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Sample records for dental wear caused

  1. Dental wear, wear rate, and dental disease in the African apes.

    PubMed

    Elgart, Alison A

    2010-06-01

    The African apes possess thinner enamel than do other hominoids, and a certain amount of dentin exposure may be advantageous in the processing of tough diets eaten by Gorilla. Dental wear (attrition plus abrasion) that erodes the enamel exposes the underlying dentin and creates additional cutting edges at the dentin-enamel junction. Hypothetically, efficiency of food processing increases with junction formation until an optimal amount is reached, but excessive wear hinders efficient food processing and may lead to sickness, reduced fecundity, and death. Occlusal surfaces of molars and incisors in three populations each of Gorilla and Pan were videotaped and digitized. The quantity of incisal and molar occlusal dental wear and the lengths of dentin-enamel junctions were measured in 220 adult and 31 juvenile gorilla and chimpanzee skulls. Rates of dental wear were calculated in juveniles by scoring the degree of wear between adjacent molars M1 and M2. Differences were compared by principal (major) axis analysis. ANOVAs compared means of wear amounts. Pearson correlation coefficients were calculated to compare the relationship between molar wear and incidence of dental disease. Results indicate that quantities of wear are significantly greater in permanent incisors and molars and juvenile molars of gorillas compared to chimpanzees. The lengths of dentin-enamel junctions were predominantly suboptimal. Western lowland gorillas have the highest quantities of wear and the most molars with suboptimal wear. The highest rates of wear are seen in Pan paniscus and Pan t. troglodytes, and the lowest rates are found in P.t. schweinfurthii and G. g. graueri. Among gorillas, G. b. beringei have the highest rates but low amounts of wear. Coefficients between wear and dental disease were low, but significant when all teeth were combined. Gorilla teeth are durable, and wear does not lead to mechanical senescence in this sample. PMID:20077466

  2. Dental wear in dolphins (Cetacea: Delphinidae) from southern Brazil.

    PubMed

    Loch, Carolina; Simões-Lopes, Paulo C

    2013-02-01

    (1) Dental wear is a common phenomenon in mammals. Its occurrence is influenced by tooth anatomy, animal physiology, biomechanics and behaviour. So far, investigations of dental wear in cetaceans have been scanty and superficial. We compare the frequencies of occurrence, location and intensity of dental wear in some species of dolphins from southern Brazil, South Atlantic Ocean. (2) Teeth of ten species were evaluated using a stereoscopic microscope to identify wear facets, which were classified according to location, anatomical position and wear intensity. (3) Frequencies of dental wear were high for all species with exception of Delphinus capensis, with less than 50% of teeth worn. Simultaneous wear facets in the apex and lateral of teeth were more common than facets restricted to the apex or lateral faces. Wear on the dental crown was more common, but some species showed less frequent wear down to the cingulum or root level. Superficial wear seems to be the general trend for dolphins, but Stenella coeruleoalba and Pseudorca crassidens showed a higher frequency of severe wear. Only for Tursiops truncatus the frequencies of wear were significantly different between males and females. When considering the ontogeny of dental wear, only for T. truncatus and Stenella frontalis indexes of dental wear were correlated with body length. (4) Whether dental wear has implications or not in fitness and feeding behaviour, severely worn teeth may expose the pulp cavity and increase the susceptibility to local infections. PMID:22939372

  3. 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

  4. 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. PMID:26230855

  5. 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. PMID:27198539

  6. 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.

  7. 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).

  8. Hunter-gatherer variability: Dental wear in South Australia.

    PubMed

    Littleton, Judith; Scott, Rachel; McFarlane, Gina; Walshe, Keryn

    2013-10-01

    Often it is assumed that hunter-gatherer dentitions are dominated by heavy attrition. Recent analyses, however, have shown unexpected variability in the pattern of wear between groups. It had been previously noted that wear differed between neighboring groups on the Murray River, Australia. This analysis extends that geographic scope as well as focusing on wear across the dentition, including the premolars. The samples came from coastal and riverine regions of southern Australia. The analysis used records from the Yorke Peninsula, Adelaide Plains (Gillman site), and Euston regions. These were compared with previously published work from the Adelaide Plains and four locations on the Murray River. The results confirm the overall severity of wear but reveal systematic differences between the samples in terms of the pattern of wear. Heavy wear on the incisors and canines is observed among males from the Euston, Kaurna, Middle A, Murray Mouth, and Yorke Peninsula samples but with marked intra-individual variability. Extensive premolar wear is noted among females from Kaurna and Middle B samples as well as among males and females from Euston. It is argued that these patterns relate to gendered non-masticatory use of teeth and reliance upon bulrush (Typha spp.) and related species for both food and fiber among some groups. We argue that analyzing the degree of variability within samples and across all teeth provides a more nuanced understanding of dental wear among hunter-gatherers. PMID:23999884

  9. 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

  10. Monitoring Wear On Dental Restoration Surfaces Using Microscope Photogrammetry

    NASA Astrophysics Data System (ADS)

    Mitchell, Harvey L.; Chadwick, R. G.; McCabe, John F.

    1989-04-01

    35mm photography of denture teeth and resin replicas through a convergent-axes microscope was used in an assessment of wear in dental restoration materials. The difficulty was to isolate and evaluate the significant photogrammetric parameters, but thereafter, the required depths could be calculated to accuracies of 0.01 mm r.m.s. using stereocomparator observations and quite simple formulae. The technique is applicable to biomedical laboratories which have access to an appropriate microscope if photogrammetric observations can be undertaken.

  11. Complex dental structure and wear biomechanics in hadrosaurid dinosaurs.

    PubMed

    Erickson, Gregory M; Krick, Brandon A; Hamilton, Matthew; Bourne, Gerald R; Norell, Mark A; Lilleodden, Erica; Sawyer, W Gregory

    2012-10-01

    Mammalian grinding dentitions are composed of four major tissues that wear differentially, creating coarse surfaces for pulverizing tough plants and liberating nutrients. Although such dentition evolved repeatedly in mammals (such as horses, bison, and elephants), a similar innovation occurred much earlier (~85 million years ago) within the duck-billed dinosaur group Hadrosauridae, fueling their 35-million-year occupation of Laurasian megaherbivorous niches. How this complexity was achieved is unknown, as reptilian teeth are generally two-tissue structures presumably lacking biomechanical attributes for grinding. Here we show that hadrosaurids broke from the primitive reptilian archetype and evolved a six-tissue dental composition that is among the most sophisticated known. Three-dimensional wear models incorporating fossilized wear properties reveal how these tissues interacted for grinding and ecological specialization. PMID:23042891

  12. 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. PMID:24909664

  13. Unravelling the Functional Biomechanics of Dental Features and Tooth Wear

    PubMed Central

    Benazzi, Stefano; Nguyen, Huynh Nhu; Kullmer, Ottmar; Hublin, Jean-Jacques

    2013-01-01

    Most of the morphological features recognized in hominin teeth, particularly the topography of the occlusal surface, are generally interpreted as an evolutionary functional adaptation for mechanical food processing. In this respect, we can also expect that the general architecture of a tooth reflects a response to withstand the high stresses produced during masticatory loadings. Here we use an engineering approach, finite element analysis (FEA), with an advanced loading concept derived from individual occlusal wear information to evaluate whether some dental traits usually found in hominin and extant great ape molars, such as the trigonid crest, the entoconid-hypoconulid crest and the protostylid have important biomechanical implications. For this purpose, FEA was applied to 3D digital models of three Gorillagorilla lower second molars (M2) differing in wear stages. Our results show that in unworn and slightly worn M2s tensile stresses concentrate in the grooves of the occlusal surface. In such condition, the trigonid and the entoconid-hypoconulid crests act to reinforce the crown locally against stresses produced along the mesiodistal groove. Similarly, the protostylid is shaped like a buttress to suffer the high tensile stresses concentrated in the deep buccal groove. These dental traits are less functional in the worn M2, because tensile stresses decrease physiologically in the crown with progressing wear due to the enlargement of antagonistic contact areas and changes in loading direction from oblique to nearly parallel direction to the dental axis. This suggests that the wear process might have a crucial influence in the evolution and structural adaptation of molars enabling to endure bite stresses and reduce tooth failure throughout the lifetime of an individual. PMID:23894570

  14. Exploring the relationship between dental wear and status in late medieval subadults from England.

    PubMed

    Dawson, Heidi; Brown, Kate Robson

    2013-03-01

    Dental wear patterns were recorded on 458 deciduous molar teeth, of 142 subadults from late medieval (AD 1086-1539) England, to explore the relationship between dental wear and burial status of children. A new ordinal method for scoring dental wear stages on the deciduous molar teeth was devised. It was postulated that if a discernible relationship between dental wear stage and burial location could be seen then this could reflect a difference in diet between those receiving higher or lower status burial. The dental wear stages recorded were statistically similar for the dentitions of subadults from different cemeteries, as well as from different burial locations, indicating a comparable diet for the children studied. PMID:23341259

  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. 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

  17. 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. PMID:26048367

  18. 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

  19. A Bayesian approach to estimate skeletal age-at-death utilizing dental wear.

    PubMed

    Prince, Debra A; Kimmerle, Erin H; Konigsberg, Lyle W

    2008-05-01

    In the forensic context, teeth are often recovered in mass disasters, armed conflicts, and mass graves associated with human rights violations. Therefore, for victim identification, techniques utilizing the dentition to estimate the first parameters of identity (e.g., age) can be critical. This analysis was undertaken to apply a Bayesian statistical method, transition analysis, based on the Gompertz-Makeham (GM) hazard model, to estimate individual ages-at-death for Balkan populations utilizing dental wear. Dental wear phases were scored following Smith's eight-phase ordinal scoring method and chart. To estimate age, probability density functions for the posterior distributions of age for each tooth phase are calculated. Transition analysis was utilized to generate a mean age-of-transition from one dental wear phase to the next. The age estimates are based on the calculated age distribution from the GM hazard analysis and the ages-of-transition. To estimate the age-at-death for an individual, the highest posterior density region for each phase is calculated. By using a Bayesian statistical approach to estimate age, the population's age distribution is taken into account. Therefore, the age estimates are reliable for the Balkan populations, regardless of population or sex differences. The results showed that a vast amount of interpersonal variation in dental wear exists within the current sample and that this method may be most useful for classifying unknown individuals into broad age cohorts rather than small age ranges. PMID:18471201

  20. 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

  1. Microtomography evaluation of dental tissue wear surface induced by in vitro simulated chewing cycles on human and composite teeth.

    PubMed

    Bedini, Rossella; Pecci, Raffaella; Notarangelo, Gianluca; Zuppante, Francesca; Persico, Salvatore; Di Carlo, Fabio

    2012-01-01

    In this study a 3D microtomography display of tooth surfaces after in vitro dental wear tests has been obtained. Natural teeth have been compared with prosthetic teeth, manufactured by three different polyceramic composite materials. The prosthetic dental element samples, similar to molars, have been placed in opposition to human teeth extracted by paradontology diseases. After microtomography analysis, samples have been subjected to in vitro fatigue test cycles by servo-hydraulic mechanical testing machine. After the fatigue test, each sample has been subjected again to microtomography analysis to obtain volumetric value changes and dental wear surface images. Wear surface images were obtained by 3D reconstruction software and volumetric value changes were measured by CT analyser software. The aim of this work has been to show the potential of microtomography technique to display very clear and reliable wear surface images. Microtomography analysis methods to evaluate volumetric value changes have been used to quantify dental tissue and composite material wear. PMID:22456018

  2. Observer error, dental wear, and the inference of new world sundadonty.

    PubMed

    Stojanowski, Christopher M; Johnson, Kent M

    2015-03-01

    Dental morphology provides important information on human evolution and interpopulation relationships. Dental wear is one of the major limitations of morphological data analysis. Wear figures heavily in existing debates about patterns of New World dental variation with some scholars finding evidence for a more generalized dentition in early New World populations (Powell: Doctoral Dissertation, Texas A&M University, TX (1995)) and others questioning these findings based on the probable effects of dental wear on trait scores (Turner, The First Americans: the Pleistocene Colonization of the New World. San Francisco: California Academy of Sciences (2002) 123-158; Turner: Am J Phys Anthropol 130 (2006) 455-461; Turner and Scott, Handbook of paleoanthropology, Vol. III: Phylogeny of Hominids. New York: Springer (2007) 1901-1941). Here we evaluate these competing claims using data from the Early Archaic Windover sample. Results confirm the dental distinctiveness of Windover with respect to other Old World Asian (i.e., sinodont/sundadont) populations. However, comparison of our results to those of Powell (1995) also highlights significant interobserver error. Statistical analysis of matched wear and morphology scores suggests trait downgrading for some traits. Patterns of missing data present a more challenging (and potentially serious) problem. Use of Little's MCAR test for missing data mechanisms indicates a complex process of data collection in which incidental and opportunistic recording of both highly worn and unerupted teeth introduce a "missing not at random" mechanism into our dataset that biases dental trait frequencies. We conclude that patterns of missingness and formal research designs for "planned missingness" are needed to help mitigate this bias. PMID:25363296

