope and a scanning electron microscope. The wear mechanism was then elucidated. Results The friction coefficients of the five veneering porcelains differ significantly. No significant correlation between hardness and wear volume was found for these veneering porcelains. Under lubrication of artificial saliva, the porcelain with higher leucite crystal content exhibited greater wear resistance. Additionally, leucite crystal size and distribution in glass matrix influenced wear behavior. The wear mechanisms for these porcelains were similar: abrasive wear dominates the early stage, whereas delamination was the main damage mode at the later stage. Furthermore, delamination was more prominent for porcelains with larger crystal sizes. Significance Wear compatibility between porcelain and natural teeth is important for dental restorative materials. Investigation on crystal content, size, and distribution in glass matrix can provide insight for the selection of dental porcelains in clinical settings. PMID:26368532

  5. Prevalence of erosive tooth wear in risk groups.

    PubMed

    Schlueter, Nadine; Tveit, Anne Bjørg

    2014-01-01

    Individuals have different risks for developing erosive lesions depending on background, behavioural, dietary and medical variables. It is anticipated that people with regular impact of gastric juice, i.e. patients with eating disorders and gastroesophageal reflux disease (GERD) have a specially high risk of developing dental erosions; the same could be true for those with special diets, regular consumption of acidic beverages, medicine and drug intake and occupational exposure to acids. Eating disorders are associated with an increased occurrence, severity and risk for dental erosion, even though not all bulimic patients show a pathological level of tooth wear. There seems also to be a tendency that in the case of GERD, erosion is more common and more severe than in healthy controls. Regarding exogenous causes, many studies, though not all, document a positive association between the consumption of acidic beverages and dental erosions and there seems to be a dose-response relationship; however, further studies are necessary for a final statement. The same applies for the association between drug or medication intake or special diet and erosion prevalence. Though only few studies exist, there seems to be a tendency for an increase of erosion prevalence amongst persons abusively consuming alcohol. Some studies show an increased risk for dental erosion for employees testing wine or working in acid processing factories. Even though some associations between acid impact and erosion prevalence appear clear, the number of studies is small. There is a lack of controlled prevalence studies, making it difficult to give final statements for all risk groups. © 2014 S. Karger AG, Basel.

  6. Early characterization of occlusal overloaded cervical dental hard tissues by en face optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Marcauteanu, Corina; Negrutiu, Meda; Sinescu, Cosmin; Stoica, Eniko Tunde; Ionita, Ciprian; Florin, Topala; Vasile, Liliana; Bradu, Adrian; Dobre, George; Podoleanu, Adrian G.

    2011-06-01

    Early diagnosis of occlusal overload is an important issue in dental medicine. The high occlusal forces can cause irreversible damage to the dental hard tissues. Our study proposes the early microstructural characterization of occlusal overloaded bicuspids, with abnormal crown morphology, by en face optical coherence tomography (eFOCT). The dental samples were investigated using an eFOCT system operating at 1300 nm in B-scan and C-scan mode. The eFOCT images obtained from these teeth visualized cracks, which didn't reach the tooth surface. The μCT and histological images confirmed the microstructural defects identified on eFOCT images. In conclusion, eFOCT is a promising imaging method for the early diagnosis of occlusal overload on bicuspids with normal crown morphology and for the prophylaxis of dental wear.

  7. Thoracoscopic removal of dental prosthesis impacted in the upper thoracic esophagus.

    PubMed

    Bonavina, Luigi; Aiolfi, Alberto; Siboni, Stefano; Rausa, Emanuele

    2014-01-14

    Dental appliances are the most common cause of accidental foreign body esophageal impaction, especially in the elderly population with decreased oral sensory perception. A 47-year-old man with history of oligophrenia and recurrent epileptic seizures was referred to our hospital following dislocation and ingestion of his upper dental prosthesis. Endoscopic removal and clipping of an esophageal tear had been unsuccessfully attempted. A chest CT scan confirmed entrapment of the dental prosthesis in the upper thoracic esophagus, the presence of pneumomediastinum, and the close proximity of one of the metal clasps of the prosthesis to the left subclavian artery. A video-assisted right thoracoscopy in the left lateral decubitus position was performed and the foreign body was successfully removed. The patient was then allowed to wear the retrieved prosthesis after dentistry consultation and repair of the wire clasps by a dental technician. At the 6-month follow-up visit the patient was doing very well without any trouble in swallowing.

  8. How to qualify and validate wear simulation devices and methods.

    PubMed

    Heintze, S D

    2006-08-01

    The clinical significance of increased wear can mainly be attributed to impaired aesthetic appearance and/or functional restrictions. Little is known about the systemic effects of swallowed or inhaled worn particles that derive from restorations. As wear measurements in vivo are complicated and time-consuming, wear simulation devices and methods had been developed without, however, systematically looking at the factors that influence important wear parameters. Wear simulation devices shall simulate processes that occur in the oral cavity during mastication, namely force, force profile, contact time, sliding movement, clearance of worn material, etc. Different devices that use different force actuator principles are available. Those with the highest citation frequency in the literature are - in descending order - the Alabama, ACTA, OHSU, Zurich and MTS wear simulators. When following the FDA guidelines on good laboratory practice (GLP) only the expensive MTS wear simulator is a qualified machine to test wear in vitro; the force exerted by the hydraulic actuator is controlled and regulated during all movements of the stylus. All the other simulators lack control and regulation of force development during dynamic loading of the flat specimens. This may be an explanation for the high coefficient of variation of the results in some wear simulators (28-40%) and the poor reproducibility of wear results if dental databases are searched for wear results of specific dental materials (difference of 22-72% for the same material). As most of the machines are not qualifiable, wear methods applying the machine may have a sound concept but cannot be validated. Only with the MTS method have wear parameters and influencing factors been documented and verified. A good compromise with regard to costs, practicability and robustness is the Willytec chewing simulator, which uses weights as force actuator and step motors for vertical and lateral movements. The Ivoclar wear method run on

  9. Hyperglycemia simultaneously induces initial caries development and enhances spontaneous occlusal surface wear in molar teeth related to parotid gland disorder in alloxan-induced diabetic rats

    PubMed Central

    Nishimoto, Taiki; Kodama, Yasushi; Matsuura, Tetsuro; Ozaki, Kiyokazu; Taniguchi, Yoshihiko

    2016-01-01

    Diabetes and salivary gland dysfunction are major factors that induce dental caries in experimental animals, but there are no reports analyzing the association of dental caries and salivary glands in an animal model of diabetes mellitus (DM). To clarify the initial development of dental caries and preceding salivary gland disorder, we performed a histopathological analysis on teeth and salivary glands in diabetic Wistar rats 7 weeks after alloxan treatment (DM group) in comparison with nondiabetic rats (Non-DM group) and functional analysis on saliva secretion during the experimental period. Pilocarpine-induced salivary fluid secretion in diabetic rats gradually decreased with continuous hyperglycemia from immediately after alloxan treatment to the time of autopsy. Histopathologically, Oil Red O-positive lipid droplets accumulated in the acinar cells of the parotid gland. No tooth was stereoscopically defined as having dental caries in any of the rats in either group; however, the external appearance remarkably changed owing to occlusal wear in almost all molars in the DM group. The initial lesions of dental caries, appearing as micro-defects in dentin with bacterial colonization on the molar surface, were identified using histopathological analysis, and the incidence in the DM group was more than twice that in the Non-DM group. In conclusion, hyperglycemia simultaneously induces initial caries development and enhances spontaneous occlusal wear in molar teeth of Wistar rats 7 weeks after alloxan treatment. The parotid gland dysfunction caused by hyperglycemia may be mostly involved in the pathogenesis of occlusal wear as well as in dental caries in this diabetic model. PMID:28190924

  10. Wear performance of substructure ceramics and veneering porcelains.

    PubMed

    Preis, Verena; Behr, Michael; Kolbeck, Carola; Hahnel, Sebastian; Handel, Gerhard; Rosentritt, Martin

    2011-08-01

    The aim of this in vitro study was to compare the two-body wear resistance of substructure zirconia and veneering porcelain versus steatite and human enamel antagonists, respectively. Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists (enamel cusps). A pin-on-block design with a vertical load of 50 N for 1.2 × 10(5) cycles; (f=1.6 Hz; lateral movement: 1mm, mouth opening: 2mm) was used for the wear test. For quantification of the wear resistance, wear tests were performed with standardized steatite spheres. Human enamel was used as a reference. Five zirconia ceramics and four veneering porcelains were investigated. One zirconia ceramic was tested with superficial glaze, which was applied after polishing or sandblasting, respectively. Surface roughness R(a) (SP6, Perthen-Feinprüf, G) and wear depth were determined using a 3D-Profilometer (Laserscan 3D, Willytec, G). SEM (Quanta FEG 400, FEI, USA) pictures were used for evaluating wear performance of both, ceramics and antagonists. No wear was found for zirconia substructures. Veneering porcelain provided wear traces between 186.1±33.2 μm and 232.9±66.9 μm (steatite antagonist) and 90.6±3.5 μm and 123.9±50.7 μm (enamel). Wear of the steatite antagonists varied between 0.812±0.256 mm(2) and 1.360±0.321 mm(2) for zirconia and 1.708±0.275 mm(2) and 2.568±0.827 mm(2) for porcelain. Enamel generally showed wear, cracks or even fractures at the ridge, regardless whether opposed by zirconia or porcelain/glaze. Enamel was polished, when opposed to zirconia, or plowed, provoked and grinded, when opposed to porcelain/glaze. The results of the wear test with steatite or enamel antagonists indicated no measurable wear on zirconia surfaces. Porcelain showed higher wear than zirconia, but comparable or lower wear than an enamel reference. Antagonistic wear against zirconia was found to be lower than wear against porcelain. Copyright © 2011 Academy of Dental Materials

  11. Degradation of experimental composite materials and in vitro wear simulation

    NASA Astrophysics Data System (ADS)

    Givan, Daniel Allen

    2001-12-01

    The material, mechanical, and clinical aspects of surface degradation of resin composite dental restorative materials by in vitro wear simulation continues to be an area of active research. To investigate wear mechanisms, a series of experimental resin composites with variable and controlled filler particle shape and loading were studied by in vitro wear simulation. The current investigation utilized a simulation that isolated the wear environment, entrapped high and low modulus debris, and evaluated the process including machine and fluid flow dynamics. The degradation was significantly affected by filler particle shape and less by particle loading. The spherical particle composites demonstrated wear loss profiles suggesting an optimized filler loading may exist. This was also demonstrated by the trends in the mechanical properties. Very little difference in magnitude was noted for the wear of irregular particle composites as a function of particulate size; and as a group they were more wear resistant than spherical particle composites. This was the result of different mechanisms of wear that were correlated with the three-dimensional particle shape. The abrasive effects of the aggregate particles and the polymeric stabilization of the irregular shape versus the destabilization and "plucking" of the spherical particles resulted in an unprotected matrix that accounted for significantly greater wear of spherical composite. A model and analysis was developed to explain the events associated with the progressive material wear loss. The initial phase was explained by fatigue-assisted microcracking and loss of material segments in a zone of high stress immediately beneath a point of high stress contact. The early phase was characterized by the development of a small facet primarily by fatigue-assisted microcracking. Although the translation effects were minimal, some three-body and initial two-body wear events were also present. In the late phases, the abrasive effects

  12. Wear Measurement System

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Lewis Research Center developed a tribometer for in-house wear tests. Implant Sciences Corporation (ISC), working on a NASA contract to develop coatings to enhance the wear capabilities of materials, adapted the tribometer for its own use and developed a commercial line of user-friendly systems. The ISC-200 is a pin-on-disk type of tribometer, functioning like a record player and creating a wear groove on the disk, with variables of speed and load. The system can measure the coefficient of friction, the wear behavior between materials, and the integrity of thin films or coatings. Applications include measuring wear on contact lenses and engine parts and testing disk drives.

  13. Paleo-tribology: development of wear measurement techniques and a three-dimensional model revealing how grinding dentitions self-wear to enable functionality

    NASA Astrophysics Data System (ADS)

    Erickson, Gregory M.; Sidebottom, Mark A.; Curry, John F.; Kay, David Ian; Kuhn-Hendricks, Stephen; Norell, Mark A.; Sawyer, W. Gregory; Krick, Brandon A.

    2016-06-01

    In most mammals and a rare few reptilian lineages the evolution of precise dental occlusion led to the capacity to form functional chewing surfaces due to pressures generated while feeding. The complex dental architectures of such teeth and the biomechanics of their self-wearing nature are poorly understood. Our research team composed of paleontologists, evolutionary biologists, and engineers have developed a protocol to: (1) determine the histological make-up of grinding dentitions in extant and fossil taxa; (2) ascertain wear-relevant material properties of the tissues; (3) determine how those properties relate to inter-tissue-biomechanics leading the dental functionality using a three-dimensional Archard’s wear model developed specifically for dental applications; (4) analyze those data in phylogenetic contexts to infer evolutionary patterns as they relate to feeding. Finally we discuss industrial applications that are emerging from our paleontologically-inspired research.

  14. Extravascular compression of the femoral vein due to wear debris-induced iliopsoas bursitis: a rare cause of leg swelling after total hip arthroplasty.

    PubMed

    Beksaç, Burak; Tözün, Remzi; Baktiroglu, Selcuk; Sener, Nadir; Gonzalez Della Valle, Alejandro

    2007-04-01

    We present a patient with unilateral, spontaneous, late leg swelling that developed 4 years after total hip arthroplasty. The etiology was the compression of the internal iliac vein by a voluminous iliopsoas bursitis caused by polyethylene debris. The expansive lesion was detected by ultrasound, arthrography, and magnetic resonance imaging. An ultrasound-guided aspiration provided transient relief of the patient's symptoms. The patient later required surgical excision through an abdominal approach. A second recurrence was detected and treated with revision surgery. We present the diagnosis and the treatment of this rare cause of late, unilateral leg swelling after total hip arthroplasty together with a review of the literature.

  15. Opinions on Dental Erosive Lesions, Knowledge of Diagnosis, and Treatment Strategies among Norwegian Dentists: A Questionnaire Survey

    PubMed Central

    Mulic, Aida; Vidnes-Kopperud, Simen; Skaare, Anne B.; Tveit, Anne Bjørg; Young, Alix

    2012-01-01

    This study aimed to investigate dentists' general experience, knowledge about diagnosis, and treatment of dental erosive wear in young adults. A questionnaire was sent to 1262 Norwegian public dental health-employed dentists. The response rate was 60%. Results indicated that most dentists recorded erosive wear, half of them used a specific scoring system, and half registered lesions at the tooth surface level. Lesions were reported most often on palatal surfaces of upper anterior teeth (79% of dentists), on occlusal surfaces of lower 1st molars (74%), and on upper 1st molars (32%). Half the dentists used clinical photographs for documentation and 60% made study models. While 40% reported more erosive lesions in males, 36% reported no gender differences. High intake of carbonated beverages and acidic juices were reported as the most common cause by 97% and 72% of the dentists, respectively. Only 21% of dentists recorded the patient's dietary history, and 73% never measured saliva secretion. The majority (78%) of the dentists treated patients with erosive wear themselves. In general, the survey suggests that the dentists are relatively up to date regarding the clinical recording, diagnosis, and treatment of dental erosive wear. However, dietary and salivary analyses were not given priority, and early, preventive treatment was lacking. PMID:22927855

  16. Nuclear fuel assembly wear sleeve

    SciTech Connect

    Cadwell, D.J.; Kmonk, S.

    1983-03-08

    An improved control rod guide tube for use in a fuel assembly in a nuclear reactor. The guide tube extends the complete length of the fuel assembly and has its upper end fastened in a cylindrical housing by swaging the guide tube material into grooves formed in the housing walls. To eliminate wear on the guide tube inner walls caused by hydraulic induced vibratory forces on a control rod adapted to move therein, a thin-walled chrome plated sleeve is threaded into the top end of the guide thimble and extends downwardly a distance sufficient to be engaged by the control rod during reactor operation. The sleeve serves as a highly resistant wear surface between the control rod and walls on the guide tube in the fuel assembly.

  17. Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel.

    PubMed

    Soares, Ana Flávia; Bombonatti, Juliana Fraga Soares; Alencar, Marina Studart; Consolmagno, Elaine Cristina; Honório, Heitor Marques; Mondelli, Rafael Francisco Lia

    2016-01-01

    Development of new materials for tooth bleaching justifies the need for studies to evaluate the changes in the enamel surface caused by different bleaching protocols. The aim of this study was to evaluate the bovine dental enamel wear in function of different bleaching gel protocols, acid etching and pH variation. Sixty fragments of bovine teeth were cut, obtaining a control and test areas. In the test area, one half received etching followed by a bleaching gel application, and the other half, only the bleaching gel. The fragments were randomly divided into six groups (n=10), each one received one bleaching session with five hydrogen peroxide gel applications of 8 min, activated with hybrid light, diode laser/blue LED (HL) or diode laser/violet LED (VHL) (experimental): Control (C); 35% Total Blanc Office (TBO35HL); 35% Lase Peroxide Sensy (LPS35HL); 25% Lase Peroxide Sensy II (LPS25HL); 15% Lase Peroxide Lite (LPL15HL); and 10% hydrogen peroxide (experimental) (EXP10VHL). pH values were determined by a pHmeter at the initial and final time periods. Specimens were stored, subjected to simulated brushing cycles, and the superficial wear was determined (μm). ANOVA and Tukey´s tests were applied (α=0.05). The pH showed a slight decrease, except for Group LPL15HL. Group LPS25HL showed the highest degree of wear, with and without etching. There was a decrease from the initial to the final pH. Different bleaching gels were able to increase the surface wear values after simulated brushing. Acid etching before bleaching increased surface wear values in all groups.

  18. Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel

    PubMed Central

    Soares, Ana Flávia; Bombonatti, Juliana Fraga Soares; Alencar, Marina Studart; Consolmagno, Elaine Cristina; Honório, Heitor Marques; Mondelli, Rafael Francisco Lia

    2016-01-01

    ABSTRACT Development of new materials for tooth bleaching justifies the need for studies to evaluate the changes in the enamel surface caused by different bleaching protocols. Objective The aim of this study was to evaluate the bovine dental enamel wear in function of different bleaching gel protocols, acid etching and pH variation. Material and Methods Sixty fragments of bovine teeth were cut, obtaining a control and test areas. In the test area, one half received etching followed by a bleaching gel application, and the other half, only the bleaching gel. The fragments were randomly divided into six groups (n=10), each one received one bleaching session with five hydrogen peroxide gel applications of 8 min, activated with hybrid light, diode laser/blue LED (HL) or diode laser/violet LED (VHL) (experimental): Control (C); 35% Total Blanc Office (TBO35HL); 35% Lase Peroxide Sensy (LPS35HL); 25% Lase Peroxide Sensy II (LPS25HL); 15% Lase Peroxide Lite (LPL15HL); and 10% hydrogen peroxide (experimental) (EXP10VHL). pH values were determined by a pHmeter at the initial and final time periods. Specimens were stored, subjected to simulated brushing cycles, and the superficial wear was determined (μm). ANOVA and Tukey´s tests were applied (α=0.05). Results The pH showed a slight decrease, except for Group LPL15HL. Group LPS25HL showed the highest degree of wear, with and without etching. Conclusion There was a decrease from the initial to the final pH. Different bleaching gels were able to increase the surface wear values after simulated brushing. Acid etching before bleaching increased surface wear values in all groups. PMID:27008254

  19. Polymer wear and its control

    SciTech Connect

    Lee, L.H.

    1985-01-01

    Recent advances in polymer (P) tribology are discussed in reviews and reports based on contributions to a symposium held by the Division of Polymeric Materials Science and Engineering of the Americal Chemical Society in St. Louis in spring 1984. Topics examined are mechanisms of P wear, controls of P wear, the tribological behavior of Ps, wear of biomaterials and P composites, characterization and measurements of P wear, and degradation and wear of polymeric films and filaments. Consideration is given to the fracture and surface energetics of P wear, fatigue-abrasive mechanisms of P wear, plasma modification of P surfaces, the wear characteristics of articular cartilage, the role of fillers in the wear of high-density polyethylene, the tribology of fiber-reinforced polyimides sliding against steel and Si3N4, laboratory and in-service wear tests of Ps, and the effect of degree of crystallinity on wear of poly(ethylene terephthalate).

  20. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  1. Consensus report of the European Federation of Conservative Dentistry: erosive tooth wear--diagnosis and management.

    PubMed

    Carvalho, T S; Colon, P; Ganss, C; Huysmans, M C; Lussi, A; Schlueter, N; Schmalz, G; Shellis, R P; Tveit, A B; Wiegand, A

    2015-09-01

    Due to an increased focus on erosive tooth wear (ETW), the European Federation of Conservative Dentistry (EFCD) considered ETW as a relevant topic for generating this consensus report. This report is based on a compilation of the scientific literature, an expert conference, and the approval by the General Assembly of EFCD. ETW is a chemical-mechanical process resulting in a cumulative loss of hard dental tissue not caused by bacteria, and it is characterized by loss of the natural surface morphology and contour of the teeth. A suitable index for classification of ETW is the basic erosive wear examination (BEWE). Regarding the etiology, patient-related factors include the pre-disposition to erosion, reflux, vomiting, drinking and eating habits, as well as medications and dietary supplements. Nutritional factors relate to the composition of foods and beverages, e.g., with low pH and high buffer capacity (major risk factors), and calcium concentration (major protective factor). Occupational factors are exposition of workers to acidic liquids or vapors. Preventive management of ETW aims at reducing or stopping the progression of the lesions. Restorative management aims at reducing symptoms of pain and dentine hypersensitivity, or to restore esthetic and function, but it should only be used in conjunction with preventive strategies. Effective management of ETW includes screening for early signs of ETW and evaluating all etiological factors. ETW is a clinical condition, which calls for the increased attention of the dental community and is a challenge for the cooperation with other medical specialities.

  2. Consensus Report of the European Federation of Conservative Dentistry: Erosive tooth wear – diagnosis and management.

    PubMed

    Carvalho, Thiago S; Colon, Pierre; Ganss, Carolina; Huysmans, Marie-Charlotte; Lussi, Adrian; Schlueter, Nadine; Schmalz, Gottfried; Shellis, Peter R; Björg Tveit, Anne; Wiegand, Annette

    2016-01-01

    Due to an increased focus on erosive tooth wear (ETW), the European Federation of Conservative Dentistry (EFCD) considered ETW as a relevant topic for generating this consensus report. This report is based on a compilation of the scientific literature, an expert conference, and the approval by the General Assembly of EFCD. ETW is a chemical-mechanical process resulting in a cumulative loss of hard dental tissue not caused by bacteria, and it is characterized by loss of the natural surface morphology and contour of the teeth. A suitable index for classification of ETW is the basic erosive wear examination (BEWE). Regarding the etiology, patient-related factors include the predisposition to erosion, reflux, vomiting, drinking and eating habits, as well as medications and dietary supplements. Nutritional factors relate to the composition of foods and beverages, e.g., with low pH and high buffer capacity (major risk factors), and calcium concentration (major protective factor). Occupational factors are exposition of workers to acidic liquids or vapors. Preventive management of ETWaims at reducing or stopping the progression of the lesions. Restorative management aims at reducing symptoms of pain and dentine hypersensitivity, or to restore esthetic and function, but it should only be used in conjunction with preventive strategies. Effective management of ETW includes screening for early signs of ETW and evaluating all etiological factors. ETW is a clinical condition, which calls for the increased attention of the dental community and is a challenge for the cooperation with other medical specialities.

  3. Fretting wear behaviour of hydroxyapatite-titanium composites in simulated body fluid, supplemented with 5 g l-1 bovine serum albumin

    NASA Astrophysics Data System (ADS)

    Kumar, Alok; Biswas, Krishanu; Basu, Bikramjit

    2013-10-01

    Damaged articulating joints can be repaired or replaced with synthetic biomaterials, which can release wear debris due to articulation, leading to the osteolysis. In a recent work, it has been shown that it is possible to achieve a better combination of flexural strength/fracture toughness as well as in vitro bioactivity and cytocompatibility properties in spark plasma sintered hydroxyapatite-titanium (HA-Ti) composites. Although hydroxyapatite and titanium are well documented for their good biocompatibility, nanosized hydroxyapatite (HA) and titanium (Ti) particles can cause severe toxicity to cells. In order to address this issue, fretting wear study of HA-Ti composites under dry and wet (1× SBF, supplemented with 5 g l-1 bovine serum albumin (BSA)) condition was performed to assess the wear resistance as well as wear debris formation, in vitro. The experimental results reveal one order of magnitude lower wear rate for HA-10 wt% Ti (7.5 × 10-5 mm3 N-1 m-1) composite than monolithic HA (3.9 × 10-4 mm3 N-1 m-1) in simulated body fluid. The difference in the tribological properties has been analyzed in the light of phase assemblages and mechanical properties. Overall, the results suggest the potential use of HA-Ti composites over existing HA-based biocomposites in orthopedic as well as dental applications.

  4. Photobiomodulation in the Prevention of Tooth Sensitivity Caused by In-Office Dental Bleaching. A Randomized Placebo Preliminary Study.

    PubMed

    Calheiros, Andrea Paiva Corsetti; Moreira, Maria Stella; Gonçalves, Flávia; Aranha, Ana Cecília Correa; Cunha, Sandra Ribeiro; Steiner-Oliveira, Carolina; Eduardo, Carlos de Paula; Ramalho, Karen Müller

    2017-08-01

    Analyze the effect of photobiomodulation in the prevention of tooth sensitivity after in-office dental bleaching. Tooth sensitivity is a common clinical consequence of dental bleaching. Therapies for prevention of sensitivity have been investigated in literature. This study was developed as a randomized, placebo blind clinical trial. Fifty patients were selected (n = 10) and randomly divided into five groups: (1) control, (2) placebo, (3) laser before bleaching, (4) laser after bleaching, and (5) laser before and after bleaching. Irradiation was performed perpendicularly, in contact, on each tooth during 10 sec per point in two points. The first point was positioned in the middle of the tooth crown and the second in the periapical region. Photobiomodulation was applied using the following parameters: 780 nm, 40 mW, 10 J/cm(2), 0.4 J per point. Pain was analyzed before, immediately after, and seven subsequent days after bleaching. Patients were instructed to report pain using the scale: 0 = no tooth sensitivity, 1 = gentle sensitivity, 2 = moderate sensitivity, 3 = severe sensitivity. There were no statistical differences between groups at any time (p > 0.05). More studies, with others parameters and different methods of tooth sensitivity analysis, should be performed to complement the results found. Within the limitation of the present study, the laser parameters of photobiomodulation tested in the present study were not efficient in preventing tooth sensitivity after in-office bleaching.

  5. Corneal epithelial permeability during extended wear of disposable contact lenses versus daily wear of soft contact lenses.

    PubMed Central

    Schurmans, L R; Boets, E P; van Best, J A

    1995-01-01

    AIMS--The corneal epithelial permeability during extended wear of disposable contact lenses was compared with that during daily wear of soft contact lenses. The study was performed to verify whether the extended wear of disposable contact lenses would result in a higher permeability value than the daily wear of soft contact lenses. A higher permeability makes the cornea more vulnerable for bacterial infections and thus could explain the higher incidence of bacterial keratitis found in extended wear of disposable contact lenses in comparison with the daily wear of soft contact lenses. METHOD--The corneal epithelial permeability was determined by fluorophotometry in 33 healthy volunteers after the wear of soft, daily wear contact lenses for at least 6 months. Thereafter the determination was repeated in each volunteer after extended wear of disposable contact lenses for 1 month. The permeability in 34 healthy non-contact lens wearing volunteers was determined as a control. The permeability value was calculated from the amount of fluorescein that passed into the cornea after application by means of an eyebath. RESULTS--The mean permeability values after daily and extended wear were 0.032 nm/s and 0.031 nm/s, respectively. The values were not significantly different (Wilcoxon paired test p > 0.5). The mean permeability for the non-contact lens wearing controls was 0.042 nm/s. CONCLUSION--The results do not sustain the explanation that a difference in permeability value is the main cause of the increased incidence of keratitis during extended wear of disposable contact lenses in comparison with daily wear. PMID:7742282

  6. Preventative measures for bulimic patients with dental erosion.

    PubMed

    Sundaram, G; Bartlett, D

    2001-03-01

    The preventative techniques suggested to bulimic patients are frequently undervalued and ignored in favour of restorative treatment, possibly because the dentist may not be aware of the eating disorder. Educating bulimic patients about fluoride application, the use of brushing techniques, antacids, cheese, xylitol chewing gum and the possible use of mouth guards may minimise the effect of acids. Together with attempts at improving patient compliance they can be a valuable adjunct to treatment of bulimic patients with dental problems. Monitoring the wear on teeth by comparing study casts is a good way to maintain control but there are circumstances when restorations are indicated, perhaps when further delay may result in the prognosis of the teeth being compromised. Following a brief introduction to causes of bulimia and the consequences to the dentition, this paper, based on a literature review, considers patient-orientated techniques for prevention and provisional management of erosion of dental hard tissues for patients with bulimia nervosa.

  7. Wear Behavior of Austenitic NiTi Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Yan, Lina; Liu, Yong

    2015-03-01

    This study aims to understand the wear behavior of austenitic NiTi SMA with the hope to provide a guideline for its better use for wear-resist purposes. Ball-on-disk sliding wear tests with alumina counter ball were conducted at different temperatures and under different loads. Based on the coefficients of friction, the surface wear features, temperature-dependent stress-strain curves and the estimated contact stresses, the deformation mechanisms involved in the wear process were examined. Two wear modes were identified. Mode I is temperature-sensitive and occurred when A f < T < M d. In this mode, wear process was dominated by the interplay among contact stress, temperature and shape recovery property. Results show that, when the contact stress causes either elastic deformation of austenite or stress-induced martensitic transformation, the wear resistance was improved with increasing temperature. This was originated from increased critical stress for stress-induced martensite which retards plastic deformation. However, when contact stress is higher than yield stress of stress-induced martensite, wear resistance is deteriorated. Mode II occurs when T > M d and it is less temperature-sensitive within the testing range. In this mode, the austenitic NiTi loses its superelasticity and obeys a conventional deformation sequence, and the key factor dominating the wear process is the magnitude of contact stress.

  8. Fret wear mediation of NIRCam filter wheel assembly

    NASA Astrophysics Data System (ADS)

    Privári, Béla I.

    2011-10-01

    We will discuss a fret wear solution developed for the James Webb Space Telescope NIRCam filter wheel assembly by implementation of a hard coating. With mechanisms and structures designed for space flight application, titanium is often selected as the choice material of construction. Titanium offers a low-density high strength material that is good for use with many optical instruments due to its' favorable thermal properties. An important factor to consider with titanium mechanisms and structures are component fits and the vibration environment that must be survived during launch. In many instances, small (slip) fits between titanium components can cause fret wear during launch induced vibration. Titanium is particularly susceptible to fret wear, although other materials also demonstrate the fret wear. Fretting is adhesive failure of a material that experiences impact and micro-slip with an adjacent part. The mechanism of fret wear involves small particles that are pulled from the surface of parts that turn into hard oxides that further accelerate the wear between the parts. To mitigate fret wear, the mechanism or structure can be designed to eliminate all slip fits altogether, lubricants may be added to the wear surfaces or hard coatings can be applied to the wear surfaces when the other approaches are not feasible. For the NIRCam filter wheel assembly, which must operate at 35K and remain optically clean, only hard coatings are feasible. A discussion of several coating alternatives and associated wear testing will be presented along with the selection of an optimal solution.

  9. Is a Basic Erosive Wear Examination (BEWE) reliable for recording erosive tooth wear on 3D models?

    PubMed

    Alaraudanjoki, Viivi; Saarela, Henna; Pesonen, Reetta; Laitala, Marja-Liisa; Kiviahde, Heikki; Tjäderhane, Leo; Lussi, Adrian; Pesonen, Paula; Anttonen, Vuokko

    2017-04-01

    To assess the reliability of the BEWE index on 3D models and to compare 3D-assessed erosive tooth wear scores with clinically detected scores. In total, 1964 members of the Northern Finland Birth Cohort 1966 participated in a standardized clinical dental examination including the Basic Erosive Wear Examination (BEWE) and dental 3D modelling at the age of 45-46 years. Of those examined, 586 were randomly selected for this study. 3D models were assessed using the same BEWE criteria as in the clinical examination. Calculated kappa values as well as the prevalence and severity of erosive wear according to the clinical examination and 3D models were compared. Re-examinations were performed to calculate intra- and inter-method and -examiner agreements. The BEWE index on 3D models was reproducible; the mean intra- and inter-examiner agreement were 0.89 and 0.87, respectively, for sextant level, and 0.64 and 1, respectively, for BEWE sum scores. Erosive tooth wear was recorded as more severe in 3D models than in the clinical examination, and inter-method agreement was 0.41 for severe erosive wear (BEWE sum>8). The biggest inter-method differences were found in upper posterior sextants. The BEWE index is reliable for recording erosive tooth wear on 3D models. 3D models seem to be especially sensitive in detecting initial erosive wear. Additionally, it seems that erosive wear may be underscored in the upper posterior sextants when assessed clinically. Due to the nature of 3D models, the assessment of erosive wear clinically and on 3D models may not be entirely comparable. 3D models can serve as an additional tool to detect and document erosive wear, especially during the early stages of the condition and in assessing the progression of wear. When scoring erosive wear clinically, care must be taken especially when assessing upper posterior sextants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Corrosive wear of cast iron under reciprocating lubrication

    SciTech Connect

    Yahagi, Y.; Nagasawa, Y.; Hotta, S.; Mizutani, Y.

    1986-01-01

    In order to study the wear of cylinder bore fundamentally, a reciprocating friction tester was produced and utilized. The friction between a cast iron and a piston-ring and the wear of the cast iron were examined under the corrosive oil with sulphuric acid. The findings indicate that the friction and wear around TDC and BDC was confirmed to be greater than between these reversal points and the friction and wear around the reversal points increased with the sulphuric acid which has caused the deficiency of oil film and the corrosion of the cast iron.

  11. Wear characterization of abrasive waterjet nozzles and nozzle materials

    NASA Astrophysics Data System (ADS)

    Nanduri, Madhusarathi

    Parameters that influence nozzle wear in the abrasive water jet (AWJ) environment were identified and classified into nozzle geometric, AWJ system, and nozzle material categories. Regular and accelerated wear test procedures were developed to study nozzle wear under actual and simulated conditions, respectively. Long term tests, using garnet abrasive, were conducted to validate the accelerated test procedure. In addition to exit diameter growth, two new measures of wear, nozzle weight loss and nozzle bore profiles were shown to be invaluable in characterizing and explaining the phenomena of nozzle wear. By conducting nozzle wear tests, the effects of nozzle geometric, and AWJ system parameters on nozzle wear were systematically investigated. An empirical model was developed for nozzle weight loss rate. To understand the response of nozzle materials under varying AWJ system conditions, erosion tests were conducted on samples of typical nozzle materials. The effect of factors such as jet impingement angle, abrasive type, abrasive size, abrasive flow rate, water pressure, traverse speed, and target material was evaluated. Scanning electron microscopy was performed on eroded samples as well as worn nozzles to understand the wear mechanisms. The dominant wear mechanism observed was grain pullout. Erosion models were reviewed and along the lines of classical erosion theories a semi-empirical model, suitable for erosion of nozzle materials under AWJ impact, was developed. The erosion data correlated very well with the developed model. Finally, the cutting efficiency of AWJ nozzles was investigated in conjunction with nozzle wear. The cutting efficiency of a nozzle deteriorates as it wears. There is a direct correlation between nozzle wear and cutting efficiency. The operating conditions that produce the most efficient jets also cause the most wear in the nozzle.

