Science.gov

Sample records for elastomeric impression materials

  1. [Elastomeric impression materials].

    PubMed

    Anagnostopoulos, T; Tsokas, K

    1990-01-01

    A review of the literature on elastomeric impression materials, is presented in this paper. The article mentions the composition and the most important properties of the elastomeric impression materials used in dental practice. The clinical significance of these materials, physical and mechanical properties are also emphasized. In addition some new elastomeric impression materials with improved properties and a new (experimental) light-cured impression material, are mentioned. Another part of this article is the biocompatibility of these materials. In the end the great significance of handling is outlined. PMID:2130039

  2. [Elastomeric impression materials].

    PubMed

    Levartovsky, S; Folkman, M; Alter, E; Pilo, R

    2011-04-01

    Elastomeric impression materials are in common use. The impression taken should be highly precise, thus, requiring specific care when manipulatingthese materials. There are 4 groups of elastomers; polysulfide, condensation silicone, addition silicone and polyether; each differ in their setting mechanism and their physical and chemical properties. This review elaborates the major properties of elastomers and its implications on their use. The impression material is inserted into the patient's mouth in a viscous state and transforms into viscoelastic state, upon withdrawal, influencing the residual deformation. The requirements are minimal residual deformation or maximal elastic recovery. As the mouth is a wet environment a major consideration is hydrophilicity. The wettability which is estimated by measuring either the contact angle of a droplet of water and the substrate post setting or the contact angle of a droplet of impression material and the wet tooth pre setting, determines the interaction of the material with both mouth fluids and gypsum. As the primary end target is to obtain a model depicting accurately the oral details, an attention to the impressions' compatibility with gypsum should also be given. Many studies were conducted to get a thorough understanding of the hydrophilic properties of each material, and the mechanism utilized, such as surfactants in hydrophilic PVS. Polyether is the only material that is truly hydrophilic; it exhibits the lowest contact angle, during and after setting. Recent studies show that during setting the Polyether hydrophilicity is increased compared to the condition after setting. Dimensional stability, a crucial property of the impression, is affected by the physical and chemical attributes of the material, such as its tear strength. Polysulfide has the highest tear strength. Tear Strength is affected by two major parameters, viscosity, a built-in property, and how fast the impression is pulled out of the mouth, the

  3. Evaluation of dimensional stability of autoclavable elastomeric impression material.

    PubMed

    Surendra, G P; Anjum, Ayesha; Satish Babu, C L; Shetty, Shilpa

    2011-03-01

    Impressions are important sources of cross contamination between patients and dental laboratories. As a part of infection control impressions contaminated with variety of micro-organisms via blood and oral secretions should be cleaned and disinfected or sterilized before being handled in dental laboratory. The purpose of this study was to determine the effect of autoclaving on dimensional stability of elastomeric impression material (polyvinyl siloxane-Affinis). In this in vitro study standardized stainless steel die as per ADA specification number 19 was fabricated. Polyvinyl siloxane (Affinis) light body and putty viscosity elastomeric impression materials were used. A total of 40 impressions of the stainless steel die were made and numeric coding system was used to identify the samples. Measurements were made using a measuring microscope. Distance between the cross lines CD and C'D' reproduced in the impression were measured before autoclaving, immediately after autoclaving and 24 hours after autoclaving and dimensional change was calculated. The data obtained was subjected to statistical analysis. The mean difference in dimensional change between the three groups was not statistically significant (P > 0.05). However the results revealed that there was higher mean dimensional change immediately after autoclaving when compared to the other 2 time intervals. It is desirable to delay the casting of an autoclavable elastomeric impression material by about 24 hours. Though disinfection of impression is routinely followed autoclaving of impression is an effective method of sterilization.

  4. Hydrophilicity of unset and set elastomeric impression materials.

    PubMed

    Rupp, Frank; Geis-Gerstorfer, Jurgen

    2010-01-01

    The aim of this study was to compare the initial hydrophilicity of unset and set elastomeric impression materials. Initial water contact angles were studied on thin unset and set films of one polyether and six polyvinyl siloxane (PVS) impression materials using high-resolution drop shape analysis at drop ages of 1 and 3 seconds. All unset PVS materials were very hydrophobic initially but showed different kinetics of hydrophilization. In contrast, the unset polyether was more hydrophilic initially but lacked distinct hydrophilization. All impression materials showed statistically significant contact angle differences between unset and set surfaces (P < .05). Dependent on the drop age, two PVS materials reached or exceeded the hydrophilicity of the polyether (P < .05). It can be concluded that studies on the wetting behavior of elastomeric impression materials should consider both the experimental drop age and set and unset material surfaces.