  3. 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. PMID:12687721

  4. Comparison of the abrasive wear resistance between amalgams, hybrid composite material and different dental cements.

    PubMed

    Gil, F J; Espias, A; Sánchez, L A; Planell, J A

    1999-12-01

    This paper reports on the abrasion wear of various restorative dental materials (three amalgams and two dental cements and a hybrid composite material) commonly used in dentistry. The mechanical properties, surface roughness and the volume loss by abrasion were determined for the different materials studied. The results showed a better profile for the amalgams versus the composite materials due to the failure of the polymeric matrix of the latter materials. However, the amalgams exhibited corrosion observed by means of Scanning Electron Microscopy. PMID:10907431

  5. Dental erosive wear and salivary flow rate in physically active young adults

    PubMed Central

    2012-01-01

    Background Little attention has been directed towards identifying the relationship between physical exercise, dental erosive wear and salivary secretion. The study aimed i) to describe the prevalence and severity of dental erosive wear among a group of physically active young adults, ii) to describe the patterns of dietary consumption and lifestyle among these individuals and iii) to study possible effect of exercise on salivary flow rate. Methods Young members (age range 18-32 years) of a fitness-centre were invited to participate in the study. Inclusion criteria were healthy young adults training hard at least twice a week. A non-exercising comparison group was selected from an ongoing study among 18-year-olds. Two hundred and twenty participants accepted an intraoral examination and completed a questionnaire. Seventy of the exercising participants provided saliva samples. The examination was performed at the fitness-centre or at a dental clinic (comparison group), using tested erosive wear system (VEDE). Saliva sampling (unstimulated and stimulated) was performed before and after exercise. Occlusal surfaces of the first molars in both jaws and the labial and palatal surfaces of the upper incisors and canines were selected as index teeth. Results Dental erosive wear was registered in 64% of the exercising participants, more often in the older age group, and in 20% of the comparison group. Enamel lesions were most observed in the upper central incisors (33%); dentine lesions in lower first molar (27%). One fourth of the participants had erosive wear into dentine, significantly more in males than in females (p = 0.047). More participants with erosive wear had decreased salivary flow during exercise compared with the non-erosion group (p < 0.01). The stimulated salivary flow rate was in the lower rage (≤ 1 ml/min) among more than one third of the participants, and more erosive lesions were registered than in subjects with higher flow rates (p < 0.01). Conclusion

  6. 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.

  7. Highly wear-resistant and biocompatible carbon nanocomposite coatings for dental implants.

    PubMed

    Penkov, Oleksiy V; Pukha, Vladimir E; Starikova, Svetlana L; Khadem, Mahdi; Starikov, Vadym V; Maleev, Maxim V; Kim, Dae-Eun

    2016-09-01

    Diamond-like carbon coatings are increasingly used as wear-protective coatings for dental implants, artificial joints, etc. Despite their advantages, they may have several weak points such as high internal stress, poor adhesive properties or high sensitivity to ambient conditions. These weak points could be overcome in the case of a new carbon nanocomposite coating (CNC) deposited by using a C60 ion beam on a Co/Cr alloy. The structure of the coatings was investigated by Raman and XPS spectroscopy. The wear resistance was assessed by using a reciprocating tribotester under the loads up to 0.4 N in both dry and wet sliding conditions. Biocompatibility of the dental implants was tested in vivo on rabbits. Biocompatibility, bioactivity and mechanical durability of the CNC deposited on a Co/Cr alloy were investigated and compared with those of bulk Co/Cr and Ti alloys. The wear resistance of the CNC was found to be 250-650 fold higher compared to the Co/Cr and Ti alloys. Also, the CNC demonstrated much better biological properties with respect to formation of new tissues and absence of negative morphological parameters such as necrosis and demineralization. Development of the CNC is expected to aid in significant improvement of lifetime and quality of implants for dental applications. PMID:27336185

  8. Wear of a composite ceramic head caused by liner fracture.

    PubMed

    Morlock, Michael M; Witt, Florian; Bishop, Nick; Behn, Rainer; Dalla Pria, Paolo; Barrow, Rob; Dymond, Ian

    2014-07-01

    Third-generation composite ceramics (eg, Delta; DePuy Orthopaedics, Warsaw, Indiana; Ceramtec, Plochingen, Germany) have greatly improved material characteristics compared with second-generation products. This case report presents a patient after total hip arthroplasty with a fractured ceramic liner and a heavily worn ceramic head (both third-generation ceramics) retrieved 9 months after surgery. The patient showed no symptoms in the involved hip but presented to the hospital because of other symptoms. The failure was caused by a tilted liner that was overlooked after surgery and fractured consecutively. Rim chipping and splitting were the 2 fracture modes observed for the liner. The head did not fracture completely because of its high strength but became roughened by the ceramic fragments, causing major wear of the metal back of the cup. The phase transformation of the zirconium grains from tetragonal to monoclinic in the aluminum oxide matrix was shown by radiographic diffraction analysis in the heavily worn areas of the head. This transformation increases the fracture strength of the head. Metal debris caused by a roughened ceramic head without fracture is an unreported phenomenon for third-generation ceramic bearings in hip arthroplasty. This case shows that proper impaction of the ceramic liner into the metal shell to prevent later tiling during reduction is as important as correct component positioning. If a tilted ceramic liner is observed postoperatively, the position must be corrected immediately to prevent the major consequences observed in this patient. PMID:24992062

  9. 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

  10. 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. PMID:27375905

  11. Assessment of the amount of tooth wear on dental casts and intra-oral photographs.

    PubMed

    Wetselaar, P; Wetselaar-Glas, M J M; Koutris, M; Visscher, C M; Lobbezoo, F

    2016-08-01

    Tooth wear is a multifactorial condition, leading to the loss of dental hard tissues. Many grading scales are available to assess the amount of tooth wear, one of which is the tooth wear evaluation system (TWES). A grading scale can be used chairside, on casts and on photographs. The aim was to test whether the grading scales of the TWES, used on casts and on photographs, resulted in comparable scores. In addition, it was tested whether these scales can be used to assess tooth wear reliably on photographs. Of 75 tooth wear patients, sets of casts and series of photographs were obtained and graded. Comparison of the grading on casts and on photographs revealed equal median values and percentiles for both occlusal/incisal grading and non-occlusal/non-incisal grading. The grading on casts and on photographs showed a high correlation for the occlusal/incisal grading and a low correlation for the non-occlusal/non-incisal grading (Spearman's rho = 0·74 and rho = 0·47; P < 0·001). Concerning the grading on photographs, the interexaminer reliability was fair-to-good (ICC = 0·41 to ICC = 0·55) while the intra-examiner reliability was fair-to-good to excellent (ICC = 0·68 to ICC = 0·86) for the occlusal/incisal grading. For the non-occlusal/non-incisal grading, the interexaminer reliability was poor to fair-to-good (ICC = 0·22 to ICC = 0·59), while the intra-examiner reliability was fair-to-good to excellent (ICC = 0·64 to ICC = 0·82). It was concluded that the scores obtained with the grading scales of the TWES on casts and on photographs are comparable. The grading scales can be used in a reliable way on photographs, which is especially the case for occlusal/incisal grading. PMID:27132187

  12. Enhanced wear resistance of ball-and-socket joints of dental implants by means of titanium gaseous nitriding.

    PubMed

    Gil, F J; Canedo, R; Padrós, A; Sada, E

    2002-07-01

    The aim of this research is the surface hardening of the ball-and-socket joint of dental implants by means of heat treatments in order to obtain titanium nitrides. These nitrides minimize the wear of the titanium used in prosthesis. In this paper the optimum heat treatment, the hardness and the wear resistance are described in relation to the ball-and-socket joint without heat treatment. PMID:12222756

  13. 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. PMID:25681013

  14. 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. PMID:25303041

  15. 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

  16. 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

  17. 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. PMID:24447258

  18. 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. PMID:26051868

  19. 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

  20. 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

  1. Filler features and their effects on wear and degree of conversion of particulate dental resin composites.

    PubMed

    Turssi, C P; Ferracane, J L; Vogel, K

    2005-08-01

    Based on the incomplete understanding on how filler features influence the wear resistance and monomer conversion of resin composites, this study sought to evaluate whether materials containing different shapes and combinations of size of filler particles would perform similarly in terms of three-body abrasion and degree of conversion. Twelve experimental monomodal, bimodal or trimodal composites containing either spherical or irregular shaped fillers ranging from 100 to 1500 nm were examined. Wear testings were conducted in the OHSU wear machine (n = 6) and quantified after 10(5) cycles using a profilometer. Degree of conversion (DC) was measured by FTIR spectrometry at the surface of the composites (n = 6). Data sets were analyzed using one-way Anova and Tukey's test at a significance level of 0.05. Filler size and geometry was found to have a significant effect on wear resistance and DC of composites. At specific sizes and combinations, the presence of small filler particles, either spherical or irregular, may aid in enhancing the wear resistance of composites, without compromising the percentage of reacted carbon double bonds. PMID:15769527

  2. 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. PMID:20872788

  3. Dental use wear in extinct lemurs: evidence of diet and niche differentiation.

    PubMed

    Godfrey, Laurie R; Semprebon, Gina M; Jungers, William L; Sutherland, Michael R; Simons, Elwyn L; Solounias, Nikos

    2004-09-01

    A new technique for molar use-wear analysis is applied to samples of all 16 species of extinct lemurs with known dentitions, as well as to a large comparative sample of extant primates. This technique, which relies on the light refractive properties of wear pits and scratches as seen under a standard stereoscopic microscope, has shown itself to be effective in distinguishing the diets of ungulates and extant primates. We draw dietary inferences for each of the 16 extinct lemur species in our database. There is a strong phylogenetic signal, with the Palaeopropithecidae showing use-wear signatures similar to those of the Indriidae; extinct lemurids (Pachylemur spp.) showing striking similarities to extant lemurids (except Hapalemur spp.); and Megaladapis showing similarities to Lepilemur spp. Only the Archaeolemuridae have dietary signatures unlike those of any extant lemurs, with the partial exception of Daubentonia. We conclude that the Archaeolemuridae were hard-object feeders; the Palaeopropithecidae were seed predators, consuming a mixed diet of foliage and fruit to varying degrees; Pachylemur was a fruit-dominated mixed feeder, but not a seed predator; and all Megaladapis were leaf browsers. There is no molar use wear evidence that any of the extinct lemurs relied on terrestrial foods (C4 grasses, tubers, rhizomes). This has possible implications for the role of the disappearance of wooded habitats in the extinction of lemurs. PMID:15337413

  4. Study of the surface wear resistance and biological properties of the Ti-Zr-Nb-Sn alloy for dental restoration.

    PubMed

    Hu, Xin; Wei, Qiang; Li, Chang-Yi; Deng, Jia-Yin; Liu, Shuang; Zhang, Lian-Yun

    2010-10-01

    A new titanium alloy (Ti-12.5Zr-3Nb-2.5Sn) was developed to meet the needs of clinical requirements for medical titanium alloys and improve the properties of existing titanium alloys. The as-prepared alloy was solution treated at 500 °C for 3 h in vacuum followed by water quenching. Tensile, wear and hardness tests were carried out to examine the mechanical properties of the Ti-Zr-Nb-Sn alloy. Oral mucous membrane irritation test was performed to evaluate the surface biological properties of the Ti-Zr-Nb-Sn alloy. The results suggested that the surface hardness and wear-resistant properties of the Ti-12.5Zr-3Nb-2.5Sn alloy were superior to commercially pure Ti. The oral mucous irritation test showed that all samples had no mucous membrane irritation. It indicates that Ti-12.5Zr-3Nb-2.5Sn has large potential to be used as dental restoration material. PMID:20876964

  5. 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

  6. Paleoenvironment of Dryopithecus brancoi at Rudabánya, Hungary: evidence from dental meso- and micro-wear analyses of large vegetarian mammals.