  12. Polyethylene Wear in Retrieved Reverse Total Shoulder Components

    PubMed Central

    Day, Judd S; MacDonald, Daniel W; Olsen, Madeline; Getz, Charles; Williams, Gerald R; Kurtz, Steven M

    2011-01-01

    Background Reverse total shoulder arthroplasty has been used to treat rotator cuff tear arthropathy, proximal humeral fractures and for failed conventional total shoulder prostheses. It has been suggested that polyethylene wear is potentially higher in reverse shoulder replacements than in conventional shoulder replacements. The modes and degree of polyethylene wear have not been completely elucidated. The purpose of this study was to evaluate polyethylene wear patterns in seven specimens retrieved at revision arthroplasty and identify factors that may be associated with increased wear. Methods Reverse total shoulder components were retrieved from 7 patients during revision arthroplasty for loosening and/or pain. Pre-operative glenoid tilt and placement, and scapular notching were evaluated using pre-operative radiographs. Polyethylene wear was evaluated using microCT and optical microscopy. Results Wear on the rim of the polyethylene humeral cup, was identified on all retrieved components. The extent of rim wear varied from a penetration depth of 0.1 to 4.7 mm. We could not demonstrate a correlation between scapular notching and rim wear. However, rim wear was more extensive when the inferior screw had made contact with the liner. Metal on metal wear between the humeral component and the inferior screw of one component was also observed. Wear of the intended bearing surface was minimal. Discussion Rim damage was the predominant cause of polyethylene wear in our retrieved specimens. Direct contact between the humeral component and inferior metaglene screws is concerning because this could lead to accelerated UHMWPE wear and also induce mechanical loosening of the glenoid component. PMID:21724419

  13. Fretting Wear of Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2001-01-01

    An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296-823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473-823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals. Keywords

  14. Optical wear monitoring

    SciTech Connect

    Kidane, Getnet S; Desilva, Upul P.; He, Chengli; Ulerich, Nancy H.

    2016-07-26

    A gas turbine includes first and second parts having outer surfaces located adjacent to each other to create an interface where wear occurs. A wear probe is provided for monitoring wear of the outer surface of the first part, and includes an optical guide having first and second ends, wherein the first end is configured to be located flush with the outer surface of the first part. A fiber bundle includes first and second ends, the first end being located proximate to the second end of the optical guide. The fiber bundle includes a transmit fiber bundle comprising a first plurality of optical fibers coupled to a light source, and a receive fiber bundle coupled to a light detector and configured to detect reflected light. A processor is configured to determine a length of the optical guide based on the detected reflected light.

  15. Enamel wear of modified porcelains.

    PubMed

    Imai, Y; Suzuki, S; Fukushima, S

    2000-12-01

    To evaluate the wear of three different modified ceramics along with a conventional porcelain and the wear of opposing enamel at initial wear cycle on a two-body and a three-body wear simulation. Modified ceramics used in this study included a low fusing/low crystal porcelain (Finesse), a high fusing/low crystal porcelain (Softspar), and a heat-pressable ceramic (IPS Empress). A conventional porcelain (Ceramco II) was used as the control material. Hemispherical shaped ceramic styli (1/8 inch in diameter) made of respective materials were fabricated according to the manufacturers' directions. Proximal surfaces of non-carious human molars were ground flat within the enamel with a silicon carbide paper to 600 grit with copious irrigation. They were perpendicularly opposed to each other with or without intermediate material as a food bolus and subjected to in vitro wear test by a UAB wear simulator. A 75.6 N load was applied vertically onto the surface at 1.2 Hz. The surface was duplicated after respective wear cycles. Seven specimens were tested for each group of both simulations. The enamel wear loss when opposing the modified ceramics was less than the Ceramco II control which exhibited the greatest values. The IPS Empress material showed the least amount of wear among them. Statistically significant differences were seen between the IPS Empress and the Ceramco II for every cycle interval evaluated (ANOVA, P < 0.05). Although the enamel wear loss when opposing the IPS Empress was significantly less (ANOVA, P < 0.05) than the others until 20,000 wear cycles, no significant differences were found among the modified ceramics at the end of 50,000 wear cycles. The concentric wear patterns were already prominent at 5,000 wear cycles on two-body wear, however, the wear facet of the three-body wear was smaller (the wear depth of 0-5 microm) than the two-body wear test, as it was quite similar to the one of the two-body wear test at 100 wear cycles. On the other hand

  16. Tooth length and incisal wear and growth in guinea pigs (Cavia porcellus) fed diets of different abrasiveness.

    PubMed

    Müller, J; Clauss, M; Codron, D; Schulz, E; Hummel, J; Kircher, P; Hatt, J-M

    2015-06-01

    Dental diseases are among the most important reasons for presenting guinea pigs (Cavia porcellus) and other rodents to veterinary clinics, but the aetiopathology of this disease complex is unclear. Clinicians tend to believe that the ever-growing teeth of rabbits and rodents have a constant growth that needs to be worn down by the mastication of an appropriate diet. In this study, we tested the effect of four different pelleted diets of increasing abrasiveness [due to both internal (phytoliths) and external abrasives (sand)] or whole grass hay fed for 2 weeks each in random order to 16 guinea pigs on incisor growth and wear, and tooth length of incisors and cheek teeth. There was a positive correlation between wear and growth of incisors. Tooth lengths depended both on internal and external abrasives, but only upper incisors were additionally affected by the feeding of whole hay. Diet effects were most prominent in anterior cheek teeth, in particular M1 and m1. Cheek tooth angle did not become shallower with decreasing diet abrasiveness, suggesting that a lack of dietary abrasiveness does not cause the typical 'bridge formation' of anterior cheek teeth frequently observed in guinea pigs. The findings suggest that other factors than diet abrasiveness, such as mineral imbalances and in particular hereditary malocclusion, are more likely causes for dental problems observed in this species. Journal of Animal Physiology and Animal Nutrition © 2014 Blackwell Verlag GmbH.

  17. Effect of incisal tooth wear and restoration on interocclusal distance during Brazilian Portuguese language speech.

    PubMed

    De Oliveira Serrano, P; Cavalcante, L M Assad; Del Bel Cury, A D; Bovi Ambrosano, G M; Rodrigues Garcia, R C M

    2008-06-01

    The aim of this study was to investigate changes in interocclusal distance (IOD) during pronunciation of /m/ and /s/ sounds in Brazilian Portuguese, in patients presenting dental wear due to bruxism, before and after placement of a stabilization appliance and restorative treatment. Subjects were divided into a control group of 19 patients with no dental wear and an experimental group of 18 patients presenting dental wear on anterior teeth due to bruxism. A stabilization appliance was placed in each patient in the experimental group and anterior teeth were restored. A magnetic jaw-tracking device measured the interocclusal distance during pronunciation of /m/ and /s/ phonemes. Interocclusal distance for the experimental group was evaluated one week before and again immediately before the appliance was inserted and 24 hours, 7 days, 1 month and 2 months after appliance insertion. The same evaluation was performed 7 days and 1 month after restorative treatment. In the control group, the measurements were carried out at the same intervals. Comparison between groups revealed a significant difference (P<0.05) in interocclusal distance for the /m/ sound at all evaluation intervals. No differences were found before and after appliance insertion and restorative treatment with either phoneme. Stabilization appliance therapy and restorative treatment of subjects with dental wear did not change the interocclusal distance during speech of /m/ and /s/ sounds in the Brazilian Portuguese language, however, when compared with normal subjects, the IOD values were higher for the dental wear group during pronunciation of the /m/ sound.

  18. Degradability of dental ceramics.

    PubMed

    Anusavice, K J

    1992-09-01

    The degradation of dental ceramics generally occurs because of mechanical forces or chemical attack. The possible physiological side-effects of ceramics are their tendency to abrade opposing dental structures, the emission of radiation from radioactive components, the roughening of their surfaces by chemical attack with a corresponding increase in plaque retention, and the release of potentially unsafe concentrations of elements as a result of abrasion and dissolution. The chemical durability of dental ceramics is excellent. With the exception of the excessive exposure to acidulated fluoride, ammonium bifluoride, or hydrofluoric acid, there is little risk of surface degradation of virtually all current dental ceramics. Extensive exposure to acidulated fluoride is a possible problem for individuals with head and/or neck cancer who have received large doses of radiation. Such fluoride treatment is necessary to minimize tooth demineralization when saliva flow rates have been reduced because of radiation exposure to salivary glands. Porcelain surface stains are also lost occasionally when abraded by prophylaxis pastes and/or acidulated fluoride. In each case, the solutes are usually not ingested. Further research that uses standardized testing procedures is needed on the chemical durability of dental ceramics. Accelerated durability tests are desirable to minimize the time required for such measurements. The influence of chemical durability on surface roughness and the subsequent effect of roughness on wear of the ceramic restorations as well as of opposing structures should also be explored on a standardized basis.

  19. New model to explain tooth wear with implications for microwear formation and diet reconstruction

    PubMed Central

    Xia, Jing; Zheng, Jing; Huang, Diaodiao; Tian, Z. Ryan; Chen, Lei; Zhou, Zhongrong; Ungar, Peter S.; Qian, Linmao

    2015-01-01

    Paleoanthropologists and vertebrate paleontologists have for decades debated the etiology of tooth wear and its implications for understanding the diets of human ancestors and other extinct mammals. The debate has recently taken a twist, calling into question the efficacy of dental microwear to reveal diet. Some argue that endogenous abrasives in plants (opal phytoliths) are too soft to abrade enamel, and that tooth wear is caused principally by exogenous quartz grit on food. If so, variation in microwear among fossil species may relate more to habitat than diet. This has important implications for paleobiologists because microwear is a common proxy for diets of fossil species. Here we reexamine the notion that particles softer than enamel (e.g., silica phytoliths) do not wear teeth. We scored human enamel using a microfabrication instrument fitted with soft particles (aluminum and brass spheres) and an atomic force microscope (AFM) fitted with silica particles under fixed normal loads, sliding speeds, and spans. Resulting damage was measured by AFM, and morphology and composition of debris were determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Enamel chips removed from the surface demonstrate that softer particles produce wear under conditions mimicking chewing. Previous models posited that such particles rub enamel and create ridges alongside indentations without tissue removal. We propose that although these models hold for deformable metal surfaces, enamel works differently. Hydroxyapatite crystallites are “glued” together by proteins, and tissue removal requires only that contact pressure be sufficient to break the bonds holding enamel together. PMID:26240350

  20. Tooth wear and the role of salivary measures in general practice patients.

    PubMed

    Ramsay, Douglas S; Rothen, Marilynn; Scott, JoAnna M; Cunha-Cruz, Joana

    2015-01-01

    The goal of this study was to investigate the association between tooth wear and salivary measures in a random sample of patients from practices of dentist members of a practice-based research network. Patients completed a questionnaire on oral self-care, health, dietary habits, medications, and socio-demographic variables. Six salivary characteristics (consistency, resting salivary flow, resting salivary pH, stimulated salivary flow, stimulated salivary pH, and buffering capacity) were measured, and a dental examination included categorizing patients according to the dentist's judgment of the degree of tooth wear (i.e., none/minimal, some, or severe/extreme). Bivariate and multinomial logistic regression models were used to relate salivary characteristics and other factors to the outcome of tooth wear. Data are reported from 1,323 patients (age range 16-97 years) from 61 practices. Patient age, gender, number of teeth, and perception of dry mouth were associated with tooth wear, but salivary and dietary factors were either weakly or not related. The findings of this cross-sectional assessment suggest that using these salivary tests and dietary assessments in real-life clinical settings is unlikely to be useful in assessing tooth wear risk. Suggestions are offered about risk assessment for tooth wear. Assessing a dental patient's risk of tooth wear using salivary measures and dietary assessments as described is not recommended for general dental practice until stronger evidence exists indicating its utility.

  1. Dental Procedures.

    PubMed

    Ramponi, Denise R

    2016-01-01

    Dental problems are a common complaint in emergency departments in the United States. There are a wide variety of dental issues addressed in emergency department visits such as dental caries, loose teeth, dental trauma, gingival infections, and dry socket syndrome. Review of the most common dental blocks and dental procedures will allow the practitioner the opportunity to make the patient more comfortable and reduce the amount of analgesia the patient will need upon discharge. Familiarity with the dental equipment, tooth, and mouth anatomy will help prepare the practitioner for to perform these dental procedures.

  2. Measurement of friction and wear

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1978-01-01

    Report reviews various techniques and surface tools available for study of wear of materials. Atomic nature of solid surfaces plays important role in wear behavior for materials in solid-state contact.

  3. Sliding Wear and Fretting Wear of DLC-Based, Functionally Graded Nanocomposite Coatings

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Pohlchuck, B.; Street, Kenneth W.; Zabinski, J. S.; Sanders, J. H.; Voevodin, A. a.; Wu, R. L. C.

    1999-01-01

    Improving the tribological functionality of diamondlike carbon (DLC) films--developing, good wear resistance, low friction, and high load-carrying capacity-was the aim of this investigation. Nanocomposite coatings consisting of an amorphous DLC (a-DLC) top layer and a functionally graded titanium-titanium carbon-diamondlike carbon (Ti-Ti(sub x) C(sub y)-DLC) underlayer were produced on AISI 440C stainless steel substrates by the hybrid technique of magnetron sputtering and pulsed-laser deposition. The resultant DLC films were characterized by Raman spectroscopy, scanning electron microscopy, and surface profilometry. Two types of wear experiment were conducted in this investioation: sliding friction experiments and fretting wear experiments. Unidirectional ball-on-disk sliding friction experiments were conducted to examine the wear behavior of an a-DLC/Ti-Ti(sub x) C(sub y)-DLC-coated AISI 440C stainless steel disk in sliding contact with a 6-mm-diameter AISI 440C stainless steel ball in ultrahigh vacuum, dry nitrogen, and humid air. Although the wear rates for both the coating and ball were low in all three environments, the humid air and dry nitrogen caused mild wear with burnishing, in the a-DLC top layer, and the ultrahigh vacuum caused relatively severe wear with brittle fracture in both the a-DLC top layer and the Ti-Ti(sub x) C(sub y)-DLC underlayer. For reference, amorphous hydrogenated carbon (H-DLC) films produced on a-DLC/Ti-Ti(sub x) C(sub y)-DLC nanocomposite coatings by using an ion beam were also examined in the same manner. The H-DLC films markedly reduced friction even in ultrahigh vacuum without sacrificing wear resistance. The H-DLC films behaved much like the a-DLC/Ti-Ti(sub x) C(sub y)-DLC nanocomposite coating in dry nitrogen and humid air, presenting low friction and low wear. Fretting wear experiments were conducted in humid air (approximately 50% relative humidity) at a frequency of 80 Hz and an amplitude of 75 micron on an a

  4. Prototyping artificial jaws for the robotic dental testing simulator.

    PubMed

    Alemzadeh, K; Raabe, D

    2008-11-01

    This paper presents a robot periphery prototyped for the six-degrees-of-freedom robotic dental testing simulator, simulating the wear of materials on dental components, such as individual teeth, crowns, bridges, or a full set of teeth. The robot periphery consists of the artificial jaws and compliance module. The jaws have been reverse engineered and represent a human-like mandible and maxilla with artificial teeth. Each clinically fabricated tooth consists of a crown and glass ceramic roots which are connected using resin cement. Normal clinical occlusion of the artificial jaws assembly was emulated by a dental articulator based on 'Andrew's six keys to occlusion'. The radii of the von Spee curve, the Monson curve, and the Wilson curve were also measured as important jaw characteristic indicators to aid normal occlusion. A compliance module had to be built between the lower jaw and the robot platform to sustain the fluctuating forces that occur during normal chewing in the occlusal contact areas, where these high bite forces are major causes of dental component failure. A strain gauge force transducer has been integrated into the machined lower jaw, underneath the second molars, to measure axial biting forces applied to the posterior teeth. The experiments conducted have shown that the sensor is able to sense small changes in the compression force satisfactorily, when applied perpendicular to the occlusal surfaces of the teeth.

  5. Dental ceramics: a review of new materials and processing methods.

    PubMed

    Silva, Lucas Hian da; Lima, Erick de; Miranda, Ranulfo Benedito de Paula; Favero, Stéphanie Soares; Lohbauer, Ulrich; Cesar, Paulo Francisco

    2017-08-28

    The evolution of computerized systems for the production of dental restorations associated to the development of novel microstructures for ceramic materials has caused an important change in the clinical workflow for dentists and technicians, as well as in the treatment options offered to patients. New microstructures have also been developed by the industry in order to offer ceramic and composite materials with optimized properties, i.e., good mechanical properties, appropriate wear behavior and acceptable aesthetic characteristics. The objective of this literature review is to discuss the main advantages and disadvantages of the new ceramic systems and processing methods. The manuscript is divided in five parts: I) monolithic zirconia restorations; II) multilayered dental prostheses; III) new glass-ceramics; IV) polymer infiltrated ceramics; and V) novel processing technologies. Dental ceramics and processing technologies have evolved significantly in the past ten years, with most of the evolution being related to new microstructures and CAD-CAM methods. In addition, a trend towards the use of monolithic restorations has changed the way clinicians produce all-ceramic dental prostheses, since the more aesthetic multilayered restorations unfortunately are more prone to chipping or delamination. Composite materials processed via CAD-CAM have become an interesting option, as they have intermediate properties between ceramics and polymers and are more easily milled and polished.

  6. Employees Wearing Religious Attire

    ERIC Educational Resources Information Center

    Zirkel, Perry

    2004-01-01

    While adherents to many religions can be identified by distinctive clothing or accessories, the wearing of such garb by teachers is not necessarily related to evangelism in the classroom. The following case and the accompanying question-and-answer discussion illustrate the problem of the principal caught between the rock of First Amendment…

  7. Employees Wearing Religious Attire

    ERIC Educational Resources Information Center

    Zirkel, Perry

    2004-01-01

    While adherents to many religions can be identified by distinctive clothing or accessories, the wearing of such garb by teachers is not necessarily related to evangelism in the classroom. The following case and the accompanying question-and-answer discussion illustrate the problem of the principal caught between the rock of First Amendment…

  8. Abrasive wear of cemented carbides

    SciTech Connect

    Hawk, Jeffrey A.; Wilson, Rick D.

    2003-10-01

    Cemented carbides are used for a wide variety of applications where wear is a problem. Usually the wear of the cemented carbides is a combination of metal-to-metal and abrasion. Wear can occur at room or elevated temperatures. This research summarizes initial research to understand the abrasive wear of various cemented carbides (various grain sizes, carbide types, carbide grain sizes and binder compositions) in terms of absolute material removal rates and material removal mechanisms.

  9. Wear Modalities and Mechanisms of the Mining Non-asbestos Composite Brake Material

    NASA Astrophysics Data System (ADS)

    Bao, Jiusheng; Yin, Yan; Zhu, Zhencai; Tong, Minming; Lu, Yuhao; Peng, Yuxing

    2013-08-01

    The mining brake material is generally made of composite materials and its wear has important influences on the braking performance of disc brakes. In order to improve the braking reliability of mine hoisters, this paper did some tribological investigations on the mining brake material to reveal its wear modalities and mechanisms. The mining non-asbestos brake shoe and 16Mn steel were selected as braking pairs and tested on a pad-on-disc friction tester. And a SEM was used to observe the worn surface of the brake shoe. It is shown that the non-asbestos brake material has mainly five wear modalities: adhesive wear, abrasive wear, cutting wear, fatigue wear and high heat wear. At the front period of a single braking the wear modality is mainly composed of some light mechanical wear such as abrasive, cutting and point adhesive. With the temperature rising at the back period it transforms to some heavy mechanical wear such as piece adhesive and fatigue. While in several repeated brakings once the surface temperature rises beyond the thermal-decomposition point of the bonding material, the strong destructive high heat wear takes leading roles on the surface. And a phenomenon called friction catastrophe (FC) occurs easily, which as a result causes a braking failure. It is considered that the friction heat has important influences on the wear modalities of the brake material. And the reduction of friction heat must be an effective technical method for decreasing wear and avoiding braking failures.

  10. Dental injuries in water polo, a survey of players in Switzerland.

    PubMed

    Hersberger, Silvan; Krastl, Gabriel; Kühl, Sebastian; Filippi, Andreas

    2012-08-01

    Water polo is a sporting activity which has a medium risk of causing dental trauma. Owing to the high speed, close body contact, and the combination of throwing and swimming that is inherent to the sport, the general injury potential is high. Using a standardized questionnaire for a total of 415 water polo players from Switzerland, this study examines the frequency of dental and facial injuries in water polo, athletes' habits regarding the wearing of mouthguards, and the general level of knowledge about emergency procedures following dental trauma. The participating players came from 6 divisions: Swiss national leagues A and B, first and second leagues, as well as the women's, and junior's league. The data were evaluated according to division and gender. Of the 415 interviewees, 185 (44.6%) had witnessed a dental injury in water polo. Eighty-seven (21.0%) players reported having suffered a tooth injury when playing water polo. Tooth fracture was the most stated dental injury [86 (16.4%)]. A similar number of tooth injuries were experienced by both male [355 (21.1%)] and female [60 (20.0%)] players. The interviewees over the age of 50 showed a higher incidence of tooth injuries than younger players (>50 years = 41.7%). Slightly more than half of the interviewed players [228 (54.9%)] were aware of the possibility of replanting avulsed teeth. As few as 43 (10.4%) players were familiar with tooth rescue boxes. Only 32 (7.7%) water polo players wore a mouthguard; the most common reason for not wearing a mouthguard was that it was seen to be unnecessary [169 (40.7%)]. This survey highlights the potential for improvement in the level of knowledge about dental injury prevention in water polo. In addition to information and guidelines from the relevant sports' associations, and coaches, dentists could also play a role in the provision of this education.

  11. Dependence of the diffusion wear of the hard alloy surface on its fractal dimension

    NASA Astrophysics Data System (ADS)

    Nesterenko, V. P.; Kondratyuk, A. A.; Belousova, E. B.; Shulepov, I. A.

    2017-02-01

    The paper presents the research results in the synergies between the wear resistance of carbide cutting tools of P-group applicability and fractal dimension of the wear surface occurring on the rake face of the tool when processing the material, which causes intensive diffusion wear. It was found that the resistance of carbide cutting tools increases as the fractal dimension of their wear surface reduces.

  12. Maintenance and repair of high-speed dental handpieces.

    PubMed

    Norkiewicz, D S; Sundberg, M A; Druckman, R F; Breault, L G

    2001-01-01

    High-speed dental handpieces constitute an integral part of the dental practice. A handpiece that is worn or malfunctions is inconvenient and may affect production. This article is designed to help practitioners understand the factors that contribute to handpiece wear and breakdown. Basic maintenance and options for repair also are discussed.

  13. Tooth wear and loss: symptomatological and rehabilitating treatments.

    PubMed

    Hotta, T H; Nunes, L J; Quatrini, A H; Bataglion, C; Nonaka, T; Bezzon, O L

    2000-01-01

    The authors report a clinical case that presented tooth wear and absence, with painful muscular and articular symptomatology, and also alteration in deglutition, mastication and speech. The clinical procedures used were re-establishment of vertical dimension of occlusion, mandibular centric relations, and occlusal contacts through therapeutic removable partial dentures. The condyle position was analyzed in habitual occlusion and in occlusion with dentures, through transcranial radiographs of the temporomandibular joints. Oral rehabilitation was achieved with dental restoration and removable partial dentures.

  14. Dental Assistants

    MedlinePlus

    ... the direction of a dentist . They may prepare materials for dental impressions or to create temporary crowns. All dental ... Nursing assistants, sometimes called nursing aides , help provide basic care for patients in hospitals and residents of ... more information about becoming a dental assistant and for a list of accredited dental ...

  15. Wear Resistance and Wear Mechanism of a Hot Dip Aluminized Steel in Sliding Wear Test

    NASA Astrophysics Data System (ADS)

    Xue, Zhiyong; Hao, Xiaoyang; Huang, Yao; Gu, Lingyun; Ren, Yu; Zheng, Ruipeng

    2016-12-01

    Sliding wear experiments were conducted on a hot dip aluminized steel to investigate its wear resistance and wear mechanism. The wear tests were also carried out on a hot dip galvanized steel and the base material (steel Q345) as a comparison. Results show that the wear resistance and hardness of the hot dip aluminized steel are significantly higher than that of the hot dip galvanized steel and the steel Q345 at room temperature. The better wear resistance of the hot dip aluminized steel attributes mainly to the formation of a transition layer containing abundant Fe-Al intermetallic compounds and the transformation of wear-resisting oxides during the friction process. The main phase in the transition layer is Fe2Al5. The thickness of the transition layer is about 90-120 μm. When the wear load increases from 3 N to 19 N, the wear type of the aluminized layer transform from adhesive wear (3 N) into abrasive wear (7 N) and finally into slight wear mixed with oxidation (higher than 11 N).

  16. Drugs that promote dental caries.

    PubMed

    2015-02-01

    Dental caries result from erosion of tooth enamel or cementum by acidic substances produced by bacteria found in dental plaque. Caries can lead to pulp necrosis and tooth loss. Risk factors include certain dietary habits, poor oral hygiene, and dry mouth. Diabetes and Sjogren's syndrome can also promote dental caries. Psychotropic substances such as cocaine, methamphetamine, heroin and cannabis can promote dental caries. Many medicinal drugs facilitate the formation of dental caries, through various mechanisms; they include formulations with a high sugar content; drugs that cause dry mouth (especially antimuscarinics); drugs that lower the buccal pH (inhaled powders, etc.); and drugs that cause demineralisation (tetracyclines, etc.). In practice, patients (and parents) should be informed that some drugs can increase the risk of dental caries. They should be encouraged to adapt and reinforce dental hygiene, and advised to visit a dentist regularly.

  17. Friction and Wear

    NASA Technical Reports Server (NTRS)

    Pomey, Jacques

    1952-01-01

    From the practical point of view, this analysis shows that each problem of friction or wear requires its particular solution. There is no universal solution; one or other of the factors predominates and defines the choice of the solution. In certain cases, copper alloys of great thermal conductivity are preferred; in others, plastics abundantly supplied with water. Sometimes, soft antifriction metals are desirable to distribute the load; at other times, hard metals with high resistance to abrasion or heat.

  18. Polymer Wear Modes.

    DTIC Science & Technology

    1977-10-01

    first was the rubbing of Nylon 6—6, Nylon 11, Delrin 500, Delrin AF, and ultra—high molecular weight polyethylene ( UHMWPE ) against 440C stainless steel...strength at* T T Measured Time to Temperature ofPolymer . room temp. _~~ _i ~2!~ U severe wear counterface substrate UHMWP E 24.1 MPa 140°C 400°C -1.47 rn/s

  19. Tribological behaviour of unveneered and veneered lithium disilicate dental material.

    PubMed

    Figueiredo-Pina, C G; Patas, N; Canhoto, J; Cláudio, R; Olhero, S M; Serro, A P; Ferro, A C; Guedes, M

    2016-01-01

    The friction and wear behaviour of a lithium disilicate dental ceramic against natural dental enamel is studied, including the effect of the presence of a fluorapatite veneering upon the tribological properties of the material. The tribological behaviour was assessed using reciprocating pin-on-plate test configuration, at pH 3 and pH 7. The surface energy of the plates was determined, as well as the zeta potential of fluorapatite, lithium disilicate and enamel particles in artificial saliva. It was found that the friction and wear behaviour of the tested enamel/plate material tribocouples is less severe in unveneered plates. Initial surface roughness of the plate does not affect wear results. However the topography of the resulting wear track affects the corresponding wear loss: a smoother final wear track is associated with lower wear. The surface topography of the wear track, and thus the tribological performance of the tested materials, is very sensitive to the pH of the sliding solution. This is because the dissolution trend, wettability and surface charge of the used materials are pH dependent. Overall friction and wear are higher under basic pH conditions, especially when plates are veneered. A wear model is proposed that correlates the effect of the described parameters with the observed tribological behaviour at pH 7. Attained results show that fluorapatite coating of lithium disilicate dental crowns affects tooth/crown wear behaviour, resulting in increased wear of both the artificial crown and the opposing natural teeth. Coating should therefore be avoided in occlusal crown surfaces.

  20. Creating a Successful School-Based Mobile Dental Program

    ERIC Educational Resources Information Center

    Jackson, David M.; Jahnke, Lauren R.; Kerber, Lisa; Nyer, Genie; Siemens, Kammi; Clark, Carol

    2007-01-01

    Background: Dental disease is one of the leading causes of school absenteeism for children. This article describes the creation and evolution of the St. David's Dental Program, a mobile school-based dental program for children. Methods: The dental program is a collaboration of community partners in Central Texas that provides free dental care to…

  1. Creating a Successful School-Based Mobile Dental Program

    ERIC Educational Resources Information Center

    Jackson, David M.; Jahnke, Lauren R.; Kerber, Lisa; Nyer, Genie; Siemens, Kammi; Clark, Carol

    2007-01-01

    Background: Dental disease is one of the leading causes of school absenteeism for children. This article describes the creation and evolution of the St. David's Dental Program, a mobile school-based dental program for children. Methods: The dental program is a collaboration of community partners in Central Texas that provides free dental care to…

  2. Wear Mechanisms in a Reliability Methodology

    NASA Astrophysics Data System (ADS)

    Tanner, Danelle M.; Dugger, Michael T.

    2003-01-01

    The main thrust in any reliability work is identifying failure modes and mechanisms. This is especially true for the new technology of MicroElectroMechanical Systems (MEMS). The methods are sometimes just as important as the results achieved. This paper will review some of the methods developed specifically for MEMS. Our methodology uses statistical characterization and testing of complex MEMS devices to help us identify dominant failure modes. We strive to determine the root cause of each failure mode and to gain a fundamental understanding of that mechanism. Test structures designed to be sensitive to a particular failure mechanism are typically used to gain understanding. The development of predictive models follows from this basic understanding. This paper will focus on the failure mechanism of wear and how our methodology was exercised to provide a predictive model. The MEMS device stressed in these studies was a Sandia-developed microengine with orthogonal electrostatic linear actuators connected to a gear on a hub. The dominant failure mechanism was wear in the sliding/contacting regions. A sliding beam-on-post test structure was also used to measure friction coefficients and wear morphology for different surface coatings and environments. Results show that a predictive model of failure-time as a function of drive frequency based on wear fits the functional form of the reliability data quite well, and demonstrates the benefit of a fundamental understanding of wear. The results also show that while debris of similar chemistry and morphology was created in the two types of devices, the dependence of debris generation on the operating environment was entirely different. The differences are discussed in terms of wear maps for ceramics, and the mechanical and thermal contact conditions in each device.

  3. Nickel-based (Ni-Cr and Ni-Cr-Be) alloys used in dental restorations may be a potential cause for immune-mediated hypersensitivity.

    PubMed

    Lu, Yin; Chen, Weiqing; Ke, Wei; Wu, Shaohua

    2009-11-01

    Although nickel-based (Ni-Cr and Ni-Cr-Be) alloy prothesis is widely used in orthodontics, its potential biologic hazards, hypersensitivity in particular, are still uncertain as yet. And only a few studies in vivo have considered the biocompatibility. However, several case reports show adverse effects of immunologic alterations, such as urticaria, respiratory disease, nickel contact dermatitis, microscopic hematuria and proteinuria, and even exacerbated to hepatocyte injury and renal injury. So nickel-based alloy used in dental restorations may be a potential cause for immune-mediated hypersensitivity. The metal surface would occur electrochemical corrosion as metal edge of porcelain-fused-to-nichrome crown exposed to oral cavity rich in electrolytes after restoration, and metal ion would release to oral cavity then come into contact with cells and tissues in the immediate environment, or be distributed throughout the body, mainly to the intestine canal. Once these ions are not biocompatible, the human system may be injured (toxicity and risk of sensitization) if they are absorbed in sufficient quantity. Thus, it is necessary to determine the long-term biocompatibility properties of nickel-based alloy, reduce sensitization, and grasp the information of individual differences in the appearance of adverse reactions in further research.

  4. Reduction of dark-band-like metal artifacts caused by dental implant bodies using hypothetical monoenergetic imaging after dual-energy computed tomography.

    PubMed

    Tanaka, Ray; Hayashi, Takafumi; Ike, Makiko; Noto, Yoshiyuki; Goto, Tazuko K

    2013-06-01

    The aim of this study was to evaluate the usefulness of hypothetical monoenergetic images after dual-energy computed tomography (DECT) for assessment of the bone encircling dental implant bodies. Seventy-two axial images of implantation sites clipped out from image data scanned using DECT in dual-energy mode were used. Subjective assessment on reduction of dark-band-like artifacts (R-DBAs) and diagnosability of adjacent bone condition (D-ABC) in 3 sets of DECT images-a fused image set (DE120) and 2 sets of hypothetical monoenergetic images (ME100, ME190)-was performed and the results were statistically analyzed. With regards to R-DBAs and D-ABC, significant differences among DE120, ME100, and ME190 were observed. The ME100 and ME190 images revealed more artifact reduction and diagnosability than those of DE120. DECT imaging followed by hypothetical monoenergetic image construction can cause R-DBAs and increase D-ABC and may be potentially used for the evaluation of postoperative changes in the bone encircling implant bodies. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. Multi technical analysis of wear mechanisms in axial piston pumps

    NASA Astrophysics Data System (ADS)

    Schuhler, G.; Jourani, A.; Bouvier, S.; Perrochat, J.-M.

    2017-05-01

    Axial piston pumps convert a motor rotation motion into hydraulic or pneumatic power. Their compactness and efficiency of approximately 0.9 make them suitable for actuation applications especially in aeronautics. However, they suffer a limited life due to the wear of their components. In the literature, studies of axial piston pumps deal with contact between its different elements under lubrication conditions. Nevertheless, they are more focused on analytic or numerical approaches. This study consists in an experimental analysis of worn pump components to highlight and understand wear mechanisms. Piston shoes are central components in the axial piston pump since they are involved in three tribological contacts. These three contacts are thereby studied: piston shoes/swashplate, piston shoes/pistons and piston shoes/shoes hold down plate (SHDP). To perform this analysis, helicopter hydraulic pumps after different operating times have been studied. The wear damage mechanisms and wear debris are analysed using SEM observations. 3D surface roughness measurements are then used to characterize worn surfaces. The observations reveal that in the contact between shoes and swashplate, the main wear mechanism is three-body abrasive wear due to coarse carbides removal. Between shoes and pistons, wear occurs in a less severe way and is mainly due to the debris generated in the first contact and conveyed by the lubricating fluid. In the third contact, the debris are also the prime cause of the abrasive wear and the generation of deep craters in the piston shoes.