  5. Hydrophilicity of unset and set elastomeric impression materials.

    PubMed

    Rupp, Frank; Geis-Gerstorfer, Jurgen

    2010-01-01

    The aim of this study was to compare the initial hydrophilicity of unset and set elastomeric impression materials. Initial water contact angles were studied on thin unset and set films of one polyether and six polyvinyl siloxane (PVS) impression materials using high-resolution drop shape analysis at drop ages of 1 and 3 seconds. All unset PVS materials were very hydrophobic initially but showed different kinetics of hydrophilization. In contrast, the unset polyether was more hydrophilic initially but lacked distinct hydrophilization. All impression materials showed statistically significant contact angle differences between unset and set surfaces (P < .05). Dependent on the drop age, two PVS materials reached or exceeded the hydrophilicity of the polyether (P < .05). It can be concluded that studies on the wetting behavior of elastomeric impression materials should consider both the experimental drop age and set and unset material surfaces. PMID:21209992

  6. Adhesion of elastomeric impression materials to trays.

    PubMed

    Bindra, B; Heath, J R

    1997-01-01

    The tensile and shear adhesive bond strengths of two addition cured silicones (Provil and Express) and a polyether (Impregum) impression material to brass, poly(methylmethacrylate) and visible light-cured (VLC) tray resin were determined. Adhesive application significantly increased the bond strength; Provil and Express adhered most strongly to brass; whilst the Impregum-VLC combination produced the strongest bond. Indeed, VLC resin generated greater adhesion than acrylic resin. Exchanging the adhesives specified for each silicone material generally resulted in higher bond strengths. No correlation was established between speed of separation of the test surfaces and bond strength. For optimum clinical performance, the impression material (adhesive) tray material giving the highest bond strength should be utilized.

  7. Comparison of Dimensional Accuracies Using Two Elastomeric Impression Materials in Casting Three-dimensional Tool Marks.

    PubMed

    Wang, Zhen

    2016-05-01

    The purpose of this study was to evaluate two types of impression materials which were frequently used for casting three-dimensional tool marks in China, namely (i) dental impression material and (ii) special elastomeric impression material for tool mark casting. The two different elastomeric impression materials were compared under equal conditions. The parameters measured were dimensional accuracies, the number of air bubbles, the ease of use, and the sharpness and quality of the individual characteristics present on casts. The results showed that dental impression material had the advantage of special elastomeric impression material in casting tool marks in crime scenes; hence, it combined ease of use, dimensional accuracy, sharpness and high quality.

  8. Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison

    PubMed Central

    De Angelis, Francesco; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

    2015-01-01

    Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas. PMID:26693227

  9. Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison.

    PubMed

    Re, Dino; De Angelis, Francesco; Augusti, Gabriele; Augusti, Davide; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

    2015-01-01

    Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas.

  10. Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison.

    PubMed

    Re, Dino; De Angelis, Francesco; Augusti, Gabriele; Augusti, Davide; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

    2015-01-01

    Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas. PMID:26693227

  11. A laboratory study of dimensional changes for three elastomeric impression materials using custom and stock trays.

    PubMed

    Boulton, J L; Gage, J P; Vincent, P F; Basford, K E

    1996-12-01

    Clinical success of fixed prosthodontic procedures is dependent in part upon the dimensional accuracy of elastomeric impression materials and impression procedures. Three elastomeric impression materials were used in custom and stock trays to determine the accuracy of impressions taken from an experimental stainless steel model representing premolar and molar bridge abutment preparations. Horizontal and vertical individual abutment and interabutment dimensions were measured on die stone replicas, and the measurements compared with those obtained from stainless steel master models. The results of this study demonstrate polysulphide is the least accurate impression material for both vertical and horizontal individual abutment dimensions. However, for interabutment horizontal dimensions, no statistical differences were noted between impression material types when using a custom tray. Stock trays produced unreliable results for all the materials tested.

  12. Tensile bond strength between custom tray and elastomeric impression material.

    PubMed

    Maruo, Yukinori; Nishigawa, Goro; Oka, Morihiko; Minagi, Shogo; Irie, Masao; Suzuki, Kazuomi

    2007-05-01

    The aim of this study was to investigate how to achieve sufficient and stable adhesive strength between impression material and tray. Impression materials were molded between autopolymerizing resin columns, and tensile strength was measured as a function of these factors: tray storage time (1, 2, 4, 7, and 10 days), adhesive drying time (0, 1, 5, 10, and 15 minutes), and tray surface roughness (air abrasion, bur-produced roughness, and no treatment). Tensile bond strength was not affected by tray storage time throughout the entire evaluation period of 10 days. As for tray adhesive drying time, Reprosil and Exaimplant yielded extremely low values for drying times of 10 minutes or less (P<0.05), while Imprint II and Impregum were not influenced by drying time. Vinyl polysiloxane achieved the highest adhesive strength with bur-produced roughness, which was significantly higher than with air abrasion or no treatment (P<0.05), whereas polyether achieved the lowest value with bur-produced roughness (P<0.05). It was concluded that surface treatment of custom tray should be adapted to the type of impression material used to achieve optimum bond strength.