    PubMed

    Merceron, Gildas; Schulz, Ellen; Kordos, László; Kaiser, Thomas M

    2007-10-01

    The environment of the hominoid Dryopithecus brancoi at Rudabánya (Late Miocene of Hungary) is reconstructed here using the dietary traits of fossil ruminants and equids. Two independent approaches, dental micro- and meso-wear analyses, are applied to a sample of 73 specimens representing three ruminants: Miotragocerus sp. (Bovidae), Lucentia aff. pierensis (Cervidae), Micromeryx flourensianus (Moschidae), and one equid, Hippotherium intrans (Equidae). The combination of meso- and micro-wear signatures provides both long- and short-term dietary signals, and through comparisons with extant species, the feeding styles of the fossil species are reconstructed. Both approaches categorize the cervid as an intermediate feeder engaged in both browsing and grazing. The bovid Miotragocerus sp. is depicted as a traditional browser. Although the dental meso-wear pattern of the moschid has affinities with intermediate feeders, its dental micro-wear pattern also indicates significant intake of fruits and seeds. Hippotherium intrans was not a grazer and its dental micro-wear pattern significantly differs from that of living browsers, which may suggest that the fossil equid was engaged both in grazing and browsing. However, the lack of extant equids which are pure browsers prevents any definitive judgment on the feeding habits of Hippotherium. Based on these dietary findings, the Rudabánya paleoenvironment is reconstructed as a dense forest. The presence of two intermediate feeders indicates some clearings within this forest; however the absence of grazers suggests that these clearings were most likely confined. To demonstrate the ecological diversity among the late Miocene hominoids in Europe, the diet and habitat of Dryopithecus brancoi and Ouranopithecus macedoniensis (Greece) are compared. PMID:17719619

  7. 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

  8. 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

  9. 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. PMID:25805253

  10. Monitoring of Burr and Prefailure Phase Caused by Tool Wear in Micro-Drilling Operations Using Thrust Force Signals

    NASA Astrophysics Data System (ADS)

    Kondo, Eiji; Kamo, Ryoga; Murakami, Hiroshi

    The purpose of this study is to investigate the effectiveness of thrust force signals for estimation of the burr occurring at the outlet of a drilled hole and the prefailure phase caused by tool wear in drilling holes through thin stainless steel plate (JIS SUS304). Micro-drilling tests, using feed rate, step feed length, and the micro-drill diameter as experimental parameters, were carried out to measure the thrust force during peck drilling operations. Tool wear of the cutting edge and burr occurring at the outlet of drilled holes were measured at intervals of a constant number of drilled holes to consider their relationships to thrust force. As a result, the thrust force caused by tool wear during peck micro-drilling is related to the height of the burr occurring at the outlet of the drilled hole and the prefailure phase of micro-drills.

  11. 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. PMID:26037598

  12. 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. PMID:20139598

  13. 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.

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

    PubMed

    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

  15. 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

  16. 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. PMID:26849309

  17. Effect of taphonomic processes on dental microwear.

    PubMed

    King, T; Andrews, P; Boz, B

    1999-03-01

    Taphonomic processes have the potential to affect microscopic wear on teeth and to modify the wear patterns so as to confound dietary reconstructions based on dental microwear which was formed during the lifetime of an animal. This study describes a series of experiments which were conducted to simulate various taphonomic agents and to record their effect on dental microwear. Three types of experiment were carried out in order to explain anomalous microscopic wear that had been found on the dentition of several hominoid specimens from the 15 M.a. site of Pasalar in Turkey. The effect of two different acids-citric and hydrochloric acid-on dental microwear was investigated. Modification to microscopic wear caused by alkali (carbonatite ash) was examined in the second set of experiments. Lastly, the effect of abrasion by three different size classes of sediment from the site of Pasalar-quartz pebbles (grain size varied from 2,000-11,000 microm), coarse sand (grain size ranged from 500-1,000 microm), and medium-sized sand (grain diameters were between 250 and 500 microm)-was investigated. Results confirm previous findings that the taphonomic modification of dental microwear is readily identifiable and causes the obliteration rather than secondary alteration of microwear features. The experiments show that both citric and hydrochloric acid affect dental microwear but to varying degrees, whereas alkali did not cause any modification of microscopic features. The different size classes of sediment also had different effects on the dental microwear. The largest size sediment (quartz pebbles) polished the enamel and removed finer microwear features. The coarse sand, however, did not have any effect on the microwear. The greatest amount of abrasion was caused by the smallest sediment particles -the medium-sized sand. Several hominoid dental specimens from Pasalar display similar microscopic wear to the two types of acid erosion and the abrasion caused by the medium

  18. 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. PMID:9823723

  19. 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. PMID:23666547

  20. 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

  1. 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. PMID:26298055

  2. A review of adaptive mechanisms in cell responses towards oxidative stress caused by dental resin monomers.

    PubMed

    Krifka, Stephanie; Spagnuolo, Gianrico; Schmalz, Gottfried; Schweikl, Helmut

    2013-06-01

    Dental composite resins are biomaterials commonly used to aesthetically restore the structure and function of teeth impaired by caries, erosion, or fracture. Residual monomers released from resin restorations as a result of incomplete polymerization processes interact with living oral tissues. Monomers like triethylene glycol dimethacrylate (TEGDMA) or 2-hydroxylethyl methacrylate (HEMA) are cytotoxic via apoptosis, induce genotoxic effects, and delay the cell cycle. Monomers also influence the response of cells of the innate immune system, inhibit specific odontoblast cell functions, or delay the odontogenic differentiation and mineralization processes in pulp-derived cells including stem cells. These observations indicate that resin monomers act as environmental stressors which inevitably disturb regulatory cellular networks through interference with signal transduction pathways. We hypothesize that an understanding of the cellular mechanisms underlying these phenomena will provide a better estimation of the consequences associated with dental therapy using composite materials, and lead to innovative therapeutic strategies and improved materials being used at tissue interfaces within the oral cavity. Current findings strongly suggest that monomers enhance the formation of reactive oxygen species (ROS), which is most likely the cause of biological reactions activated by dental composites and resin monomers. The aim of the present review manuscript is to discuss adaptive cell responses to oxidative stress caused by monomers. The particular significance of a tightly controlled network of non-enzymatic as well as enzymatic antioxidants for the regulation of cellular redox homeostasis and antioxidant defense in monomer-exposed cells will be addressed. The expression of ROS-metabolizing antioxidant enzymes like superoxide dismutase (SOD1), glutathione peroxidase (GPx1/2), and catalase in cells exposed to monomers will be discussed with particular emphasis on the role

  3. 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

  4. 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

  5. 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. PMID:26630866

  6. 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

  7. A syndrome of microcephaly, short stature, polysyndactyly, and dental anomalies caused by a homozygous KATNB1 mutation.

    PubMed

    Yigit, Gökhan; Wieczorek, Dagmar; Bögershausen, Nina; Beleggia, Filippo; Möller-Hartmann, Claudia; Altmüller, Janine; Thiele, Holger; Nürnberg, Peter; Wollnik, Bernd

    2016-03-01

    Using whole-exome sequencing, we identified a homozygous acceptor splice-site mutation in intron 6 of the KATNB1 gene in a patient from a consanguineous Turkish family who presented with congenital microcephaly, lissencephaly, short stature, polysyndactyly, and dental abnormalities. cDNA analysis revealed complete loss of the natural acceptor splice-site resulting either in the usage of an alternative, exonic acceptor splice-site inducing a frame-shift and premature protein truncation or, to a minor extent, in complete skipping of exon 7. Both effects most likely lead to complete loss of KATNB1 function. Homozygous and compound heterozygous mutations in KATNB1 have very recently been described as a cause of microcephaly with brain malformations and seizures. We extend the KATNB1 associated phenotype by describing a syndrome characterized by primordial dwarfism, lissencephaly, polysyndactyly, and dental anomalies, which is caused by a homozygous truncating KATNB1 mutation. PMID:26640080

  8. 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

  9. 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. PMID:27411727

  10. 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…

  11. Systemically alendronate was incorporated into dental tissues but did not cause morphological or mechanical changes in rats teeth.

    PubMed

    Nelson-Filho, Paulo; Lucisano, Marília Pacífico; Da Silva, Raquel Assed Bezerra; Da Silva, Roberto Santana; Serra, Mônica Campos; Gerlach, Raquel Fernanda; Neto, Francisco Carlos Rehder; Carneiro, Zumira Aparecida; Zamarioli, Ariane; Morse, Leslie; Battaglino, Ricardo

    2012-09-01

    This study evaluated the effect of the systemic use of sodium alendronate in rats in vivo. Forty-five Wistar rats aged 36 to 42 days and weighing 200 to 230 g were randomly assigned to a control group (n = 20), which received distilled water, and an experimental group (n = 25), which received 2 weekly doses of 1 mg/kg of chemically pure sodium alendronate. The animals were killed after 60 days of treatment. The tibias were removed for analysis of bone mineral density by dual-energy X-ray absorptiometry (DXA). Then, the maxillary incisors were extracted for analysis of the mineralized dental tissues using fluorescence spectroscopy (FS), scanning electron microscopy (SEM), bright field microscopy (BFM), and cross-sectional microhardness (CSMH) testing. DXA and CSMH data were subjected to statistical analysis by Kruskal-Wallis test (5% significance level). The experimental group presented higher bone mineral density than the control group by DXA. FS analysis revealed presence of alendronate in the mineralized dental tissues of the specimens of the experimental group. Significant morphological differences were not found by SEM and BFM. Enamel and dentin (100 and 300 μm from the dentinoenamel junction) CSMH data did not show significant difference between the control and experimental groups. Based on the obtained results, we conclude that while alendronate increased the bone mineral density and was incorporated into the mineralized dental tissues it did not cause significant alterations in the morphology and microhardness of rat incisor enamel and dentin. PMID:22508272

  12. 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

  13. The influence of dental alloys on three-body wear of human enamel and dentin in an inlay-like situation.

    PubMed

    Graf, K; Johnson, G H; Mehl, A; Rammelsberg, P

    2002-01-01

    This in vitro study evaluated the effect of metal alloys on three-body wear resistance of enamel and dentin, and vice versa. Three-body wear of human enamel, dentin, a soft gold alloy (BiOcclus Inlay), a CoCr alloy (Remanium 2000), a resin cement (Variolink II) and a zinc oxide phosphate cement (Harvard) was investigated using the ACTA-machine. Sample chambers of eight sample wheels were prepared with pure materials or combinations of human tooth substance, alloys and cement, simulating an inlay-like situation. After 100,000 and 200,000 cycles in a millet suspension with a spring force of 20 N, the amount of abraded material was profilometrically measured and evaluated by 3D surface data analysis. After 200,000 cycles, the materials demonstrated a mean loss of 0.41 microm for CoCr, 51 microm for gold, 57 microm for enamel, 164 microm for dentin, 79 microm for Variolink and 369 microm for Harvard. Using ANOVA and the Games-Howell-test, resin cement, enamel and gold were a subset not shown to differ, as was zinc phosphate cement and dentin. CoCr demonstrated the least wear and differed significantly from all materials. Enamel wear was significantly reduced in mixed chambers with CoCr, and gold after 200,000 cycles compared to enamel in pure chambers. In summary, a soft gold alloy can be recommended for inlays when considering three-body abrasion since the wear rate of the "soft" gold alloy corresponded to that of human enamel. PMID:11931136

  14. 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. PMID:24953664

  15. 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

  16. 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. PMID:26249603

  17. 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. PMID:21074315

  18. Eye Wear

    MedlinePlus

    Eye wear protects or corrects your vision. Examples are Sunglasses Safety goggles Glasses (also called eyeglasses) Contact ... jobs and some sports carry a risk of eye injury. Thousands of children and adults get eye ...

  19. [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. PMID:10574050

  20. 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.

  1. 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. PMID:16629884

  2. [Infection after dental intervention. Iatrogenic or general medical cause? Case report].

    PubMed

    Gander, Thomas; Bingoel, Alperen Sabri; Mascolo, Luana; Grätz, Klaus W; Lübbers, Heinz-Theo

    2013-01-01

    Whenever a dentist is dealing with abscess formation in the oral and maxillofacial region, it is mostly from dental origins. However, sometimes uncommon (co-)factors are present and responsible for major complications. Many general conditions or medications can significantly influence the course of an inflammation. It might spread faster and wider and also be resistant to "correct" therapy. This case report should raise awareness about general conditions supporting inflammation and demonstrate the importance of interdisciplinary treatment in these situations. A 76-year-old patient was referred to the maxillofacial surgery clinic after extraction of two teeth resulted in therapy-resistant painful swelling. Her dentist already had initiated "standard" therapy including Ponstan® (mefenamic acid) and Clamoxyl® (amoxicillin) without success. Initial blood testing came back with severe agranulocytosis. Immediately all potentially myelosuppressing drugs were stopped while myelosupporting drugs were prescribed. Under close interdisciplinary treatment conditions, healing was then uneventful without the necessity of surgical intervention. The challenge in inflammation treatment is to identify patients with uncommonly severe, fast-progressing, or therapy-resistant disease as early as possible. Further examination including blood workup for several medical parameters is indispensable in those patients. PMID:23426587

  3. New Perspectives on Tooth Wear

    PubMed Central

    Lucas, Peter W.; Omar, Ridwaan

    2012-01-01

    Some of the efforts that have been made to document tooth wear are reviewed here with an emphasis on nonhuman mammals, literature with which dentists may not be very familiar. We project a change in research strategy from the description of wear at various scales of measurement towards investigation of the mechanical mechanisms that actually create the texture of a worn surface. These studies should reveal exactly how tooth tissue is lost and what aspects of the structure of dental tissues affect this. The most important aspects of the interaction between the tooth surface and wear particles would appear to be particle size, particle shape, their mechanical properties with respect to those of tooth tissues, and the influence of saliva. PMID:22536239

  4. 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.