  6. Not of African Descent: Dental Modification among Indigenous Caribbean People from Canímar Abajo, Cuba

    PubMed Central

    Roksandic, Mirjana; Alarie, Kaitlynn; Rodríguez Suárez, Roberto; Huebner, Erwin; Roksandic, Ivan

    2016-01-01

    Dental modifications in the Caribbean are considered to be an African practice introduced to the Caribbean archipelago by the influx of enslaved Africans during colonial times. Skeletal remains which exhibited dental modifications are by default considered to be Africans, African descendants, or post-contact indigenous people influenced by an African practice. Individual E-105 from the site of Canímar Abajo (Cuba), with a direct 14C AMS date of 990–800 cal BC, provides the first unequivocal evidence of dental modifications in the Antilles prior to contact with Europeans in AD 1492. Central incisors showing evidence of significant crown reduction (loss of crown volume regardless of its etiology) were examined macroscopically and with a scanning electron microscope (SEM) to determine if the observed alterations were due to deliberate modification or other (unintentional) factors considered: postmortem breakage, violent accidental breakage, non-dietary use of teeth, and wear caused by habitual or repeated actions. The pattern of crown reduction is consistent with deliberate dental modification of the type commonly encountered among African and African descendent communities in post-contact Caribbean archaeological assemblages. Six additional individuals show similar pattern of crown reduction of maxillary incisors with no analogous wear in corresponding mandibular dentition. PMID:27071012

  7. Not of African Descent: Dental Modification among Indigenous Caribbean People from Canímar Abajo, Cuba.

    PubMed

    Roksandic, Mirjana; Alarie, Kaitlynn; Rodríguez Suárez, Roberto; Huebner, Erwin; Roksandic, Ivan

    2016-01-01

    Dental modifications in the Caribbean are considered to be an African practice introduced to the Caribbean archipelago by the influx of enslaved Africans during colonial times. Skeletal remains which exhibited dental modifications are by default considered to be Africans, African descendants, or post-contact indigenous people influenced by an African practice. Individual E-105 from the site of Canímar Abajo (Cuba), with a direct 14C AMS date of 990-800 cal BC, provides the first unequivocal evidence of dental modifications in the Antilles prior to contact with Europeans in AD 1492. Central incisors showing evidence of significant crown reduction (loss of crown volume regardless of its etiology) were examined macroscopically and with a scanning electron microscope (SEM) to determine if the observed alterations were due to deliberate modification or other (unintentional) factors considered: postmortem breakage, violent accidental breakage, non-dietary use of teeth, and wear caused by habitual or repeated actions. The pattern of crown reduction is consistent with deliberate dental modification of the type commonly encountered among African and African descendent communities in post-contact Caribbean archaeological assemblages. Six additional individuals show similar pattern of crown reduction of maxillary incisors with no analogous wear in corresponding mandibular dentition.

  8. Ultralow wear of gallium nitride

    NASA Astrophysics Data System (ADS)

    Zeng, Guosong; Tan, Chee-Keong; Tansu, Nelson; Krick, Brandon A.

    2016-08-01

    Here, we reveal a remarkable (and surprising) physical property of GaN: it is extremely wear resistant. In fact, we measured the wear rate of GaN is approaching wear rates reported for diamond. Not only does GaN have an ultralow wear rate but also there are quite a few experimental factors that control the magnitude of its wear rate, further contributing to the rich and complex physics of wear of GaN. Here, we discovered several primary controlling factors that will affect the wear rate of III-Nitride materials: crystallographic orientation, sliding environment, and coating composition (GaN, InN and InGaN). Sliding in the ⟨ 1 2 ¯ 10 ⟩ is significantly lower wear than ⟨ 1 1 ¯ 00 ⟩ . Wear increases by 2 orders of magnitude with increasing humidity (from ˜0% to 50% RH). III-Nitride coatings are promising as multifunctional material systems for device design and sliding wear applications.

  9. 3D Simulation Modeling of the Tooth Wear Process

    PubMed Central

    Dai, Ning; Hu, Jian; Liu, Hao

    2015-01-01

    Severe tooth wear is the most common non-caries dental disease, and it can seriously affect oral health. Studying the tooth wear process is time-consuming and difficult, and technological tools are frequently lacking. This paper presents a novel method of digital simulation modeling that represents a new way to study tooth wear. First, a feature extraction algorithm is used to obtain anatomical feature points of the tooth without attrition. Second, after the alignment of non-attrition areas, the initial homogeneous surface is generated by means of the RBF (Radial Basic Function) implicit surface and then deformed to the final homogeneous by the contraction and bounding algorithm. Finally, the method of bilinear interpolation based on Laplacian coordinates between tooth with attrition and without attrition is used to inversely reconstruct the sequence of changes of the 3D tooth morphology during gradual tooth wear process. This method can also be used to generate a process simulation of nonlinear tooth wear by means of fitting an attrition curve to the statistical data of attrition index in a certain region. The effectiveness and efficiency of the attrition simulation algorithm are verified through experimental simulation. PMID:26241942

  10. 3D Simulation Modeling of the Tooth Wear Process.

    PubMed

    Dai, Ning; Hu, Jian; Liu, Hao

    2015-01-01

    Severe tooth wear is the most common non-caries dental disease, and it can seriously affect oral health. Studying the tooth wear process is time-consuming and difficult, and technological tools are frequently lacking. This paper presents a novel method of digital simulation modeling that represents a new way to study tooth wear. First, a feature extraction algorithm is used to obtain anatomical feature points of the tooth without attrition. Second, after the alignment of non-attrition areas, the initial homogeneous surface is generated by means of the RBF (Radial Basic Function) implicit surface and then deformed to the final homogeneous by the contraction and bounding algorithm. Finally, the method of bilinear interpolation based on Laplacian coordinates between tooth with attrition and without attrition is used to inversely reconstruct the sequence of changes of the 3D tooth morphology during gradual tooth wear process. This method can also be used to generate a process simulation of nonlinear tooth wear by means of fitting an attrition curve to the statistical data of attrition index in a certain region. The effectiveness and efficiency of the attrition simulation algorithm are verified through experimental simulation.

  11. Complete denture wearing and fractures among edentulous patients treated in university clinics.

    PubMed

    Takamiya, Aline S; Monteiro, Douglas R; Marra, Juliê; Compagnoni, Marco A; Barbosa, Debora B

    2012-06-01

    The prevalence of wearing and fracture of complete dentures was evaluated among edentulous patients treated in two dental schools in Brazil. Acceptance and wearing of complete dentures are related to adaptive behaviour of edentulous patients. However, one reason that could interfere with the wearing dentures is their potential to fracture, which is still a common complication in denture rehabilitation practice. Two hundred and twenty-four edentulous patients rehabilitated with complete dentures from 2000 to 2005 in Araçatuba and Araraquara Dental School, University of State of São Paulo, were assessed in 2006 and 2007 to answer a questionnaire about wearing and fracture of their dentures. Statistical analysis were performed using Epi Info software and chi-squared test to compare maxillary and mandibular data (α = 0.05). Almost 26% of the patients did not wear their dentures, and among the remainder, the majority wore the maxillary denture. About 30% of the dentures were fractured, with higher prevalence in the maxillary arch (p = 0.003). Discontinuation of wearing dentures was quite high, especially considering the treatment which was carried out in university clinics. Prevalence of fractures was also high, greater for the maxillary denture, and was one of the main reasons for non-wearing of complete dentures. © 2011 The Gerodontology Society and John Wiley & Sons A/S.

  12. Influence of Fretting Wear on Lifetime of Tin Plated Connectors

    NASA Astrophysics Data System (ADS)

    Ikeda, Hirosaka; Ito, Tetsuya; Sawada, Shigeru; Hattori, Yasuhiro; Saitoh, Yasushi; Tamai, Terutaka; Iida, Kazuo

    Due to the recent increase in electronic devices mounted on automobiles, a large number of connectors, especially low-cost tin plated connectors are being used. As a result, their contact reliability has become problematic. Furthermore, for the connectors which are subjected to fretting wear caused by heat cycle and vibrations, the contact resistance increases because of wear of tin and deposition of oxides, which generates problems of poor contact. This study is intended to analyze the change in contact resistance of tin plated connectors from the start of fretting wear to the end of their lifetime from the viewpoint of practical reliability, and to observe the trace and the characteristics of fretting wear microscopically. This study found that wear and oxidation of tin plated connectors start immediately with fretting wear, and thus accumulation of abrasion powder on fretting areas causes connectors to reach to the end of their useful lifetime quickly. Especially, it was demonstrated that amplitude of fretting has a considerable influence on a connector's lifetime. It is made clear that air-tightness, so-called “gas-tight” of tin in a fretting area influences fretting wear considerably.

  13. Metal wear in Lillehei-Kaster heart valve prostheses.

    PubMed

    Silver, M D; Koppenhoefer, H; Heggtveit, H A; Reif, T H

    1985-08-01

    Ten Lillehei-Kaster heart valve prostheses, in situ for up to 10 years and recovered at surgery or necropsy, were examined by light and scanning electron microscopy. All showed metal wear on the luminal aspect of their struts. The volume of wear related to the duration a prosthesis had been in situ. The worn metal showed distinct, transverse surface corrugations, which became more obvious with time. Aortic prostheses wore more and faster than mitral ones. One strut usually showed more wear than the other, a change likely due to specific manufacturing methods. It is believed that the pattern of wear is caused by a velocity-controlled stick-slip abrasive wear process, resulting from an interaction between the edge of the moving pyrolytic carbon disc, the struts' titanium surface, and the protein coat covering that surface. None of the patients had prosthesis dysfunction attributable to metal wear. Disc escape seems unlikely considering the degree of wear observed after 10 years. Furthermore, the surface corrugations did not appear to cause disc sticking or other problems. However, clinicians might consider monitoring patients who have borne these prostheses for greater than 10 years.

  14. Two- and three-body wear of composite resins.

    PubMed

    Koottathape, Natthavoot; Takahashi, Hidekazu; Iwasaki, Naohiko; Kanehira, Masafumi; Finger, Werner J

    2012-12-01

    The aim of the present study was to investigate two- and three-body wear of microfilled, micro-hybrid and nano-hybrid composite resins using a ball-on-disc sliding device. One microfilled (Durafill VS), one micro-hybrid (Filtek Z250), one hybrid (Clearfil AP-X), one nanofilled (Filtek Supreme XT), and two nano-hybrid (MI Flow, Venus Diamond) composite resins were examined. The composites were filled in a cylindrical cavity, and light polymerized. After storage in 37°C distilled water for 7days, all specimens were tested with a custom-made ball-on-disc sliding device with a zirconia ball as antagonist (50N loads, 1.2Hz, 10,000 cycles) immersed in water, poppy seed slurry and polymethyl methacrylate slurry, respectively. Maximum wear depth and volume loss of worn surfaces were quantified by a digital CCD microscope and analyzed with two-way analysis of variance. The interactions between composite resin and condition of their maximum wear depth and volume loss were significant (p<0.01). The abrasive wear produced at three-body loading with poppy seed slurry was very large for the microfilled composite, and small for all other composites tested. In contrast, two-body wear of the microfilled composite, and one nano-hybrid composite was very low. The ball-on-disc sliding device used is considered suitable to simulate sliding of an antagonist cusp on an opposing occlusal composite restoration, either in the two- or the three-body wear mode. All tested materials except for the microfilled composite showed low surface wear when exposed to poppy seed as the third-body medium. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  15. Wear in Fluid Power Systems.

    DTIC Science & Technology

    1979-11-30

    reference, it is mentioned that sodium , potassium , calcium, etc,, were found on the slide and presumably originated from the oil. Ref. [6] re- ports...technique. These tests showed that changes in the wear rate of a system or component could be readily detected by the ferrograph. The lack of...Concentrations in Terms of Wear Rate Fluid Sampling Wear Debris Recovery VII. FERROGRAPHIC STANDARDIZATION 54 The Case for Standardization TTCP Results VIIl

  16. Wearing someone else's shoes.

    PubMed

    Rae, Kym

    2010-06-01

    This paper recounts a journey of discovery by a scientist who inadvertently takes on coordination of an ArtsHealth programme. The dynamics of role change are explored showcasing the vulnerabilities and fears that often accompany these career adjustments. The associated ArtsHealth programme (Gomeroi gaaynggal) works with Aboriginal and Torres Strait Islander women in Australia throughout their pregnancy to improve understanding of issues that impact the health of themselves and their developing baby. By wearing someone else shoes, the scientist is immersed in the project and must confront issues including skill mix, learning and cultural diversity.

  17. Dental (Odontogenic) Pain

    PubMed Central

    Renton, Tara

    2011-01-01

    This article provides a simple overview of acute trigeminal pain for the non dentist. This article does not cover oral mucosal diseases (vesiculobullous disorders) that may cause acute pain. Dental pain is the most common in this group and it can present in several different ways. Of particular interest for is that dental pain can mimic both trigeminal neuralgia and other chronic trigeminal pain disorders. It is crucial to exclude these disorders whilst managing patients with chronic trigeminal pain. PMID:26527224

  18. Dental radiology.

    PubMed

    Woodward, Tony M

    2009-02-01

    Dental radiology is the core diagnostic modality of veterinary dentistry. Dental radiographs assist in detecting hidden painful pathology, estimating the severity of dental conditions, assessing treatment options, providing intraoperative guidance, and also serve to monitor success of prior treatments. Unfortunately, most professional veterinary training programs provide little or no training in veterinary dentistry in general or dental radiology in particular. Although a technical learning curve does exist, the techniques required for producing diagnostic films are not difficult to master. Regular use of dental x-rays will increase the amount of pathology detected, leading to healthier patients and happier clients who notice a difference in how their pet feels. This article covers equipment and materials needed to produce diagnostic intraoral dental films. A simplified guide for positioning will be presented, including a positioning "cheat sheet" to be placed next to the dental x-ray machine in the operatory. Additionally, digital dental radiograph systems will be described and trends for their future discussed.

  19. DENTAL MATERIALS.

    DTIC Science & Technology

    The study deals with the determination of characteristic physical and mechanical properties of restorative dental materials, and effect of...manipulative variables on these properties. From the study an entirely new dental gold inlay casting technic was developed, based on the principle of...controlled water added hygroscopic technic. The method has had successful dental applications and is a recognized method of dental inlay casting procedure

  20. Elucidation of wear mechanisms by ferrographic analysis

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1981-01-01

    The use of ferrographic analysis in conjunction with light and scanning electron microscopy is described for the elucidation of wear mechanisms taking place in operating equipment. Example of adhesive wear, abrasive wear, corrosive wear, rolling element fatigue, lubricant breakdown, and other wear modes are illustrated. In addition, the use of magnetic solutions to precipitate nonmagnetic debris from aqueous and nonaqueous fluids is described.

  1. Antibacterial Dental Composites with Chlorhexidine and Mesoporous Silica

    PubMed Central

    Zhang, J.F.; Wu, R.; Fan, Y.; Liao, S.; Wang, Y.; Wen, Z.T.; Xu, X.

    2014-01-01

    One of the leading causes for the failure of dental composite restorations is secondary caries. Effectively inhibiting cariogenic biofilms and reducing secondary caries could extend the service life of composite restorations. Dental composites releasing antibacterial agents such as chlorhexidine (CHX) have shown biofilm-inhibitory efficacy, but they usually have poor physical and mechanical properties. Herein, we present a study of a new method to encapsulate and release CHX from dental composite using mesoporous silica nanoparticles (MSNs). SBA-15 MSNs were synthesized according to a reported procedure. CHX (62.9 wt%) was encapsulated into dried MSN from 0.3 M CHX ethanol solution. The dental composites containing 0% (control), 3%, 5%, and 6.3% CHX or the same amounts of CHX entrapped in MSN (denoted as CHX@MSN) were fabricated with methacrylate monomers and silanized glass fillers (CHX or CHX@MSN + glass filler particle = 70 wt%). The monomer mixture consisted of bisphenol A glycidyl methacrylate (BisGMA), hexanediol dimethacrylate (HDDMA), ethoxylated bisphenol A dimethacrylate (EBPADMA), and urethane dimethacrylates (UEDMA) at a weight ratio of 40:30:20:10. The composites were tested for CHX release and recharge, flexural strength and modulus (at 24 hr and 1 mo), surface roughness, in vitro wear, and antibacterial activity against Streptococcus mutans and Lactobacillus casei (in both planktonic growth and biofilm formation). The results showed that the composites with CHX@MSN largely retained mechanical properties and smooth surfaces and showed controlled release of CHX over a long time. In contrast, the composites with directly mixed CHX showed reduced mechanical properties, rough surfaces, and burst release of CHX in a short time. The composites with CHX either directly mixed or in MSN showed strong inhibition to S. mutans and L. casei. This research has demonstrated the successful application of MSNs as a novel nanotechnology in dental materials to inhibit

  2. Antibacterial dental composites with chlorhexidine and mesoporous silica.

    PubMed

    Zhang, J F; Wu, R; Fan, Y; Liao, S; Wang, Y; Wen, Z T; Xu, X

    2014-12-01

    One of the leading causes for the failure of dental composite restorations is secondary caries. Effectively inhibiting cariogenic biofilms and reducing secondary caries could extend the service life of composite restorations. Dental composites releasing antibacterial agents such as chlorhexidine (CHX) have shown biofilm-inhibitory efficacy, but they usually have poor physical and mechanical properties. Herein, we present a study of a new method to encapsulate and release CHX from dental composite using mesoporous silica nanoparticles (MSNs). SBA-15 MSNs were synthesized according to a reported procedure. CHX (62.9 wt%) was encapsulated into dried MSN from 0.3 M CHX ethanol solution. The dental composites containing 0% (control), 3%, 5%, and 6.3% CHX or the same amounts of CHX entrapped in MSN (denoted as CHX@MSN) were fabricated with methacrylate monomers and silanized glass fillers (CHX or CHX@MSN + glass filler particle = 70 wt%). The monomer mixture consisted of bisphenol A glycidyl methacrylate (BisGMA), hexanediol dimethacrylate (HDDMA), ethoxylated bisphenol A dimethacrylate (EBPADMA), and urethane dimethacrylates (UEDMA) at a weight ratio of 40:30:20:10. The composites were tested for CHX release and recharge, flexural strength and modulus (at 24 hr and 1 mo), surface roughness, in vitro wear, and antibacterial activity against Streptococcus mutans and Lactobacillus casei (in both planktonic growth and biofilm formation). The results showed that the composites with CHX@MSN largely retained mechanical properties and smooth surfaces and showed controlled release of CHX over a long time. In contrast, the composites with directly mixed CHX showed reduced mechanical properties, rough surfaces, and burst release of CHX in a short time. The composites with CHX either directly mixed or in MSN showed strong inhibition to S. mutans and L. casei. This research has demonstrated the successful application of MSNs as a novel nanotechnology in dental materials to inhibit

  3. Wear mechanisms and improvements of wear resistance in cobalt-chromium alloy femoral components in artificial total knee joints

    NASA Astrophysics Data System (ADS)

    Que, Like

    Wear is one of the major causes of artificial total knee arthroplasty (TKA) failure. Wear debris can cause adverse reactions to the surrounding tissue which can ultimately lead to loosening of the prosthesis. The wear behavior of UHMWPE tibial components have been studied extensively, but relatively little attention has been paid to the CoCrMo femoral component. The goal of the present study was to investigate the wear mechanisms of CoCrMo femoral components, to study the effect of CoCrMo alloy surface roughness on the wear of UHMWPE, and to determine the effect of heat treatments on the wear resistance of the CoCrMo implant alloys. The surface roughness of twenty-seven retrieved CoCrMo femoral components was analyzed. A multiple station wear testing machine and a wear fixture attached to an MTS 858 bionix system were built and used for in vitro wear studies of the CoCrMo/UHMWPE bearing couple. Solution and aging treatments were applied to the CoCrMo alloys. A white light interference surface profilometer (WLISP) and a scanning electron microscope (SEM) were used to measure the surface roughness and to study wear mechanisms of CoCrMo alloy. An optical microscope was used for alloy microstructure study. X-ray diffraction tests were performed to identify alloy phase transformation after aging. The micro-structure, hardness, and wear resistance of the alloys were studied. Surface roughness was used to quantify alloy wear, and the minimum number of surface roughness measurements required to obtain a reliable and repeatable characterization of surface roughness for a worn alloy surface was determined. The surfaces of the retrieved CoCrMo femoral components appeared to be damaged by metal particles embedded in the UHMWPE tibial component and metal-on-metal wear due to UHMWPE tibial component through-wear. Surface roughness of the femoral components was not correlated with patient age, weight, sex, or length of implantation. In vitro wear tests showed that when the Co

  4. Role of aqueous extract of morinda citrifolia (Indian noni) ripe fruits in inhibiting dental caries-causing streptococcus mutans and streptococcus mitis.

    PubMed

    Kumarasamy, Barani; Manipal, Sunayana; Duraisamy, Prabu; Ahmed, Adil; Mohanaganesh, Sp; Jeevika, C

    2014-11-01

    Use of alternative medicine to control oral streptococci is a new topic worthy of further investigation. This study aimed to elucidate the dose-dependent anti-bacterial activity of crude aqueous extract of ripe Morinda citrifolia L. (Family: Rubiaceae) fruits against oral streptococci i.e. Streptococcus mutans and Streptococcus mitis, that cause dental caries in humans. Fresh ripe M. citrifolia fruits (750g) were ground in an electronic blender with sterile water (500ml). The crude aqueous extract was lyophilized to yield a brown colored powder. Various concentrations (1000-100μg/ ml) of the extract were tested for its antibacterial activity (Kirby and Bauer method) against whole cells of S. mutans and S. mitis. Minimum Inhibitory Concentration (MIC) was determined by micro-dilution method, using serially diluted (2 folds) fruit extract, according to the National Committee for Clinical Laboratory Standards (NCCLS). Crude aqueous extract (1000μg/ ml) of ripe M. citrifolia fruits effectively inhibited the growth of S. mutans (19±0.5 mm) and S. mitis (18.6±0.3 mm) compared to the streptomycin control (21.6±0.3 mm). The growth inhibition was clearly evident with "nil" bacteriostasis, even after 48 hours of incubation at 37°C. The MIC of the extract for S. mutans and S. mitis was 125 μg and 62.5 μg, respectively. Our results suggest that phytochemicals naturally synthesized by M. citrifolia have an inhibitory effect on oral streptococci. Furthermore, purification and molecular characterization of the "bioactive principle" would enable us to formulate a sustainable oral hygiene product.

  5. Role of Aqueous Extract of Morinda Citrifolia (Indian Noni) Ripe Fruits in Inhibiting Dental Caries-Causing Streptococcus Mutans and Streptococcus Mitis

    PubMed Central

    Kumarasamy, Barani; Manipal, Sunayana; Duraisamy, Prabu; Ahmed, Adil; Mohanaganesh, SP; Jeevika, C

    2014-01-01

    Objectives: Use of alternative medicine to control oral streptococci is a new topic worthy of further investigation. This study aimed to elucidate the dose-dependent anti-bacterial activity of crude aqueous extract of ripe Morinda citrifolia L. (Family: Rubiaceae) fruits against oral streptococci i.e. Streptococcus mutans and Streptococcus mitis, that cause dental caries in humans. Methods: Fresh ripe M. citrifolia fruits (750g) were ground in an electronic blender with sterile water (500ml). The crude aqueous extract was lyophilized to yield a brown colored powder. Various concentrations (1000-100μg/ ml) of the extract were tested for its antibacterial activity (Kirby and Bauer method) against whole cells of S. mutans and S. mitis. Minimum Inhibitory Concentration (MIC) was determined by micro-dilution method, using serially diluted (2 folds) fruit extract, according to the National Committee for Clinical Laboratory Standards (NCCLS). Results: Crude aqueous extract (1000μg/ ml) of ripe M. citrifolia fruits effectively inhibited the growth of S. mutans (19±0.5 mm) and S. mitis (18.6±0.3 mm) compared to the streptomycin control (21.6±0.3 mm). The growth inhibition was clearly evident with “nil” bacteriostasis, even after 48 hours of incubation at 37°C. The MIC of the extract for S. mutans and S. mitis was 125 μg and 62.5 μg, respectively. Conclusion: Our results suggest that phytochemicals naturally synthesized by M. citrifolia have an inhibitory effect on oral streptococci. Furthermore, purification and molecular characterization of the “bioactive principle” would enable us to formulate a sustainable oral hygiene product. PMID:25628701

  6. Influence of wearing schedule on extended-wear complications.

    PubMed

    Kenyon, E; Polse, K A; Seger, R G

    1986-02-01

    The effect of wearing schedule on extended-wear (EW) success was evaluated over a nine-month period by assigning 36 subjects to 5 different wearing schedules (removal every 4, 7, 14, or 28 days, or daily wear [DW]). All but one EW patient required interruption of extended wear at least once; half of the DW patients completed the study without interruption. The most prevalent (100%) complication in the EW group was epithelial microcysts; 54% had to discontinue EW for 67 +/- 30 days while severe microcysts subsided. Evidence is given for a hypoxic etiology of microcysts. Other EW complications included: persistent punctate keratitis, infiltrative keratitis, infection, and idiopathic red eye. Neither the level of overnight corneal swelling nor the period between removals influenced the incidence or severity of complications. Data is given on the recovery of corneal parameters after EW is discontinued.

  7. Dental OCT

    NASA Astrophysics Data System (ADS)

    Colston, Bill W.; Sathyam, Ujwal S.; Dasilva, Luiz B.; Everett, Matthew J.; Stroeve, Pieter; Otis, L. L.

    1998-09-01

    We present here the first in vivo optical coherence tomography (OCT) images of human dental tissue. A novel dental optical coherence tomography system has been developed. This system incorporates the interferometer sample arm and transverse scanning optics into a handpiece that can be used intraorally to image human dental tissues. The average imaging depth of this system varied from 3 mm in hard tissues to 1.5 mm in soft tissues. We discuss the application of this imaging system for dentistry and illustrate the potential of our dental OCT system for diagnosis of periodontal disease, detection of caries, and evaluation of dental restorations.

  8. [Infants wearing teething necklaces].

    PubMed

    Taillefer, A; Casasoprana, A; Cascarigny, F; Claudet, I

    2012-10-01

    Numerous infants wear teething necklaces, a quack remedy with a real risk of strangulation or aspiration of small beads. Evaluate parental perceptions and beliefs about the use of teething necklaces and analyze parental knowledge about the associated dangers. Between March and July 2011, in three different pediatric units of a tertiary children's hospital and a general hospital in Toulouse and Montauban (southwest France), voluntary parents were invited to be interviewed about their child wearing a teething necklace. The interviews were conducted following an anthropological approach: they were recorded and then fully transcribed and analyzed. Parents were informed that the conversation was recorded. During the study period, 48 children were eligible. Eleven families refused to participate, 29 parents were interviewed face to face. The children's mean age was 14 years ± 7 months, the male:female ratio was equal to 0.8 (12 boys, 15 girls). The mean age of children when necklace wearing was started was equal to 4 ± 2 months. The mean mother's age was 31 ± 5 years and 33 ± 4 years for fathers. The parents' religion was mostly Catholic (60%). Teething necklaces were mainly made of amber (n=23). Sales information about the risks associated with the necklaces was for the most part absent (92%). The most frequent positive parental perceptions were analgesic properties and a soothing remedy (73%); a birth accessory and memory (64%); an esthetic accessory (60%); a protective amulet (60%); and an alternative or additional element to other traditional therapeutics (55%). The negative parental perceptions (n=4) were an unnecessary accessory, costume jewelry, a pure commercial abuse of a popular belief, a dangerous item with a risk of strangulation, and the absence of proof of its efficacy. Although parents concede that teeth eruption is benign, they fear its related symptoms. To a natural phenomenon a natural response: they use a necklace to satisfy the analogy. The

  9. Risk Assessment for Tooth Wear.

    PubMed

    Kontaxopoulou, Isavella; Alam, Sonia

    2015-08-01

    Tooth wear has an increasing prevalence in the UK population. The aetiology is commonly multifactorial, and the aetiopathology is through a combination of erosion, attrition, abrasion and abfraction. Erosion is associated with intrinsic or extrinsic acids, and therefore subjects with reflux disease and eating disorders are at increased risk. Fruit juice, fruits and carbonated drink consumption, frequency of consumption and specific habits are also risk factors. Attrition is more prevalent in bruxists. Other habits need to be considered when defining the risk of tooth wear. Abrasion is usually associated with toothbrushing and toothpastes, especially in an already acidic environment. Patients with extensive lesions that affect dentin may be at higher risk, as well as those presenting with unstained lesions. Monitoring of the progress of tooth wear is recommended to identify those with active tooth wear. Indices for tooth wear are a helpful aid.

  10. Switch wear leveling

    DOEpatents

    Wu, Hunter; Sealy, Kylee; Gilchrist, Aaron

    2015-09-01

    An apparatus for switch wear leveling includes a switching module that controls switching for two or more pairs of switches in a switching power converter. The switching module controls switches based on a duty cycle control technique and closes and opens each switch in a switching sequence. The pairs of switches connect to a positive and negative terminal of a DC voltage source. For a first switching sequence a first switch of a pair of switches has a higher switching power loss than a second switch of the pair of switches. The apparatus includes a switch rotation module that changes the switching sequence of the two or more pairs of switches from the first switching sequence to a second switching sequence. The second switch of a pair of switches has a higher switching power loss than the first switch of the pair of switches during the second switching sequence.

  11. Low friction wear resistant graphene films

    DOEpatents

    Sumant, Anirudha V.; Berman, Diana; Erdemir, Ali

    2017-02-07

    A low friction wear surface with a coefficient of friction in the superlubric regime including graphene and nanoparticles on the wear surface is provided, and methods of producing the low friction wear surface are also provided. A long lifetime wear resistant surface including graphene exposed to hydrogen is provided, including methods of increasing the lifetime of graphene containing wear surfaces by providing hydrogen to the wear surface.

  12. Tool wear mechanisms in the machining of Nickel based super-alloys: A review

    NASA Astrophysics Data System (ADS)

    Akhtar, Waseem; Sun, Jianfei; Sun, Pengfei; Chen, Wuyi; Saleem, Zawar

    2014-06-01

    Nickel based super-alloys are widely employed in aircraft engines and gas turbines due to their high temperature strength, corrosion resistance and, excellent thermal fatigue properties. Conversely, these alloys are very difficult to machine and cause rapid wear of the cutting tool, frequent tool changes are thus required resulting in low economy of the machining process. This study provides a detailed review of the tool wear mechanism in the machining of nickel based super-alloys. Typical tool wear mechanisms found by different researchers are analyzed in order to find out the most prevalent wear mechanism affecting the tool life. The review of existing works has revealed interesting findings about the tool wear mechanisms in the machining of these alloys. Adhesion wear is found to be the main phenomenon leading to the cutting tool wear in this study.

  13. Tooth-wear patterns in subjects with Class II Division 1 malocclusion and normal occlusion.

    PubMed

    Janson, Guilherme; Oltramari-Navarro, Paula Vanessa Pedron; de Oliveira, Renata Biella Salles; Quaglio, Camila Leite; Sales-Peres, Sílvia Helena de Carvalho; Tompson, Bryan

    2010-01-01

    The aim of this study was to investigate the prevalence of tooth wear in adolescents with Class II malocclusion, compared with those with normal occlusion. The sample consisted of dental casts obtained from 310 subjects, divided into 3 groups: group 1, 110 subjects with normal occlusion (mean age, 13.51 years); group 2, 100 complete Class II Division 1 patients (mean age, 13.44 years); and group 3, 100 half-cusp Class II Division 1 patients (mean age, 13.17 years). Dental wear was assessed by using a modified version of the tooth-wear index. The 3 groups were compared by means of the Kruskal-Wallis and Dunn tests, considering the frequency and the severity of wear on each surface of each group of teeth. The level of statistical significance was set at 5%. The normal occlusion group had statistically greater tooth wear on the palatal surfaces of the maxillary central incisors and the incisal surfaces of the maxillary canines than the corresponding surfaces in both Class II malocclusion groups. The complete and half-cusp Class II Division 1 malocclusion groups had statistically greater tooth wear on the occlusal surfaces of the maxillary second premolar and first molar, the occlusal surfaces of the mandibular premolars, and the buccal surfaces of the mandibular posterior teeth compared with the normal occlusion group. The half-cusp Class II Division 1 malocclusion group had significantly greater tooth wear on the incisal surfaces of the mandibular incisors compared with the complete Class II Division 1 malocclusion group. Subjects with normal occlusion and complete or half-cusp Class II Division 1 malocclusions have different tooth-wear patterns. Tooth wear on the malocclusion subjects should not be considered pathologic but rather consequent to the different interocclusal tooth arrangement. Copyright 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

  14. Wear resistance and wear mechanisms in polymer + metal composites.

    PubMed

    Olea-Mejia, Oscar; Brostow, Witold; Buchman, Eli

    2010-12-01

    We have investigated composites containing metallic micro-size and nano-sized particles as the 10 wt% dispersed phase. Branched low density polyethylene (LDPE) was the matrix. Microsized metals were Al, Ag and Ni; nanosized metals were Al and Ag. Several mechanisms of wear are observed in function of the kind and size of metal used: deformation, delamination, abrasion, adhesion and rolls formation. The presence of Ag particles increases the wear rate as compared to neat LDPE. The presence of Al particles lowers the wear of LDPE significantly; nanoparticles are more effective than microparticles.

  15. Wear rates of resin composites.

    PubMed

    Barkmeier, W W; Erickson, R I; Latta, M A; Wilwerding, T M

    2013-01-01

    SUMMARY A laboratory study was conducted to examine the wear of resin composite materials using a generalized wear simulation model. Ten specimens each of five resin composites (Esthet•X [EX], Filtek Supreme Plus [SP], Filtek Z250 [Z2], Tetric EvoCeram [EC], and Z100 Restorative [Z1]) were subjected to wear challenges of 100,000, 400,000, 800,000, and 1,200,000 cycles. The materials were placed in cylinder-shaped stainless-steel fixtures, and wear was generated using a flat stainless-steel antagonist in a slurry of polymethylmethacrylate beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2000) with Proscan and ProForm software. Statistical analysis of the laboratory data using analysis of variance and Tukey's post hoc test showed a significant difference (p<0.05) for mean wear facet depth and volume loss for both the number of cycles and resin composite material. Linear regression analysis was used to develop predictive wear rates and volume loss rates. Linear wear was demonstrated with correlation coefficients (R(2)) ranging from 0.914 to 0.995. Mean wear values (mean facet depth [μm]) and standard deviations (SD) for 1200K cycles were as follows: Z1 13.9 (2.0), Z2 26.7 (2.7), SP 30.1 (4.1), EC 31.8 (2.3), and EX 67.5 (8.2). Volume loss (mm(3)) and SDs for 1200K cycles were as follows: Z1 0.248 (0.036), Z2 0.477 (0.044), SP 0.541 (0.072), EC 0.584 (0.037), and EX 1.162 (0.139). The wear rate (μm) and volume loss rate (mm(3)) per 100,000 cycles for the five resin composites were as follows: wear rate Z1 0.58, EC 1.27, Z2 1.49, SP 1.62, and EX 4.35, and volume loss rate Z1 0.009, EC 0.024, Z2 0.028, SP 0.029, and EX 0.075. The generalized wear model appears to be an excellent method for measuring relative wear of resin composite materials.