  13. Dimensional stability of elastomeric impression materials in custom-made and stock trays.

    PubMed

    Valderhaug, J; Fløystrand, F

    1984-10-01

    Elastomeric impression materials for fixed prosthodontics are considered most stable when they have an even thickness of 2 to 4 mm. To obtain this, a custom-made impression tray is recommended. The purpose of the present study was to compare the stability of impressions made in custom trays and trays made of chromium-plated brass. The impression materials chosen were polyether and silicone. Two master models of the upper jaw were made of metal. The canines and first molars represented abutment teeth with flat occlusal surfaces. An engraved cross on each surface made it possible to measure in a microscope the distances between the abutment teeth on the models and in the impressions. The accuracy of the method was within +/- 8 micron. Twelve standardized impressions were made with each impression material in the two types of trays. The distances between the abutment teeth were measured immediately on removal of the impression, and after 1 and 24 hours. Although ample amount of impression material (2 to 9 mm) was allowed, the linear dimensional stability of the impressions made in stock trays was not inferior to the stability of impressions made in custom-made trays.

  14. Elastomeric impression materials and cleaning systems for residue removal

    NASA Astrophysics Data System (ADS)

    Prochazka, T. M.

    1983-01-01

    A materials evaluation program was conducted to characterize castable resin compounds as suitable dimensional inspection aids. A fast curing dimethylsilicone based compound was selected as the best performer of the eleven compounds tested. Evaluation of physical properties revealed an inherent problem of particle adherence to metal surfaces tested. A cleaning study was conducted to determine the effectiveness of the solvent systems in removing particulate matter from test surfaces. Silicon residues which can adversely affect bonding characteristics of the metals were identified in cleaning study tests. One solvent system composed of alkylarylsulfonic acids, toluene, and dichloromethane, gave superior results in breaking down and removing these polymerized compounds.

  15. The Effect of Disinfectants and a Surface Wetting Agent on the Wettability of Elastomeric Impression Materials: An In Vitro Study

    PubMed Central

    Lad, Pritam P; Gurjar, Minal; Gunda, Sachin; Gurjar, Vivek; Rao, Nandan K

    2015-01-01

    Background: This study was carried out to evaluate the effect of two commercially available chemical disinfectants namely sodium hypochlorite and glutaraldehyde and a surface wetting agent on the wettability of three high precision elastomeric impression materials, addition silicone, condensation silicone and polyether. Materials and Methods: Three different types of elastomeric impression materials commonly used in prosthodontic practice were selected. The glutaraldehyde and sodium hypochloride solutions were employed to disinfect the impressions made with the above-mentioned elastomeric impression materials. True Blue surface wetting agent was selected. GBX contact angle analyzer was used to measure advancing and receding contact angle. Results: The results of this study have demonstrated that the polyether impression material was the most hydrophilic of all the materials, followed by hydrophilic addition silicone. Condensation silicone was least hydrophilic. All materials showed improvement in the wettability when a topical surfactant was used. Conclusion: The short term disinfection of the three elastomeric impression materials does not affect the wettability of these impression materials. PMID:26124605

  16. Dimensional stability of elastomeric impression materials: a critical review of the literature.

    PubMed

    Gonçalves, F S; Popoff, D A V; Castro, C D L; Silva, G C; Magalhães, C S; Moreira, A N

    2011-12-01

    The aim of the present paper was to review the literature concerning the dimensional stability of dental elastomeric impression materials, to support recommendations to control the variables that influence the accuracy of these materials. An electronic search of the Scopus and PubMed databases was performed in November 2010. Articles were selected according to the following inclusion criteria: investigation of the dimensional stability of dental elastomers, an experimental study, sample size reported, laboratory tests described, and published in an English language peer-reviewed journal. The search resulted in 47 articles published between 1958 and 2008; of these, 24 were selected for inclusion in the present study. Great variability was discovered in the experimental methodologies used, such as different working times, temperatures and storage mediums for the impressions, impression techniques, material thicknesses, tray types, and methods of evaluation. Despite the lack of standardization among the studies, this review supports the following recommendations to control the dimensional stability: impressions should be stored at temperatures between 21 +/- 2 degrees C; polyether impressions should be stored in an environment with a relative humidity below 50%; time until pouring has been settled for each elastomer material.