  5. 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. PMID:8509756

  6. 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.

  7. Wear of metal fiber brushes

    NASA Astrophysics Data System (ADS)

    Brown, Lloyd Perryman, Jr.

    The goal of this dissertation was determining the wear mechanism of metal fiber brushes on commutators and slip rings with the goal of achieving the lowest possible wear rate. To this end, metal fiber brushes were operated, while conducting direct current, on gold-plated copper rotors with and without unfilled gaps to simulate slip rings and commutators, respectively. Wear rates on unfilled-groove commutators were found to be only modestly higher than on slip ring style rotors. Three possible causes for enhanced metal fiber brush wear on commutators were considered: (i) accelerated "adhesive" wear controlled by contact spots, (ii) fatigue induced wear and (iii) "fiber chopping". Similarly, SEM analysis of fiber tips and wear particles produced scant, if any, evidence of fiber chopping, which would occur as, again, fiber tips extend elastically into the commutator grooves and small slices of them would be "chopped" off by oncoming edges of commutator bars. Finally considered was "modified chopping", wherein fiber tips would be dragged over groove edges, resulting in tensile fracture and chopping. Only a single fiber fragment showed damage that might be compatible with that mechanism. Moreover, the fact that it was exemplified by a single tenuous case, rules it out as significant. The same conclusion also follows from comparing commutator wear rates with that on slip rings. These show good correlation in terms of effective brush pressure, which on commutators is increased because only bars conduct current and gaps do not support load. (Abstract shortened by UMI.)

  8. Erosive tooth wear in children.

    PubMed

    Carvalho, Thiago S; Lussi, Adrian; Jaeggi, Thomas; Gambon, Dein L

    2014-01-01

    Erosive tooth wear in children is a common condition. Besides the anatomical differences between deciduous and permanent teeth, additional histological differences may influence their susceptibility to dissolution. Considering laboratory studies alone, it is not clear whether deciduous teeth are more liable to erosive wear than permanent teeth. However, results from epidemiological studies imply that the primary dentition is less wear resistant than permanent teeth, possibly due to the overlapping of erosion with mechanical forces (like attrition or abrasion). Although low severity of tooth wear in children does not cause a significant impact on their quality of life, early erosive damage to their permanent teeth may compromise their dentition for their entire lifetime and require extensive restorative procedures. Therefore, early diagnosis of erosive wear and adequate preventive measures are important. Knowledge on the aetiological factors of erosive wear is a prerequisite for preventive strategies. Like in adults, extrinsic and intrinsic factors, or a combination of them, are possible reasons for erosive tooth wear in children and adolescents. Several factors directly related to erosive tooth wear in children are presently discussed, such as socio-economic aspects, gastroesophageal reflux or vomiting, and intake of some medicaments, as well as behavioural factors such as unusual eating and drinking habits. Additionally, frequent and excessive consumption of erosive foodstuffs and drinks are of importance. PMID:24993274

  9. Dental Fear among Medical and Dental Undergraduates

    PubMed Central

    Hakim, H.; Razak, I. A.

    2014-01-01

    Objective. To assess the prevalence and level of dental fear among health related undergraduates and to identify factors causing such fear using Kleinknecht's Dental Fear Survey (DFS) questionnaire. Methods. Kleinknecht's DFS questionnaire was used to assess dental fear and anxiety among the entire enrollment of the medical and dental undergraduates' of the University of Malaya. Results. Overall response rate was 82.2%. Dental students reported higher prevalence of dental fear (96.0% versus 90.4%). However, most of the fear encountered among dental students was in the low fear category as compared to their medical counterpart (69.2 versus 51.2%). Significantly more medical students cancelled dental appointment due to fear compared to dental students (P = 0.004). “Heart beats faster” and “muscle being tensed” were the top two physiological responses experienced by the respondents. “Drill” and “anesthetic needle” were the most fear provoking objects among respondents of both faculties. Conclusion. Dental fear and anxiety are a common problem encountered among medical and dental undergraduates who represent future health care professionals. Also, high level of dental fear and anxiety leads to the avoidance of the dental services. PMID:25386615

  10. Can a chronic dental infection be considered a cause of cardiovascular disease? A review of the literature.

    PubMed

    Cotti, Elisabetta; Dessì, Cristina; Piras, Alessandra; Mercuro, Giuseppe

    2011-04-01

    Cardiovascular diseases (CVD) have a complex etiology determined by risk factors, which are in turn associated to a strong genetic component and to environmental factors. In the biological background for the development of CVD, low-grade chronic inflammation plays a role as a pathogenetic determinant of atherosclerosis. Dental infections have been associated with CVD. Periodontal disease is a chronic infection of the supporting tissues of the tooth that can lead to teeth loss. In recent years, a number of reports have demonstrated the possible relationship between periodontal disease and CVD. Apical periodontitis, on the other hand, is the late consequence of an endodontic infection, which is caused by the persistence of coronal caries and involves the root canal system of the tooth. Most of the time, it is a chronic infection. Some studies have found a correlation between a "composite status" of oral health (eg. caries, tooth loss, periodontal disease) and CVD, but only a few of them have addressed the association between apical periodontitis and CVD. This "state of the art" paper represents the first stage of an incoming study on the relationship between chronic endodontic infection and CVD. PMID:20851474

  11. 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

  12. Medication-related dental erosion: a review.

    PubMed

    Thomas, Manuel S; Vivekananda Pai, A R; Yadav, Amit

    2015-10-01

    Dental erosion has become a major problem that affects the long-term health of the dentition. Among the various potential causes for erosive tooth wear, the different drugs prescribed for patients may be overlooked. Several therapeutic medications can directly or indirectly be associated with dental erosion. It is the responsibility of oral health providers to make both patients and colleagues aware of drugs that may contribute to this condition. Therefore, the purpose of this discussion is to provide an overview of the various therapeutic medications that can be related to tooth erosion. The authors also include precautionary measures-summarized as The 9 Rs-to avoid or at least reduce medication-induced erosion. PMID:26448149

  13. Dental Amalgam

    MedlinePlus

    ... Products and Medical Procedures Dental Devices Dental Amalgam Dental Amalgam Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Dental amalgam is a dental filling material which is ...

  14. 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

  15. 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.

  16. Fish-eaters and farmers: dental pathology in the Arabian Gulf.

    PubMed

    Littleton, J; Frohlich, B

    1993-12-01

    Twelve skeletal samples, previously published, from the Arabian Gulf have been used to trace differences in diet and subsistence patterns through an analysis of dental pathology. The skeletons date from 3,000 BC to AD 1,500 and cover a variety of geographical locations: off-shore islands, Eastern Arabia, and Oman. The dental conditions analyzed are attrition, caries, calculus, abscessing, and antemortem tooth loss (AMTL). Results indicate four basic patterns of dental disease which, while not mutually exclusive, correspond to four basic subsistence patterns. Marine dependency, represented by the Ras el-Hamra population, is indicated by severe attrition, low caries rates, wear-caused abscessing, and a lack of AMTL. The second group of dental diseases--moderate attrition and calculus, low rates of caries, wear-caused abscessing, and low-moderate rates of AMTL--affects populations subsisting on a mixture of pastoralism or fishing and agriculture (Failaka, Umm an-Nar, Bronze Age Maysar, Bronze Age Shimal, and Iron Age Galilah). Mixed farming populations (Iron Age Maysar and Islamic Bahrain) experienced low-moderate attrition, high rates of caries and calculus, abscessing due to caries, and severe AMTL. The final group of dental diseases affects populations practicing intensive gardening (Bronze and Iron Age Bahrain, and Sites 3 and 5, Ras al-Khaimah). These groups experienced slight attrition, high rates of caries, low rates of calculus deposition, and severe AMTL. PMID:8296873

  17. 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. PMID:17939353

  18. 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

  19. [Hardening of dental instruments].

    PubMed

    Gerasev, G P

    1981-01-01

    The possibility of prolonging the service life of stomatological instruments by the local hardening of their working parts is discussed. Such hardening should be achieved by using hard and wear-resistant materials. The examples of hardening dental elevators and hard-alloy dental drills are given. New trends in the local hardening of instruments are the treatment of their working parts with laser beams, the application of coating on their surface by the gas-detonation method. The results of research work and trials are presented. PMID:7300627

  20. 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.

  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. 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

  3. 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. PMID:24993255

  4. 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.

  5. 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

  6. 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. PMID:24993259

  7. Natural enamel wear--a physiological source of hydroxylapatite nanoparticles for biofilm management and tooth repair?

    PubMed

    Hannig, C; Hannig, M

    2010-04-01

    Dental caries is a widespread chronic disease caused by glucolytic biofilms. Despite considerable success in prophylaxis, there is still a strong demand for biomimetic biofilm management. Reflections on the abraded, but mostly caries-free teeth observed in prehistoric sculls or omnivorous primates, respectively, offer perspectives for developing new approaches in preventive dentistry. It is hypothesized that nano-sized hydroxylapatite crystallites occur in the oral cavity during extensive physiological wear of the hierarchical structured enamel surface due to dental abrasion and attrition. These nano-scaled apatite enamel crystallites might promote re-mineralization and physiological biofilm management at the tooth surface. Indeed, modern bioinspired nanomaterials in preventive dentistry containing nano-sized hydroxylapatite particles have shown efficacy in reducing oral biofilm formation and yield re-mineralizing effects. Accordingly, they seem to mimic extensive abrasions which do not occur with modern diet. PMID:19962245

  8. 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

  9. 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

  10. 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.

  11. Spectroscopic wear detector

    NASA Technical Reports Server (NTRS)

    Madzsar, George C. (Inventor)

    1993-01-01

    The elemental composition of a material exposed to hot gases and subjected to wear is determined. Atoms of an elemental species not appearing in this material are implanted in a surface at a depth based on the maximum allowable wear. The exhaust gases are spectroscopically monitored to determine the exposure of these atoms when the maximum allowable wear is reached.

  12. 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

  13. 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.

  14. 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.

  15. Effect of resin monomer composition on toothbrush wear resistance.

    PubMed

    Kawai, K; Iwami, Y; Ebisu, S

    1998-04-01

    The purpose of this study was to compare the toothbrush abrasion resistance of seven different experimental resins which were made by changing the composition of resin monomers. The experimental resins were made by mixing four kinds of dental resin monomers (Bis-GMA, UDMA, TMPT and TEGDMA), camphorquinone (1 wt%), dimethylaminoethyl methacrylate (2 wt%) and 2,6-di-tert-butyl-p-cresol (0.05 wt%). The resin specimens were stored in air for 2 weeks, and then put on a toothbrush abrasion testing machine. After 100000 strokes, the wear loss of each specimen was determined by weight change during the wear test. TMPT-TEGDMA resin showed the most wear resistance, while Bis-GMA- and UDMA-based resins showed increased wear resistance with an increased content of TEGDMA. Also, a inverse relationship between the microhardness number and the amount of wear of the respective resins was confirmed. PMID:9610853

  16. 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. PMID:11695131

  17. Dental Sealants

    MedlinePlus

    ... Data & Statistics > Find Data by Topic > Dental Sealants Dental Sealants Main Content Dental sealants are thin plastic coatings that protect the chewing surfaces of children’s back teeth from tooth decay. Overall, the prevalence of sealants ...