  16. Wear resistance of four types of vacuum-formed retainer materials: a laboratory study.

    PubMed

    Raja, Taiyub A; Littlewood, Simon J; Munyombwe, Theresa; Bubb, Nigel L

    2014-07-01

    To investigate the resistance to wear of four different vacuum-formed retainer (VFR) materials: Essix C+, Essix ACE, Duran, and Tru-Tain. Essix C+ is a polypropylene polymer; the other materials are polyethylene co-polymers. The study was undertaken at the Leeds Dental Institute, Leeds, UK, with 26 samples in each group. The specimens were vacuum-formed according to the manufacturers' guidelines, and a custom-made wear-simulation machine was used to conduct the test. Each specimen was subjected to 1000 cycles of the wear simulation, with steatite balls as the antagonist material. The resistance to wear of the VFR materials was evaluated by measuring the maximum wear depth using noncontact, three-dimensional surface profilometry. The wear depth was given in micrometers. The median wear depth was 63.20 µm for the Essix C+ group, 7.88 µm for the Essix ACE group, 9.75 µm for the Duran group, and 12.08 µm for the Tru-Tain group. The Kruskal-Wallis test to compare the four VFR materials detected a statistically significant difference between the groups (P < .001). Comparisons of the groups using the Mann-Whitney U-test demonstrated that the Essix C+ group had significantly greater wear than the other three groups (P < .001). There was no statistically significant difference in median wear depth between the two groups with the least amount of wear-the Essix ACE and Duran groups. Under the standardized conditions of this laboratory study, the three polyethylene co-polymer materials-Essix ACE, Duran, and Tru-Tain-exhibited significantly less wear than the polypropylene material, Essix C+.

  17. The effect of pH, fluoride and tribocorrosion on the surface properties of dental archwires.

    PubMed

    Močnik, Petra; Kosec, Tadeja; Kovač, Janez; Bizjak, Milan

    2017-09-01

    Nickel-titanium and stainless steel are the most commonly used alloys for orthodontic treatments. Even though both are known to be resistant to corrosion, there are circumstances that can lead to undesired situations, like localized types of corrosion attack, wear during sliding of an archwire though brackets and breakdowns due to iatrogenic causes. The aim of this research was to analyse the influence of environmental effects on the corrosion and tribocorrosion properties of NiTi and stainless steel dental alloys. The effects of pH and fluorides on the electrochemical properties were studied using the cyclic potentiodynamic technique. The migration of ions from the alloy into saliva during exposure to saliva with and without the presence of wear was analysed using ICP-MS analyses. Auger spectroscopy was used to study the formation of a passive oxide layer on different dental alloys. It was found that lowering the pH preferentially affects the corrosion susceptibility of NiTi alloys, whereas stainless steel dental archwires are prone to local types of corrosion. The NiTi alloy is not affected by smaller increases of fluoride ions up to 0.024M, while at 0.076M (simulating the use of toothpaste) the properties are affected. A leaching test during wear-assisted corrosion showed that the concentrations of Ni ions released into the saliva exceeded the limit value of 0.5μg/cm(2)/week. The oxide films on the NiTi and stainless steel alloys after the tribocorrosion experiment were thicker than those exposed to saliva only. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Dental and General Trauma in Team Handball.

    PubMed

    Petrović, Mateja; Kühl, Sebastian; Šlaj, Martina; Connert, Thomas; Filippi, Andreas

    Handball has developed into a much faster and high-impact sport over the past few years because of rule changes. Fast sports with close body contact are especially prone to orofacial trauma. Handball belongs to a category of sports with medium risk for dental trauma. Even so, there is only little literature on this subject. The aim of this study was to examine the prevalence and the type of injuries, especially the occurrence of orofacial trauma, habits of wearing mouthguards, as well as degree of familiarity with the tooth rescue box. For this purpose, 77.1% (n=542/703) of all top athletes and coaches from the two highest Swiss leagues (National League A and National League B), namely 507 professional players and 35 coaches, were personally interviewed using a standardized questionnaire. 19.7% (n=100/507) of the players experienced dental trauma in their handball careers, with 40.8% (n=51/125) crown fractures being the most frequent by far. In spite of the relatively high risk of lip or dental trauma, only 5.7% (n=29/507) of the players wear mouthguards. The results of this study show that dental trauma is common among Swiss handball players. In spite of the high risk of dental trauma, the mouthguard as prevention is not adequately known, and correct procedure following dental trauma is rarely known at all.

  19. Dynamic superlubricity and the elimination of wear on the nanoscale.

    PubMed

    Lantz, Mark A; Wiesmann, Dorothea; Gotsmann, Bernd

    2009-09-01

    One approach to ultrahigh-density data storage involves the use of arrays of atomic force microscope probes to read and write data on a thin polymer film, but damage to the ultrasharp silicon probe tips caused by mechanical wear has proved problematic. Here, we demonstrate the effective elimination of wear on a tip sliding on a polymer surface over a distance of 750 m by modulating the force acting on the tip-sample contact. Friction measurements as a function of modulation frequency and amplitude indicate that a reduction of friction is responsible for the reduction in wear to below our detection limit. In addition to its relevance to data storage, this approach could also reduce wear in micro- and nanoelectromechanical systems and other applications of scanning probe microscopes.

  20. Dynamic superlubricity and the elimination of wear on the nanoscale

    NASA Astrophysics Data System (ADS)

    Lantz, Mark A.; Wiesmann, Dorothea; Gotsmann, Bernd

    2009-09-01

    One approach to ultrahigh-density data storage involves the use of arrays of atomic force microscope probes to read and write data on a thin polymer film, but damage to the ultrasharp silicon probe tips caused by mechanical wear has proved problematic. Here, we demonstrate the effective elimination of wear on a tip sliding on a polymer surface over a distance of 750 m by modulating the force acting on the tip-sample contact. Friction measurements as a function of modulation frequency and amplitude indicate that a reduction of friction is responsible for the reduction in wear to below our detection limit. In addition to its relevance to data storage, this approach could also reduce wear in micro- and nanoelectromechanical systems and other applications of scanning probe microscopes.

  1. Wear Behavior and Mechanism of H13 Steel in Different Environmental Media

    NASA Astrophysics Data System (ADS)

    Li, Xinxing; Zhou, Yin; Cao, Huan; Li, Yixian; Wang, Lan; Wang, Shuqi

    2016-10-01

    Sliding wear tests were performed for H13 steel in atmosphere, distilled water, 3.5% NaCl, and 5% NaOH water solutions under various loads on a pin-on-disk wear tester. The results showed that for different environmental media, the wear rate of H13 steel in atmosphere was the maximum and that in 3.5% NaCl solution was the minimum. The maximum wear rate in atmosphere was caused by a larger quantity of heat produced in the friction process. In this case, the adhesive wear prevailed. In three wet environments, the mild wear prevailed due to the good lubrication and cooling capacity of media as well as corrosion product film on worn surface. In distilled water, the wear mechanism was a typical fatigue wear. On the other hand, in 3.5% NaCl and 5% NaOH solutions, corrosive wear prevailed. The minimum wear rate in 3.5% NaCl solution was attributed to the protective function of corrosion product film. On the contrary, noncompact corrosion product film in 5% NaOH solution resulted in higher wear rate.

  2. The Central Role of Wear Debris in Periprosthetic Osteolysis

    PubMed Central

    Koulouvaris, Panagiotis; Nestor, Bryan J.; Sculco, Thomas P.

    2006-01-01

    Periprosthetic osteolysis remains the leading complication of total hip arthroplasty, often resulting in aseptic loosening of the implant, and a requirement for revision surgery. Wear-generated particular debris is the main cause of initiating this destructive process. The purpose of this article is to review recent advances in our understanding of how wear debris causes osteolysis, and emergent strategies for the avoidance and treatment of this disease. The most important cellular target for wear debris is the macrophage, which responds to particle challenge in two distinct ways, both of which contribute to increased bone resorption. First, it is well known that wear debris activates proinflammatory signaling, which leads to increased osteoclast recruitment and activation. More recently, it has been established that wear also inhibits the protective actions of antiosteoclastogenic cytokines such as interferon gamma, thus promoting differentiation of macrophages to bone-resorbing osteoclasts. Osteoblasts, fibroblasts, and possibly lymphocytes may also be involved in responses to wear. At a molecular level, wear particles activate MAP kinase cascades, NFκB and other transcription factors, and induce expression of suppressors of cytokine signaling. Strategies to reduce osteolysis by choosing bearing surface materials with reduced wear properties (such as metal-on-metal) should be balanced by awareness that reducing particle size may increase biological activity. Finally, although therapeutic agents against proinflammatory mediators [such as tumor necrosis factor (TNF)] and osteoclasts (bisphosphonates and molecules blocking RANKL signaling) have shown promise in animal models, no approved treatments are yet available to osteolysis patients. Considerable efforts are underway to develop such therapies, and to identify novel targets for therapeutic intervention. PMID:18751821

  3. A review of equine dental disorders.

    PubMed

    Dixon, P M; Dacre, I

    2005-03-01

    Equine dentistry is a very important but until recently rather neglected area of equine practice, with many horses suffering from undiagnosed, painful dental disorders. A thorough clinical examination using a full mouth speculum is a pre-requisite to performing any equine dental procedure. Common incisor disorders include: prolonged retention of deciduous incisors, supernumerary incisors and overjet--the latter usually accompanied by cheek teeth (CT) overgrowths. Overjet can be surgically corrected, but perhaps should not be in breeding animals. In younger horses, traumatically fractured incisors with pulpar exposure may survive by laying down tertiary dentine. Loss or maleruption of incisors can cause uneven occlusal wear that can affect mastication. Idiopathic fractures and apical infection of incisors are rare. The main disorder of canine teeth is the development of calculus of the lower canines, and occasionally, developmental displacements and traumatic fractures. The main indications for extraction of "wolf teeth" (Triadan 05s) are the presence of displaced or enlarged wolf teeth, or their presence in the mandible. Developmental abnormalities of the CT include; rostral positioning of the upper CT rows in relation to the lower CT rows--with resultant development of focal overgrowths on the upper 06s and the lower 11s. Displaced CT develop overgrowths on unopposed aspects of the teeth and also develop periodontal disease in the inevitable abnormal spaces (diastemata) that are present between displaced and normal teeth. Diastemata of the CT due to excessive developmental spacing between the CT or to inadequate compression of the CT rows is a common but under diagnosed problem in many horses and causes very painful periodontal disease and quidding. Supernumerary CT mainly occur at the caudal aspect of the CT rows and periodontal disease commonly occurs around these teeth. Eruption disorders of CT include prolonged retention of remnants of deciduous CT ("caps

  4. Graphitic polymer nanocomposites: Wear performance and wear debris analysis

    NASA Astrophysics Data System (ADS)

    Liu, Tian

    With the addition of appropriate nanofillers, nanocomposites have been shown to be an effective avenue to achieve a multitude of enhanced properties, even extending to multi-functionalities not normally considered possible for conventional polymer materials. However, the structure and properties of polymeric nanocomposites can be influenced by some environmental factors in practical use, such as wear and temperature, due to the nature of viscoelasticity of polymer matrix. The large interfacial areas exist between matrix and nanofillers are also susceptible to the wear/temperature-related changes. In this work, I was devoted to developing high wear and/or thermal performance graphitic nanofiller reinforced high density polyethylene (HDPE) composites. Two critical issues, including appropriate filler-matrix interactions and proper dispersion of the nano-reinforcement, were addressed through the effective nanofiller surface modification. Wear, thermal and mechanical properties of the resultant nanocomposites were systematically investigated. Meanwhile, the wear debris generated on the sliding surface of composite materials was analyzed morphologically and quantitatively. In particular, the research regarding the possibility of determining the effects of wear and thermal processes on the nanocomposites by detecting dielectric signals over the lifetime of polymeric materials was conducted. Correlations that exist between effects of wear or thermal processes and dielectric properties of the nanocomposites were then explored. Based on the studies of HDPE nanocomposites, high quality ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite reinforced by graphitic nanofillers was finally extended in this thesis. UHMWPE is an extremely viscous polymer and thus cannot be processed conventionally, typically resulting in dispersion issues far worse than that of other composite systems. The research presented aims at solving the issue by using ultrasonication-assisted melt

  5. Tooth wear and the role of salivary measures in general practice patients

    PubMed Central

    Rothen, Marilynn; Scott, JoAnna; Cunha-Cruz, Joana

    2014-01-01

    Objectives The goal of this study was to investigate the association between tooth wear and salivary measures in a random sample of patients from practices of dentist members of a practice-based research network. Materials and methods Patients completed a questionnaire on oral self-care, health, dietary habits, medications, and socio-demographic variables. Six salivary characteristics (consistency, resting salivary flow, resting salivary pH, stimulated salivary flow, stimulated salivary pH, and buffering capacity) were measured, and a dental examination included categorizing patients according to the dentist’s judgment of the degree of tooth wear (i.e., none/minimal, some, or severe/extreme). Bivariate and multinomial logistic regression models were used to relate salivary characteristics and other factors to the outcome of tooth wear. Results Data are reported from 1,323 patients (age range 16–97 years) from 61 practices. Patient age, gender, number of teeth, and perception of dry mouth were associated with tooth wear, but salivary and dietary factors were either weakly or not related. Conclusions The findings of this cross-sectional assessment suggest that using these salivary tests and dietary assessments in real-life clinical settings is unlikely to be useful in assessing tooth wear risk. Suggestions are offered about risk assessment for tooth wear. Clinical relevance Assessing a dental patient’s risk of tooth wear using salivary measures and dietary assessments as described is not recommended for general dental practice until stronger evidence exists indicating its utility. PMID:24647789

  6. Dental crowns

    MedlinePlus

    ... off when the child loses the baby tooth. Metal crowns: Hold up to chewing and teeth grinding ... porcelain crowns: Wear down opposing teeth more than metal crowns Match the color of other teeth May ...

  7. Dental sepsis.

    PubMed

    Mueller, P O; Lowder, M Q

    1998-08-01

    Dental sepsis or periapical abscess formation constitutes a large percentage of dental conditions that afflict horses. Dental sepsis occurs when the pulp chamber of the tooth is exposed to the oral cavity or external environment, allowing bacterial localization with resulting infection. Although acute, primary, septic pulpitis in horses is rare, dental sepsis often results from colonization of the pulp chamber with pathogenic bacteria secondary to maleruption or impaction of teeth with secondary alveolar bone lysis, primary fractures of the tooth, mandible, or maxilla, periodontal disease, or infundibular necrosis. The sequela to pulpal infection are extensions into the periradicular tissues and mandibular or maxillary periapical abscess formation.

  8. They shall wear fringes.

    PubMed

    Sugar, M

    1999-01-01

    The multiple functions of clothes include utility, protection, rivalry, disguise, camouflage, display for seduction purposes, aggression, totemism, and status. Here the focus is on a decorative and distinctive hierarchical aspect of ancient dress, the tsitsit or fringes, whose original function is long absent, but that has endured for 3,500 years in Judaism. The beginning of their use beyond the totemic appears related to issues of changing identity from slavery to liberty, endowing noble status, exhibitionism, a symbol of identity, identification with the aggressor, a talisman, and potency. It is conceptualized that they became a symbol, or a specifier, that helped promote group cohesion in ex-slaves who were frightened, dependent, anxious, and not hopeful about their future. The tsitsit aided the development of a new identity and made all Israelites equal and noble to the observer. The durability of this symbol to the present is evident in its daily wear, as an accompaniment to daily prayers, as well as in its use as a burial shroud for males. It appears that the tsitsit have additional multiple functions. These are the promise of oral and genital satisfaction, and the pleasure of the after-life, superego warnings and control of sexual impulses, protection, survival value, and affirmation. Since they offer sublimation with acceptable gratification of instincts, the tsitsit have become ritualized and endure.

  9. Prediction of Polyethylene Wear Rates from Gait Biomechanics and Implant Positioning in Total Hip Replacement.

    PubMed

    Ardestani, Marzieh M; Amenábar Edwards, Pedro P; Wimmer, Markus A

    2017-08-01

    wear differences are caused by a combination of wear factors rather than single variables. The linear discriminant analysis model correctly predicted the level of wear in 80% of patients with low wear, 87% of subjects with moderate wear, and 73% of subjects with high wear based on a combination of gait and positioning variables. For every wear level, multiple linear and nonlinear regression showed strong associations between gait biomechanics, implant positioning, and wear rate, with the nonlinear model having a higher prediction accuracy. Flexion-extension ROM and hip moments in the sagittal and transverse planes explained 42% to 60% of wear rate while positioning factors, (such as cup medialization and cup inclination angle) explained only 10% to 33%. Patient-specific wear rates are associated with patients' gait patterns. Gait pattern has a greater influence on wear than component positioning for traditional metal-on-polyethylene bearings. The consideration of individual gait bears potential to further reduce implant wear in THR. In the future, a predictive wear model may identify individual, modifiable wear factors for modern materials.

  10. Hardfacing fights wear in oil sands operation

    SciTech Connect

    Llewellyn, R.; Tuite, C.

    1995-03-01

    Wear attack is responsible for high production losses and over $40 million per year in equipment repairs and replacement costs at Syncrude`s synthetic crude oil plant near Fort McMurray in Northern Alberta. Most of this damage is caused by the fine quartz particle constituents which predominate in oil sands. It occurs in a multiplicity of forms which can be classified into three primary mechanisms: Sliding abrasive wear and sporadic impact, which affects mainly mining equipment; Slurry abrasion and erosion, which occur in bitumen extraction, separation plants, and in tailings lines; and High-temperature erosion, which is often augmented by corrosion in bitumen upgrading operations. Process streams in this area also contain fine coke particles and catalyst debris. The paper gives an overview of Syncrude`s operations in mining, extraction, and upgrading, then describes the following: wear materials and protection systems, surface engineering systems, weld deposited hardfacing, benefits, surface modification system experience, thermal spray coating experience, disk centrifuge bowls, investigation of plasma arc spraying, and combating pump erosion.

  11. Intelligent Detection of Drill Wear

    NASA Astrophysics Data System (ADS)

    Liu, T. I.; Chen, W. Y.; Anatharaman, K. S.

    1998-11-01

    Backpropagation neural networks (BPNs) were used for on-line detection of drill wear. The neural network consisted of three layers: input, hidden, and output. The input vector comprised drill size, feed rate, spindle speed, and eight features obtained by processing the thrust and torque signals. The output was the drill wear state which either usable or failure. Drilling experiments with various drill sizes, feed rates and spindle speeds were carried out. The learning process was performed effectively by utilising backpropagation with smoothing and an activation function slope. The on-line detection of drill wear states using BPNs achieved 100% reliability even when the drill size, feed rate and spindle speed were changed. In other words, the developed on-line drill wear detection systems have very high robustness and hence can be used in very complex production environments, such as flexible manufacturing systems.

  12. Nanoscale friction and wear maps.

    PubMed

    Tambe, Nikhil S; Bhushan, Bharat

    2008-04-28

    Friction and wear are part and parcel of all walks of life, and for interfaces that are in close or near contact, tribology and mechanics are supremely important. They can critically influence the efficient functioning of devices and components. Nanoscale friction force follows a complex nonlinear dependence on multiple, often interdependent, interfacial and material properties. Various studies indicate that nanoscale devices may behave in ways that cannot be predicted from their larger counterparts. Nanoscale friction and wear mapping can help identify some 'sweet spots' that would give ultralow friction and near-zero wear. Mapping nanoscale friction and wear as a function of operating conditions and interface properties is a valuable tool and has the potential to impact the very way in which we design and select materials for nanotechnology applications.

  13. DENTAL CARIES

    PubMed Central

    Boucher, George O.

    1951-01-01

    The most generally accepted theory as to the cause of dental caries is that certain bacteria in the mouth, in the presence of fermentable sugars, cause the formation of acids which in turn decalcify teeth. Physicians may help reduce the incidence of caries by recommending elimination of refined sugars from the diet, or at least control of the amount consumed. Cleaning the teeth with a well designed tooth brush after each meal will to a certain extent mechanically remove the fermentable sugar and debris from the teeth. One step further in oral hygiene that may be beneficial is to use a dentifrice with 5 per cent dibasic ammonium phosphate and 3 per cent urea to reduce the formation of acid. Anything that will increase salivation will aid in buffering any acids that may be present. A 2 per cent solution of sodium fluoride applied to the thoroughly dried “intact” enamel surface may prevent caries. Sodium fluoride added to drinking water to a concentration of 1 part per million is utilized by the body in formation of an enamel that is particularly resistant to caries. PMID:14801729

  14. Low-shrink monomers for dental restorations.

    PubMed

    Palin, W M; Fleming, G J P

    2003-04-01

    The main disadvantages of resin-based composites (RBCs) for use in load-bearing posterior restorations include the polymerization shrinkage following curing and inadequate wear resistance in service. These properties are largely influenced by the monomer system and research is currently being undertaken to decrease polymerization shrinkage and improve resin wear characteristics in an attempt to increase RBC restoration longevity. The scope of the current review will identify the development of resin-based restoratives, indicating the reported advantages and disadvantages of resin types routinely used in dental practice today and review the most recent advancements in resin technology.

  15. Sour sweets and acidic beverage consumption are risk indicators for dental erosion.

    PubMed

    Søvik, Jenny Bogstad; Skudutyte-Rysstad, Rasa; Tveit, Anne B; Sandvik, Leiv; Mulic, Aida

    2015-01-01

    This study aimed to investigate the association between dental erosive wear and potential background, behavioural and dietary risk indicators and to assess whether there is a dose-response relationship between the level of acidic beverage consumption and dental erosive wear among adolescents. Of 846 adolescents (aged 16-18 years) scheduled for dental recall examinations, 795 (94%) accepted to participate. All participants completed a self-administered questionnaire regarding their background (gender and age), tooth-brushing frequency and dietary habits (the amount and frequency of acidic food and beverage consumption as well as the chosen method and manner of consuming acidic drinks). The association between the presence of erosive lesions and the possible risk indicators was assessed by logistic regression analyses. Of all participants examined, 37% had ≥3 surfaces with dental erosions and were considered to be affected individuals. In the present study, multivariate logistic analyses revealed a significant association between the dental erosive wear and high consumption of sour sweets and sports drinks. The tooth-brushing frequency was not significantly associated with dental erosive wear. Additionally, to the best of our knowledge, the results are the first to indicate a dose-response relationship between the daily consumption of acidic drinks and dental erosive wear.

  16. Wear resistance properties of austempered ductile iron

    NASA Astrophysics Data System (ADS)

    Lerner, Y. S.; Kingsbury, G. R.

    1998-02-01

    A detailed review of wear resistance properties of austempered ductile iron (ADI) was undertaken to examine the potential applications of this material for wear parts, as an alternative to steels, alloyed and white irons, bronzes, and other competitive materials. Two modes of wear were studied: adhesive (frictional) dry sliding and abrasive wear. In the rotating dry sliding tests, wear behavior of the base material (a stationary block) was considered in relationship to countersurface (steel shaft) wear. In this wear mode, the wear rate of ADI was only one-fourth that of pearlitic ductile iron (DI) grade 100-70-03; the wear rates of aluminum bronze and leaded-tin bronze, respectively, were 3.7 and 3.3 times greater than that of ADI. Only quenched DI with a fully martensitic matrix slightly outperformed ADI. No significant difference was observed in the wear of steel shafts running against ADI and quenched DI. The excellent wear performance of ADI and its countersurface, combined with their relatively low friction coefficient, indicate potential for dry sliding wear applications. In the abrasive wear mode, the wear rate of ADI was comparable to that of alloyed hardened AISI 4340 steel, and approximately one-half that of hardened medium-carbon AISI 1050 steel and of white and alloyed cast irons. The excellent wear resistance of ADI may be attributed to the strain-affected transformation of high-carbon austenite to martensite that takes place in the surface layer during the wear tests.

  17. Wear behavior of human enamel against lithium disilicate glass ceramic and type III gold.

    PubMed

    Lee, Ahreum; Swain, Michael; He, Lihong; Lyons, Karl

    2014-12-01

    The wear behavior of human enamel that opposes different prosthetic materials is still not clear. The purpose of this in vitro study was to investigate and compare the friction and wear behavior of human tooth enamel that opposes 2 indirect restorative materials: lithium disilicate glass ceramic and Type III gold. Friction-wear tests on human enamel (n=5) that opposes lithium disilicate glass ceramic (n=5) and Type III gold (n=5) were conducted in a ball-on-flat configuration with a reciprocating wear testing apparatus. The wear pairs were subjected to a normal load of 9.8 N, a reciprocating amplitude of approximately 200 μm, and a reciprocating frequency of approximately 1.6 Hz for up to 1100 cycles per test under distilled water lubrication. The frictional force of each cycle was recorded, and the corresponding friction coefficient for different wear pairs was calculated. After wear testing, the wear scars on the enamel specimens were examined under a scanning electron microscope. Type III gold had a significantly lower steady-state friction coefficient (P=.009) and caused less wear damage on enamel than lithium disilicate glass ceramic. Enamel that opposed lithium disilicate glass ceramic exhibited cracks, plow furrows, and surface loss, which indicated abrasive wear as the prominent wear mechanism. In comparison, the enamel wear scar that opposed Type III gold had small patches of gold smear adhered to the surface, which indicated a predominantly adhesive wear mechanism. A lower friction coefficient and better wear resistance were observed when human enamel was opposed by Type III gold than by lithium disilicate glass ceramic in vitro. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  18. Gaze Tracking System for User Wearing Glasses

    PubMed Central

    Gwon, Su Yeong; Cho, Chul Woo; Lee, Hyeon Chang; Lee, Won Oh; Park, Kang Ryoung

    2014-01-01

    Conventional gaze tracking systems are limited in cases where the user is wearing glasses because the glasses usually produce noise due to reflections caused by the gaze tracker's lights. This makes it difficult to locate the pupil and the specular reflections (SRs) from the cornea of the user's eye. These difficulties increase the likelihood of gaze detection errors because the gaze position is estimated based on the location of the pupil center and the positions of the corneal SRs. In order to overcome these problems, we propose a new gaze tracking method that can be used by subjects who are wearing glasses. Our research is novel in the following four ways: first, we construct a new control device for the illuminator, which includes four illuminators that are positioned at the four corners of a monitor. Second, our system automatically determines whether a user is wearing glasses or not in the initial stage by counting the number of white pixels in an image that is captured using the low exposure setting on the camera. Third, if it is determined that the user is wearing glasses, the four illuminators are turned on and off sequentially in order to obtain an image that has a minimal amount of noise due to reflections from the glasses. As a result, it is possible to avoid the reflections and accurately locate the pupil center and the positions of the four corneal SRs. Fourth, by turning off one of the four illuminators, only three corneal SRs exist in the captured image. Since the proposed gaze detection method requires four corneal SRs for calculating the gaze position, the unseen SR position is estimated based on the parallelogram shape that is defined by the three SR positions and the gaze position is calculated. Experimental results showed that the average gaze detection error with 20 persons was about 0.70° and the processing time is 63.72 ms per each frame. PMID:24473283

  19. Tool Wear in Friction Drilling

    SciTech Connect

    Miller, Scott F; Blau, Peter Julian; Shih, Albert J.

    2007-01-01

    This study investigated the wear of carbide tools used in friction drilling, a nontraditional hole-making process. In friction drilling, a rotating conical tool uses the heat generated by friction to soften and penetrate a thin workpiece and create a bushing without generating chips. The wear of a hard tungsten carbide tool used for friction drilling a low carbon steel workpiece has been investigated. Tool wear characteristics were studied by measuring its weight change, detecting changes in its shape with a coordinate measuring machine, and making observations of wear damage using scanning electron microscopy. Energy dispersive spectroscopy was applied to analyze the change in chemical composition of the tool surface due to drilling. In addition, the thrust force and torque during drilling and the hole size were measured periodically to monitor the effects of tool wear. Results indicate that the carbide tool is durable, showing minimal tool wear after drilling 11000 holes, but observations also indicate progressively severe abrasive grooving on the tool tip.

  20. Gear Tooth Wear Detection Algorithm

    NASA Technical Reports Server (NTRS)

    Delgado, Irebert R.

    2015-01-01

    Vibration-based condition indicators continue to be developed for Health Usage Monitoring of rotorcraft gearboxes. Testing performed at NASA Glenn Research Center have shown correlations between specific condition indicators and specific types of gear wear. To speed up the detection and analysis of gear teeth, an image detection program based on the Viola-Jones algorithm was trained to automatically detect spiral bevel gear wear pitting. The detector was tested using a training set of gear wear pictures and a blind set of gear wear pictures. The detector accuracy for the training set was 75 percent while the accuracy for the blind set was 15 percent. Further improvements on the accuracy of the detector are required but preliminary results have shown its ability to automatically detect gear tooth wear. The trained detector would be used to quickly evaluate a set of gear or pinion pictures for pits, spalls, or abrasive wear. The results could then be used to correlate with vibration or oil debris data. In general, the program could be retrained to detect features of interest from pictures of a component taken over a period of time.

  1. Dental therapists in general dental practices: an economic evaluation.

    PubMed

    Beazoglou, Tryfon J; Lazar, Vickie F; Guay, Albert H; Heffley, Dennis R; Bailit, Howard L

    2012-08-01

    Dental access disparities are well documented and have been recognized as a national problem. Their major cause is the lack of reasonable Medicaid reimbursement rates for the underserved. Specifically, Medicaid reimbursement rates for children average 40 percent below market rates. In addition, most state Medicaid programs do not cover adults. To address these issues, advocates of better oral health for the underserved are considering support for a new allied provider--a dental therapist--capable of providing services at a lower cost per service and in low-income and rural areas. Using a standard economic analysis, this study estimated the potential cost, price, utilization, and dentist's income effects of dental therapists employed in general dental practices. The analysis is based on national general dental practice data and the broadest scope of responsibility for dental therapists that their advocates have advanced, including the ability to provide restorations and extractions to adults and children, training for three years, and minimum supervision. Assuming dental therapists provide restorative, extraction, and pulpal services to patients of all ages and dental hygienists continue to deliver all hygiene services, the mean reduction in a general practice costs ranges between 1.57 and 2.36 percent. For dental therapists treating children only, the range is 0.31 to 0.47 percent. The effects on price and utilization are even smaller. In addition, the effects on most dentists' gross income, hours of work, and net income are negative. The estimated economic impact of dental therapists in the United States on private dental practice is very limited; therefore, the demand for dental therapists by private practices also would probably be very limited.

  2. Fractal characterization of wear-erosion surfaces

    SciTech Connect

    Rawers, J.; Tylczak, J.

    1999-12-01

    Wear erosion is a complex phenomenon resulting in highly distorted and deformed surface morphologies. Most wear surface features have been described only qualitatively. In this study wear surfaces features were quantified using fractal analysis. The ability to assign numerical values to wear-erosion surfaces makes possible mathematical expressions that will enable wear mechanisms to be predicted and understood. Surface characterization came from wear-erosion experiments that included varying the erosive materials, the impact velocity, and the impact angle. Seven fractal analytical techniques were applied to micrograph images of wear-erosion surfaces. Fourier analysis was the most promising. Fractal values obtained were consistent with visual observations and provided a unique wear-erosion parameter unrelated to wear rate. In this study stainless steel was evaluated as a function of wear erosion conditions.

  3. Three-dimensional in vitro measurements of tooth wear using fluoridated dentifrices.

    PubMed

    Al-Mashhadani, A; Plygkos, I; Bozec, L; Rodriguez, J M

    2016-09-01

    The aim of this study was to compare differences in wear of human enamel and dentine in vitro using a 3D measurement method comparing silica versus non-silica containing fluoridated dentifrices (Colgate Total(™) [CT] or Fluor Protector Gel(™) [FPG]). Mounted native enamel (n = 36) and polished dentine (n = 36) samples were subjected to 10 wear cycles. Each cycle consisted of: (1) 1 hour remineralization in artificial saliva (AS); (2) 10 minute erosion (0.3% citric acid; pH = 2.8); (3) 2 minute toothbrush abrasion in AS (G1, control) or a slurry of 3:1 by weight of AS:dentifrice (G2 = CT; G3 = FPG) under a load of 2 N. Each group contained 12 enamel and 12 dentine samples. Paired pre- and post-wear scans made with a contacting scanner were digitally superimposed using ball bearings as datum. Mean and (SD) enamel wear was G1 = 21.9 μm (6.4); G2 = 15.2 μm (2.8); G3 = 16.9 μm (3.2). Enamel wear was not different between dentifrices (p = 0.99). Both dentifrices resulted in less enamel wear compared to the control (p < 0.05). Dentine wear was G1 = 41.3 μm (8.1); G2 = 29.1 μm (4.4); G3 = 22.1 μm (3.5). Differences in measurements were observed between dentifrices and control (p < 0.05) and between dentifrices (p = 0.014) with FPG showing less dentine wear than CT. FPG offered protection against erosive/abrasive tooth wear in dentine compared to CT. FPG did not offer such protective effect on enamel wear. © 2015 Australian Dental Association.

  4. Three years in vivo wear: core-ceramic, veneers, and enamel antagonists.

    PubMed

    Esquivel-Upshaw, Josephine F; Rose, William F; Barrett, Allyson A; Oliveira, Erica R; Yang, Mark C K; Clark, Arthur E; Anusavice, Kenneth J

    2012-06-01

    Test the hypotheses that there are equivalent wear rates for enamel-versus-enamel and ceramic-versus-enamel, analyzing the in vivo wear of crown ceramics, their natural enamel antagonists, and the corresponding two contralateral teeth; and, that bite force does not correlate with the wear. A controlled, clinical trial was conducted involving patients needing full coverage crowns opposing enamel antagonists. Bite forces were measured using a bilateral gnathodynamometer. Single-unit restorations of metal/ceramic (Argedent 62, Argen Corp/IPS d.SIGN veneer); or, core-ceramic/veneer from either, Empress2/Eris, or e.max Press core/e.max Ceram glaze (ceramics: Ivoclar Vivadent, USA) were randomly assigned, fabricated and cemented. Impressions were made of the ceramic crowns, as well as each maxillary and mandibular quadrant at one week (baseline) and one, two and three years. Resulting models were scanned (3D laser scanner). Maximum wear was calculated by superimposing baseline with annual images. There were a total of thirty-six crowns required for thirty-one patients. Each restoration had three associated enamel teeth: crown, (1) antagonist, (2) contralateral and (3) contralateral-antagonist. SAS PROC MIXED (α=0.05) indicated no statistical significance for mean maximum wear among crown ceramics, enamel antagonists and contralaterals. However, enamel wear was statistically significant in relation to intraoral location (p=0.04) and among years (p<0.02). Analyzed alone, the enamel contralateral-antagonist exhibited significantly greater wear (p<0.001). Considering all wear sites, there was no correlation with bite force (p=0.15). The ceramics and their antagonists exhibited in vivo wear rates within the range of normal enamel. Future studies should examine the wear implications of the contralateral-antagonist enamel. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  5. Wear patterns on tibial plateau from varus osteoarthritic knees.