  18. Wear of materials used in dentistry: a review of the literature.

    PubMed

    Sulong, M Z; Aziz, R A

    1990-03-01

    This is a review of the literature concerning wear related to the following materials used in dentistry: dental amalgam, composite resins, and glass-ionomer cements, as well as natural tooth substance. Discussions are included on both in vivo and in vitro studies in which various methods were used to help determine wear resistance. PMID:2407832

  19. Dental microwear. Morphological, functional and phylogenetic correlations.

    PubMed

    Villa, G; Giacobini, G

    1998-01-01

    Dental wear, at first considered a pathological condition, is now regarded as a physiological mechanism of teeth adaptation to continuous masticatory stresses. Excessive wear is limited by characteristic structural adaptations of dental hard tissues showing a phylogenetic trend and specialisation. Enamel is the main tissue subjected to wear; however, advanced enamel wear exposes increasingly large areas of dentine. Enamel hardness and anisotropy are the major factors contrasting wear and microfractures. Anisotropy is mainly related to the different orientation of prism bundles (and of hydroxiapatite cristals). Enamel wear development is also related to differences in microhardness, density, mineral composition and protein distribution. Masticatory loads distributed along the enamel-dentine junction uniformly disperse in the underlying dentine. In spite of its structural characteristics, dentine is relatively isotropic by the functional point of view. Even if its lower hardness opposes less efficaciously to wear, its biomechanical characteristics successfully contrast microfractures. The study of microwear (namely the microscopic analysis of worn dental surfaces) can be made both on original surfaces and on high definition silicone-resin replicas. Scanning electron microscope observations allow identification of surface damage (microtraces) produced by different physical and chemical agents. Microwear analysis may provide indications about alimentary and non alimentary habits, masticatory biomechanics and pathological situations (e.g., bruxism). PMID:9766174

  20. 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. PMID:27482994

  1. 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.

  2. A case of severe caries and demineralisation in a patient wearing an essix-type retainer.

    PubMed

    Birdsall, Jo; Robinson, Stephen

    2008-04-01

    This case report presents a patient who developed significant caries and demineralisation due to consumption of large quantities of cariogenic drinks while he was wearing an Essix retainer. The risks to dental health during orthodontic retention and the responsibilities of general dental practitioners, orthodontists and patients are highlighted. PMID:18397593

  3. 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

  4. 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

  5. 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

    2016-02-01

    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. 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

  6. Tooth wear in three ethnic groups in Sabah (northern Borneo).

    PubMed

    Milosevic, A; Lo, M S

    1996-12-01

    The prevalence and associated aetiologies of tooth wear were investigated in three ethnic groups in Sabah (Northern Borneo) using the Tooth Wear Index (TWI). The number of surfaces with enamel wear only, dentine exposed for less than a third or dentine exposed for more than a third were categorised into the TW minimal, moderate or severe respectively. A structured questionnaire was used to elicit medical/dental history, oral hygiene practices, satisfaction with body image, diet and other personal habits/details. The sample comprised of a self selected sample of 148 dental hospital attenders; 47 (32 per cent) each of ethnic Chinese and Malay and 54 (36 per cent) of ethnic Kadazan, matched for age and with a similar number of scoreable teeth per subject. Dentine exposure within the total sample was a common finding (95 per cent TW with moderate, 41 per cent TW severe). The Kadazan group had significantly (P < 0.05) more surfaces with severe tooth wear than the Chinese or Malay. Tobacco chewing was positively associated (rho = +0.4, P < 0.05) with both moderate and severe tooth wear, as was the habit of crushing/eating bones. Neither carbonated beverages or fresh fruit intake were associated with tooth wear, but their frequency of consumption was low. The buccal and occlusal surfaces of the posterior teeth were the most severely worn. Generally, wear was greater in the upper anterior sextant compared to the lower anterior sextant, with the exception of the lower incisal edges in the Kadazan group. Tooth wear into dentine was a common occurrence, especially among the Kadazan subjects and least among the Chinese subjects. The aetiological factors associated with this tooth wear are different to those encountered in Western cultures. PMID:9023582

  7. 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. PMID:25802916

  8. Wear of resin-modified glass ionomers: an in vitro study.

    PubMed

    Futatsuki, M; Nozawa, M; Ogata, T; Nakata, M

    2001-01-01

    The purpose of this study was to evaluate the wear resistance and clinical applicability of resin-modified glass ionomer cements as restorative or fissure-sealing materials. The in vitro wear of resin-modified glass ionomers was compared to conventional glass ionomers, a resin-based sealant, and a composite resin. A three-body wear test (enamel block--polymethylmethacrylate powder--experimental dental material) was performed by 20,000 cycles with a load of 4 kgf/cm2. The depth of wear of the experimental materials was measured and calculated using a computerized laser surface scanner. The glass ionomers generally showed more wear than the resin-based sealant and the composite resin, but there was no difference in wear between resin-modified and conventional glass ionomers. Type III ionomers (used for sealant) showed lower wear resistance than type II ionomers (used for restoration). PMID:11497010

  9. 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…

  10. 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.

  11. Tooth wear: the view of the anthropologist.

    PubMed

    Kaidonis, John A

    2008-03-01

    Anthropologists have for many years considered human tooth wear a normal physiological phenomenon where teeth, although worn, remain functional throughout life. Wear was considered pathological only if pulpal exposure or premature tooth loss occurred. In addition, adaptive changes to the stomatognathic system in response to wear have been reported including continual eruption, the widening of the masticatory cycle, remodelling of the temporomandibular joint and the shortening of the dental arches from tooth migration. Comparative studies of many different species have also documented these physiological processes supporting the idea of perpetual change over time. In particular, differential wear between enamel and dentine was considered a physiological process relating to the evolution of the form and function of teeth. Although evidence of attrition and abrasion has been known to exist among hunter-gatherer populations for many thousands of years, the prevalence of erosion in such early populations seems insignificant. In particular, non-carious cervical lesions to date have not been observed within these populations and therefore should be viewed as 'modern-day' pathology. Extrapolating this anthropological perspective to the clinical setting has merits, particularly in the prevention of pre-mature unnecessary treatment. PMID:17938977

  12. First molar size and wear within and among modern hunter-gatherers and agricultural populations.

    PubMed

    Górka, Katarzyna; Romero, Alejandro; Pérez-Pérez, Alejandro

    2015-08-01

    Apart from reflecting modern human dental variation, differences in dental size among populations provide a means for studying continuous evolutionary processes and their mechanisms. Dental wear, on the other hand, has been widely used to infer dietary adaptations and variability among or within diverse ancient human populations. Few such studies have focused on modern foragers and farmers, however, and diverse methods have been used. This research aimed to apply a single, standardized, and systematic quantitative procedure to measure dental size and dentin exposure in order to analyze differences among several hunter-gatherer and agricultural populations from various environments and geographic origins. In particular, we focused on sexual dimorphism and intergroup differences in the upper and lower first molars. Results indicated no sexual dimorphism in molar size and wear within the studied populations. Despite the great ethnographic variation in subsistence strategies among these populations, our findings suggest that differences in sexual division of labor do not affect dietary wear patterns. PMID:26032341

  13. A Study on Tactile Friction and Wear

    NASA Astrophysics Data System (ADS)

    Sugishita, Junji; Usami, Hatsuhiko; Hattori, Tomokazu

    The tactile wear (“tezure” in Japanese) is an abrasion phenomenon of material surfaces caused by the contact of human hand over a long period of time. Though this phenomenon has been the focus of various articles, an extensive study with regard to the wear characteristics is of a profound importance. To date, we have several remarkable examples such as the statue of Pindola Bharadvaja (Buddhist) and the St. Peter statue (Christian). Followers of the respective religions who are deeply attached and rooted have been touching the statues as part of their rituals for many generations over centuries. In this study, an attempt is done to verify the friction and wear characteristics of various soft metals with contact of human finger. The results of our experiments show that the friction coefficient upon the contact of the human finger and pure copper are very high and thus proving tactile wear of soft metals can be generated easily.

  14. Geometry of wear in the sliding four-ball wear test

    NASA Astrophysics Data System (ADS)

    Strunks, Gregory A.; Toth, Douglas K.; Saba, Costandy S.

    1992-10-01

    The geometry of the four-ball test configuration was examined to develop a method to calculate the wear volume of noncircular scars. It was found that the length of the scar normal to the direction of sliding is related to the relative displacement between the upper and lower balls. The width of the scar parallel to the direction of sliding is dependent upon the curvature of the scar normal to the sliding direction. This curvature is a function of upper ball wear, and it is the upper ball wear that causes noncircularity of the lower ball scars. A model was developed to calculate wear volumes for the upper and lower balls using the length and width of the scars on the lower balls to generate a dimensionless profile parameter, alpha. For an inhibited polyphenyl ether-based lubricant, the wear volume of the upper ball is consistently greater than the total wear volume of the three lower balls. In addition to wear volume calculations, this model can also be used to predict the scar shape for given lengths and widths of the lower ball wear scar.

  15. Wear Behavior of a Novel Aluminum-Based Hybrid Composite

    NASA Astrophysics Data System (ADS)

    Show, Bijay Kumar; Mondal, Dipak Kumar; Maity, Joydeep

    2014-02-01

    In the current research, the dry sliding wear behaviors of 6351 Al alloy and its composite with hybrid reinforcement ( ex situ SiC and in situ Al4SiC4) were investigated at low sliding speed (1 m s-1) against a hardened EN 31 disk at different loads. The wear mechanism involved adhesion and microcutting-abrasion at lower load. On the other hand, at higher load, abrasive wear involving microcutting and microplowing along with adherent oxide formation was observed. Initially, under higher load, the abrasive wear mechanism caused rapid wear loss up to a certain sliding distance. Afterward, by virtue of frictional heat generation and associated temperature rise, an adherent oxide layer was developed at the pin surface which drastically reduced the wear loss. The overall wear rate increased with load in alloy as well as in composite. Moreover, the overall wear rate of the composite was found lower than that of the 6351 Al alloy at all applied loads. The ex situ SiC particles were found to resist abrasive wear, while, in situ Al4SiC4 particles offered resistance to adhesive wear. Accordingly, the 6351 Al (SiC + Al4SiC4) hybrid composite exhibited superior wear resistance relative to the 6351 Al alloy.

  16. Assessment HVOF sprayed coatings for reducing wear on pump components

    SciTech Connect

    Kaufold, R.; McCaul, C.; Brunhouse, S.

    1994-12-31

    Long-term pump efficiency and durability are directly related to the wear and corrosion resistance of materials used to manufacture pump components. Conventional OEM design materials often do not provide long-term resistance to wear caused by abrasive grains, particle erosion, corrosion, and cavitation. As a result, pump components can fail prematurely causing pump downtime and interrupting service life. Thermal-sprayed coatings, in particular, those deposited by HVOF, can help prevent this loss by reducing premature pump failure resulting from accelerated wear. The intent of this paper is to assess the degree of wear protection provided by various materials deposited by HVOF as compared to those coatings accepted by pump manufacturers. The materials tested ranged from tungsten carbide to chromium carbide to nickel-base alloys. The coating properties were analyzed by metallographic characterization, abrasive wear, corrosive wear, and anti-galling.

  17. 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. PMID:25980530

  18. Study of Tool Wear Mechanisms and Mathematical Modeling of Flank Wear During Machining of Ti Alloy (Ti6Al4V)

    NASA Astrophysics Data System (ADS)

    Chetan; Narasimhulu, A.; Ghosh, S.; Rao, P. V.

    2014-12-01

    Machinability of titanium is poor due to its low thermal conductivity and high chemical affinity. Lower thermal conductivity of titanium alloy is undesirable on the part of cutting tool causing extensive tool wear. The main task of this work is to predict the various wear mechanisms involved during machining of Ti alloy (Ti6Al4V) and to formulate an analytical mathematical tool wear model for the same. It has been found from various experiments that adhesive and diffusion wear are the dominating wear during machining of Ti alloy with PVD coated tungsten carbide tool. It is also clear from the experiments that the tool wear increases with the increase in cutting parameters like speed, feed and depth of cut. The wear model was validated by carrying out dry machining of Ti alloy at suitable cutting conditions. It has been found that the wear model is able to predict the flank wear suitably under gentle cutting conditions.

  19. Dental Hygienists

    MedlinePlus

    ... anatomy, patient management, and periodontics, which is the study of gum disease. High school students interested in becoming dental hygienists should take courses in biology, chemistry, and math. Most dental hygiene programs also require applicants to have completed at ...

  20. Dental sealants

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000779.htm Dental sealants To use the sharing features on this ... case a sealant needs to be replaced. How Dental Sealants Are Applied Your dentist applies sealants on ...

  1. 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

  2. Pyorrhoea as cause of pyrexia.

    PubMed Central

    Berry, E; Silver, J

    1976-01-01

    Three patients with fever and malaise, one of whom also had joint pains, were extensively investigated before their condition was attributed to dental sepsis. Each patient recovered fully after appropriate dental treatment. Dental sepsis should be added to the list of possible causes of pyrexia of undetermined origin, and a routine dental examination should be carried out in each case. PMID:1000197

  3. 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. PMID:25041439

  4. 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. PMID:26342288

  5. 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

  6. Theory of powdery rubber wear

    NASA Astrophysics Data System (ADS)

    Persson, B. N. J.