    PubMed

    Moschella, D; Blasi, A; Leardini, A; Ensini, A; Catani, F

    2006-02-01

    The knowledge of cartilage wear patterns at the medial tibial plateau is important to understand the main causes of arthritis in varus knees. The most important factors influencing knee arthritis in fact seem to be the severity of the degenerative changes determined by the lower limb mechanical axis and the abnormal knee joint kinematics which frequently results from dysfunction of the anterior cruciate ligament. We studied the wear patterns of cartilage damage in 70 medial tibial plateaus resected at operation during total knee arthroplasty indicated for varus osteoarthritic knee. Anterior cruciate ligament and medial meniscus integrity was assessed intra-operatively. Calibrated digital images were used to measure the wear patterns with a standard software tool. The medial compartment of the tibial plateau was divided into six zones, and the amount of cartilage and bone destruction in each zone was classified into two grades. The wear pattern was found to be highly dependent upon knee varus deformity (Mann Whitney P<0.001) and anterior cruciate ligament integrity (Friedman P<0.0005). Anterior cruciate ligament was found intact in 35.7% of the cases. Wear patterns on intact anterior cruciate ligament knees occurred in the central to medial aspect of the tibial plateau. Anterior cruciate ligament deficient knees had significantly larger wear patterns anteriorly and posteriorly in the most medial region of the medial plateau. These observations suggest altered joint mechanics exist in anterior cruciate ligament deficient varus knees, which would worsen cartilage degeneration and osteoarthritis progression.

  6. Factors affecting polyethylene wear in total knee arthroplasty.

    PubMed

    Kuster, Markus S; Stachowiak, Gwidon W

    2002-02-01

    A complication of total knee arthroplasty (TKA) is fatigue-type wear, which can destroy a tibial inlay in <10 years. This deleterious wear mechanism occurs during cyclic loading if the yield stress of polyethylene is exceeded. Because increased stress on and within the polyethylene inlay is associated with increased wear, it is important to reduce the inlay stress by either activity restrictions or conformity changes of design. All stress parameters are more sensitive to conformity changes (eg, design changes) than to load changes (eg, activity restrictions). However, the reduction of stress on and within the polyethylene through increased conformity will increase the stress at the tibial fixation interfaces. An attempt was made to solve this problem with the introduction of mobile-bearing designs. Many mobile-bearing designs exist with good long-term results. One important difference among the various designs is the amount of flexion range with full conformity between the femoral component and the tibial inlay. Although a single radius design reduces polyethylene stress throughout the flexion range, it may be disadvantageous for a revision design to intraoperatively adapt to different degrees of constraint. Aseptic loosening and osteolysis due to small abrasive and adhesive wear particles have also been reported as a cause of failure. The design and material parameters affecting polyethylene wear in TKAs, as well as the potential detrimental effects of wear particle size, are the key issues in defining the life of a TKA.

  7. A life course approach to assessing causes of dental caries experience: the relationship between biological, behavioural, socio-economic and psychological conditions and caries in adolescents.

    PubMed

    Nicolau, B; Marcenes, W; Bartley, M; Sheiham, A

    2003-01-01

    The objective of this study was to further elucidate the relationship between relevant biological, behavioural, socio-economic and psychological conditions, experienced in very early life and along the life course, and dental caries experience using the life course approach. A two-phase study was carried out in Brazil. In the first phase, 652 13-year-olds were clinically examined and interviewed. In the second phase, 330 families were randomly selected for interview to collect information on the teenagers' early years of life. Clinical assessment included dental caries, periodontal and traumatic dental injury status. The data analysis involved multiple logistic regression analysis. Adolescents born in a non-brick house, those with a low birth weight and those who were the second or later child in the family were statistically significantly more likely to have a high DMF-T. In conclusion, the results of this study show that there is an association between socio-economic and biological factors in very early life and levels of caries in adolescents. Copyright 2003 S. Karger AG, Basel

  8. The wear of cross-linked polyethylene against itself.

    PubMed

    Joyce, T J; Ash, H E; Unsworth, A

    1996-01-01

    Cross-linked polyethylene (XLPE) may have an application as a material for an all-plastic surface replacement finger joint. It is inexpensive, biocompatible and can be injection-moulded into the complex shapes that are found on the ends of the finger bones. Further, the cross-linking of polyethylene has significantly improved its mechanical properties. Therefore, the opportunity exists for an all-XLPE joint, and so the wear characteristics of XLPE sliding against itself have been investigated. Wear tests were carried out on both reciprocating pin-on-plate machines and a finger function simulator. The reciprocating pin-on-plate machines had pins loaded at 10 N and 40 N. All pin-on-plate tests show wear factors from the plates very much greater than those of the pins. After 349 km of sliding, a mean wear factor of 0.46 x 10(-6) mm3/N m was found for the plates compared with 0.021 x 10(-6) mm3/N m for the pins. A fatigue mechanism may be causing this phenomenon of greater plate wear. Tests using the finger function simulator give an average wear rate of 0.22 x 10(-6) mm3/N m after 368 km. This sliding distance is equivalent to 12.5 years of use in vivo. The wear factors found were comparable with those of ultra-high molecular weight polyethylene (UHMWPE) against a metallic counterface and, therefore, as the loads across the finger joint are much less than those across the knee or the hip, it is probable that an all-XLPE finger joint will be viable from a wear point of view.

  9. Wear Assessment of Conical Pick used in Coal Cutting Operation

    NASA Astrophysics Data System (ADS)

    Dewangan, Saurabh; Chattopadhyaya, Somnath; Hloch, Sergej

    2015-09-01

    Conical pick is a widely used tool for cutting coal in mines. It has a cemented carbide tip inserted in a steel body. Cemented carbide has been in use for many years for coal/rock cutting because it has the optimum combination of hardness, toughness and resistance against abrasive wear. As coal/rock is a heterogeneous substance, the cutting tool has to undergo various obstructions at the time of excavation that cause the tool to wear out. The cracks and fractures developing in the cemented carbide limit the life of the tool. For a long time, different wear mechanisms have been studied to develop improved grades of cemented carbide with high wear resistance properties. The research is still continuing. Moreover, due to the highly unpredictable nature of coal/rock, it is not easy to understand the wear mechanisms. In the present work, an attempt has been made to understand the wear mechanisms in four conical picks, which were used in a continuous miner machine for underground mining of coal. The wearing pattern of the conical pick indicates damage in its cemented carbide tip as well as the steel body. The worn out parts of the tools have been critically examined using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) point analysis. Mainly four types of wear mechanisms, namely, coal/rock intermixing, plastic deformation, rock channel formation and crushing and cracking, have been detected. The presence of coal/rock material and their respective concentrations in the selected area of worn out surface were observed using the spectra generated by EDX analysis.

  10. Dental Hygienist.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document, which is designed for use in developing a tech prep competency profile for the occupation of dental hygienist, lists technical competencies and competency builders for 13 units pertinent to the health technologies cluster in general and 9 units specific to the occupation of dental hygienist. The following skill areas are covered in…

  11. Dental Hygienist.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document, which is designed for use in developing a tech prep competency profile for the occupation of dental hygienist, lists technical competencies and competency builders for 13 units pertinent to the health technologies cluster in general and 9 units specific to the occupation of dental hygienist. The following skill areas are covered in…

  12. Wear properties of a novel resin composite compared to human enamel and other restorative materials.

    PubMed

    D'Arcangelo, C; Vanini, L; Rondoni, G D; Pirani, M; Vadini, M; Gattone, M; De Angelis, F

    2014-01-01

    The purpose of this in vitro study was to compare the two-body wear resistance of human enamel, a pressable glass-ceramic (Imagine PressX), a type 3 gold alloy (Aurocast8), three resins composites currently available on the market (Enamel plus HRi, Filtek Supreme XTE, Ceram.X duo), and one recently introduced resin composite (Enamel plus HRi-Function). Resin composites were tested after simple light curing and after a further heat polymerization cycle. Ten cylindrical specimens (7 mm in diameter) were manufactured with each dental material according to standard laboratory procedures. Ten flat enamel specimens were obtained from freshly extracted human molars and included in the control group. All samples were subjected to a two-body wear test in a dual-axis chewing simulator over up to 120,000 loading cycles, against yttria stabilized tetragonal zirconia polycrystal cusps. Wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed using one-way analysis of variance (ANOVA) (wear depth and volume loss) and Kruskal-Wallis one-way ANOVA on ranks (antagonist wear). Heat-cured HRi function and Aurocast8 showed similar mean values for wear depth and volumetric loss, and their results did not statistically differ in comparison with the human enamel.

  13. Age estimation of an Indian population by using the Kim's scoring system of occlusal tooth wear

    PubMed Central

    Telang, Lahari A.; Patil, Karthikeya; Mahima, V. G.

    2014-01-01

    Context: Age is one of the prime factors employed to establish the identity of an individual and the use of teeth for this purpose has been considered reliable. Tooth wear is widely accepted as a physiological consequence of aging and evaluation of tooth wear can be a simple and convenient tool to estimate age in adults. Aims: The present study was conducted to record the degree of tooth wear among Indian adults and to estimate their ages from the degree of tooth wear based on Kim's scoring system. Materials and Methods: Dental stone casts of 120 participants were used to assess the degree of occlusal tooth wear based on the criteria given by Kim et al. Statistical Analysis Used: The age of all subjects was estimated based on these scores using multiple regression analysis function. Results: The degree of tooth wear showed a significant positive correlation with age in each and every examined tooth of both males and females. The predicted age was within ± 5 years of actual age in 70% of males and 68.3% females, and within ± 3 years of actual age in 50% of males and 50.1% of females. Conclusions: Kim's scoring system has proven to be a useful tool in estimation of age using occlusal wear in an Indian population with a high level of accuracy in adults. PMID:24695780

  14. Age estimation of an Indian population by using the Kim's scoring system of occlusal tooth wear.

    PubMed

    Telang, Lahari A; Patil, Karthikeya; Mahima, V G

    2014-01-01

    Age is one of the prime factors employed to establish the identity of an individual and the use of teeth for this purpose has been considered reliable. Tooth wear is widely accepted as a physiological consequence of aging and evaluation of tooth wear can be a simple and convenient tool to estimate age in adults. The present study was conducted to record the degree of tooth wear among Indian adults and to estimate their ages from the degree of tooth wear based on Kim's scoring system. Dental stone casts of 120 participants were used to assess the degree of occlusal tooth wear based on the criteria given by Kim et al. The age of all subjects was estimated based on these scores using multiple regression analysis function. The degree of tooth wear showed a significant positive correlation with age in each and every examined tooth of both males and females. The predicted age was within ± 5 years of actual age in 70% of males and 68.3% females, and within ± 3 years of actual age in 50% of males and 50.1% of females. Kim's scoring system has proven to be a useful tool in estimation of age using occlusal wear in an Indian population with a high level of accuracy in adults.

  15. Dental Implants.

    PubMed

    Zohrabian, Vahe M; Sonick, Michael; Hwang, Debby; Abrahams, James J

    2015-10-01

    Dental implants restore function to near normal in partially or completely edentulous patients. A root-form implant is the most frequently used type of dental implant today. The basis for dental implants is osseointegration, in which osteoblasts grow and directly integrate with the surface of titanium posts surgically embedded into the jaw. Radiologic assessment is critical in the preoperative evaluation of the dental implant patient, as the exact height, width, and contour of the alveolar ridge must be determined. Moreover, the precise locations of the maxillary sinuses and mandibular canals, as well as their relationships to the site of implant surgery must be ascertained. As such, radiologists must be familiar with implant design and surgical placement, as well as augmentation procedures utilized in those patients with insufficient bone in the maxilla and mandible to support dental implants.

  16. Associated factors of tooth wear among Malaysian 16-year-olds: a case-control study in Kota Bharu, Kelantan.

    PubMed

    Saerah, N B; Mastura, N; bin Ismail, A R; Sadiq, M A

    2012-03-01

    To determine the associated factors of tooth wear (TW) among 16-year-old school children. A random selection of secondary school children from 8 government secondary schools in Kota Bharu, Kelantan, Malaysia, participated in this case-control study. The Smith and Knight Tooth Wear Index and WHO criteria were used to chart tooth wear and dental caries respectively. Saliva analyses used standards recommended by GC Asia Dental. Self-administered questionnaire provided socio-demographic profile of the family, general knowledge of tooth wear, oral hygiene, food and drinks practices and other associated variables for tooth wear. Analysis using multiple logistic regression was performed. Of the 576 children sampled, 40% of the 460 controls were male as were 57% of the 116 in the case group. Multivariate analysis showed gender, monthly household income, carbonated drinks, caries experience, pool swimming, duration of intake of orange juice and hydration rate and viscosity were significantly associated with wear. The factors associated with tooth wear were similar to those encountered in other studies. Oral health promotion activities should emphasise those factors which can be changed. The erosive potential of some foods and drinks require further investigation.

  17. TOPICAL REVIEW: Tribology of dental materials: a review

    NASA Astrophysics Data System (ADS)

    Zhou, Z. R.; Zheng, J.

    2008-06-01

    The application of tribology in dentistry is a growing and rapidly expanding field. Intensive research has been conducted to develop an understanding of dental tribology for successful design and selection of artificial dental materials. In this paper, the anatomy and function of human teeth is presented in brief, three types of current artificial dental materials are summarized, and their advantages and disadvantages, as well as typical clinical applications, are compared based on the literature. Possible tribological damage of tooth structure, which is induced by complex interfacial motion, and friction-wear test methods are reported. According to results obtained by the authors and from the literature, the main progress in the area of dental tribology on both natural teeth and artificial dental materials is reviewed. Problems and challenges are discussed and future research directions for dental tribology are recommended.

  18. Ignition of a Combustible Atmosphere by Incandescent Carbon Wear Particles

    NASA Technical Reports Server (NTRS)

    Buckley, Donald H.; Swikert, Max A.; Johnson, Robert L.

    1960-01-01

    A study was made to determine whether carbon wear particles from carbon elements in sliding contact with a metal surface were sufficiently hot to cause ignition of a combustible atmosphere. In some machinery, electric potential differences and currents may appear at the carbon-metal interface. For this reason the effect of these voltages and currents on the ability of carbon wear particles to cause ignition was evaluated. The test specimens used in the investigation were carbon vanes taken from a fuel pump and flat 21-inch-diameter 2 metal disks (440-C stainless steel) representing the pump housing. During each experiment a vane was loaded against a disk with a 0.5-pound force, and the disk was rotated to give a surface speed of 3140 feet per minute. The chamber of the apparatus that housed the vane and the disk was filled with a combustible mixture of air and propane. Various voltages and amperages were applied across the vane-disk interface. Experiments were conducted at temperatures of 75, 350, 400, and 450 F. Fires were produced by incandescent carbon wear particles obtained at conditions of electric potential as low as 106 volts and 0.3 ampere at 400 F. Ignitions were obtained only with carbon wear particles produced with an electric potential across the carbon-vane-disk interface. No ignitions were obtained with carbon wear particles produced in the absence of this potential; also, the potential difference produced no ignitions in the absence of carbon wear particles. A film supplement showing ignition by incandescent wear particles is available.

  19. Growth and wear of incisor and cheek teeth in domestic rabbits (Oryctolagus cuniculus) fed diets of different abrasiveness.

    PubMed

    Müller, Jacqueline; Clauss, Marcus; Codron, Daryl; Schulz, Ellen; Hummel, Jürgen; Fortelius, Mikael; Kircher, Patrick; Hatt, Jean-Michel

    2014-06-01

    Although patterns of tooth wear are crucial in palaeo-reconstructions, and dental wear abnormalities are important in veterinary medicine, experimental investigations on the relationship between diet abrasiveness and tooth wear are rare. Here, we investigated the effect of four different pelleted diets of increasing abrasiveness (due to both internal [phytoliths] and external abrasives [sand]) or whole grass hay fed for 2 weeks each in random order to 16 rabbits (Oryctolagus cuniculus) on incisor and premolar growth and wear, and incisor and cheek tooth length. Wear and tooth length differed between diets, with significant effects of both internal and external abrasives. While diet abrasiveness was linked to tooth length for all tooth positions, whole forage had an additional effect on upper incisor length only. Tooth growth was strongly related to tooth wear and differed correspondingly between diets and tooth positions. At 1.4-3.2 mm/week, the growth of cheek teeth measured in this study was higher than previously reported for rabbits. Dental abnormalities were most distinct on the diet with sand. This study demonstrates that concepts of constant tooth growth in rabbits requiring consistent wear are inappropriate, and that diet form (whole vs. pelleted) does not necessarily affect cheek teeth. Irrespective of the strong effect of external abrasives, internal abrasives have the potential to induce wear and hence exert selective pressure in evolution. Detailed differences in wear effects between tooth positions allow inferences about the mastication process. Elucidating feedback mechanisms that link growth to tooth-specific wear represents a promising area of future research. © 2014 Wiley Periodicals, Inc.

  20. Selected fretting-wear-resistant coatings for Ti-6 pct Al-4 pct V alloy

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1985-01-01

    The ability of several wear-resistant coatings to reduce fretting in the Ti-6Al-4V alloy is investigated. The experimental apparatus and procedures for evaluating fretting in uncoated Ti-6Al-4V alloy and in the alloy with plasma-sprayed coatings, polymer-bonded coating, and surface treatments are described. The wear volume and wear rate for the alloys are measured and compared. It is concluded that Al2O3 with 13 percent TiO2, preoxidation and nitride surface treatments, and MoS2 sputtering result in wear-resistant surfaces; however, the polyimide coating is the most wear resistant coating in both dry and moist air, and it causes the least wear to the uncoated alloy surface.

  1. Selected fretting-wear-resistant coatings for Ti-6 pct Al-4 pct V alloy

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1985-01-01

    The ability of several wear-resistant coatings to reduce fretting in the Ti-6Al-4V alloy is investigated. The experimental apparatus and procedures for evaluating fretting in uncoated Ti-6Al-4V alloy and in the alloy with plasma-sprayed coatings, polymer-bonded coating, and surface treatments are described. The wear volume and wear rate for the alloys are measured and compared. It is concluded that Al2O3 with 13 percent TiO2, preoxidation and nitride surface treatments, and MoS2 sputtering result in wear-resistant surfaces; however, the polyimide coating is the most wear resistant coating in both dry and moist air, and it causes the least wear to the uncoated alloy surface.

  2. A retrospective evaluation of traumatic dental injury in children who applied to the dental hospital, Turkey.

    PubMed

    Sari, M E; Ozmen, B; Koyuturk, A E; Tokay, U; Kasap, P; Guler, D

    2014-01-01

    The purpose of this study was to analyze traumatic dental injuries in children visiting the dental hospital emergency department in Samsun of Turkey, in the period from 2007 to 2011. Data of age, gender, causes of dental trauma, injured teeth, type of dental injuries, the application period, the dental treatments, and traumatic dental injuries according to the seasons were obtained from the records at dental hospital. Of all 320 patients with traumatic dental injury, 205 were boys and 115 were girls with a boys/girls ratio 1.78:1. Traumatic dental injury was observed more frequently in the 7-12 age groups: 52.5% in girls and 67.8% in boys. Falls are the major cause of traumatic dental injury in the age group 6-12 (51.4%). Sport activities are a common cause of traumatic dental injury in the 7-12 age group (34.2%). Patients visited a dentist within approximately 2 h (57.1%). The upper anterior teeth were subjected to trauma more frequently than the lower anterior teeth. The maxillary central incisors were the most commonly affected teeth, and the mandibular canins were the least affected teeth. In primary teeth, avulsion was the most common type of dental injury (23%); on the other hand, enamel fractures were the most common type of dental injury (30.6%) observed in permanent teeth. In the primary dentition, the most commonly performed treatments were dental examination and prescribing (70%). The most common treatment choices in permanent teeth were restoration and dental examination (49.7 and 15.8%, respectively). The results of the study show that the emergency intervention to traumatized teeth is important for good prognosis of teeth and oral tissues. Therefore, the parents should be informed about dental trauma in schools, and dental hospital physicians should be subjected to postgraduate training.

  3. Friction and wear of ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, Donald H.

    1986-01-01

    The adhesion, friction, wear, and lubricated behaviors of both oxide and non-oxide ceramics are reviewed. Ceramics are examined in contact with themselves, other harder materials, and metals. Elastic, plastic, and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both the free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing.

  4. Friction and wear of ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Miyoshi, K.

    1984-01-01

    The adhesion, friction, wear and lubricated behaviors of both oxide and non-oxide ceramics are reviewed. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Grit size effects in two- and three-body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing.

  5. Wear resistance of ductile irons

    NASA Astrophysics Data System (ADS)

    Lerner, Y. S.

    1994-06-01

    This study was undertaken to evaluate the wear resistance of different grades of ductile iron as alterna-tives to high- tensile- strength alloyed and inoculated gray irons and bronzes for machine- tool and high-pressure hydraulic components. Special test methods were employed to simulate typical conditions of reciprocating sliding wear with and without abrasive- contaminated lubricant for machine and press guideways. Quantitative relationships were established among wear rate, microstructure and micro-hardness of structural constituents, and nodule size of ductile iron. The frictional wear resistance of duc-tile iron as a bearing material was tested with hardened steel shafts using standard test techniques under continuous rotating movement with lubricant. Lubricated sliding wear tests on specimens and compo-nents for hydraulic equipment and apparatus were carried out on a special rig with reciprocating motion, simulating the working conditions in a piston/cylinder unit in a pressure range from 5 to 32 MPa. Rig and field tests on machine- tool components and units and on hydraulic parts have confirmed the test data.

  6. Fractal characterization of wear-erosion surfaces

    SciTech Connect

    Rawers, James C.; Tylczak, Joseph H.

    1999-12-01

    Wear erosion is a complex phenomenon resulting in highly distorted and deformed surface morphologies. Most wear surface features have been described only qualitatively. In this study wear surfaces features were quantified using fractal analysis. The ability to assign numerical values to wear-erosion surfaces makes possible mathematical expressions that will enable wear mechanisms to be predicted and understood. Surface characterization came from wear-erosion experiments that included varying the erosive materials, the impact velocity, and the impact angle. Seven fractal analytical techniques were applied to micrograph images of wear-erosion surfaces. Fourier analysis was the most promising. Fractal values obtained were consistent with visual observations and provided a unique wear-erosion parameter unrelated to wear rate.

  7. Model for the evaluation of root wear by histometric analysis.

    PubMed

    de Oliveira, Guilherme José Pimentel Lopes; Silveira Faeda, Rafael; Marcantonio, Elcio; Marcantonio, Rosemary Adriana Chiérici

    2011-10-01

    Knowledge of the wear to the root surface caused by different instruments is essential in the choice of the type of tool used in relation to the phase of periodontal treatment which the patient is undergoing. The objective of this study was to present a new methodology for evaluating tooth wear produced by the instrumentation of the root surface. The present study used five teeth, the proximals of which were divided in three regions: coronal, median, and an apical. The coronal region was scaled with a curette, the apical region was irradiated with the Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet laser (Er,Cr:YSGG laser) and the medial region was left untreated, which served as control. The teeth underwent a histological process and were analyzed histometrically. The t test (P < 0.05) was used to analyze the root wear. The regions that were irradiated with the Er,Cr:YSGG laser presented less wear (113.37 ± 32.94 μm) in comparison to the regions that were scaled with manual curettes (169.83 ± 24.76 μm) (P < 0.05). The methodology proposed was efficient in the measurement of the wear caused by the root instrumentation and proved easy to execute, easy to reproduce, and of low cost and with high calibration accuracy. Copyright © 2010 Wiley-Liss, Inc.

  8. Assessment of Tooth Wear Among Glass Factory Workers: WHO 2013 Oral Health Survey.

    PubMed

    Chaturvedi, Pulkit; Bhat, Nagesh; Asawa, Kailash; Tak, Mridula; Bapat, Salil; Gupta, Vivek Vardhan

    2015-08-01

    Glass factory workers are often exposed to the hazardous environment that leads to deleterious oral health and subsequently, general health. We planned to determine the effects of the particulates present in the milieu on the tooth wear among workers. To assess tooth wear among glass factory workers in Jaipur, Rajasthan, India. A descriptive cross-sectional survey was conducted among 936 glass workers in Jaipur, Rajasthan, India from January-June 2014. A survey proforma was designed for tooth wear evaluation with the help of WHO Oral Health Assessment form 2013 (for adults). Information regarding oral health practices, adverse habits and dietary habits, demographic details was gathered and clinical parameters were recorded. The Chi-square test, t-test, One-way Analysis of Variance and a Stepwise multiple linear regression analysis. The most prevalent form of erosion was enamel erosion (589, 62.93%) with few subjects of deeper dentinal erosion and the difference was statistically significant (p=0.001). Dental erosion was found to be higher among males compared to females. Years of experience and educational status were identified as best predictors for dental erosion. It was concluded that there was considerable evidence of dental erosion found among the factory workers. Due to ignorance on social, cultural and health aspects, professional approach with regular dental care services for detection of early symptoms and planning of preventive strategies is warranted.

  9. Assessment of Tooth Wear Among Glass Factory Workers: WHO 2013 Oral Health Survey

    PubMed Central

    Bhat, Nagesh; Asawa, Kailash; Tak, Mridula; Bapat, Salil; Gupta, Vivek Vardhan

    2015-01-01

    Background Glass factory workers are often exposed to the hazardous environment that leads to deleterious oral health and subsequently, general health. We planned to determine the effects of the particulates present in the milieu on the tooth wear among workers. Aim To assess tooth wear among glass factory workers in Jaipur, Rajasthan, India. Settings and Design A descriptive cross-sectional survey was conducted among 936 glass workers in Jaipur, Rajasthan, India from January-June 2014. Materials and Methods A survey proforma was designed for tooth wear evaluation with the help of WHO Oral Health Assessment form 2013 (for adults). Information regarding oral health practices, adverse habits and dietary habits, demographic details was gathered and clinical parameters were recorded. Statistical Analysis The Chi–square test, t–test, One-way Analysis of Variance and a Stepwise multiple linear regression analysis. Results The most prevalent form of erosion was enamel erosion (589, 62.93%) with few subjects of deeper dentinal erosion and the difference was statistically significant (p=0.001). Dental erosion was found to be higher among males compared to females. Years of experience and educational status were identified as best predictors for dental erosion. Conclusion It was concluded that there was considerable evidence of dental erosion found among the factory workers. Due to ignorance on social, cultural and health aspects, professional approach with regular dental care services for detection of early symptoms and planning of preventive strategies is warranted. PMID:26436050

  10. Relationship of children's anxiety to their potential dental health behaviour.

    PubMed

    Wright, F A

    1980-08-01

    In this study of 200 New Zealand schoolchildren aged 7-13 years, a questionnaire interview was used to gain information related to estimating dental anxiety and general illness anxiety. Information related to sociodemographic differences, belief differences, and an estimate of potential health behaviour was also collected. Oral examinations were performed and the number of dental restorations present recorded. Dental anxiety was associated with memory of pain during a dental visit. The number of restorations present, and a history of pain during a dental visit, were important predictors of illness anxiety. Neither dental anxiety nor illness anxiety operating alone provided an estimate of future dental health behaviour. Dental anxiety and illness anxiety operated through a complex interplay of variables. A stepwise multiple regression technique was used to determine the possible pathways to potential dental health behaviour. Perceived vulnerability to dental caries and perceived severity of dental disease were important in the prediction of potential denture wearing; school attended and ethnic background were useful predictors of potential extraction seeking; and school grade and level of perceived internal control were predictors of potential preventive visitation.

  11. Dental pulp stem cells

    PubMed Central

    Ashri, Nahid Y.; Ajlan, Sumaiah A.; Aldahmash, Abdullah M.

    2015-01-01

    Inflammatory periodontal disease is a major cause of loss of tooth-supporting structures. Novel approaches for regeneration of periodontal apparatus is an area of intensive research. Periodontal tissue engineering implies the use of appropriate regenerative cells, delivered through a suitable scaffold, and guided through signaling molecules. Dental pulp stem cells have been used in an increasing number of studies in dental tissue engineering. Those cells show mesenchymal (stromal) stem cell-like properties including self-renewal and multilineage differentiation potentials, aside from their relative accessibility and pleasant handling properties. The purpose of this article is to review the biological principles of periodontal tissue engineering, along with the challenges facing the development of a consistent and clinically relevant tissue regeneration platform. This article includes an updated review on dental pulp stem cells and their applications in periodontal regeneration, in combination with different scaffolds and growth factors. PMID:26620980

  12. Dental OCT

    NASA Astrophysics Data System (ADS)

    Wilder-Smith, Petra; Otis, Linda; Zhang, Jun; Chen, Zhongping

    This chapter describes the applications of OCT for imaging in vivo dental and oral tissue. The oral cavity is a diverse environment that includes oral mucosa, gingival tissues, teeth and their supporting structures. Because OCT can image both hard and soft tissues of the oral cavity at high resolution, it offers the unique capacity to identity dental disease before destructive changes have progressed. OCT images depict clinically important anatomical features such as the location of soft tissue attachments, morphological changes in gingival tissue, tooth decay, enamel thickness and decay, as well as the structural integrity of dental restorations. OCT imaging allows for earlier intervention than is possible with current diagnostic modalities.

  13. DENTAL PULP TISSUE ENGINEERING

    PubMed Central

    Demarco, FF; Conde, MCM; Cavalcanti, B; Casagrande, L; Sakai, V; Nör, JE

    2013-01-01

    Dental pulp is a highly specialized mesenchymal tissue, which have a restrict regeneration capacity due to anatomical arrangement and post-mitotic nature of odontoblastic cells. Entire pulp amputation followed by pulp-space disinfection and filling with an artificial material cause loss of a significant amount of dentin leaving as life-lasting sequelae a non-vital and weakened tooth. However, regenerative endodontics is an emerging field of modern tissue engineering that demonstrated promising results using stem cells associated with scaffolds and responsive molecules. Thereby, this article will review the most recent endeavors to regenerate pulp tissue based on tissue engineering principles and providing insightful information to readers about the different aspects enrolled in tissue engineering. Here, we speculate that the search for the ideal combination of cells, scaffolds, and morphogenic factors for dental pulp tissue engineering may be extended over future years and result in significant advances in other areas of dental and craniofacial research. The finds collected in our review showed that we are now at a stage in which engineering a complex tissue, such as the dental pulp, is no longer an unachievable and the next decade will certainly be an exciting time for dental and craniofacial research. PMID:21519641

  14. A study of the abrasive resistance of metal alloys with applications in dental prosthetic fixators.

    PubMed

    Gil, F J; Fernández, E; Manero, J M; Planell, J A; Sabrià, J; Cortada, M; Giner, L

    1995-01-01

    Wear is one of the main surface failure mechanisms in materials and it will play a leading role in substitutive dental biomaterials. The aim of the present study is to compare the abrasive wear of different metallic materials used in dental applications. The results show that the abrasive wear of alloys based on precious metals such as Pt, Pd, Au and Ag is higher than for Ti and Ti based alloys. The alloy with the highest wear resistance is the Co-Cr which exhibits as well the highest hardness and Young's modulus. Since the method corresponds to a well-established abrasive wear standard, the behaviour of the different materials can be easily compared.

  15. Biocompatibility of dental casting alloys.

    PubMed

    Geurtsen, Werner

    2002-01-01

    Most cast dental restorations are made from alloys or commercially pure titanium (cpTi). Many orthodontic appliances are also fabricated from metallic materials. It has been documented in vitro and in vivo that metallic dental devices release metal ions, mainly due to corrosion. Those metallic components may be locally and systemically distributed and could play a role in the etiology of oral and systemic pathological conditions. The quality and quantity of the released cations depend upon the type of alloy and various corrosion parameters. No general correlation has been observed between alloy nobility and corrosion. However, it has been documented that some Ni-based alloys, such as beryllium-containing Ni alloys, exhibit increased corrosion, specifically at low pH. Further, microparticles are abraded from metallic restorations due to wear. In sufficient quantities, released metal ions-particularly Cu, Ni, Be, and abraded microparticles-can also induce inflammation of the adjacent periodontal tissues and the oral mucosa. While there is also some in vitro evidence that the immune response can be altered by various metal ions, the role of these ions in oral inflammatory diseases such as gingivitis and periodontitis is unknown. Allergic reactions due to metallic dental restorations have been documented. Ni has especially been identified as being highly allergenic. Interestingly, from 34% to 65.5% of the patients who are allergic to Ni are also allergic to Pd. Further, Pd allergy always occurrs with Ni sensitivity. In contrast, no study has been published which supports the hypothesis that dental metallic materials are mutagenic/genotoxic or might be a carcinogenic hazard to man. Taken together, very contradictory data have been documented regarding the local and systemic effects of dental casting alloys and metallic ions released from them. Therefore, it is of critical importance to elucidate the release of cations from metallic dental restorations in the oral

  16. Registered Dental Hygienists as Dental Students.

    ERIC Educational Resources Information Center

    Arnold, Janet; Shugars, Daniel A.

    1985-01-01

    Surveys conducted to (1) investigate why dental hygienists choose to become dentists, (2) evaluate their success in dental school, (3) assess the experience of those who had entered dental school, and (4) gauge the level of interest among dental hygienists in applying to dental school are discussed. (Author/MLW)

  17. The effect of mango and neem extract on four organisms causing dental caries: Streptococcus mutans, Streptococcus salivavius, Streptococcus mitis, and Streptococcus sanguis: an in vitro study.

    PubMed

    Prashant, G M; Chandu, G N; Murulikrishna, K S; Shafiulla, M D

    2007-01-01

    Chewing twigs of the mango or neem tree is a common way of cleaning the teeth in the rural and semi-urban population. These twigs are also believed to possess medicinal properties. The present study was conducted to evaluate the antimicrobial effects of these chewing sticks on the microorganisms Streptococcus mutans , Streptococcus salivarius , Streptococcus mitis , and Streptococcus sanguis which are involved in the development of dental caries. An additional objective was to identify an inexpensive, simple, and effective method of preventing and controlling dental caries. The sticks were sun dried, ground into a coarse powder, and weighed into 5 gm, 10 gm, and 50 gm amounts. These were added to 100 ml of deionized distilled water. After soaking for 48 h at 4 degrees C, the water was filtered. The filtrate was inoculated onto blood agar plates containing individual species of microorganisms and incubated at 37 degrees C for 48 h. Mango extract, at 50% concentration, showed maximum zone of inhibition on Streptococcus mitis . Neem extract produced the maximum zone of inhibition on Streptococcus mutans at 50% concentration. Even at 5% concentration neem extract showed some inhibition of growth for all the four species of organisms. A combination of neem and mango chewing sticks may provide the maximum benefit. We recommend the use of both the chewing sticks.

  18. Characterization of third-body media particles and their effect on in vitro composite wear

    PubMed Central

    Lawson, Nathaniel C.; Cakir, Deniz; Beck, Preston; Litaker, Mark S.; Burgess, John O.

    2012-01-01

    Objectives The purpose of this study was to compare four medium particles currently used for in vitro composite wear testing (glass and PMMA beads and millet and poppy seeds). Methods Particles were prepared as described in previous wear studies. Hardness of medium particles was measured with a nano-indentor, particle size was measured with a particle size analyzer, and the particle form was determined with light microscopy and image analysis software. Composite wear was measured using each type of medium and water in the Alabama wear testing device. Four dental composites were compared: a hybrid (Z100), flowable microhybrid (Estelite Flow Quick), micromatrix (Esthet-X), and nano-filled (Filtek Supreme Plus). The test ran for 100,000 cycles at 1.2Hz with 70N force by a steel antagonist. Volumetric wear was measured by non-contact profilometry. A two-way analysis of variance (ANOVA) and Tukey's test was used to compare both materials and media. Results Hardness values (GPa) of the particles are (glass, millet, PMMA, poppy respectively): 1.310(0.150), 0.279(.170), 0.279(0.095), and 0.226(0.146). Average particle sizes (μm) are (glass, millet, PMMA, poppy respectively): 88.35(8.24), 8.07(4.05), 28.95(8.74), and 14.08(7.20). Glass and PMMA beads were considerably more round than the seeds. During composite wear testing, glass was the only medium that produced more wear than the use of water alone. The rank ordering of the materials varied with each medium, however, the glass and PMMA bead medium allowed better discrimination between materials. Significance PMMA beads are a practical and relevant choice for composite wear testing because they demonstrate similar physical properties as seeds but reduce the variability of wear measurements. PMID:22578990

  19. 75 FR 16511 - Pentron Clinical Technologies, a Wholly-Owned Subsidiary of Kerr Dental/Sybron Dental...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-01

    ... such as dental prosthetics, dental composites, dental impressions, dental adhesives, and other dental... prosthetics, dental composites, dental impressions, dental adhesives, and other dental materials to...

  20. Dental sealants

    MedlinePlus

    ... few quick steps. There is no drilling or scraping of the molars. Your dentist will: Clean the ... Dental sealants. Updated October 19, 2016. ADA.org Web site. www.ada.org/en/member-center/oral- ...

  1. Dental Hygienists

    MedlinePlus

    ... hygienists to be licensed; requirements vary by state. Education Dental hygienists typically need an associate’s degree in ... the skills needed in this occupation. Entry-level Education Typical level of education that most workers need ...

  2. Dental Fluorosis

    MedlinePlus

    ... when children regularly consume fluoride during the teeth-forming years, age 8 and younger. Most dental fluorosis ... over a long period when the teeth are forming under the gums. Only children aged 8 years ...

  3. Dental Sealants

    MedlinePlus

    ... form does not collect any actual information. External Web Site Policy This graphic notice ( ) means that you are ... the link. Home Contact Us Viewers and Players Site Map FOIA Web Policies Privacy Policy National Institute of Dental and ...

  4. Wear resistance and mechanisms of composite hardfacings at abrasive impact erosion wear

    NASA Astrophysics Data System (ADS)

    Surzhenkov, A.; Viljus, M.; Simson, T.; Tarbe, R.; Saarna, M.; Casesnoves, F.

    2017-05-01

    Tungsten carbide based hardmetal containing sprayed and melted composite hardfacings are prospective for protection against abrasive wear. For selection of abrasive wear resistant hardfacings under intensive impact wear conditions, both mechanical properties (hardness, fracture toughness, etc.) and abrasive wear conditions (type of abrasive, impact velocity, etc.) should be considered. This study focuses on the wear (wear rate and mechanisms) of thick metal-matrix composite hardfacings with hardmetal (WC-Co) reinforcement produced by powder metallurgy technology. The influence of the hardmetal reinforcement type on the wear resistance at different abrasive impact erosion wear (AIEW) conditions was studied. An optimal reinforcement for various wear conditions is described. Based on wear mechanism studies, a mathematical model for wear prediction was drafted.

  5. Dental Emergencies

    PubMed Central

    Symington, J.M.

    1988-01-01

    Patients with dental emergencies sometimes present to their physician. This article outlines the role of the physician in the management of dental patients who have suffered traumatic injuries, postoperative hemorrhage, pain, and infection. It deals with those difficulties for which the physician may easily prescribe treatment and outlines the treatment that would be undertaken by a dentist who receives such a patient on referral. PMID:21253249

  6. Surface roughness and wear of resin cements after toothbrush abrasion.

    PubMed

    Ishikiriama, Sérgio Kiyoshi; Ordoñéz-Aguilera, Juan Fernando; Maenosono, Rafael Massunari; Volú, Fernanda Lessa Amaral; Mondelli, Rafael Francisco Lia

    2015-01-01

    Increased surface roughness and wear of resin cements may cause failure of indirect restorations. The aim of this study was to evaluate quantitatively the surface roughness change and the vertical wear of four resin cements subjected to mechanical toothbrushing abrasion. Ten rectangular specimens (15 × 5 × 4 mm) were fabricated according to manufacturer instructions for each group (n = 10): Nexus 3, Kerr (NX3); RelyX ARC, 3M ESPE (ARC); RelyX U100, 3M ESPE (U100); and Variolink II, Ivoclar/Vivadent (VL2). Initial roughness (Ra, µm) was obtained through 5 readings with a roughness meter. Specimens were then subjected to toothbrushing abrasion (100,000 cycles), and further evaluation was conducted for final roughness. Vertical wear (µm) was quantified by 3 readings of the real profile between control and brushed surfaces. Data were subjected to analysis of variance, followed by Tukey's test (p < 0.05). The Pearson correlation test was performed between the surface roughness change and wear (p < 0.05). The mean values of initial/final roughness (Ra, µm)/wear (µm) were as follows: NX3 (0.078/0.127/23.175); ARC (0.086/0.246/20.263); U100 (0.296/0.589/16.952); and VL2 (0.313/0.512/22.876). Toothbrushing abrasion increased surface roughness and wear of all resin cements tested, although no correlation was found between those variables. Vertical wear was similar among groups; however, it was considered high and may lead to gap formation in indirect restorations.

  7. [Allergies to dental materials and dental pharmacologic agents].

    PubMed

    Gall, H

    1983-07-01

    Allergic reactions to dental materials and remedies cause stomatitis in the patient and a contact dermatitis in the dental personnel. Topical contact (acrylic resin denture materials, heat accumulation, plaques on the denture) and endogenic (symptom of internal and psychiatric illnesses) factors are the cause for denture sore mouth. In metallic alloys corrosions and electric currents can effect an irritation to the oral mucosa. The application of amalgam fillings can possibly result in a mercurialism. Dental remedies used for treatment of wounds and dental roots are potent sensitizers. Surface anesthetics with tetracaine are the most frequent contact allergens for dentists. Injectable local anesthetics produce anaphylactic type reactions as well as toxic side-effects in the patient.

  8. Infant dental care (image)

    MedlinePlus

    ... sugar water. As the child grows, establishing proper dental hygiene will promote healthy teeth and gums which are essential to overall good health. Poor dental development, dental disease, and dental trauma can result ...

  9. Research on the effect of wear-ring clearances to the performance of centrifugal pump

    NASA Astrophysics Data System (ADS)

    Zhao, W. G.; Li, Y. B.; Wang, X. Y.; Sun, J. P.; Wu, G. X.

    2012-11-01

    In order to study the effect of wear-ring clearance on the performance of centrifugal pump, based on the Reynolds Time-Averaged N-S equations and RNG k-ε turbulence model, a centrifugal pump was simulated with three variable styles of the wear-rings: Only the clearance of the front wear-ring was changed, only the clearance of the back wear-ring was changed and both were changed. Numerical results agree well with the experimental results. In the three changing styles of the clearance, the variable of the clearance of front wear-ring has the most influence on the performance of centrifugal pump. The existence of wear-ring not only has an effect on the volumetric loss of the centrifugal pump, but also on the performance of the centrifugal pump. Relative to the experimental studies, numerical simulation methods have some advantages, such as low cost, fast and efficient, and easy to get the detailed structure of the internal flow characteristics, so it has been widely used in the fluid machinery study. In order to study the effect of wear-ring clearance on the performance of centrifugal pump, based on the Reynolds Time-Averaged N-S equations and RNG k-ε turbulence model, a centrifugal pump was simulated with three variable styles of the wear-rings: Only the clearance of the front wear-ring was changed, only the clearance of the back wear-ring was changed and both were changed. Numerical results agree well with the experimental results. In the three changing styles of the clearance, the variable of the clearance of front wear-ring has the most influence on the performance of centrifugal pump.

  10. [Outcomes of Infection Control Team Inspections at the Dental Hospital, Tokyo Medical and Dental University].

    PubMed

    Sunakawa, Mitsuhiro; Matsumoto, Hiroyuki; Okihata, Rie; Tsuruoka, Hiromi; Yamada, Yuichi; Adachi, Toshiko; Izumi, Yuichi

    2015-07-01

    In the Dental Hospital, Tokyo Medical and Dental University, an infection control team (ICT) has been formed to inspect each diagnosis department of clinics and wards in order to identify problems regarding nosocomial infection control. In this study, we analyzed the inspection reports and highlighted the following serious problems: 1) inadequate hygienic hand-washing for out- and in-patient treatment, 2) incomplete wearing of personal protective equipment (PPE) by dental health care workers, 3) necessity of environmental improvement in the clinics, and 4) cross-infection risk induced by. the continuous use of treatment devices without appropriate disinfection. The ICT provided feedback to the inspected departments, suggesting solutions to problems regarding nosocomial infection control. In order to enhance infection control in our hospital, dental healthcare practitioners must make further efforts on nosocomial infection control and prevention, and act according to their position by continuously educating students and enlightening hospital staff about the importance of infection control.

  11. Critical length scale controls adhesive wear mechanisms

    PubMed Central

    Aghababaei, Ramin; Warner, Derek H.; Molinari, Jean-Francois

    2016-01-01

    The adhesive wear process remains one of the least understood areas of mechanics. While it has long been established that adhesive wear is a direct result of contacting surface asperities, an agreed upon understanding of how contacting asperities lead to wear debris particle has remained elusive. This has restricted adhesive wear prediction to empirical models with limited transferability. Here we show that discrepant observations and predictions of two distinct adhesive wear mechanisms can be reconciled into a unified framework. Using atomistic simulations with model interatomic potentials, we reveal a transition in the asperity wear mechanism when contact junctions fall below a critical length scale. A simple analytic model is formulated to predict the transition in both the simulation results and experiments. This new understanding may help expand use of computer modelling to explore adhesive wear processes and to advance physics-based wear laws without empirical coefficients. PMID:27264270

  12. Dental disorders in brown howler monkeys (Alouatta guariba clamitans) maintained in captivity.

    PubMed

    Dias Neto, Ramiro das Neves; Fecchio, Roberto Silva; Rahal, Sheila Canevese; Teixeira, Carlos Roberto; Gioso, Marco Antônio; Pereira, Camila Trevisan; Santos, Maria Augusta Adami Pereira Dos; Milanelo, Liliane

    2016-04-01

    The aim of this study was to investigate dental disorders of brown howler monkeys maintained in captivity. The hypothesis is that the identification and diagnosis of the lesions may contribute to control and prevention. Sixteen intact brown howler monkeys (Alouatta guariba clamitans), eight females and eight males, weighing from 3.9 to 6.8 kg, were studied. Under general anesthesia, the teeth were evaluated by visual inspection, probing, palpation, and intra-oral radiographic exam. The findings were registered on a dental chart specific for primates. Of the 16 monkeys evaluated in the present study, 94% (n = 15) had some type of dental disorder. The lesions observed were dental calculus (88%), dental wear (81%), missing teeth (38%), gingivitis (19%), gingival recession (6%), dental fracture (19%), pulp exposure (19%), and dental staining (25%). Alouatta guariba clamitans maintained in captivity have a high rate of dental problems. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Wear Resistant Coatings for Titanium.

    DTIC Science & Technology

    1980-10-01

    resistant, chromium-molybdenum, electroplating, pulse- plating , surface treatment, heat treatment, dry-film lubricants. 20. Abstract (Continue on...to acknowledge the contributions provided by the following individuals. Messrs. S. Tefft and B. Zelazek conducted the plating and performed wear...Chromium-Molybdenum Application Procedure for Steels 28 APPENDIX C - Suggested Military Specification - Chromium-Molybdenum Plating (Electrodeposited

  14. Rigid gas permeable extended wear.

    PubMed

    Maehara, J R; Kastl, P R

    1994-04-01

    We have reviewed the pertinent literature on rigid gas permeable (RGP) extended wear contact lenses, and we discuss the benefits and adverse reactions of this contact lens modality, drawing conclusions from reviewed studies. We suggest parameters for success with these lenses and guidelines for the prevention of adverse reactions.

  15. Should School Nurses Wear Uniforms?

    ERIC Educational Resources Information Center

    Journal of School Health, 2001

    2001-01-01

    This 1958 paper questions whether school nurses should wear uniforms (specifically, white uniforms). It concludes that white uniforms are often associated with the treatment of ill people, and since many people have a fear reaction to them, they are not necessary and are even undesirable. Since school nurses are school staff members, they should…

  16. First ISS crew, wearing LES

    NASA Image and Video Library

    2000-05-12

    Photographic documentation showing the first crew of the ISS posing together in bldg. 9N during descent training, wearing orange Launch & Entry Suits (LES) and clasping right hands in a sign of unity. From left to right: Sergei Krikalev, William Shepherd and Yuri Gidzenko.

  17. Roughness Measurement of Dental Materials

    NASA Astrophysics Data System (ADS)

    Shulev, Assen; Roussev, Ilia; Karpuzov, Simeon; Stoilov, Georgi; Ignatova, Detelina; See, Constantin von; Mitov, Gergo

    2016-06-01

    This paper presents a roughness measurement of zirconia ceramics, widely used for dental applications. Surface roughness variations caused by the most commonly used dental instruments for intraoral grinding and polishing are estimated. The applied technique is simple and utilizes the speckle properties of the scattered laser light. It could be easily implemented even in dental clinic environment. The main criteria for roughness estimation is the average speckle size, which varies with the roughness of zirconia. The algorithm used for the speckle size estimation is based on the normalized autocorrelation approach.

  18. Wear of two pit and fissure sealants in contact with primary teeth

    PubMed Central

    Galo, Rodrigo; Contente, Marta Maria Martins Giamatei; Borsatto, Maria Cristina

    2014-01-01

    Objectives: Wear simulations may provide an indication of the clinical performance of pit-and-fissure sealants when associated with primary teeth as counterbody, restricting the involved variables. The aim of this study was to evaluate wear of dental materials used as pit-and-fissure sealants in contact with primary teeth. Materials and Methods: A resinous sealant (Fluroshield®) and a resin-modified glass ionomer cement (Vitremer®) were selected in a post-plate design, using as counterbody primary tooth pins (4 × 4 × 2 mm) at 3 and 10 N vertical load, 1 Hz frequency, 900 wear cycles in artificial saliva (n = 15). Attrition coefficient values were obtained and the material and primary tooth volumes were analyzed. Data were analyzed statistically by ANOVA and Duncan's test (P < 0.05). Results: Fluroshield® presented the highest attrition coefficient values for the 3 N but these values decreased significantly for the 10 N load. The means for volume loss (3 mm) of the different samples after the wear test were not statistically different for the materials. The volume loss values for the primary teeth were statistically different and there was an increase in volume loss with the increase of the load applied in the wear tests. Conclusions: Differences were also observed with regard to the surface deformation characteristics. The wear rates of primary tooth enamel vary according to the type of material and the load applied during mastication. PMID:24966777

  19. Reducing tool wear when machining austenitic stainless steels

    SciTech Connect

    Magee, J.H.; Kosa, T.

    1998-07-01

    Austenitic stainless steels are considered more difficult to machine than carbon steels due to their high work hardening rate, large spread between yield and ultimate tensile strength, high toughness and ductility, and low thermal conductivity. These characteristics can result in a built-up edge or excessive tool wear during machining, especially when the cutting speed is too high. The practical solution is to lower the cutting speed until tool life reaches an acceptable level. However, lower machining speed negatively impacts productivity. Thus, in order to overcome tool wear at relatively high machining speeds for these alloys, on-going research is being performed to improve cutting fluids, develop more wear-resistant tools, and to modify stainless steels to make them less likely to cause tool wear. This paper discusses compositional modifications to the two most commonly machined austenitic stainless steels (Type 303 and 304) which reduced their susceptibility to tool wear, and allowed these grades to be machined at higher cutting speeds.

  20. Characterization of polyethylene wear particle: The impact of methodology.

    PubMed

    Schröder, Christian; Reinders, Jörn; Zietz, Carmen; Utzschneider, Sandra; Bader, Rainer; Kretzer, J Philippe

    2013-12-01

    Due to the prevalence of problems caused by wear particles, the reduced durability of total joint replacements is well documented. The characterization of wear debris enables the size and morphology of these wear particles to be measured and provides an assessment of the biological response in vivo. However, the impact of different methodologies of particle analysis is not yet clear. Hence, the aim of this investigation was to analyze the influence of different particle characterization methods performed by three research centers within the scope of a "round robin test". To obtain knowledge about possible pitfalls, single steps of the particle characterization process (storage, pore size of the filter, coating durations by gold sputtering and scanning electron microscopy (SEM) magnification) were analyzed. The round robin test showed significant differences between the research groups, especially for the morphology of the particles. The SEM magnification was identified as having the greatest influence on the size and shape of the particles, followed by the storage conditions of the wear particle containing lubricant. Gold sputter coating and filter pore size also exhibit significant effects. However, even though they are statistically significant, it should be emphasized that the differences are small. In conclusion, particle characterization is a complex analytical method with a multiplicity of influencing factors. It becomes apparent that a comparison of wear particle results between different research groups is challenging.

  1. Steenbeek Brace: Patterns of Wear.

    PubMed

    Agarwal, Anil; Shaharyar, Abbas; Kumar, Anubrat; Bhat, Mohd Shafi; Mishra, Madhusudan

    2016-02-01

    Steenbeek foot abduction brace (SFAB) is an essential orthotic for maintaining correction in congenital talipes equinovarus treated with Ponseti method. As the brace is used up to 3 to 4 years of age, we examined the brace wear pattern according to a child's development and age. We studied 100 SFABs that were rendered unusable or returned by parents due to advanced brace wear. SFABs returned due to other reasons such as foot outgrowing shoe size were excluded. Each part of the brace (outer sole, insole, upper leather, abduction bar, shoe laces) was carefully inspected to observe any pattern of damage. We grouped the pattern of brace wear as per the probable causative factors into 3 broad categories: due to general use in all age groups, sitters and crawlers, and walking children. Shredded tongue, elongated/torn shoelace hole, peeled paint of metal abduction bar, shredded outer sole, and frayed shoelace were due to general use. Due to sitting and crawling with the brace on, shoe wore on its anteromedial, anterolateral, and posterolateral parts at the junction of the upper leather and outer sole. The commonest area of shoe wear in walkers was the abduction bar, which either broke from the welded junction between bar and metal or was bent at midpoint. The SFAB wear pattern was related to the age of the child and his/her activities. The reusability of the brace can probably be extended with simple improvisations and instructing parents about the correct use of the brace. Prognostic, Level IV: Case series. © 2015 The Author(s).

  2. Needs and challenges in precision wear measurement

    SciTech Connect

    Blau, P.J.

    1996-01-10

    Accurate, precise wear measurements are a key element in solving both current wear problems and in basic wear research. Applications range from assessing durability of micro-scale components to accurate screening of surface treatments and thin solid films. Need to distinguish small differences in wear tate presents formidable problems to those who are developing new materials and surface treatments. Methods for measuring wear in ASTM standard test methods are discussed. Errors in using alterate methods of wear measurement on the same test specimen are also described. Human judgemental factors are a concern in common methods for wear measurement, and an experiment involving measurement of a wear scar by ten different people is described. Precision in wear measurement is limited both by the capabilities of the measuring instruments and by the nonuniformity of the wear process. A method of measuring wear using nano-scale indentations is discussed. Current and future prospects for incorporating advanced, higher-precision wear measurement methods into standards are considered.

  3. Wear particle analysis using the ferrograph

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1983-01-01

    The use of the Ferrograph in analyzing wear particles from a variety of different sources is reported. Examples of wear particles from gas turbine engines, bearing tests, friction and wear tests, hydraulic systems, and human joints are illustrated. In addition, the separation of bacteria and human cells is described.

  4. Wear-mechanism modelling. Final report

    SciTech Connect

    Ashby, M.F.

    1993-03-01

    Goals of the program are to calculate the surface temperatures in dry sliding, develop a soft wear tester for ceramics, survey the wear mechanisms in brittle solids, and couple the temperature calculations with models to give wear maps for brittle solids. (DLC)

  5. Investigation of the time-dependent wear behavior of veneering ceramic in porcelain fused to metal crowns during chewing simulations.

    PubMed

    Guo, Jiawen; Tian, Beimin; Wei, Ran; Wang, Weiguo; Zhang, Hongyun; Wu, Xiaohong; He, Lin; Zhang, Shaofeng

    2014-12-01

    The excessive abrasion of occlusal surfaces in ceramic crowns limits the service life of restorations and their clinical results. However, little is known about the time-dependent wear behavior of ceramic restorations during the chewing process. The aim of this in vitro study was to investigate the dynamic evolution of the wear behavior of veneering porcelain in PFM crowns as wear progressed, as tested in a chewing simulator. Twenty anatomical metal-ceramic crowns were prepared using Ceramco III as the veneering porcelain. Stainless steel balls served as antagonists. The specimens were dynamically loaded in a chewing simulator with 350N up to 2.4×10(6) loading cycles, with additional thermal cycling between 5 and 55°C. During the testing, several checkpoints were applied to measure the substance loss of the crowns' occlusal surfaces and to evaluate the microstructure of the worn areas. After 2.4×10(6) cycles, the entire wear process of the veneering porcelain in the PFM crowns revealed three wear stages (running-in, steady and severe wear stages). The occlusal surfaces showed traces of intensive wear on the worn areas during the running-in wear stage, and they exhibited the propagation of cracks in the subsurface during steady wear stage. When the severe wear stage was reached, the cracks penetrated the ceramic layer, causing the separation of porcelain pieces. It also exhibited a good correlation among the microstructure, the wear loss and the wear rate of worn ceramic restorations. The results suggest that under the conditions of simulated masticatory movement, the wear performance of the veneering porcelain in PFM crowns indicates the apparent similarity of the tribological characteristics of the traditional mechanical system. Additionally, the evaluation of the wear behavior of ceramic restorations should be based on these three wear stages.

  6. Case report: Blue chromogenic dental staining in child with West syndrome.

    PubMed

    Bussell, R M; Deery, C

    2010-12-01

    Tooth discolouration can be caused by a variety of local and systemic factors. Extrinsic dental stains may be caused by predisposing factors, and other factors such as dental plaque, foods and beverages, chromogenic bacteria, metallic compounds and medications. Studies have reported a correlation between the colour of extrinsic staining and caries risk. A 4-year-old boy with West syndrome, characterised by epileptic seizures and severe muscle spasm, was referred to the paediatric dentistry clinic at School of Clinical Dentistry, Sheffield. He had a percutaneous endoscopic gastrostomy (PEG) tube and had no oral food or fluid intake. The presenting complaint was his parent's concern of trauma to the oral tissues from epileptic fits. An examination revealed an unusual navy-blue staining to his teeth that appeared extrinsic in nature. There was evidence of tooth-wear of his primary dentition, and marked calculus deposits. No caries was detected. A further dental examination and treatment was carried out under general anaesthesia. The mandibular central incisors were extracted, due to imminent pulp exposure from bruxism, and were sent for histopathology to determine the nature of the staining. A moderate growth of Pseudomonas aeruginosa, a blue pigment-producing bacteria usually implicated in chronic pulmonary infections, was recovered from a swab sample. The patient was reviewed at 4 months at which time the staining had returned. The patient had no oral intake of food or drink, which placed him in a low caries risk category despite limited oral hygiene practice. His extensive lists of medications were not found to have extrinsic dental staining as a possible side effect. However, these may have altered the oral flora such that growth of pigmented bacteria, normally absent from the oral cavity, was favoured, causing generalised extrinsic staining.

  7. (v) Simulation and measurement of wear in metal-on-metal bearings in vitro- understanding the reasons for increased wear

    PubMed Central

    Fisher, John; Al Hajjar, Mazen; Williams, Sophie; Tipper, Joanne; Ingham, Eileen; Jennings, Louise

    2012-01-01

    A new Stratified Approach For Enhanced Reliability (SAFER) pre-clinical simulation testing of joint prostheses has been described in a preceding paper in this volume. The application of SAFER in vitro simulation and testing to metal-on-metal bearings is described in this review paper. The review aims to provide further understanding of the reasons for, and causes of, increased wear in metal-on-metal hips in a proportion of patients. Variation in positioning (mal-positioning) of the head and cup in hip prostheses results in the head contacting the rim of the cup and producing increased wear. Variation in both translational and rotational positioning has been investigated. Variation in translational positioning of the centres of the head and cup, which is not detected on radiographs, is a frequent occurrence clinically and can result in a substantial increase in wear rate. The variation in translational positioning acts synergistically with variation in rotational positioning to produce substantial increases in wear. These recent findings are consistent with the wear mechanisms and formation of stripe wear reported for ceramic-on-ceramic bearings over a decade ago, and provide insight into the reasons for the variation and increases in the wear rate found clinically in metal-on-metal hips in specific patients, which may cause premature failure. PMID:23335950

  8. The influence of malrotation and femoral component material on patellofemoral wear during gait.

    PubMed

    Vanbiervliet, J; Bellemans, J; Verlinden, C; Luyckx, J P; Labey, L; Innocenti, B; Vandenneucker, H

    2011-10-01

    Complications involving the patellofemoral joint, caused by malrotation of the femoral component during total knee replacement, are an important cause of persistent pain and failure leading to revision surgery. The aim of this study was to determine and quantify the influence of femoral component malrotation on patellofemoral wear, and to determine whether or not there is a difference in the rate of wear of the patellar component when articulated against oxidised zirconium (OxZr) and cobalt-chrome (CoCr) components. An in vitro method was used to simulate patellar maltracking for both materials. Both rates of wear and changes in height on the patellar articular surface were measured. The mean rates of wear measured were very small compared to standard tibiofemoral wear rates. When data for each femoral component material were pooled, the mean rate of wear was 0.19 mm3/Mcycle (sd 0.21) for OxZr and 0.34 mm3/Mcycle (sd 0.335) for CoCr. The largest change in height on each patella varied from -0.05 mm to -0.33 mm over the different configurations. The results suggest that patellar maltracking due to an internally rotated femoral component leads to an increased mean patellar wear. Although not statistically significant, the mean wear production may be lower for OxZr than for CoCr components.

  9. General dental practitioner's views on dental general anaesthesia services.

    PubMed

    Threlfall, A G; King, D; Milsom, K M; Blinkhom, A S; Tickle, M

    2007-06-01

    Policy has recently changed on provision of dental general anaesthetic services in England. The aim of this study was to investigate general dental practitioners' views about dental general anaesthetics, the reduction in its availability and the impact on care of children with toothache. Qualitative study using semi-structured interviews and clinical case scenarios. General dental practitioners providing NHS services in the North West of England. 93 general dental practitioners were interviewed and 91 answered a clinical case scenario about the care they would provide for a 7-year-old child with multiple decayed teeth presenting with toothache. Scenario responses showed variation; 8% would immediately refer for general anaesthesia, 25% would initially prescribe antibiotics, but the majority would attempt to either restore or extract the tooth causing pain. Interview responses also demonstrated variation in care, however most dentists agree general anaesthesia has a role for nervous children but only refer as a last resort. The responses indicated an increase in inequalities, and that access to services did not match population needs, leaving some children waiting in pain. Most general dental practitioners support moving dental general anaesthesia into hospitals but some believe that it has widened health inequalities and there is also a problem associated with variation in treatment provision. Additional general anaesthetic services in some areas with high levels of tooth decay are needed and evidence based guidelines about caring for children with toothache are required.

  10. Tribological characteristics of enamel-dental material contacts investigated in vitro.

    PubMed

    Wojda, Sylwia; Szoka, Bogusława; Sajewicz, Eugeniusz

    2015-01-01

    The aim of this study was to investigate wear and friction behaviour of tooth enamel against selected dental restorative materials. The experimental material was obtained under simulated mastication, during which human tooth enamel was sub- jected to friction and wear in contact with composite dental materials: Estelite Sigma and FulFil Extra. The results have shown that the enamel's resistance to tribological wear is significantly higher than the resistance of the dental materials tested. The microscopic observations of the sample surfaces subsequent to the tribological research as well as the analysis of the chemical composition of the surface layer confirm the existence of diverse tribological wear mechanisms dependent on the type of dental materials used. Composite materials such as Estellite Sigma and FulFil Extra are characterized by greater resistance to wear and are less destructive to enamel than the material investigated by the authors earlier. It has also been stated that the spherical shape of the filler particles (Estellite Sigma) has a beneficial effect in reducing enamel wear.

  11. Clinical performance and wear characteristics of veneered lithia-disilicate-based ceramic crowns.

    PubMed

    Suputtamongkol, Kallaya; Anusavice, Kenneth J; Suchatlampong, Chatcharee; Sithiamnuai, Phira; Tulapornchai, Chantana

    2008-05-01

    The objectives of this study were to characterize the clinical performance and wear characteristics of lithia-disilicate-based ceramic crowns. Thirty posterior crowns were made using the heat-pressing technique and lithia-disilicate-based core ceramic. Subjects were recalled annually. The quality of crowns and adjacent gingival tissues were examined using nine criteria for acceptability. All crowns were examined and ranked from 4 (Excellent) to 1 (Unacceptable) for each criterion. Impressions were made for replica models at each appointment. Wear characteristics of dental ceramic and enamel were obtained by comparing the surface of the original model with the follow-up model using a laser scanner. Twenty-nine subjects returned for the 1-year recall examination. The maximum clenching force for the 30 subjects ranged from 125 to 815 N. All clinical criteria were ranked good to excellent at the 1-year recall exam and no fractures were observed. The mean occlusal wear volumes for the ceramic crowns after 1 year were 0.19 (0.065)mm3 for premolar sites and 0.34 (0.08)mm3 for molar sites. The mean occlusal wear volumes of opposing enamel after 1 year were 0.21 (0.06)mm3 for premolar teeth and 0.50 (0.22)mm3 for molar teeth. The mean occlusal wear volume of ceramic molar crowns was significantly lower than the volume of enamel wear of the opposing teeth (pwear volume of ceramic molar crowns was significantly lower than the enamel wear volume of the opposing teeth.

  12. Clinical performance and wear characteristics of veneered lithia-disilicate-based ceramic crowns

    PubMed Central

    Suputtamongkol, Kallaya; Anusavice, Kenneth J.; Suchatlampong, Chatcharee; Sithiamnuai, Phira; Tulapornchai, Chantana

    2008-01-01

    Objectives The objectives of this study were to characterize the clinical performance and wear characteristics of lithia-disilicate-based ceramic crowns. Methods Thirty posterior crowns were made using the heat-pressing technique and lithia-disilicate-based core ceramic. Subjects were recalled annually. The quality of crowns and adjacent gingival tissues were examined using nine criteria for acceptability. All crowns were examined and ranked from 4 (Excellent) to 1 (Unacceptable) for each criterion. Impressions were made for replica models at each appointment. Wear characteristics of dental ceramic and enamel were obtained by comparing the surface of the original model with the follow-up model using a laser scanner. Results Twenty nine subjects returned for the one-year recall examination. The maximum clenching force for the 30 subjects ranged from 125 to 815 N. All clinical criteria were ranked good to excellent at the one-year recall exam and no fractures were observed. The mean occlusal wear volumes for the ceramic crowns after one year were 0.19 (0.065) mm3 for premolar sites and 0.34 (0.08) mm3 for molar sites. The mean occlusal wear volumes of opposing enamel after one year were 0.21 (0.06) mm3 for premolar teeth and 0.50 (0.22) mm3 for molar teeth. The mean occlusal wear volume of ceramic molar crowns was significantly lower than the volume of enamel wear of the opposing teeth (p≤0.05). Conclusions The quality of the overall prostheses and the gingival tissues were acceptable after one year. The mean occlusal wear volume of ceramic molar crowns was significantly lower than the enamel wear volume of the opposing teeth. PMID:17727943

  13. Osseoperception in Dental Implants: A Systematic Review.

    PubMed

    Mishra, Sunil Kumar; Chowdhary, Ramesh; Chrcanovic, Bruno Ramos; Brånemark, Per-Ingvar

    2016-04-01

    Replacement of lost teeth has significant functional and psychosocial effects. The capability of osseointegrated dental implants to transmit a certain amount of sensibility is still unclear. The phenomenon of developing a certain amount of tactile sensibility through osseointegrated dental implants is called osseoperception. The aim of this article is to evaluate the available literature to find osseoperception associated with dental implants. To identify suitable literature, an electronic search was performed using Medline and PubMed database. Articles published in English and articles whose abstract is available in English were included. The articles included in the review were based on osseoperception, tactile sensation, and neurophysiological mechanoreceptors in relation to dental implants. Articles on peri-implantitis and infection-related sensitivity were not included. Review articles without the original data were excluded, although references to potentially pertinent articles were noted for further follow-up. The phenomenon of osseoperception remains a matter of debate, so the search strategy mainly focused on articles on osseoperception and tactile sensibility of dental implants. This review presents the histological, neurophysiological, and psychophysical evidence of osseoperception and also the role of mechanoreceptors in osseoperception. The literature on osseoperception in dental implants is very scarce. The initial literature search resulted in 90 articles, of which 81 articles that fulfilled the inclusion criteria were included in this systematic review. Patients restored with implant-supported prostheses reported improved tactile and motor function when compared with patients wearing complete dentures. © 2016 by the American College of Prosthodontists.

  14. Holography And Holometry Applications In Dental Research

    NASA Astrophysics Data System (ADS)

    Willenborg, George C.

    1987-06-01

    The earliest reference to holographic applications appeared in the dental literature in 1972 when Wictorin, Bjelkhagen and Abramson described a method to study elastic deformation of defective gold solder joints in simulated fixed bridges. Their paper, published in the Swedish dental literature, offered a concise presentation of the interferometry technique which led to the development of other research applications of holographic interferometry(holometry) in dentistry. In this presentation, the development and application of the interferometry technique in the dental field will be discussed. Various interesting and potentially useful applications of holography have appeared in the dental literature over the past decade. Some of these, which will be discussed, include the use of holograms as a storage medium for dental study models, multiplexing of computer(CT) scan sections to form white light viewable holograms and the potential application of holographic training aids in the teaching of the basic courses of dental anatomy and restorative dentistry. In addition, some unique related applications will be mentioned including a laser reflection method for accurate non-contact measurement of tooth mobility/movement and a technique for contour mapping of occlusal surfaces to measure wear of restorative materials.

  15. Dental Calculus Arrest of Dental Caries

    PubMed Central

    Keyes, Paul H.; Rams, Thomas E.

    2016-01-01

    Background An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human teeth for the presence and location of dental caries, dental calculus, and dental plaque biofilms. Materials and methods A total of 1,200 teeth were preserved in 10% buffered formal saline, and viewed while moist by a single experienced examiner using a research stereomicroscope at 15-25× magnification. Representative teeth were sectioned and photographed, and their dental plaque biofilms subjected to gram-stain examination with light microscopy at 100× magnification. Results Dental calculus was observed on 1,140 (95%) of the extracted human teeth, and no dental carious lesions were found underlying dental calculus-covered surfaces on 1,139 of these teeth. However, dental calculus arrest of dental caries was found on one (0.54%) of 187 evaluated teeth that presented with unrestored proximal enamel caries. On the distal surface of a maxillary premolar tooth, dental calculus mineralization filled the outer surface cavitation of an incipient dental caries lesion. The dental calculus-covered carious lesion extended only slightly into enamel, and exhibited a brown pigmentation characteristic of inactive or arrested dental caries. In contrast, the tooth's mesial surface, without a superficial layer of dental calculus, had a large carious lesion going through enamel and deep into dentin. Conclusions These observations further document the potential protective effects of dental calculus mineralization against dental caries. PMID:27446993

  16. Corrosive Wear in Wet Ore Grinding Systems

    NASA Astrophysics Data System (ADS)

    Jones, Denny A.