    2009-12-01

    Rubber wear typically involves the removal of small rubber particles from the rubber surface. On surfaces with not too sharp roughness, e.g. most road surfaces, this involves (slow) crack propagation. In this paper I shall present a theory of mild rubber wear. I shall derive the distribution of wear particle sizes Φ(D), which is in excellent agreement with experiment. I shall also show that the calculated wear rate is consistent with experimental data for tire tread block wear.

  7. Wear analysis of revolute joints with clearance in multibody systems

    NASA Astrophysics Data System (ADS)

    Bai, ZhengFeng; Zhao, Yang; Wang, XingGui

    2013-08-01

    In this work, the prediction of wear for revolute joint with clearance in multibody systems is investigated using a computational methodology. The contact model in clearance joint is established using a new hybrid nonlinear contact force model and the friction effect is considered by using a modified Coulomb friction model. The dynamics model of multibody system with clearance is established using dynamic segmentation modeling method and the computational process for wear analysis of clearance joint in multibody systems is presented. The main computational process for wear analysis of clearance joint includes two steps, which are dynamics analysis and wear analysis. The dynamics simulation of multibody system with revolute clearance joint is carried out and the contact forces are drawn and used to calculate the wear amount of revolute clearance joint based on the Archard's wear model. Finally, a four-bar multibody mechanical system with revolute clearance joint is used as numerical example application to perform the simulation and show the dynamics responses and wear characteristics of multibody systems with revolute clearance joint. The main results of this work indicate that the contact between the joint elements is wider and more frequent in some specific regions and the wear phenomenon is not regular around the joint surface, which causes the clearance size increase non-regularly after clearance joint wear. This work presents an effective method to predict wear of revolute joint with clearance in multibody systems.

  8. 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.

  9. 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

  10. Dental hyponatraemia.

    PubMed

    Simpson, R M

    2011-08-01

    A 14-year-old girl developed dental pain and was treated for acute infected pulpitis of her right upper lateral incisor with drilling and filling. The pain continued and was helped by analgesia, sucking ice cubes and drinking cold water. Forty-eight hours later, she became confused and disoriented. She started to vomit and complained of headache. Investigations revealed hyponatraemia with normal serum potassium levels and initially normal urinary sodium excretion. Over the next 24 hours, she passed 5.45 L of urine and her serum sodium rose from 125 to 143 mmol/L. Self-induced water intoxication has been described during drinking games and initiation ceremonies, but this would appear to an unusual cause. Conservative management proved successful in allowing this girl to recover without sequelae. PMID:21873727

  11. 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

  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. 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

  14. 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

  15. Wear Independent Similarity.

    PubMed

    Steele, Adam; Davis, Alexander; Kim, Joohyung; Loth, Eric; Bayer, Ilker S

    2015-06-17

    This study presents a new factor that can be used to design materials where desired surface properties must be retained under in-system wear and abrasion. To demonstrate this factor, a synthetic nonwetting coating is presented that retains chemical and geometric performance as material is removed under multiple wear conditions: a coarse vitrified abradant (similar to sanding), a smooth abradant (similar to rubbing), and a mild abradant (a blend of sanding and rubbing). With this approach, such a nonwetting material displays unprecedented mechanical durability while maintaining desired performance under a range of demanding conditions. This performance, herein termed wear independent similarity performance (WISP), is critical because multiple mechanisms and/or modes of wear can be expected to occur in many typical applications, e.g., combinations of abrasion, rubbing, contact fatigue, weathering, particle impact, etc. Furthermore, these multiple wear mechanisms tend to quickly degrade a novel surface's unique performance, and thus many promising surfaces and materials never scale out of research laboratories. Dynamic goniometry and scanning electron microscopy results presented herein provide insight into these underlying mechanisms, which may also be applied to other coatings and materials. PMID:26018058

  16. 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

  17. [Research progress of polyethylene inserts wear measurement and evaluation in total knee arthroplasty].

    PubMed

    Zhao, Feng; Wang, Chuan; Fan, Yubo

    2015-01-01

    Wear of polyethylene (PE) tibial inserts is a significant cause of implant failure of total knee arthroplasty (TKA). PE inserts wear measurement and evaluation is the key in TKA researches. There are many methods to measure insert wear. Qualitative methods such as observation are used to determine the wear and its type. Quantitative methods such as gravimetric analysis, coordinate measuring machines (CMM) and micro-computed tomography (micro-CT) are used to measure the mass, volume and geometry of wear. In this paper, the principle, characteristics and research progress of main insert wear evaluation method were introduced and the problems and disadvantages were analyzed. PMID:26027291

  18. Optical wear monitoring

    DOEpatents

    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.

  19. 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

  20. 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.

  1. 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.

  2. Dental and General Trauma in Team Handball.

    PubMed

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

    2016-01-01

    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. PMID:27622524

  3. 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…

  4. Erosive Tooth Wear and Related Risk Factors in 8- and 14-Year-Old Greek Children.

    PubMed

    Provatenou, Efthymia; Kaklamanos, Eleftherios G; Kevrekidou, Aikaterini; Kosma, Ismini; Kotsanos, Nikolaos

    2016-01-01

    The aim of the present study was to investigate the erosive tooth wear of primary and permanent teeth and its association with related risk factors. Two groups of Greek children aged 8 (n = 329) and 14 years (n = 263) were examined in the classroom using the Basic Erosive Wear Examination (BEWE) index. Data concerning risk factors were collected using questionnaires. Dental caries (DMFS/dmfs) was also recorded. The data were analyzed using the t test, one-way ANOVA, multiple regression analysis, Fisher's exact test, and the χ2 test. In the 8-year-olds, the primary teeth showed a predominantly medium level of wear and the permanent teeth no wear. A majority of the 14-year-olds exhibited low risk levels of wear. The most frequently affected dental surface in both age groups was the occlusal surface of the mandibular posterior teeth. In the 8-year-olds, BEWE scores and the prevalence of wear in the primary teeth was influenced by gender (p = 0.020). In their permanent teeth, soft drink consumption (p < 0.0001) and preference for lemon/vinegar (p = 0.041) significantly affected wear prevalence and BEWE scores, while habitually retaining soft drinks in the mouth influenced wear prevalence (p = 0.008), risk (p = 0.004), and BEWE scores (p = 0.022). In the 14-year-olds, wear prevalence was significantly affected by the consumption of lemon-flavored candies (p = 0.016) and soft drinks (p = 0.050). BEWE scores were significantly affected by gender (p = 0.022) and soft drink consumption (p = 0.030). Gender influenced tooth wear risk in both age groups (p = 0.010 and p = 0.021, respectively). The results of this study indicate that erosive tooth wear differed between primary and permanent teeth and was influenced by gender and dietary factors. PMID:27286713

  5. 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. PMID:22855595

  6. The lexicon of polyethylene wear in artificial joints.

    PubMed

    McKellop, Harry A

    2007-12-01

    The analysis of wear on polyethylene components that have been retrieved after use in patients has provided invaluable understanding of how wear occurs in vivo, and how it may be minimized through improved materials and implant design. The great number of such studies that have been published over the past three decades has lead to an extensive vocabulary to describe the tribology of prosthetic joints. However, these also have led to some confusion, due to the occasional misuse of terms from classical tribology, along with the use of multiple terms to describe the same wear phenomenon, and vice versa. The author has proposed that our understanding of wear in artificial joints may be enhanced by recognizing that there are four general subject areas: Modes, Mechanisms, Damage and Debris. Wear Mode 1 occurs when the two bearing surfaces are articulating against each other in the manner intended by the implant designer. Mode 2 occurs when a bearing surface articulates against a non-bearing surface. Mode 3 occurs when third-body abrasive particles have become entrapped between the two bearing surfaces, and Mode 4 occurs when two non-bearing surfaces are wearing against each other. The least wear occurs in Mode 1, whereas severe wear typically occurs in Modes 2, 3 and 4. The classical wear mechanisms that apply to prosthetic joints include adhesion, abrasion and fatigue. These can occur in varying amounts in either of the four wear modes. As used in the literature for the past three decades, wear "damage" can best be defined as the change surface texture or morphology that is caused by the action of the wear mechanisms. Although a wide variety of terms have been used, an overview of the literature indicates that about eight terms have been sufficient to describe the types of damage that occur on retrieved polyethylene components, i.e., burnishing, abrasion, scratches, plastic deformation, cracks, pits, delamination, and embedded third bodies. The author suggests that, as

  7. 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…

  8. 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. PMID:19410234

  9. Theory of powdery rubber wear.

    PubMed

    Persson, B N J

    2009-12-01

    Rubber wear typically involves the removal of small rubber particles from the rubber surface. On surfaces with not too sharp roughness, e.g. most road surfaces, this involves (slow) crack propagation. In this paper I shall present a theory of mild rubber wear. I shall derive the distribution of wear particle sizes Φ(D), which is in excellent agreement with experiment. I shall also show that the calculated wear rate is consistent with experimental data for tire tread block wear. PMID:21832508

  10. 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.

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

    PubMed

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

    2014-01-01

    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. PMID:24422752

  12. 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

  13. Wear processes in rocks at slow to high slip rates

    NASA Astrophysics Data System (ADS)

    Hirose, Takehiro; Mizoguchi, Kauzo; Shimamoto, Toshihiko

    2012-05-01

    Frictional wear experiments are performed on diorite, granite and sandstone at sliding velocities of 0.004-0.27 m/s under normal stresses of 0.21-6.3 MPa using a rotary-shear apparatus, to establish velocity-dependent wear laws of rocks and to determine the partition of frictional work used for gouge generation. Power-laws between normal/shear stresses and steady-state wear rate, defined as (thickness of gouge formed)/(fault displacement), account for our data for diorite and granite at low velocities and most experimental data on wear of rocks reported in the literature. But an exponential law holds for wear of diorite at velocities greater than 0.11 m/s and its wear rate increases dramatically at seismic slip rates. A change from the power-law to the exponential law seems to be caused by frictional heating and thermal fracturing. Both power and exponential laws can describe data for granite. Sandstones exhibit complex wear behavior possibly due to development of shiny slickenside surface that suppresses wear. Our data for diorite indicate that, at the investigated normal stresses, only 0.004% of frictional work is consumed for gouge formation at velocities less than 0.11 m/s, but this fraction increases markedly with increasing velocity. Energy partition for gouge formation is not constant and changes with velocity during earthquakes.

  14. 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. PMID:25765077

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. Facial and Dental Injuries Facial and Dental Injuries in Karate.

    PubMed

    Vidovic-Stesevic, Vesna; Verna, Carlalberta; Krastl, Gabriel; Kuhl, Sebastian; Filippi, Andreas

    2015-01-01

    Karate is a martial art that carries a high trauma risk. Trauma-related Swiss and European karate data are currently unavailable. This survey seeks to increase knowledge of the incidence of traumatic facial and dental injuries, their emergency management, awareness of tooth rescue boxes, the use of mouthguards and their modifications. Interviews were conducted with 420 karate fighters from 43 European countries using a standardized questionnaire. All the participants were semi-professionals. The data were evaluated with respect to gender, kumite level (where a karate practitioner trains against an adversary), and country. Of the 420 fighters interviewed, 213 had experienced facial trauma and 44 had already had dental trauma. A total of 192 athletes had hurt their opponent by inflicting a facial or dental injury, and 290 knew about the possibility of tooth replantation following an avulsion. Only 50 interviewees knew about tooth rescue boxes. Nearly all the individuals interviewed wore a mouthguard (n = 412), and 178 of them had made their own modifications to the guard. The results of the present survey suggest that more information and education in wearing protective gear are required to reduce the incidence of dental injuries in karate. PMID:26345152

  1. Dental Implants

    MedlinePlus Videos and Cool Tools

    ... facts so you can make an informed decision as to whether dental implants are right for your ... the jaw bone. It’s obviously not the same as the original connection , but functions just the same. ...

  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 Caries (Tooth Decay)

    MedlinePlus

    ... Find Data by Topic > Dental Caries (Tooth Decay) Dental Caries (Tooth Decay) Main Content Dental caries (tooth decay) remains the most prevalent chronic ... important source of information on oral health and dental care in the United States since the early ...

  4. Wear Characteristics of Sintered Cermets

    NASA Astrophysics Data System (ADS)

    Bidulský, Róbert; Bidulská, Jana; Arenas, Freddy; Grande, Marco Actis

    2012-02-01

    The present paper deals with the tribological behaviour of the boride and carbide hardmetals evaluated by performing comparative dry sliding pin-on-disc experiments using normal contact loads. Analyses of the wear performance results, microstructural evaluation and processing conditions effect indicate that microstructure inhomogenities play an important role in abrasive wear behaviour of cermets. In term of grain size and chemical composition, the addition of VC also play an important role in increasing the wear resistance.

  5. Limiting dogleg is a key to reducing casing wear

    SciTech Connect

    Bettis, F.E.; Schwanitz, B.J. ); Crane, L. )

    1994-08-01

    A field study, involving logging runs with an ultrasonic imaging tool, of several wells drilled in Alaska indicates causing wear from drill pipe rotation can be reduced if the dogleg severity is kept less than 5[degree]/1,000 ft. Factors related to casing pipe wear include drill pipe hardbanding, hole deviation, and directional dogleg severity. Excessively worn casing may not withstand pressure tests, may develop holes, or may cause operational problems. The Ultra Sonic Imaging (USI) tool measures the extent of casing wear from normal drillstring rotation. USI logs are run to evaluate cement and measure casing thickness (results are presented in terms of metal loss). Field examples clearly illustrate the strong correlation between increased dog-leg severity and increased casing wear.

  6. Wear mechanism based on adhesion

    NASA Technical Reports Server (NTRS)

    Yamamoto, T.; Buckley, D. H.

    1982-01-01

    Various concepts concerning wear mechanisms and deformation behavior observed in the sliding wear track are surveyed. The mechanisms for wear fragment formation is discussed on the basis of adhesion. The wear process under unlubricated sliding conditions is explained in relation to the concept of adhesion at the interface during the sliding process. The mechanism for tearing away the surface layer from the contact area and forming the sliding track contour is explained by assuming the simplified process of material removal based on the adhesion theory.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. Switch wear leveling

    SciTech Connect

    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.

  15. 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

    2016-08-01

    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.

  16. 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.

  17. Dental crowns

    MedlinePlus

    ... cover a tooth Replace a misshapen tooth or dental implant Correct a misaligned tooth Talk to your dentist ... the tooth pulled and replaced with a tooth implant. Your crown could chip or crack: If you grind your teeth or clench your jaw, you may need to ...

  18. Dental Assistant.

    ERIC Educational Resources Information Center

    Michigan State Univ., East Lansing. Coll. of Agriculture and Natural Resources Education Inst.

    This curriculum guide, developed for use in dental assistant education programs in Michigan, describes a task-based curriculum that can help a teacher to develop a classroom management system where students learn by doing. It is based on task analysis and reflects the skills, knowledge, and attitudes that employers expect entry-level dental…

  19. 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

  20. 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,…

  1. 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

  2. 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

  3. Chemical vapour deposition diamond coating on tungsten carbide dental cutting tools

    NASA Astrophysics Data System (ADS)

    Sein, H.; Ahmed, W.; Rego, C. A.; Jones, A. N.; Amar, M.; Jackson, M.; Polini, R.

    2003-10-01

    Diamond coatings on Co cemented tungsten carbide (WC-Co) hard metal tools are widely used for cutting non-ferrous metals. It is difficult to deposit diamond onto cutting tools, which generally have a complex geometry, using a single step growth process. This paper focuses on the deposition of polycrystalline diamond films onto dental tools, which possess 3D complex or cylindrical shape, employing a novel single step chemical vapour deposition (CVD) growth process. The diamond deposition is carried out in a hot filament chemical vapour deposition (HFCVD) reactor with a modified filament arrangement. The filament is mounted vertically with the drill held concentrically in between the filament coils, as opposed to the commonly used horizontal arrangement. This is a simple and inexpensive filament arrangement. In addition, the problems associated with adhesion of diamond films on WC-Co substrates are amplified in dental tools due to the very sharp edges and unpredictable cutting forces. The presence of Co, used as a binder in hard metals, generally causes poor adhesion. The amount of metallic Co on the surface can be reduced using a two step pre-treatment employing Murakami etching followed by an acid treatment. Diamond films are examined in terms of their growth rate, morphology, adhesion and cutting efficiency. We found that in the diamond coated dental tool the wear rate was reduced by a factor of three as compared to the uncoated tool.

  4. 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

  5. Bacterial conditions of water in dental units.

    PubMed

    Thé, S D; Van't Hof, M A

    1975-01-01

    Stagnant water in the boiler of a dental unit can cause a high bacterial density. A spiral unit is somewhat superior to a boiler in this respect. Normal unchlorinated tapwater is the main problem in achieving hygienic conditions in dental practice. The technical performance of the unit is only partly responsible for the water quality. PMID:1058859

  6. 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

  7. Wearing gloves in the hospital

    MedlinePlus

    Wearing gloves in the hospital helps prevent the spread of germs. This helps protect both patients and health care ... Gloves are called personal protective equipment (PPE). Other types of PPE are gowns, masks, and shoe and ...

  8. Wear resistance properties of austempered ductile iron

    SciTech Connect

    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.

  9. 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.

  10. Evaluation of Wear between Pin and Bush in Roller Chain

    NASA Astrophysics Data System (ADS)

    Noguchi, Shoji; Yoshiba, Hideaki; Nakayama, Satoshi; Kanada, Tohru

    A roller chain is a typical machine element used in bicycles, motorcycles and many other devices for power transmission. The life of a roller chain is determined by elongation. As a rule of thumb, a chain begins to skip cogs on the sprocket wheel when the percentage of elongation reaches approximately 3%. Mechanical wear between pins and bushes causes elongation of the roller chain. However, research on the evaluation of wear of the roller chain is rare and the achievement is unstated. We describe the following initiatives in the study of wear between pins and bushes of a roller chain: (1) development of a wear tester using only two chain links, (2) establishment of a specific evaluation method using a roundness tester, and (3) causal explanation of non-uniform wear using the finite-element method (FEM). The experimental results show that pins and bushes are not in contact at the centerline, and that wear occurs exclusively at the tips of the pins owing to the bending deformation under the condition of tensile load.

  11. Dental x-rays

    MedlinePlus

    ... or impacted teeth The presence and extent of dental caries (cavities) Bone damage (such as from periodontitis ) Abscessed ... Dental x-rays can reveal dental cavities (tooth decay) before they ... take yearly bitewings for the early development of cavities.

  12. 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.

  13. 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.

  14. 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.

  15. 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. PMID:25943712

  16. Dental Holography

    NASA Astrophysics Data System (ADS)

    Dirtoft, Ingegerd

    1983-12-01

    Ten years have passed since the first articles appeared in this new field. The qualities of the laser light together with the need of contactless 3-D measurements for different dental purposes seemed to be extremely promising, but still just a few scientists have used the method and mostly for laboratory studies. For some reason there has been a preponderance for orthodontic measurements. This seems to be a bit peculiar from holographic view compared with measurements for engineering purposes, which usually are made on metals. So naturally holography can become a clinical tool for measurements in the field of fixed bridges, removable partial dentures and implants. One of the problems is that the need for holography in dental research must be fulfilled in collaboration with physicists. Only a two-way communication during an entire experiment can balance both technical and odontological demands and thus give practical and clinical important results. The need for an easy way of handling the evaluation to get all required information is another problem and of course the holographic equipment must be converted to a box easy to handle for everyone. At last the position of dental holography today is going to be carefully examined together with an attempt to look into the hopefully exciting and not to utopic future for this research field.

  17. 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

  18. Widespread Legionella pneumophila contamination of dental stations in a dental school without apparent human infection.

    PubMed Central

    Oppenheim, B. A.; Sefton, A. M.; Gill, O. N.; Tyler, J. E.; O'Mahony, M. C.; Richards, J. M.; Dennis, P. J.; Harrison, T. G.

    1987-01-01

    Following isolation of Legionella pneumophila from a special dental station water circuit, used primarily to cool high-speed dental drills which produce fine aerosols, a case finding and environmental survey was undertaken. Widespread colonization of the dental stations was found and the results suggested that amplification of the background levels of L. pneumophila was taking place within the stations. However there was no evidence for transmission causing human infection. PMID:3609170

  19. 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.

  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. 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

  2. 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.

  3. Wear resistance of ductile irons

    SciTech Connect

    Lerner, Y.S. )

    1994-06-01

    This study was undertaken to evaluate the wear resistance of different grades of ductile iron as alternatives 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 microhardness of structural constituents, and nodule size of ductile iron. The frictional wear resistance of ductile iron as a bearing material was tested with hardened steel shafts using standard test techniques under continuous rotating movement with lubricant. Lubricant sliding wear tests on specimens and components for hydraulic equipment and apparatus were carried out on a special rig with reciprocating motion, simulating the working conditions in a piston/cylindrical 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.

  4. [Biocompatibility of dental amalgam].

    PubMed

    Missias, P

    1990-10-01

    The purpose of the present review was to present a detailed description of those current scientific results and opinions relative to the biocompatibility of dental amalgam. The first section of the percent review to the pulpar reactions caused by amalgam fillings, especially when no protective base has been used, while the second part concerns itself with the biocompatibility of the dental amalgam per se. Specifically, reference is made to: a) the adverse reactions due to amalgam fillings both on the patient's physiological system and on the dentist's employing the material under consideration. b) those investigation results bearing a relation on the amount of mercury liberated during the amalgam filling procedures, i.e., mixing, condensation, finishing and polishing and/or removal of old amalgam fillings. c) Liberation of mercury, as well as metallic ions in the patients mouth cavity during chewing and/or during the process of intrabuccal galvanization and corrosion, and d) on the amount of mercury traced in the blood and urine of the patient following amalgam fillings. No conclusive evidence on any adverse reactions on the patient's health, attributable to the liberation of mercury from amalgam fillings, could be presented by the scientific investigations under consideration. Moreover, the number of cases reported on toxic reactions due to dental amalgam is negligible compared to the immense number of amalgam fillings performed in practice. It merits mentioning in this connection, however, the fact that the total amount of mercury attained by the patient from any other source, in conjunction with that liberated from amalgam fillings, could by all means contribute to a number of toxic reactions on the patient's health in general. Conclusively, one could state without reservations, that dental amalgam fillings per se are by and large free of toxic reactions on the patient, based on current scientific observations. Mentioning is finally made on several simple but

  5. 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 living and extinct mammals, with commentary on areas of future research.

  6. 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

  7. Infant dental care (image)

    MedlinePlus

    ... child to bed with a bottle of milk, juice, or 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 ...

  8. Dental indicators of ancient dietary patterns: dental analysis in archaeology.

    PubMed

    Forshaw, R

    2014-05-01

    What can the study of ancient teeth tell us about the dietary habits of our ancestors? Diet plays a prominent role in the organisation and evolution of human cultures and an increasingly diverse array of analytical techniques are available to help reconstruct diet in ancient populations. Dental palaeopathology is particularly important as it can provide direct evidence of the type of diet an individual consumed during life. Heavy occlusal tooth wear is the most frequent condition recognisable and an examination of both macro and microscopic patterns of wear can establish the differences between the hard fibrous diet typical of a hunter-gatherer, and a diet primarily consisting of softer plant foods consumed by an agriculturist. The distributions of trace elements and stable isotopes in food webs make it possible to use them as natural tracers of foodstuffs. Through a consideration of photosynthetic pathways, the ratios of the different stable isotopes of carbon and nitrogen can determine which specific groups of plants and animals were dominant in the food chains of various populations - a fact that has been used to trace the spread of agriculture in ancient civilisations. PMID:24809573

  9. Dental education in Colombia

    PubMed Central

    Jaramillo, Jorge A.; Pulido, Jairo H. Ternera; Núñez, Jaime A. Castro; Bird, William F.; Komabayashi, Takashi

    2014-01-01

    This article describes Colombia's development of formal dentistry, its dental school system, curriculum, and dental licensure, and current issues in oral health care. In 1969, there were only 4 dental schools in Colombia; at this writing there are 21. Five dental schools are public and the other 16 are private. Nearly all classes are conducted in Spanish. Undergraduate pre-dental coursework is not a prerequisite for dental school in Colombia. To obtain licensure, Colombian dental students must complete 5 years of study in dental school, earn a diploma, and work for the government for 1 year. There are approximately 41,400 dentists in Colombia, and the number is increasing quickly. However, the unemployment rate among dentists is very high, even though graduation from dental school is extremely difficult. Although the 1,100:1 ratio of citizens to dentists is considered satisfactory, access to dental care is limited due to the high rate of poverty. PMID:20339245

  10. Prototyping artificial jaws for the Bristol Dento-Munch Robo-Simulator. 'A parallel robot to test dental components and materials'.