    1985-06-01

    Wear processes in ball and rod mills have recently received increased attention in order to increase efficiency and conserve grinding media. Direct removal of metal from the grinding media surface by abrasive wear occurs in both dry and wet grinding. Additional corrosive wear is apparent during wet grinding, in which less resistant corrosion product films are abraded away. Inhibitors and higher pH solutions, in which corrosion product films are more tenacious, improve wear resistance during wet grinding. Softer surfaces are less resistant to corrosive wear, suggesting that film formation and subsequent film abrasion on newly furrowed surfaces must be a factor.

  17. Influence of dental materials on dental MRI

    PubMed Central

    Tymofiyeva, O; Vaegler, S; Rottner, K; Boldt, J; Hopfgartner, AJ; Proff, PC; Richter, E-J; Jakob, PM

    2013-01-01

    Objectives: To investigate the potential influence of standard dental materials on dental MRI (dMRI) by estimating the magnetic susceptibility with the help of the MRI-based geometric distortion method and to classify the materials from the standpoint of dMRI. Methods: A series of standard dental materials was studied on a 1.5 T MRI system using spin echo and gradient echo pulse sequences and their magnetic susceptibility was estimated using the geometric method. Measurements on samples of dental materials were supported by in vivo examples obtained in dedicated dMRI procedures. Results: The tested materials showed a range of distortion degrees. The following materials were classified as fully compatible materials that can be present even in the tooth of interest: the resin-based sealer AH Plus® (Dentsply, Maillefer, Germany), glass ionomer cement, gutta-percha, zirconium dioxide and composites from one of the tested manufacturers. Interestingly, composites provided by the other manufacturer caused relatively strong distortions and were therefore classified as compatible I, along with amalgam, gold alloy, gold–ceramic crowns, titanium alloy and NiTi orthodontic wires. Materials, the magnetic susceptibility of which differed from that of water by more than 200 ppm, were classified as non-compatible materials that should not be present in the patient’s mouth for any dMRI applications. They included stainless steel orthodontic appliances and CoCr. Conclusions: A classification of the materials that complies with the standard grouping of materials according to their magnetic susceptibility was proposed and adopted for the purposes of dMRI. The proposed classification can serve as a guideline in future dMRI research. PMID:23610088

  18. Comparative investigation of smooth polycrystalline diamond films on dental burs by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Sein, Htet; Ahmed, Waqar; Rego, Christopher; Jackson, Mark; Polini, Riccardo

    2006-04-01

    Depositions of hot filament chemical vapor-deposited diamond on cobalt-cemented tungsten carbide (WC-Co) rotary cutting dental burs are presented. Conventional dental tools made of sintered polycrystalline diamond have a number of problems associated with the heterogeneity of the crystallite, decreased cutting efficiency, and short life. A preferential (111) faceted diamond was obtained after 15 h of deposition at a growth rate of 1.1 µm/h. Diamond-coated WC-Co dental burs and conventional sintered burs are mainly used in turning, milling, and drilling operations for machining metal ceramic hard alloys such as CoCr, composite teeth, and aluminum alloy in the dental laboratory. The influence of structure, the mechanical characteristics of both diamond grains and hard alloys on the wear behavior, as well as the regimen of grinding on diamond wear are considered. Erosion wear properties are also investigated under air-sand erosion testing. After machining with excessive cutting performance, calculations can be made on flank and crater wear areas. Diamond-coated WC-Co dental burs offered significantly better erosion and wear resistance compared with uncoated WC-Co tools and sintered burs.

  19. [Dental biofilms].

    PubMed

    Simain, F; Rompen, E; Heinen, E

    2010-10-01

    Orodental pathologies are generally classified into two main groups: caries and parodontopathies. They result from polymicrobial infections based on the dental plaque's theory which has constantly evolved. Therefore, the concept of acquired biological pellicle or biofilm has been described and largely elaborated.A bacterial biofilm is a unit of bacterial microcolonies embedded within an exopolymeric matrix and adherent to an inert or living surface. The aim of this paper is to provide a review of the literature with regard to the formation, and composition of the biofilm, as well as to point out the close link that exists between biofilm and dental medicine.

  20. Dental Caries

    PubMed Central

    Burgess, Ralph C.

    1988-01-01

    Dental caries is one of the most prevalent diseases afflicting mankind. It reached a peak in the 1950s but has been declining drastically in recent years in children and young adults. This article describes the three contributing factors in dental caries: microbial plaque, tooth susceptibility, and diet, and discusses practical preventive measures which help to reduce caries incidence. Some of these, such as vaccines and antimicrobial varnishes, are still in the research stages, while others, such as sucrose substitutes, low-calorie sweeteners, and limitation of frequency of sugar snacks are well established and can be promoted by family physicians. PMID:21253193

  1. The efficacy of neem extract on four microorganisms responsible for causing dental caries viz Streptococcus mutans, Streptococcus salivarius, Streptococcus mitis and Streptococcus sanguis: an in vitro study.

    PubMed

    Chava, Venkateswara Rao; Manjunath, S M; Rajanikanth, A V; Sridevi, N

    2012-11-01

    HISTORY AND OBJECTIVES: From the ancient time, neem used to be the traditional medicine for many diseases and was mainly used for cleaning the oral cavity. The incidence of dental caries was less a few decades ago but now the incidence of caries is very aggressive. This might be due to change in dietary habits, life style and more tendency toward processed food. The objective of this study is to find out the truth that if the neem is really efficacious against caries-inducing microorganisms, mainly Streptococcus mutans, Streptococcus salivarius, Streptococcus mitis and Streptococcus sanguis. The dried neem sticks ground into a coarse powder and weighed into 5, 10 and 50 gm were added to 100 ml of deionized double distilled water. After soaking for 2 days, the water was filtered at 4 °C and the fine filtrate was inoculated onto blood agar plates contains individual species of microorganisms and incubated at 37 °C for 2 days. At maximum concentrations, neem extract has shown the maximum zone of inhibition on Streptococcus mutans. At less concentration, the efficacy of neem has shown some inhibition of growth for all the four species of microorganisms. Neem chewing provides the maximum benefits. Hence, the use of chewing sticks of neem can be recommended.

  2. Comparison of injection pain caused by the DentalVibe Injection System versus a traditional syringe for inferior alveolar nerve block anaesthesia in paediatric patients.

    PubMed

    Elbay, M; Şermet Elbay, Ü; Yıldırım, S; Uğurluel, C; Kaya, C; Baydemir, C

    2015-06-01

    To compare paediatric patients' pain during needle insertion and injection in inferior alveoler nerve block (IANB) anaesthesia injected by either a traditional syringe (TS) or the DentalVibe Injection Comfort System (DV). the study was a randomised controlled crossover clinical trial, comprised of 60 children aged 6-12 requiring an operative procedure with IANB anaesthesia on their mandibular molars bilaterally. One of the molar teeth was treated with TS and the contralateral tooth was treated with DV. On each visit, subjective and objective pain was evaluated using the Wond-Baker Faces Pain Rating Scale (PRS) and the Face, Legg, Cry, Consolability Scale (FLACC Scale). Patients were asked which anaesthesia technique they preferred. Data were analysed using Wilcoxon signed rank, Spearman correlation, and Mann-Whitney U tests. There were no statistically significant differences for pain evalution during needle insertion and injection of each injection system. However, a negative correlation was found on the FLACC between age and pain scores during injection after using DV. Paediatric patients experienced similar pain during IANB anaesthesia administered with TS and DV. With increased age, pain values reduced during anaesthetic agent injection with DV according to FLACC. The traditional procedure was preferred to DV in paediatric patients.

  3. Contact dermatitis from beryllium in dental alloys.

    PubMed

    Haberman, A L; Pratt, M; Storrs, F J

    1993-03-01

    An increasing number of metals with the potential to cause allergic contact dermatitis have found their way into dental alloys for economic and practical reasons. 2 patients are reported who developed gingivitis adjacent to the Rexillium III alloy in their dental prostheses. Patch testing demonstrated positive reactions to beryllium sulfate, a component of the alloy. Components of dental alloys and the mechanism of the contact dermatitis are discussed.

  4. Abrasion: A Common Dental Problem Revisited.

    PubMed

    Milosevic, Alex

    2017-02-28

    Dental abrasion is most commonly seen at the cervical necks of teeth, but can occur in any area, even inter-dentally from vigorous and incorrect use of dental floss. Acid erosion has been implicated in the initiation and progress of the cervical lesion, while tooth-brush abrasion has long been held as the prime cause of cervical abrasion. Identification of the risk factors is clearly important in order to modify any habits and provide appropriate advice.

  5. Coatings for wear and lubrication

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1978-01-01

    Recent advances in the tribological uses of rf-sputtered and ion plated films of solid film lubricants (laminar solids, soft metals, organic polymers) and wear resistant refractory compounds (carbides, nitrides, silicides) are reviewed. The sputtering and ion plating potentials and the corresponding coatings formed were evaluated relative to the friction coefficient, wear endurance life and mechanical properties. The tribological and mechanical properties for each kind of film are discussed in terms of film adherence, coherence, density, grain size, morphology, internal stresses, thickness, and substrate conditions such as temperature, topography, chemistry and dc-biasing. The ion plated metallic films in addition to improved tribological properties also have better mechanical properties such as tensile strength and fatigue life.

  6. Low wear partially fluorinated polyimides

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.; Hady, W. F.

    1984-01-01

    Tribological studies were conducted on five different polyimide solid bodies formulated from the diamine 2,2-bis 4-(4-aminophenoxy)phenyl hexafluoropropane (4-BDAF) and the dianhydrides pyromellitic acid (PMDS) and benzophenonetetracarboxylic acid (BTDA). The following polyimides were evaluated 4-BDAF/PMDA, 4-BDAF/BTDA, 4-BDAF/80 mole percent PMDA, 20 mole percent BTDA, 4-BDAF/60 mole percent BTDA. Friction coefficients, polyimide wear rates, polyimide surface morphology and transfer films were evaluated at sliding speeds of 0.31 to 11.6 m/s and at temperatures of 25 C to 300 C. The results indicate that the tribological properties are highly dependent on the composition of the polyimide and on the experimental conditions. Two polyimides were found which produced very low wear rates but very high friction coefficients (greater than 0.85) under ambient conditions. They offer considerable potential for high traction types of application such as brakes.

  7. Low wear partially fluorinated polyimides

    SciTech Connect

    Fusaro, R.L.; Hady, W.F.

    1984-01-01

    Tribological studies were conducted on five different polyimide solid bodies formulated from the diamine 2,2-bis 4-(4-aminophenoxy)phenyl hexafluoropropane (4-BDAF) and the dianhydrides pyromellitic acid (PMDS) and benzophenonetetracarboxylic acid (BTDA). The following polyimides were evaluated 4-BDAF/PMDA, 4-BDAF/BTDA, 4-BDAF/80 mole percent PMDA, 20 mole percent BTDA, 4-BDAF/60 mole percent BTDA. Friction coefficients, polyimide wear rates, polyimide surface morphology and transfer films were evaluated at sliding speeds of 0.31 to 11.6 m/s and at temperatures of 25 C to 300 C. The results indicate that the tribological properties are highly dependent on the composition of the polyimide and on the experimental conditions. Two polyimides were found which produced very low wear rates but very high friction coefficients (greater than 0.85) under ambient conditions. They offer considerable potential for high traction types of application such as brakes.

  8. Coatings for wear and lubrication

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1978-01-01

    In this paper we review the recent advances in the tribological uses of R.F.-sputtered and ion-plated films of solid film lubricants (laminar solids, soft metals, organic polymers) and wear-resistant refractory compounds (carbides, nitrides, silicides). The sputtering and ion-plating potentials and the corresponding coatings formed are evaluated relative to the friction coefficient, wear endurance life and mechanical properties. The tribological and mechanical properties of each kind of film are discussed in terms of film adherence, coherence, density, grain size, morphology, internal stresses and thickness and substrate conditions such as temperature, topography, chemistry and d.c. biasing. The ion-plated metallic films in addition to improved tribological properties also have better mechanical properties such as tensile strength and fatigue life.

  9. Wear testing of crosslinked polyethylene: wear rate variability and microbial contamination.

    PubMed

    Brandt, J-M; Vecherya, A; Guenther, L E; Koval, S F; Petrak, M J; Bohm, E R; Wyss, U P

    2014-06-01

    The wear performance of two types of crosslinked polyethylene (Marathon™ and XLK™, DePuy Synthes Inc., Warsaw, IN) was evaluated in a pin-on-disc wear tester, a hip wear simulator, and a knee wear simulator. Sodium azide was used as the microbial inhibitor in the calf serum-based lubricant. In the pin-on-disc wear tester, the Marathon wear rate of 5.33±0.54mm(3)/Mc was significantly lower (p=0.002) than the wear rate of 6.43±0.60mm(3)/Mc for XLK. Inversely, the Marathon wear rate of 15.07±1.03mm(3)/Mc from the hip wear simulator was 2.2-times greater than the XLK wear rate of 6.71±1.03mm(3)/Mc from the knee wear simulator. Differences in implant design, conformity, GUR type, and kinematic test conditions were suggested to account for the difference between the wear rates generated in the different types of wear testing apparati. In all wear tests, sodium azide was ineffective at inhibiting microbial growth in the lubricant. Eight different organisms were identified in the lubricant samples from the wear tests, which suggested the necessity of using an alternative, more effective microbial inhibitor. Careful sample preparation and thorough cleaning has shown to improve the consistency of the wear results. The wear rates generated in the hip and knee wear simulators closely reflected the wear behaviour of Marathon and XLK reported in published data that were tested under similar conditions.

  10. Hydraulic System Wear Debris Analysis.

    DTIC Science & Technology

    1982-08-03

    drawn. Each one-=L sample was drawn with a clean plastic pipette of one-mL capacity. The samples were placed in clean Ferrogram preparation bottles ...and from cavities in a block which held linear seals into sampling bottles . Several photographs of this debris , which was deposited on Ferro- grams...silicon in the glass overshadowed the elements of the wear debris . To overcome this difficulty, the Ferrogram should be pre- pared on a carbon-filled

  11. Wear of steel by rubber

    NASA Technical Reports Server (NTRS)

    Gent, A. N.; Pulford, C. T. R.

    1978-01-01

    Wear of a steel blade used as a scraper to abrade rubber surfaces has been found to take place much more rapidly on a cis-polyisoprene (natural rubber) surface than on a cis-polybutadiene surface, and much more rapidly in an inert atmosphere than in air. These observations are attributed to the direct attack upon steel of free-radical species generated by mechanical rupture of elastomer molecules during abrasion.

  12. Wear of steel by rubber

    NASA Technical Reports Server (NTRS)

    Gent, A. N.; Pulford, C. T. R.

    1978-01-01

    Wear of a steel blade used as a scraper to abrade rubber surfaces has been found to take place much more rapidly on a cis-polyisoprene (natural rubber) surface than on a cis-polybutadiene surface, and much more rapidly in an inert atmosphere than in air. These observations are attributed to the direct attack upon steel of free-radical species generated by mechanical rupture of elastomer molecules during abrasion.

  13. Trends in dental and allied dental education.

    PubMed

    Neumann, Laura M

    2004-09-01

    Educational programs play an important role in preparing a qualified dental work force. This article reviews the current status and trends in dental, advanced dental and allied dental education programs in the United States and examines their impact on the dental work force. This analysis focuses on survey data collected by the American Dental Association during the past 10 to 15 years and compares recent patterns in applications, enrollment and graduation with previous trends. The numbers of educational programs, applicants, enrollees and graduates have increased in dentistry, dental hygiene and dental assisting, while dental laboratory technology has declined in all measures. The proportion of women in dentistry has increased, while the ethnic profile of dental and allied personnel has shown little change. Both the cost of dental education and student debt continue to increase. Despite increases in the number of educational programs and overall numbers of graduates from dental and allied dental education programs, the proportion of underrepresented groups still lags behind their representation in the overall population, and the number of allied personnel falls short of practice needs. Patterns in applications, enrollment and graduation are important determinants of the dental and allied dental work force. The cost and funding of education significantly affect the attractiveness of dental careers and the sustainability of educational programs and should be monitored carefully by the profession.

  14. Attitude and beliefs of Nigerian undergraduates to spectacle wear.

    PubMed

    Ebeigbe, J A; Kio, F; Okafor, L I

    2013-06-01

    Uncorrected refractive error is a common cause of preventable visual impairment. Glasses are the cheapest and commonest form of correction of refractive errors. To achieve this, patients must exhibit good compliance to spectacle wear. Patients' attitude and perception of glasses and eye health could affect compliance to spectacle wear. To determine the attitude and beliefs of Nigerian undergraduates to spectacle wear. A cross sectional study of 500 undergraduates of the University of Benin, Nigeria. Age range was from 18 to 30 years, mean age 23 ± 2.7 years. There were 269 males and 231 females. Semi structured questionnaires were distributed to the participants and collected same day after completion. Two-thirds (68%) of the total population studied had not heard of refractive error. About a third (38%) believed wearing eyeglasses was one of the methods used to correct refractive error. Half (50%) believed they would wear spectacles if prescribed with one by their doctor. Sixty-four percent believed eyeglasses are harmful to the eyes; and 65% did not know that eyeglasses could be used to relieve other forms of ocular discomfort like headache and tearing. Fifty-seven per cent of respondents saw people who wore eyeglasses as visually handicapped, while 60% believed that eyeglasses were meant for old people. Majority of the respondents (56%) believed that they would be teased if they wore glasses. Knowledge of refractive errors and acceptance of glasses for the correction of refractive errors among Nigerian undergraduates is not encouraging. Public enlightenment programs to promote benefits of wearing prescribed spectacles are needed.

  15. Wearing ambidextrous vinyl gloves does not impair manual dexterity.

    PubMed

    Drabek, Tomas; Boucek, Charles D; Buffington, Charles W

    2013-01-01

    Universal precautions mandate that health care workers wear gloves to prevent the unintended spread of bloodborne pathogens. Gloves may affect manual dexterity, generally delaying task completion. Our previous study showed that wearing the wrong size latex surgical glove degraded manual dexterity. The use of non-sterile and non-latex gloves may limit certain risks and be more cost-effective. However, such gloves may produce different results. We hypothesized that ambidextrous vinyl examination gloves would degrade manual dexterity compared with bare hands. We studied 20 random subjects from a medical environment. Subjects performed a standard battery of Grooved Pegboard tasks while bare-handed, wearing ambidextrous non-sterile vinyl gloves that were their preferred size, a size too small, and a size too large. The order was randomized with a Latin Square design to minimize the effects of time, boredom, and fatigue on the subjects. Subjects were also invited to comment on the fit of different size gloves. Wearing vinyl gloves of both the preferred size and a size up or down failed to affect manual dexterity vs. bare hands on time to insert pegs, and pegs dropped during insertion or removal. In contrast, the time to remove pegs was reduced by wearing preferred size vinyl gloves compared with performing the task with bare hands (P<0.05). Subjects reported a generally poor fit in all sizes. Vinyl gloves that were too small caused significant hand discomfort. Vinyl gloves surprisingly do not degrade manual dexterity even when worn in ill-fitting sizes. Wearing a preferred size vinyl glove vs. bare hands may improve dexterity in selected tasks. Choosing a comfortable, large size seems the best strategy when the preferred size is unavailable. Thinner vinyl gloves may improve grip and may not degrade touch as much as latex surgical gloves and may thus represent a reasonable choice for selected tasks.

  16. Wear resistance of hydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Martinez, MA; Abenojar, J.; Pantoja, M.; López de Armentia, S.

    2017-05-01

    Nature has been an inspiration source to develop artificial hydrophobic surfaces. During the latest years the development of hydrophobic surfaces has been widely researched due to their numerous ranges of industrial applications. Industrially the use of hydrophobic surfaces is being highly demanded. This is why many companies develop hydrophobic products to repel water, in order to be used as coatings. Moreover, these coating should have the appropriated mechanical properties and wear resistance. In this work wear study of a hydrophobic coating on glass is carried out. Hydrophobic product used was Sika Crystal Dry by Sika S.A.U. (Alcobendas, Spain). This product is currently used on car windshield. To calculate wear resistance, pin-on-disk tests were carried out in dry and water conditions. The test parameters were rate, load and sliding distance, which were fixed to 60 rpm, 5 N and 1000 m respectively. A chamois was used as pin. It allows to simulate a real use. The friction coefficient and loss weight were compared to determinate coating resistance

  17. [Transmission electron microscopy image of wear particles of joint endoprostheses and ultrastructural cell changes].

    PubMed

    Bos, I; Johannisson, R

    2003-01-01

    Wear particles from joint endoprostheses vary considerably in size, and may be detectable in tissue only by electron microscopy. Wear debris plays a central role in the non-infectious late loosening of prostheses, and it has been estimated that the submicron particles induce increased liberation of mediators of osteolysis by activated macrophages. From the types of prostheses currently in use, bone cement and polyethylene particles greatly predominate over metallic and ceramic particles. Since it had formerly not been possible to reliably identify wear particles in the transmission electron microscopy, and descriptions of them in the literature varied considerably, we analysed ultrathin sections obtained from periprosthetic tissue containing wear particles previously identified by laser microprobe mass analysis. Using this method, it proved possible to classify almost all the wear particles detected in the electron microscope, to determine their size range and to represent the cellular alterations caused by them.

  18. Sliding wear behaviors of steam generator tube materials in high temperature water environment

    NASA Astrophysics Data System (ADS)

    Park, Gi Sung; Kim, Gyung Guk; Kim, Seon Jin

    2006-06-01

    Wear damage of steam generator tubes for nuclear power plants can cause the leakage of radioactive substances. Therefore, the evaluation of the tube integrity is very important in the view point of nuclear safety. In the present study, to investigate the effects of the applied normal load and sliding distance on wear volume in 575 K water environment, sliding wear tests were performed with Inconel 600 and 690 steam generator tube materials mated with 409 stainless steel commonly used as support plate. Based on the accumulated data, the newly modified Archard equation was proposed and then the wear coefficients of tube materials were estimated with both Archard equation and the modified Archard equation. The reliabilities, which are parameters to assess how well a model fits a set of data, for prediction of wear behaviors of Inconel 600 and 690 improved from 20.5% to 65.5% and from 38.5 to 65.3%, respectively.

  19. Special cluster issue on tribocorrosion of dental materials

    NASA Astrophysics Data System (ADS)

    Mathew, Mathew T.; Stack, Margaret M.

    2013-10-01

    Tribocorrosion affects all walks of life from oil and gas conversion to biomedical materials. Wear can interact with corrosion to enhance it or impede it; conversely, corrosion can enhance or impede wear. The understanding of the interactions between physical and chemical phenomena has been greatly assisted by electrochemical and microscopic techniques. In dentistry, it is well recognized that erosion due to dissolution (a term physicists use to denote wear) of enamel can result in tooth decay; however, the effects of the oral environment, i.e. pH levels, electrochemical potential and any interactions due to the forces involved in chewing are not well understood. This special cluster issue includes investigations on the fundamentals of wear-corrosion interactions involved in simulated oral environments, including candidate dental implant and veneer materials. The issue commences with a fundamental study of titanium implants and this is followed by an analysis of the behaviour of commonly used temporomandibular devices in a synovial fluid-like environment. The analysis of tribocorrosion mechanisms of Ti6Al4V biomedical alloys in artificial saliva with different pHs is addressed and is followed by a paper on fretting wear, on hydroxyapatite-titanium composites in simulated body fluid, supplemented with protein (bovine serum albumin). The effects of acid treatments on tooth enamel, and as a surface engineering technique for dental implants, are investigated in two further contributions. An analysis of the physiological parameters of intraoral wear is addressed; this is followed by a study of candidate dental materials in common beverages such as tea and coffee with varying acidity and viscosity and the use of wear maps to identify the safety zones for prediction of material degradation in such conditions. Hence, the special cluster issue consists of a range of tribocorrosion contributions involving many aspects of dental tribocorrosion, from analysis of physiological

  20. Dental erosion in archaeological human remains: A critical review of literature and proposal of a differential diagnosis protocol.

    PubMed

    Coupal, Isabelle; Sołtysiak, Arkadiusz

    2017-09-18

    Although studies of dental wear on archaeological human remains have largely focused on mechanical wear (attrition and abrasion) in the past, chemical wear (erosion) is being increasingly identified as a separate form of wear. This paper aims to review the current state of research and to develop a protocol that may be universally used by biorchaeologists to specifically identify dental erosion. A critical review of literature has been done in order to highlight the issues related to diagnosis of dental erosion in archaeological human remains. The bodies of work based on the analysis of both modern and archaeological dentitions raise their separate problems. In addition to a need to re-evaluate symptoms of dental erosion, notably dentin 'cupping', it is apparent that no specific protocol is adapted from medical to archaeological sciences. Authors rather rely on tooth wear indices and photographs of modern clinical cases for diagnosis. Furthermore, the diagenetic chemical alternation has rarely been considered as a bias. Here we suggest a three-step protocol: the primary method is the microscopic identification of dental erosion by SEM, followed by the exclusion of taphonomic aetiology on surrounding bone and soil pH analysis. Archaeologists should also explore possible causative agents of wear using archaeological and historic knowledge about the population being analyzed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Copper deficit as a potential pathogenic factor of reduced bone mineral density and severe tooth wear.

    PubMed

    Sierpinska, T; Konstantynowicz, J; Orywal, K; Golebiewska, M; Szmitkowski, M

    2014-02-01

    The study evaluated if men and women with severe tooth wear were at increased risk of general bone loss. Enamel biopsies obtained from 50 subjects aged 47.5 ± 5 years showed decreased copper content, which was associated with reduced spine bone mineral density, suggesting deficits of this trace element contributing to bone demineralization, enamel attrition, and deteriorated quality of mineralized tissues. The objective of this cross-sectional study was to assess associations between enamel trace minerals and bone mineral density (BMD) in severe tooth wear. We hypothesized that similar factors contributed to both the excessive abrasion of dental enamel and reduced BMD in subjects with tooth wear. Fifty patients aged 47.5 ± 5 years with severe tooth wear and 20 age-, sex-, and body mass index (BMI)-matched healthy volunteers with normal dental status were studied regarding dietary intakes of trace elements, serum and salivary copper (Cu), zinc (Zn), and calcium (Ca) concentrations, and serum PTH, osteocalcin, and hydroxyvitamin D levels. Tooth wear was determined using clinical examination based on standard protocol according to Smith and Knight. In all subjects, acid biopsies of the maxillary central incisors were carried out to assess mineral composition of the enamel. Atomic absorption spectroscopy with an air/acetylene flame was used to measure Ca and Zn, and graphite furnace atomic absorption spectroscopy was used to analyze Cu content. BMD was examined using dual energy X-ray absorptiometry. Tooth wear patients had reduced lumbar spine, but not femoral, BMD relative to controls (p < 0.001). No differences were found in enamel Ca concentration and Zn content was slightly higher in tooth wear patients than in controls whereas Cu content was significantly decreased in the patients: 19.59 ± 16.4 vs 36.86 ± 26.1 μg/l (p = 0.01) despite similar levels of Cu in serum and saliva. The differences were independent of serum 25-OH-D, osteocalcin concentrations or PTH

  2. Morbidly obese patient with non-alcoholic steatohepatitis-related cirrhosis who died from sepsis caused by dental infection of Porphyromonas gingivalis: A case report.

    PubMed

    Omura, Yuno; Kitamoto, Mikiya; Hyogo, Hideyuki; Yamanoue, Takao; Tada, Yoshihiro; Boku, Noriko; Nishisaka, Takashi; Miyauchi, Mutsumi; Takata, Takashi; Chayama, Kazuaki

    2016-03-01

    Non-alcoholic steatohepatitis (NASH) is associated with increased risks of developing lifestyle-related diseases including type 2 diabetes, cardiovascular disease and cerebral vessel disease. While the two-hit hypothesis and, recently, multiple parallel hits hypothesis of NASH pathogenesis were proposed, further details have not emerged. Recently, dental infection of Porphyromonas gingivalis (P. gingivalis) has been reported as a critical risk factor for NASH progression, which acts as multiple parallel hits to induce inflammation and fibrogenic responses in steatosis. We describe here a 54-year-old woman who died from sepsis and was diagnosed with NASH. Briefly, her body mass index (BMI) at the age of 35 years old had been 25.6 kg/m(2) , but she became obese after withdrawing into her home at the age of 45 years. Severe obesity continued over 19 years without diabetes mellitus. She was admitted to our hospital due to a sudden disturbance of consciousness. On admission, her BMI was 48.5 kg/m(2) . Computed tomography revealed cirrhotic liver with massive ascites, and laboratory data indicated increased inflammatory responses, renal failure and C grade Child-Pugh classification, suggesting the diagnosis of sepsis. Also, severe periodontal disease was present, because the patient's front teeth fell out easily during intubation. Although the focus of infection was not specified, the oral flora Parvimonas micra, a periodontal pathogen, was detected in venous blood. In spite of intensive care including artificial respiration management and continuous hemodiafiltration, she died on the 43rd day after admission. Surprisingly, P. gingivalis was detected in her hepatocytes. This case may represent the significance of P. gingivalis in the progress to cirrhosis in NASH patients.

  3. Relationship Between Simulated Gap Wear and Generalized Wear of Resin Luting Cements.

    PubMed

    Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miayazaki, M

    The relationship between the simulated gap wear and generalized wear of resin luting cements was investigated. Five resin luting cements, G-Cem LinkForce (GL), Multilink Automix (MA), NX3 Nexus, Panavia V5 (PV), and RelyX Ultimate were evaluated and subsequently subjected to a wear challenge in a Leinfelder-Suzuki (Alabama) wear simulation device. Half of the specimens from each resin luting cement were photo-cured for 40 seconds and the other half were not photo-cured. The simulated gap and generalized wear were generated using a flat-ended stainless steel antagonist. Wear testing was performed in a water slurry of polymethyl methacrylate beads, and the simulated gap and generalized wear were determined using a noncontact profilometer (Proscan 2100) in conjunction with the Proscan and AnSur 3D software. A strong relationship was found between the gap wear and generalized wear simulation models. The simulated gap wear and generalized wear of the resin luting cements followed similar trends in terms of both volume loss and mean depth of wear facets with each curing method. Unlike the simulated gap wear and generalized wear of GL and PV, those of MA, NX, and RU were influenced by the curing method. The results of this study indicate that simulated gap wear of resin luting cements is very similar to simulated generalized wear. In most cases, dual curing appears to ensure greater wear resistance of resin luting cements than chemical curing alone. The wear resistance of some resin luting cements appears to be material dependent and is not influenced by the curing method.

  4. Synovial fluid differential cell count in wear debris synovitis after total knee replacement.

    PubMed

    Schwarzkopf, Ran; Carlson, Evan M; Tibbo, Meagan E; Josephs, Lee; Scott, Richard D

    2014-12-01

    Determining the cause of synovitis following total knee arthroplasty (TKA) can be challenging. The differential diagnoses include infection, hemarthrosis, instability, crystalline disease, wear debris or idiopathic causes. Wear particle synovitis can mimic periprosthetic infection with symptoms of pain and effusion. Radiographs and physical exam are often inconclusive in differentiating the two. Synovial fluid analysis is routinely used in evaluating periprosthetic infections. We examined the association between synovial white blood cell count and differentials, and polyethylene wear and osteolysis, to see if fluid analysis can aid in establishing the diagnosis of wear particle synovitis. A cell count and differential was obtained from synovial fluid samples from 54 TKAs undergoing revision for aseptic failure. Explanted polyethylene inserts were analyzed for linear and volumetric wear, oxidation (ketone peak height), and damage features. Analysis was performed to assess the relationship between cell counts and polyethylene wear indicators as well as severity of intra-operative and radiographic osteolysis. Total and percent mononuclear (monocyte and lymphocyte) cell counts were found to be elevated in the presence of documented wear debris synovitis and an association was suggested between their levels and maximum ketone levels. The present study implies that the differential cell count of knee fluid can help distinguish wear debris from infection as a source of synovitis following TKA and identifies the value of the mononuclear cell count as a possible tool to assess abnormal wear rates of the polyethylene insert. Further research into identifying the exact role of monocytes in the wear debris synovitis and osteolytic pathways is warranted. Level II, diagnostic study. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Tooth wear pattern analysis in a sample of Italian Early Bronze Age population. Proposal of a 3-D sampling sequence.

    PubMed

    Masotti, Sabrina; Bogdanic, Nika; Arnaud, Julie; Cervellati, Franco; Gualdi-Russo, Emanuela

    2017-02-01

    The purpose of this study was to assess the prevalence, distribution and intensity of tooth wear in a sample of an ancient Italian population in order to explain the pattern in terms of dietary habits and/or non-dietary tooth-use behaviors during the Early Bronze Age, with a focus on possible age-group and sex differences. Well-preserved permanent teeth of individuals from the Bronze Age site of Ballabio (Lecco) in northern Italy were examined for tooth wear by different methods. Eight 3D models of teeth at increasing severity of wear were created. In total, 357 permanent teeth belonging to male and female individuals were included in the study. Dental wear was present in 96.6% of the total sample. Males showed significantly greater levels of wear than females in the mandibular teeth. Both sexes exhibited a significantly different wear direction between the anterior (oblique and flat) and posterior (oblique and concave) teeth. Significant age differences were observed in the direction and level of wear in the incisors, canines and premolars, with higher wear in the older group. Complete and rotatable virtual 3D images of different wear patterns are proposed. The findings of the present study confirm the data from archaeological studies on this site and on northern Italian habits during the Early Bronze Age suggesting a diet rich in vegetables. The observed wear patterns can be related both to the diet of this Bronze age population, based on hard and abrasive food requiring vigorous mastication, and to sex differences in cultural practices. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Assessment of wear coefficients of nuclear zirconium claddings without and with pre-oxidation

    DOE PAGES

    Qu, Jun; Cooley, Kevin M.; Shaw, Austin H.; ...

    2016-03-16

    In the cores of pressurized water nuclear reactors, water-flow induced vibration is known to cause claddings on the fuel rods to rub against their supporting grids. Such grid-to-rod-fretting (GTRF) may lead to fretting wear-through and the leakage of radioactive species. The surfaces of actual zirconium alloy claddings in a reactor are inevitably oxidized in the high-temperature pressurized water, and some claddings are even pre-oxidized. As a result, the wear process of the surface oxide film is expected to be quite different from the zirconium alloy substrate. In this paper, we attempt to measure the wear coefficients of zirconium claddings withoutmore » and with pre-oxidation rubbing against grid samples using a bench-scale fretting tribometer. Results suggest that the volumetric wear coefficient of the pre-oxidized cladding is 50 to 200 times lower than that of the untreated cladding. In terms of the linear rate of wear depth, the pre-oxidized alloy wears about 15 times more slowly than the untreated cladding. Finally, fitted with the experimentally-determined wear rates, a stage-wise GTRF engineering wear model demonstrates good agreement with in-reactor experience in predicting the trend of cladding lives.« less

  7. Polyethylene wear of mobile-bearing unicompartmental knee replacement at 20 years.

    PubMed

    Kendrick, B J L; Simpson, D J; Kaptein, B L; Valstar, E R; Gill, H S; Murray, D W; Price, A J

    2011-04-01

    The Oxford unicompartmental knee replacement (UKR) was designed to minimise wear utilising a fully-congruent, mobile, polyethylene bearing. Wear of polyethylene is a significant cause of revision surgery in UKR in the first decade, and the incidence increases in the second decade. Our study used model-based radiostereometric analysis to measure the combined wear of the upper and lower bearing surfaces in 13 medial-compartment Oxford UKRs at a mean of 20.9 years (17.2 to 25.9) post-operatively. The mean linear penetration of the polyethylene bearing was 1.04 mm (0.307 to 2.15), with a mean annual wear rate of 0.045 mm/year (0.016 to 0.099). The annual wear rate of the phase-2 bearings (mean 0.022 mm/year) was significantly less (p = 0.01) than that of phase-1 bearings (mean 0.07 mm/year). The linear wear rate of the Oxford UKR remains very low into the third decade. We believe that phase-2 bearings had lower wear rates than phase-1 implants because of the improved bearing design and surgical technique which decreased the incidence of impingement. We conclude that the design of the Oxford UKR gives low rates of wear in the long term.