    PubMed

    Alemzadeh, Kazem; Raabe, Daniel

    2007-01-01

    This paper presents the robot periphery for the Robotic Dental Testing Simulator based on a Parallel Robot (i.e. Stewart Platform) to simulate the wear of materials on dental components, such as individual teeth, crowns or a full set of teeth. Current chewing simulators move in only 1 or 2 degrees of freedom (DOF) and therefore lack accuracy. The Bristol simulator has been developed to replicate accurate human chewing patterns in 6-DOF. This paper describes the artificial jaws and compliance module of the robot. 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. Correct occlusion of the artificial jaws assembly was assessed by a dental teaching simulator. 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. PMID:18002240

  11. Dental stem cell patents.

    PubMed

    Morsczeck, Christian; Frerich, Bernhard; Driemel, Oliver

    2009-01-01

    A complex human tissue harbors stem cells that are responsible for its maintenance or repair. These stem cells have been isolated also from dental tissues such as the periodontal ligament, dental papilla or dental follicle and they may offer novel applications in dentistry. This following review summarizes patents about dental stem cells for dental tissue engineering and considers their value for regenerative dentistry. PMID:19149737

  12. Atypical Forensic Dental Identifications.

    PubMed

    Cardoza, Anthony R; Wood, James D

    2015-06-01

    Forensic dental identification specialists are typically the last conventional option for postmortem identification. Forensic dental identification is most often accomplished by comparing radiographs of the decedent's teeth with the dental radiographs obtained from the dentist of the suspected victim. Unfortunately, antemortem dental radiographs are not always available. When presented with this challenge, the authors of this article have been successful in completing identifications using means other than dental radiographic comparison. PMID:26126345

  13. Nanoscale friction and wear properties of silicon wafer under different lubrication conditions

    NASA Astrophysics Data System (ADS)

    Chen, Xiaochun; Zhao, Yongwu; Wang, Yongguang; Zhou, Hailan; Ni, Zhifeng; An, Wei

    2013-10-01

    The nanoscale friction and wear properties of single crystal silicon wafer under different lubrication conditions are studied in this paper. The experiments were performed with Si3N4 ball sliding on the surface of silicon wafer under four different lubrication conditions: dry friction, water lubrication, hydrogen peroxide lubrication and the static hydrogen peroxide dry friction. The results from the experiments have been analyzed showing the different friction and wear properties of the silicon wafer in different lubrication conditions. It is concluded that the wear rates under the water lubrication and under the hydrogen peroxide lubrication are both small, the chemical reactions are facilitated by the mechanical processes when the load and the sliding speed reach certain levels. This is mainly resulted by the enhanced lubricant performance with the formed silicon hydroxide Si(OH)4 film. Under the water lubrication, the wear is found in a way of material removed in molecule scale. Under the hydrogen peroxide lubrication, the wear is mainly caused by the spalling of micro-cracks. Under the dry friction condition, the wear is found being adhesive wear. And under the static peroxide dry friction, the wear is prevailing adhesive wear. These results are essential and valuable to the development of the efficient and environmental-friendly slurry for the chemical mechanical polishing (CMP) process.

  14. Characterisation of alumina hip-joint wear by FIB Microscopy

    NASA Astrophysics Data System (ADS)

    Zeng, Peng; Inkson, Beverley J.; Rainforth, W. Mark

    2006-02-01

    The wear of hip-joints is a significant clinical problem, which causes adverse tissue reactions leading to bone absorption and consequent loosening of the fixation. Artificial hip joints retrieved after use and tested on simulators typically exhibit a 'stripe' wear area on the surface of the alumina bearing components. Focused Ion Beam (FIB) microscopy has been used to investigate the sub-surface damage mechanisms in worn alumina hip-joints for the first time. The alumina acetabular cup, both inside and outside the 'stripe' wear trace, has been cross-sectioned by FIB milling. The sub-surface microstructures revealed by the FIB machining, outside, inside and at the edge of the 'stripe' have been imaged by SEM and FIB and are compared with the microstructure of unworn bulk material. The advantage of this technique is that it enables site specific selected areas of the worn surface to be analysed.

  15. 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.

  16. 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

  17. Critical length scale controls adhesive wear mechanisms.

    PubMed

    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

  18. Critical length scale controls adhesive wear mechanisms

    NASA Astrophysics Data System (ADS)

    Aghababaei, Ramin; Warner, Derek H.; Molinari, Jean-Francois

    2016-06-01

    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.

  19. In vitro wear of composite with varied cure, filler level, and filler treatment.

    PubMed

    Condon, J R; Ferracane, J L

    1997-07-01

    For the clinical wear of composite filing materials to be reduced, compositional factors such as degree of cure, filler level, and silanation level should be optimized. An oral-wear-stimulating machine was used to explore the effects of these factors on abrasion and attrition wear as well as on opposing enamel wear. The composites were made from Sr glass (1-2 micron avg) and a 50/50 Bis-GMA/TEGDMA resin. Series I (A-D, E) were light-cured (Triad II) for 9, 12, 25, and 40 sec/side to produce degree of cure (DC) as measured by FTIR of 56, 60, 61, and 63%, respectively. E received an additional heat cure (120 degrees C for 10 min) to reach a DC of 66%. Series II (D, F-I) were filled to 62, 53, 48, 37, and 28 vol%, respectively. In series III (D, J-M), the portion of fillers treated with a silane coupler (MPS) was 100, 80, 60, 40, and 20%, respectively. Samples were cycled 50,000 times against an enamel antagonist in a poppy seed/PMMA slurry in the oral wear simulator to produce abrasion (load = 20 N) and attrition (load = 70 N) simultaneously. Wear depth (micron: n = 5) was measured by profilometry. Results for each series were analysed by ANOVA/Turkey's (p < or = 0.05). The wear depths did reflect cure values, though only the abrasion difference for E < A was significant. Greater wear was correlated with lower filler levels (r2 = 0.88; p < 0.05), significantly increasing below 48 vol% (G). Wear increased linearly as the percent of silane-treated fillers was reduced (r2 = 0.99; p < 0.05). Abrasion and attrition did not differ significantly for any composite. Wear of the opposing enamel was largely unchanged by these factors. Compositional factors including degree of cure, filler level, and silanation directly affected the wear resistance of dental composites evaluated in an oral wear simulator. PMID:9207774

  20. Detecting Inter-Cusp and Inter-Tooth Wear Patterns in Rhinocerotids

    PubMed Central

    Taylor, Lucy A.; Kaiser, Thomas M.; Schwitzer, Christoph; Müller, Dennis W. H.; Codron, Daryl; Clauss, Marcus; Schulz, Ellen

    2013-01-01

    a uniform wear pattern and dental function along the tooth row, which could relate to the observed evolution towards homodonty. PMID:24312507

  1. 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…

  2. A clinician guide to patients afraid of dental injections and numbness.

    PubMed

    Armfield, Jason M; Milgrom, Peter

    2011-01-01

    Fears of dental injections remain a clinical problem often requiring cognitive behavioural psychology counselling and sedation in order to carry out needed dental treatment. This study, based on a national survey in Australia, compared patient concerns about numbness caused by local anaesthesia and fears of the injection itself. It also examined associations between dental fearfulness and avoidance associated with patient self-reported negative experiences and treatment need. Clinical advice on how to approach such patients is offered. Relatively high levels of dental anxiety and fear have been reported in several industrialised Western societies (McGrath & Bedi, 2004; Armfield, Spencer & Stewart, 2006; Lahti et al., 2007; Enkling, Marwinski Jöhren, 2006). In the U.K., almost one in three adults consider themselves to always be anxious about going to the dentist (Nuttall et al., 2001). Of concern is that this dental fear may be passed on to the children of anxious adults (Nuttall, Gilbert & Morris, 2008), leading to an inter-generational perpetuation of the problem. There is considerable evidence that dental fear is related to poorer oral health, reduced dental attendance and increased treatment stress for the attending dentist. There are many aspects of going to a dentist that might elicit feelings of apprehension, concern or anxiety in prospective patients (Liddell & Gosse, 1998; Oosterink, de Jongh & Aartman, 2008). One of the most commonly reported concerns relates to receiving injections. Indeed, fear of needles and the treatment of injection fear has been an important focus of a research in the U.K. (Boyle, Newton & Milgrom, 2010). Needle fear, in particular, is a major issue given that the delivery of local anaesthesia via injection is the central plank of pain relief techniques in dentistry (Malamed, 2009) and dentists as well as patients often avoid difficult injections as a consequence, resulting in poor pain control. A less well described anxiety of

  3. 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.

  4. 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.

  5. N,N-dimethyl-p-toluidine, a component in dental materials, causes hematologic toxic and carcinogenic responses in rodent model systems.

    PubMed

    Dunnick, June K; Brix, A; Sanders, J M; Travlos, G S

    2014-01-01

    Because of the potential for exposure to N,N-dimethyl-p-toluidine (DMPT) in medical devices and the lack of toxicity and carcinogenicity information available in the literature, the National Toxicology Program conducted toxicity and carcinogenicity studies of DMPT in male and female F344/N rats and B6C3F1/N mice. In these studies, a treatment-related macrocytic regenerative anemia characterized by increased levels of methemoglobin and Heinz body formation developed within a few weeks of DMPT exposure in rats and mice. DMPT induced nasal cavity, splenic, and liver toxicity in rats and mice at 3 months and 2 years. DMPT carcinogenic effects were seen in the liver of male and female rats and mice, the nasal cavity of male and female rats, and the lung and forestomach of female mice. In rodents, DMPT is distributed to many of the sites where toxic and carcinogenic effects occurred. DMPT-induced oxidative damage at these target sites may be one mechanism for the treatment-related lesions. Methemoglobinemia, as seen in these DMPT studies, is caused by oxidation of the heme moiety, and this end point served as an early alert for other target organ toxicities and carcinogenic responses that followed with longer term exposure. PMID:23867143

  6. Dental staff doses with handheld dental intraoral x-ray units.

    PubMed

    Gray, Joel E; Bailey, Edgar D; Ludlow, John B

    2012-02-01

    A handheld portable dental intraoral x-ray system is available in the United States and elsewhere. The system is designed to minimize the user's radiation dose. It includes specially designed shielding of the x-ray tube housing and an integral radiation shield to minimize backscatter. Personnel radiation dose records were obtained from 18 dental facilities using both the handheld system and a wall mounted dental x-ray system, providing 661 individual dose measurements. Dental staff doses were also compared for the handheld and conventional systems using both film and digital imaging for the same facilities and staff members. The results indicate that the doses for the handheld systems are significantly less than for wall-mounted systems. The average monthly dose for the handheld systems was 0.28 μSv vs. 7.86 μSv (deep dose equivalent) for the wall-mounted systems, a difference that is statistically significant at the p = 0.01 level. Consequently, there should be no concern about the use of this handheld dental intraoral x-ray system. Additional shielding efforts, (e.g., wearing a lead apron) will not provide significant benefit nor reduce staff radiation dose. PMID:22217586

  7. Dental health in Malaysia.

    PubMed

    Majid, Z A

    1984-12-01

    Three epidemiological surveys have been carried out in Malaysia since 1971. All showed a high level of caries prevalence. Ninety per cent of school children between the ages of 6 and 18 suffered from dental caries, with a DMFT of approximately 3 and a dft of approximately 2. Ninety-five per cent of the adult population had caries experience, with the mean DMFT being 13.2. Approximately 55 per cent of children showed the presence of gingivitis with the mean number of inflamed gingival units per child ranging from 1.9 to 2.8, while 72.4 per cent of adults had some form of periodontal disease with 29 per cent having pockets deeper than 3 mm. The OHI-S score for adults was 2.2 and 81 per cent used toothbrushes to clean their teeth. A further 5.1 per cent used twigs and fingers with powdered charcoal or salt. One-third of the child population needed orthodontic treatment, with 0.3 per cent examined in peninsular Malaysia having cleft lip or palate or both. In the adult population 10.4 per cent of those examined required some form of orthodontic treatment. Twenty per cent of the children in the survey were in need of dentures; 54.7 per cent of the adults were either in need of dentures or were wearing dentures. Of these 25 per cent had complete dentures. The smoking habit was most commonly associated with pre-cancerous/cancerous lesions with alcohol consumption a close competitor; 114 adults, that is 1.3 per cent of those examined, suffer from leukoplakia but only one case of oral cancer was detected.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6597132

  8. [Dental records and responsibility].

    PubMed

    Brands, W G

    2006-03-01

    Dental records are more than a small part of the bookkeeping. In most dental practises, keeping records is the task of a dental assistant. In civil court, the dentist is in most countries liable for the mistakes of his employees. In disciplinary court however there may be doubt whether the dentist is responsible for the mistakes of his assistant. Contrary to their American colleagues, Dutch dental assistants and dental hygienists cannot be summoned before a disciplinary court. As these para-medics perform more and more dental treatment, independently or after delegation, they should be assigned there own disciplinary responsibility. PMID:16566401

  9. 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. PMID:26889000

  10. 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. PMID:26916680