  8. Assessment of wear coefficients of nuclear zirconium claddings without and with pre-oxidation

    SciTech Connect

    Qu, Jun; Cooley, Kevin M.; Shaw, Austin H.; Lu, Roger Y.; Blau, Peter J.

    2016-03-16

    In the cores of pressurized water nuclear reactors, water-flow induced vibration is known to cause claddings on the fuel rods to rub against their supporting grids. Such grid-to-rod-fretting (GTRF) may lead to fretting wear-through and the leakage of radioactive species. The surfaces of actual zirconium alloy claddings in a reactor are inevitably oxidized in the high-temperature pressurized water, and some claddings are even pre-oxidized. As a result, the wear process of the surface oxide film is expected to be quite different from the zirconium alloy substrate. In this paper, we attempt to measure the wear coefficients of zirconium claddings without and with pre-oxidation rubbing against grid samples using a bench-scale fretting tribometer. Results suggest that the volumetric wear coefficient of the pre-oxidized cladding is 50 to 200 times lower than that of the untreated cladding. In terms of the linear rate of wear depth, the pre-oxidized alloy wears about 15 times more slowly than the untreated cladding. Finally, fitted with the experimentally-determined wear rates, a stage-wise GTRF engineering wear model demonstrates good agreement with in-reactor experience in predicting the trend of cladding lives.

  9. The current status of dental graduates in India

    PubMed Central

    Yadav, Sankalp; Rawal, Gautam

    2016-01-01

    The dental profession is a noble profession. It takes years of devotion towards the subject of dentistry to get the graduate degree of Bachelor of Dental Surgery. However, even after such painstaking efforts the current situation of dental graduates in India is grave. There are a lot of issues that are the main cause for this problem. The dental graduates are in a state of crisis due to lack of support from the Government. If this situation continues it will lead to a negative effect on the integrity of the dental profession, and highly trained dental manpower of the country will go in vain. PMID:27200127

  10. DENTAL ABNORMALITIES OF EIGHT WILD QINLING GIANT PANDAS (AILUROPODA MELANOLEUCA QINLINGENSIS), SHAANXI PROVINCE, CHINA.

    PubMed

    Jin, Yipeng; Chen, Si; Chao, Yanqiao; Pu, Tianchun; Xu, Hongqian; Liu, Xiaobin; Zhao, Kaihui; Nie, Yonggang; Wei, Wei; Lin, Degui

    2015-10-01

    Eight adult (six male and two female) wild Qinling giant pandas (Ailuropoda melanoleuca qinlingensis) from China National Foping Nature Reserve were tracked, and their dental data collected and recorded from October 2010 to April 2014. Each panda had dental abnormalities of varying severity. Dental wear and fracture were the most common conditions. Absent teeth were common, with premolars missing most often. Mild caries were present in five molar teeth between two animals. Different degrees of dental plaque and calculus occurred in all animals but without severe periodontal disease. Two animals with severe dental abnormalities died due to intestinal problems. Large segments of bamboo were found in their intestinal tracts, and intestinal perforation and ulcers were evident, indicating dental abnormalities can be an important factor in the health of wild giant pandas and may lead to death. Further research with larger sample sizes of wild and captive giant pandas will be required to substantiate the relationship between dental abnormalities and mortality in giant pandas.

  11. Dental Training Films.

    ERIC Educational Resources Information Center

    Veterans Administration Medical Center, Washington, DC.

    This dental training films catalog is organized into two sections. Section I is a category listing of the films by number and title, indexed according to generalized headings; categories are as follow: anatomy, articulator systems, complete dentures, dental assisting, dental laboratory technology, dental materials, dental office emergencies,…

  12. Finding Dental Care

    MedlinePlus

    ... Finding Dental Care Where can I find low-cost dental care? Dental schools often have clinics that allow dental ... can I find more information? See Finding Low Cost Dental Care . ​​​​ WWNRightboxRadEditor2 Contact Us 1-866-232-4528 nidcrinfo@ ...

  13. Silicon-based plant defences, tooth wear and voles.

    PubMed

    Calandra, Ivan; Zub, Karol; Szafrańska, Paulina A; Zalewski, Andrzej; Merceron, Gildas

    2016-02-01

    Plant-herbivore interactions are hypothesized to drive vole population cycles through the grazing-induced production of phytoliths in leaves. Phytoliths act as mechanical defences because they deter herbivory and lower growth rates in mammals. However, how phytoliths impair herbivore performance is still unknown. Here, we tested whether the amount of phytoliths changes tooth wear patterns. If confirmed, abrasion from phytoliths could play a role in population crashes. We applied dental microwear texture analysis (DMTA) to laboratory and wild voles. Lab voles were fed two pelleted diets with differing amounts of silicon, which produced similar dental textures. This was most probably due to the loss of food mechanical properties through pelletization and/or the small difference in silicon concentration between diets. Wild voles were trapped in Poland during spring and summer, and every year across a population cycle. In spring, voles feed on silica-rich monocotyledons, while in the summer they also include silica-depleted dicotyledons. This was reflected in the results; the amount of silica therefore leaves a traceable record in the dental microwear texture of voles. Furthermore, voles from different phases of population cycles have different microwear textures. We tentatively propose that these differences result from grazing-induced phytolith concentrations. We hypothesize that the high amount of phytoliths in response to intense grazing in peak years may result in malocclusion and other dental abnormalities, which would explain how these silicon-based plant defences help provoke population crashes. DMTA could then be used to reconstruct vole population dynamics using teeth from pellets or palaeontological material. © 2016. Published by The Company of Biologists Ltd.

  14. Wear mechanism and wear prevention in coal-fueled diesel engines. Task 3, Traditional approaches to wear prevention

    SciTech Connect

    Schwalb, J.A.

    1991-06-01

    Contamination of the lube-oil with hard abrasive particles leads to a three-body abrasive wear mechanism that highly accelerates piston ring/cylinder liner wear in coal-fueled diesel engines. One approach to reducing that wear is to modify the size and orientation of surface asperities on the cylinder to enhance the formation of a hydrodynamic film, and to provide avenues of escape for particles that would otherwise be trapped in the wear zone. Another approach is to introduce additives into the contaminated lube-oil that further enhance hydrodynamic film formation, form chemical films on the wearing surfaces, or form films on the contaminant particles. This work focuses on defining the effects of cylinder liner surface finish, various configurations of slots in the cylinder liner surface, and various additives in the contaminated lube-oil on the wear process. Wear tests were initiated in a bench apparatus using coal-ash contaminated lube-oil to test the various wear configurations. The results of these tests indicate that the formation of a hydrodynamic film between the ring and cylinder specimens is enhanced by increasing surface roughness, and by orienting the surface asperities normal to the direction of ring travel but modifications to the cylinder liner surface did not greatly reduce the wear rate. Additives to the lubricant seemed to have a much more significant effect on wear, with a dispersant additive highly accelerating the wear, while a detergent additive was able to reduce the wear almost to the rate achieved where there was no contaminant.

  15. Dermatitis from a chromium dental plate.

    PubMed

    Hubler, W R; Hubler, W R

    1983-09-01

    Systemic absorption of metal or metallic salts from dental and orthopedic surgical implants can produce a cutaneous allergic dermatitis in susceptible individuals. Mercury, nickel and cobalt are the most common metals to elicit such systemic allergic reactions from chronic internal exposure. A case is presented of a generalized eczematoid dermatitis apparently caused by allergy to chromium liberated from a metal dental plate.

  16. Dental education and dental practice.

    PubMed Central

    Moore, J R

    1984-01-01

    This paper relates recent modes of dental practice to changes that the public and government are likely to ask the health care professions to make in the future. As usual they are asking for the best of all worlds. First, that we maintain the clinical model to the highest standards of personal dental care based and tested against the best research at our disposal, whilst we ensure there is no reduction in the high technical standards for which british dentists have a reputation. Second, that the profession is required to consider ways of providing care on the medicosocial model for the whole community at an economic level the country will afford. The broad changes in dental education have been reviewed, from the technical apprenticeship to the establishment of strong university departments in teaching hospitals. The importance of a sound biomedical foundation and of research both to education and the credibility of dental practice as a primary health care profession is stressed if the profession is to retain its position as a sister to medicine and not slide down to that of a technical ancillary. PMID:6374141

  17. Electron beam irradiation of dental composites.

    PubMed

    Behr, Michael; Rosentritt, Martin; Faltermeier, Andreas; Handel, Gerhard

    2005-09-01

    Electron beam irradiation can be used to influence the mechanical properties of polymers. It was the aim of this study to investigate whether dental composites can benefit from irradiation in order to achieve increased fracture toughness, work of fracture, hardness or less wear. Two hundred rectangular specimens of five veneering composites were electron beam irradiated with 25, 100 and 200 kGy using an electron accelerator of 10 MeV. Fracture toughness, work of fracture, Vickers hardness, color changes and three-medium wear were measured and compared with non-irradiated specimens. Visible color changes (DeltaE>3) were observed with all composites and with all dose rates. Fracture toughness, work of fracture, Vickers hardness and resistance against wear increased significantly with few exceptions. Composites with a simple curing process needed higher dose rates while systems with a more complex curing procedure should be irradiated with lower dose rates. Electron beam irradiation can significantly change the mechanical properties of dental composites. However, color changes can limit the use of irradiation for dentistry.

  18. Conjoint corrosion and wear in titanium alloys.

    PubMed

    Khan, M A; Williams, R L; Williams, D F

    1999-04-01

    When considering titanium alloys for orthopaedic applications it is important to examine the conjoint action of corrosion and wear. In this study we investigate the corrosion and wear behaviour of Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr in phosphate buffered saline (PBS), bovine albumin solutions in PBS and 10% foetal calf serum solutions in PBS. The tests were performed under four different conditions to evaluate the influence of wear on the corrosion and corrosion on the wear behaviour as follows: corrosion without wear, wear-accelerated corrosion, wear in a non-corrosive environment and wear in a corrosive environment. The corrosion behaviour was investigated using cyclic polarisation studies to measure the ability of the surface to repassivate following breakdown of the passive layer. The properties of the repassivated layer were evaluated by measuring changes in the surface hardness of the alloys. The amount of wear that had occurred was assessed from weight changes and measurement of the depth of the wear scar. It was found that in the presence of wear without corrosion the wear behaviour of Ti-13Nb-13Zr was greater than that of Ti-6Al-7Nb or Ti-6Al-4V and that in the presence of proteins the wear of all three alloys is reduced. In the presence of corrosion without wear Ti-13Nb-13Zr was more corrosion resistant than Ti-6Al-7Nb which was more corrosion resistant than Ti-6Al-4V without proteins whereas in the presence of protein the corrosion resistance of Ti-13Nb-13Zr and Ti-6Al-7Nb was reduced and that of Ti-6Al-4V increased. In the presence of corrosion and wear the corrosion resistance of Ti-13Nb-13Zr is higher than that of Ti-6Al-7Nb or Ti-6Al-4V in PBS but in the presence of proteins the corrosion resistance of Ti-13Nb-13Zr and Ti-6Al-7Nb are very similar but higher than that of Ti-6Al-4V. The wear of Ti-13Nb-13Zr is lower than that of Ti-6Al-7Nb and Ti-6Al-4V with or without the presence of proteins in a corrosive environment. Therefore the overall

  19. Comparison of wear and clinical performance between amalgam, composite and open sandwich restorations: 2-year results.

    PubMed

    Sachdeo, A; Gray, Gordon B; Sulieman, M A; Jagger, Daryll C

    2004-03-01

    There has been some disquiet over the use of mercury containing restorative materials. The most commonly used alternative is composite resin but this has the potential disadvantage associated with wear and marginal leakage, which in turn, has proven to result in secondary caries and sensitivity. To overcome the shortcomings of a directly placed composite restoration, the glass-ionomer/composite open sandwich technique was introduced followed by the subsequent introduction of compomer systems. The aims of this study were to evaluate the wear and clinical performance of a control group of amalgam restorations compared with that of a group of posterior composite resin restorations fillings and a group of compomer/composite open sandwich restorations placed by a single general dental practitioner. The duration of the study was 2 years. One hundred and thirty three (71.4%) patients were successfully recalled and the wear and clinical performance of each restoration after 6, 12 and 24 months was measured, indirectly. There was no statistically significant difference recorded between the groups at 6 months or 1 year (p > 0.05). However, at the end of the 2-year study, there was a significantly lower rate of wear recorded for the control amalgam restorations compared with other two groups (p = 0.033). There was no statistically significant difference in wear recorded between the two groups of tooth-coloured restorations (p > 0.05). With regards to clinical performance of the restorations, occlusal and proximal contacts in each group of restoration remained satisfactory throughout the study.

  20. [Mercury and health in the dental practice].

    PubMed

    Morales Fuentes, Ivelin; Reyes Gil, Rosa

    2003-04-01

    Mercury is a heavy metal widely used by man. It is considered very toxic causing conditions in the central nervous system, behavior disturbances, and renal and sexual disorders. For a century, mercury has been used in the dental practice for its capacity of joining metals (amalgamate), its low cost and its rapid fixing in dental pieces repair. Currently, there is much controversy about the safety of dental amalgams and it has been demonstrated it poses occupational risks to dental practitioners and their assistants. The objective of this study is review aspects related to metallic mercury toxicity for personnel involved in the dental practice and patients with dental amalgams. Routes of mercury exposure in dentistry, occupational risks and measures to prevent mercury poisoning are presented here. A literature review was conducted mostly on data from Biological Abstracts and the Science Citation Index for the period between 1990 and 2000.

  1. The monitoring of micro milling tool wear conditions by wear area estimation

    NASA Astrophysics Data System (ADS)

    Zhu, Kunpeng; Yu, Xiaolong

    2017-09-01

    In micro milling, the tool wear condition is key to the geometrical and surface integrity of the product. This study proposes a novel tool wear surface area monitoring approach based on the full tool wear image, which can reflect the tool conditions better than the traditional tool wear width criteria. To meet the challenges of heavy noise, blur boundary, and mis-alignment of the captured tool wear images, this paper develops a region growing algorithm based on morphological component analysis (MCA) to solve the problems. It decomposes the original micro milling tool image into target tool images, background image and noise image. Then, the region growing algorithm is used to detect the defect and extract the wear region of the target tool image. In addition, rotation invariant features are extracted from wear region to overcome the inconsistency of wear image orientation. The experiment results show that region growing based on MCA algorithm can extract the wear region of the target tool image effectively and the extracted wear region also has good indication of tool wear conditions. It also demonstrates that the estimation of wear area can generalize the tool wear width estimation approach, and yield more accurate results than the traditional approaches.

  2. The chewing robot: a new biologically-inspired way to evaluate dental restorative materials.

    PubMed

    Raabe, D; Alemzadeh, K; Harrison, A L; Ireland, A J

    2009-01-01

    This paper presents a novel in vitro dental wear simulator based on 6-6 parallel kinematics to replicate mechanical wear formation on dental materials and components, such as individual teeth, crowns or bridges. The human mandible, guided by a range of passive structures moves with up to six degrees of freedom (DOF). Currently available wear simulators lack the ability to perform these complex chewing movements. In addition simulators are unable to replicate the normal range of chewing forces as they have no control system able to mimic the natural muscle function controlled by the human central nervous system. Such discrepancies between true in vivo and simulated in vitro movements will influence the outcome and reliability of wear studies using such approaches. This paper summarizes the development of a new dynamic jaw simulator based on the kinematics of the human jaw.

  3. Wear evaluation of a cross-linked medical grade polyethylene by ultra thin layer activation compared to gravimetry

    NASA Astrophysics Data System (ADS)

    Stroosnijder, Marinus F.; Hoffmann, Michael; Sauvage, Thierry; Blondiaux, Gilbert; Vincent, Laetitia

    2005-01-01

    Most of today's artificial joints rely on an articulating couple consisting of a CoCrMo alloy and a medical grade polyethylene. The wear of the polyethylene component is the major cause for long-term failure of these prostheses since the wear debris leads to adverse biological reactions. The polyethylene wear is usually measured by gravimetric methods, which are limited due to a low sensitivity and accuracy. To demonstrate the reliability of ultra thin layer activation (UTLA) as an alternative technique, wear tests on a cross-linked ultra-high-molecular weight polyethylene (XLPE) sliding against CoCrMo were performed on a wear tester featuring multi-directional sliding motion. The amount of polyethylene wear was evaluated by both UTLA and gravimetry. The particular TLA method used in this work employed the implantation of 7Be radioactive recoils into the polyethylene surface by means of a light mass particle beam. The results indicate that apart from its relatively high sensitivity, UTLA also offers the possibility for on-line measurements of polyethylene wear. This makes it a viable and complementary technique in wear test studies for medical implant purposes especially for those involving wear resistant materials and for rapid wear screening.

  4. Alternate paddle configuration for improved wear resistance in the saltstone mixer

    SciTech Connect

    Reigel, M.; Fowley, M.

    2013-09-23

    same way. The wear rate from wear test 2a was approximately double the wear rate from wear test 2b for paddle pairs 4 and 5. For both configurations, there was little or no wear on paddle pairs 1, 2, 3 and 6 based on mass change, indicating that the un-wetted and fully wetted premix materials cause less wear than the partially wetted premix. Additionally, inspection of the wear surface of the paddles showed more deformation on the flat paddles than the helical paddles which was consistent with the wear rates. Aligning of the auger discharge flight with paddle pair 1 resulted in a lower wear rate paddle pair 1 rather than having them misaligned with the feed augers. During the paddle wear tests, polishing wear was observed on the inside barrel of the mixer. The polishing wear is evident on the upper housing clamshell and the lower housing clamshell primarily at paddle pairs 4 and 5, which is the transition region of the mixer. Wear on the mixer barrel increases the space between the paddles and the barrel, resulting in increased grout build up on the barrel. Since the mixer barrel cannot be reconfigured or replaced in the SPF, the method for mitigating wear on the barrel is to move the more viscous grout through the transition region as quickly as possible. In addition, the location of the liquid inlet does not allow for sufficient cleaning of the mixer since residual grout remains on paddle pairs 1 - 4. As the paddles continue to wear and the self-cleaning capability of the paddles is lost, the lack of sufficient flushing would aid in grout build up between the barrel and the paddles which could eventually lead to decreased throughput capacity of the dry feeds. Changing the paddle configuration from flat to helical resulted in no change to the rheological properties of the grout mixture. Both tests produced a grout that is within the processing range of the SPF. Based on the results of this testing, it is recommended for the currently installed SPF mixer that paddle

  5. Enhancing Fracture and Wear Resistance of Dentures/Overdentures Utilizing Digital Technology: A Case Series Report.

    PubMed

    Afify, Ahmed; Haney, Stephan

    2016-08-01

    Since it was first introduced into the dental world, computer-aided design/computer-aided manufacturing (CAD/CAM) technology has improved dramatically in regards to both data acquisition and fabrication abilities. CAD/CAM is capable of providing well-fitting intra- and extraoral prostheses when sound guidelines are followed. As CAD/CAM technology encompasses both surgical and prosthetic dental applications as well as fixed and removable aspects, it could improve the average quality of dental prostheses compared with the results obtained by conventional manufacturing methods. The purpose of this article is to provide an introduction into the methods in which this technology may be used to enhance the wear and fracture resistance of dentures and overdentures. This article will also showcase two clinical reports in which CAD/CAM technology has been implemented.

  6. Primate dental ecology: How teeth respond to the environment.

    PubMed

    Cuozzo, Frank P; Ungar, Peter S; Sauther, Michelle L

    2012-06-01

    Teeth are central for the study of ecology, as teeth are at the direct interface between an organism and its environment. Recent years have witnessed a rapid growth in the use of teeth to understand a broad range of topics in living and fossil primate biology. This in part reflects new techniques for assessing ways in which teeth respond to, and interact with, an organism's environment. Long-term studies of wild primate populations that integrate dental analyses have also provided a new context for understanding primate interactions with their environments. These new techniques and long-term field studies have allowed the development of a new perspective-dental ecology. We define dental ecology as the broad study of how teeth respond to, or interact with, the environment. This includes identifying patterns of dental pathology and tooth use-wear, as they reflect feeding ecology, behavior, and habitat variation, including areas impacted by anthropogenic disturbance, and how dental development can reflect environmental change and/or stress. The dental ecology approach, built on collaboration between dental experts and ecologists, holds the potential to provide an important theoretical and practical framework for inferring ecology and behavior of fossil forms, for assessing environmental change in living populations, and for understanding ways in which habitat impacts primate growth and development. This symposium issue brings together experts on dental morphology, growth and development, tooth wear and health, primate ecology, and paleontology, to explore the broad application of dental ecology to questions of how living and fossil primates interact with their environments. Copyright © 2012 Wiley Periodicals, Inc.

  7. Wear rate control of peek surfaces modified by femtosecond laser

    NASA Astrophysics Data System (ADS)

    Hammouti, S.; Pascale-Hamri, A.; Faure, N.; Beaugiraud, B.; Guibert, M.; Mauclair, C.; Benayoun, S.; Valette, S.

    2015-12-01

    This paper presents the effect of laser texturing on the tribological properties of PEEK surfaces under a ball-on-flat contact configuration. Thus, surfaces with circular dimples of various diameters and depth were created. Tests were conducted with a normal load of 5 N and a sliding velocity of 0.01 m s-1, using bovine calf serum at 37.5 °C as a lubricant. The tribological conditions including the sliding frequency and the lubricant viscosity indicate that tests were performed under boundary lubrication regime. Results showed that discs with higher dimple depth exhibited higher friction coefficient and caused more abrasive wear on the ball specimen. Nevertheless, tribosystems (ball and disc) with dimpled disc surfaces showed a higher wear resistance. In the frame of our experiments, wear rates obtained for tribosystems including dimpled surfaces were 10 times lower than tribosystems including limited patterned or untextured surfaces. Applications such as design of spinal implants may be concerned by such a surface treatment to increase wear resistance of components.

  8. Molecular wear of microtubules propelled by surface-adhered kinesins

    NASA Astrophysics Data System (ADS)

    Dumont, Emmanuel L. P.; Do, Catherine; Hess, Henry

    2015-02-01

    Wear is the progressive loss of material from a body caused by contact and relative movement and is a major concern in both engineering and biology. Advances in nanotechnology have allowed the origins of wear processes to be studied at the atomic and molecular scale, but also demand that wear in nanoscale systems can be predicted and controlled. Biomolecular systems can undergo a range of active movements at the nanoscale, which are enabled by the transduction of chemical energy into mechanical work by polymerization processes and motor proteins. The active movements are accompanied by dissipative processes that can be conceptually understood as ‘protein friction’. Here, we show that wear also occurs in an in vitro system consisting of microtubules gliding across a surface coated with kinesin-1 motor proteins, and that energetic considerations suggest a molecule-by-molecule removal of tubulin proteins. The rates of removal show a complex dependence on sliding velocity and kinesin density, which, in contrast to the friction behaviour between microtubules and kinesin-8, cannot be explained by simple chemical reaction kinetics.

  9. Impact of wear and diet on molar row geometry and topography in the house mouse.

    PubMed

    Renaud, Sabrina; Ledevin, Ronan

    2017-09-01

    Dental evolution affects the geometry of the tooth, but the adaptive relevance of these changes is related to tooth sharpness, complexity, and relief (topography). On a set of laboratory mice, we assessed how wear related to age and food consistency affected molar geometry and topography. Three groups of laboratory inbred mice (C57BL/6J strain) were considered: Four week old mice close to weaning, six month old mice fed on regular rodent pellets, and six month old mice fed on rodent pellets that were powdered and served as jelly. Their upper and lower molar rows were imaged in 3D. The geometry of the surfaces was quantified using a template describing the whole surface of the rows. Topographic indices were estimated on the same surfaces. The geometry of the molar rows was heavily affected by age-related wear. Food consistency affected mostly the upper molar row, which was more worn and less helical in soft food eaters. Tooth sharpness and relief decreased with age-related wear. Tooth relief was lower in soft food eaters, but only on the upper molar row. Tooth complexity was insensitive to wear. The primary factor affecting tooth geometry and topography is age-related wear, as wear erodes the molar surfaces. Tooth complexity, however, appears to be insensitive to wear, making this index relevant for comparison of tooth morphology among wild mice of unknown age. Soft food eaters displayed more worn teeth, with less helical molar row occlusal surface, possibly because behavior and jaw morphology were disturbed due to this unusual food resource. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Polymer infiltrated ceramic network structures for resistance to fatigue fracture and wear.

    PubMed

    El Zhawi, Haifa; Kaizer, Marina R; Chughtai, Asima; Moraes, Rafael R; Zhang, Yu

    2016-11-01

    To investigate fatigue fracture resistance and wear behavior of a polymer infiltrated ceramic network (PICN) material (ENAMIC, Vita Zahnfabrik). Anatomically shaped ENAMIC monolithic crowns were milled using a CAD/CAM system. The crowns were cemented on aged dentin-like composite abutments (Z100, 3M ESPE) with resin-based cement (Vita DUO Cement, Vita). The specimens were subjected to 2 types of fatigue and wear tests: (1) accelerated sliding-contact mouth-motion step-stress fatigue test (n=24) in water; and (2) long-term sliding-contact mouth-motion fatigue/wear test using a clinically relevant load (P=200N, n=8) in water. Failure was designated as chip-off or bulk fracture. Optical and scanning electron microscopes were used to examine the occlusal surface and subsurface damage, as well as to reveal the material's microstructure. In addition, wear volume and depth were measured by X-ray micro-computed tomography. For accelerated mouth-motion step-stress fatigue testing, 3 out of the 24 ENAMIC crowns fractured following cyclic loading up to 1700N. Minor occlusal damage and contact-induced cone cracks were observed in all surviving specimens, but no flexural radial cracks were seen. For long-term mouth-motion fatigue/wear testing under a 200N load in water, a small wear scar without significant cracks was observed in all 8 tested ENAMIC crowns. Monolithic CAD/CAM ENAMIC crowns showed superior resistance to sliding-contact fatigue fracture and wear. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Occlusal wear and occlusal condition in a convenience sample of young adults.

    PubMed

    Van't Spijker, A; Kreulen, C M; Bronkhorst, E M; Creugers, N H J

    2015-01-01

    To study progression of tooth wear quantitatively in a convenient sample of young adults and to assess possible correlations with occlusal conditions. Twenty-eight dental students participated in a three-year follow up study on tooth wear. Visible wear facets on full arch gypsum casts were assessed using a flatbed scanner and measuring software. Regression analyses were used to assess possible associations between the registered occlusal conditions 'occlusal guidance scheme', 'vertical overbite', 'horizontal overbite', 'depth of sagittal curve', 'canine Angle class relation', 'history of orthodontic treatment', and 'self-reported grinding/clenching' (independent variables) and increase of wear facets (dependent variable). Mean increase in facet surface areas ranged from 1.2 mm2 (premolars, incisors) to 3.4 mm2 (molars); the relative increase ranged from 15% to 23%. Backward regression analysis showed no significant relation for 'group function', 'vertical overbite', 'depth of sagittal curve', 'history of orthodontic treatment' nor 'self-reported clenching. The final multiple linear regression model showed significant associations amongst 'anterior protected articulation' and 'horizontal overbite' and increase of facet surface areas. For all teeth combined, only 'anterior protected articulation' had a significant effect. 'Self reported grinding' did not have a significant effect (p>0.07). In this study 'anterior protected articulation' and 'horizontal overbite', were significantly associated with the progression of tooth wear. Self reported grinding was not significantly associated with progression of tooth wear. Occlusal conditions such as anterior protected articulation and horizontal overbite seem to have an effect on the progression of occlusal tooth wear in this convenient sample of young adults. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Surface Wear Measurement Using Optical Correlation Technique

    NASA Astrophysics Data System (ADS)

    Acinger, Kresimir

    1983-12-01

    The coherent optical correlation technique was applied for measuring the surface wear of a tappet (part of car engine), worn by friction with the camshaft. It was found that maximum correlation intensity decays exponentially with the number of wear cycles (i.e. camshaft revolutions). Tappets of the same make have an identical rate of correlation decay. Tappets of different makes have different rates of correlation decay which are in agreement with observed long term wear.

  13. Investigation of wear phenomena by microscopy

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1982-01-01

    The various wear mechanisms involved in the loss of material from metallic and nonmetallic surfaces are discussed. The results presented indicate how various microscopy techniques used in conjunction with other analytical tools can assist in the elucidation of a wear mechanism. Without question, microscopy is the single most important tool for the study of the wear of surfaces, to assess and address inherent mechanisms of the material removal process.

  14. Dental Implant Surgery

    MedlinePlus

    Dental implant surgery Overview By Mayo Clinic Staff Dental implant surgery is a procedure that replaces tooth roots ... that look and function much like real ones. Dental implant surgery can offer a welcome alternative to dentures ...

  15. Study on effects of scan parameters on the image quality and tip wear in AFM tapping mode.

    PubMed

    Xue, Bo; Yan, Yongda; Hu, Zhenjiang; Zhao, Xuesen

    2014-01-01

    Due to the tip-sample interaction which is the measurement principle of Atomic Force Microscope (AFM), tip wear constantly occurs during scanning. The blunt tip caused by the wear process makes more tip geometry information involved in the image, and correspondingly it increases the measurement error. In the present study, the scan parameters of AFM in tapping mode which affect the wear of single crystal silicon tips, such as the approaching rate, the scan rate, the scan amplitude, and the integral gain are investigated. By proposing a parameter reflecting the imaging quality, the tip state tracing the sample surface is evaluated quantitatively. The influences of scan parameters on this imaging quality parameter are obtained by experiments. Finally, in order to achieve the perfect images with little tip wear influence, tip wear experiments are carried out and then the optimal parameter settings which can lighten the tip wear are obtained.

  16. The Concomitant Evolution of Wear and Squeaking in Dual-Severity, Lubricated Wear Testing of Ceramic-on-Ceramic Hip Prostheses

    PubMed Central

    Sanders, Anthony; Tibbitts, Ira; Brannon, Rebecca

    2012-01-01

    Ceramic-on-ceramic hip bearings were tested in short-term wear tests with a systematically varied contact force. Continuous vibration and intermittent surface roughness measurements were obtained to elucidate potential causes of in vivo hip joint squeaking. The three-phase test comprised alternating cycles of edge loading and concentric articulation, always using ample serum lubricant. A 50,000-cycle wear trial in which the contact force during concentric articulation was distant from the head’s wear patch yielded no squeaking and practically no liner roughening. In 10-cycle trials of an edge-worn head coupled with a pristine liner, the contact force was varied in magnitude and point of application; immediate, recurrent squeaking occurred only when the contact force exceeded a critical threshold value and was centered upon the head’s wear patch. In a 27,000-cycle wear trial with the contact force applied near the margin of the head’s wear patch, recurrent squeaking emerged progressively as the liner’s inner surface was roughened via its articulation with the worn portion of the head. The results reveal key conditions that yield recurrent squeaking in vitro in various scenarios without resorting to implausible dry conditions. A fundamental theory explains that hip squeaking is induced by myriad stress waves emanating from asperity collisions; yet, the root cause is edge loading. PMID:22354674

  17. Dental Implants.

    PubMed

    Griggs, Jason A

    2017-10-01

    Systematic reviews of literature over the period between 2008 and 2017 are discussed regarding clinical evidence for the factors affecting survival and failure of dental implants. The factors addressed include publication bias, tooth location, insertion torque, collar design, implant-abutment connection design, implant length, implant width, bone augmentation, platform switching, surface roughness, implant coatings, and the use of ceramic materials in the implant body and abutment. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Failure mechanisms of anterior cruciate ligament prostheses: in vitro wear study.

    PubMed

    Poddevin, N; King, M W; Guidoin, R G

    1997-01-01

    Previous retrieval studies analyzing the cause of failure of anterior cruciate ligament (ACL) prostheses identified a wear mechanism. However, the relative importance of yarn on bone compared to yarn on yarn wear has not been clearly understood. Therefore, the objective of this study was to elucidate which type of wear is the dominant cause of clinical failure. A variety of ACL prosthetic structures were exposed to two in vitro tests: one for yarn on yarn and the other for a novel yarn on bone wear test system. The latter included the use of both smooth (uncut) and rough (cut) bone surfaces to simulate the conditions around the condyle and at the exit of the tibial tunnel, respectively. The damaged textile structures were viewed by SEM. The various fiber fracture morphologies were identified and classified for the two types of wear tests; for the smooth and rough bone surfaces; for the braided, knitted, woven, and twisted textile structures; and for the three types of fibers that were included: polyethylene terephthalate, polypropylene, and ultrahigh molecular weight polyethylene. The results confirmed that yarn on bone and yarn on yarn wear phenomena are associated with significantly different failure mechanisms. While the more aggressive rough (or cut) bone causes more rapid and intense fiber damage and faster ACL failure than the smooth (uncut) osseous surface, both abradants cause the same type of abrasive wear phenomenon. Differences in failure mechanisms were identified between the different textile structures and the different fiber types. By interpreting the damaged fiber images from clinically failed and retrieved ACL prostheses, we are now able to confirm that the predominant cause of synthetic ACL failure is yarn on bone abrasion. Improvements in future ACL prosthesis designs will only be possible by eliminating or minimizing the effect of this type of abrasive wear.

  19. Dental microwear textures: reconstructing diets of fossil mammals

    NASA Astrophysics Data System (ADS)

    DeSantis, Larisa R. G.

    2016-06-01

    Dietary information of fossil mammals can be revealed via the analysis of tooth morphology, tooth wear, tooth geochemistry, and the microscopic wear patterns on tooth surfaces resulting from food processing. Although dental microwear has long been used by anthropologists and paleontologists to clarify diets in a diversity of mammals, until recently these methods focused on the counting of wear features (e.g., pits and scratches) from two-dimensional surfaces (typically via scanning electron microscopes or low-magnification light microscopes). The analysis of dental microwear textures can instead reveal dietary information in a broad range of herbivorous, omnivorous, and carnivorous mammals by characterizing microscopic tooth surfaces in three-dimensions, without the counting of individual surface features. To date, dental microwear textures in ungulates, xenarthrans, marsupials, carnivorans, and primates (including humans and their ancestors) are correlated with known dietary behavior in extant taxa and reconstruct ancient diets in a diversity of prehistoric mammals. For example, tough versus hard object feeding can be characterized across disparate phylogenetic groups and can distinguish grazers, folivorous, and flesh consumers (tougher food consumers) from woody browsers, frugivores, and bone consumers (harder object feeders). This paper reviews how dental microwear textures can be useful to reconstructing diets in a broad array of