  17. Evaluation of Different Disinfactants on Dimensional Accuracy and Surface Quality of Type IV Gypsum Casts Retrieved from Elastomeric Impression Materials

    PubMed Central

    Pal, P K; Kamble, Suresh S; Chaurasia, Ranjitkumar Rampratap; Chaurasia, Vishwajit Rampratap; Tiwari, Samarth; Bansal, Deepak

    2014-01-01

    Background: The present study was done to evaluate the dimensional stability and surface quality of Type IV gypsum casts retrieved from disinfected elastomeric impression materials. Materials and Methods: In an in vitro study contaminated impression material with known bacterial species was disinfected with disinfectants followed by culturing the swab sample to assess reduction in level of bacterial colony. Changes in surface detail reproduction of impression were assessed fallowing disinfection. Results: All the three disinfectants used in the study produced a 100% reduction in colony forming units of the test organisms. Conclusion: All the three disinfectants produced complete disinfection, and didn’t cause any deterioration in surface detail reproduction. How to cite the article: Pal PK, Kamble SS, Chaurasia RR, Chaurasia VR, Tiwari S, Bansal D. Evaluation of dimensional stability and surface quality of type IV gypsum casts retrieved from disinfected elastomeric impression materials. J Int Oral Health 2014;6(3):77-81. PMID:25083038

  18. Comparative Evaluation of Dimensional Accuracy of Elastomeric Impression Materials when Treated with Autoclave, Microwave, and Chemical Disinfection

    PubMed Central

    Kamble, Suresh S; Khandeparker, Rakshit Vijay; Somasundaram, P; Raghav, Shweta; Babaji, Rashmi P; Varghese, T Joju

    2015-01-01

    Background: Impression materials during impression procedure often get infected with various infectious diseases. Hence, disinfection of impression materials with various disinfectants is advised to protect the dental team. Disinfection can alter the dimensional accuracy of impression materials. The present study was aimed to evaluate the dimensional accuracy of elastomeric impression materials when treated with different disinfectants; autoclave, chemical, and microwave method. Materials and Methods: The impression materials used for the study were, dentsply aquasil (addition silicone polyvinylsiloxane syringe and putty), zetaplus (condensation silicone putty and light body), and impregum penta soft (polyether). All impressions were made according to manufacturer’s instructions. Dimensional changes were measured before and after different disinfection procedures. Result: Dentsply aquasil showed smallest dimensional change (−0.0046%) and impregum penta soft highest linear dimensional changes (−0.026%). All the tested elastomeric impression materials showed some degree of dimensional changes. Conclusion: The present study showed that all the disinfection procedures produce minor dimensional changes of impression material. However, it was within American Dental Association specification. Hence, steam autoclaving and microwave method can be used as an alternative method to chemical sterilization as an effective method. PMID:26435611

  19. Thiol-Ene functionalized siloxanes for use as elastomeric dental impression materials

    PubMed Central

    Cole, Megan A.; Jankousky, Katherine C.; Bowman, Christopher N.

    2014-01-01

    Objectives Thiol- and allyl-functionalized siloxane oligomers are synthesized and evaluated for use as a radical-mediated, rapid set elastomeric dental impression material. Thiol-ene siloxane formulations are crosslinked using a redox-initiated polymerization scheme, and the mechanical properties of the thiol-ene network are manipulated through the incorporation of varying degrees of plasticizer and kaolin filler. Formulations with medium and light body consistencies are further evaluated for their ability to accurately replicate features on both the gross and microscopic levels. We hypothesize that thiol-ene functionalized siloxane systems will exhibit faster setting times and greater detail reproduction than commercially available polyvinylsiloxane (PVS) materials of comparable consistencies. Methods Thiol-ene functionalized siloxane mixtures formulated with varying levels of redox initiators, plasticizer, and kaolin filler are made and evaluated for their polymerization speed (FTIR), consistency (ISO4823.9.2), and surface energy (goniometer). Feature replication is evaluated quantitatively by SEM. The Tg, storage modulus, and creep behavior are determined by DMA. Results Increasing redox initiation rate increases the polymerization rate but at high levels also limits working time. Combining 0.86 wt% oxidizing agent with up to 5 wt% plasticizer gave a working time of 3 min and a setting time of 2 min. The selected medium and light body thiol-ene formulations also achieved greater qualitative detail reproduction than the commercial material and reproduced micrometer patterns with 98% accuracy. Significance Improving detail reproduction and setting speed is a primary focus of dental impression material design and synthesis. Radical-mediated polymerizations, particularly thiol-ene reactions, are recognized for their speed, reduced shrinkage, and ‘click’ nature. PMID:24553250

  20. A Comparative Evaluation of the Dimensional Stability of Three Different Elastomeric Impression Materials after Autoclaving – An Invitro Study

    PubMed Central

    Thota, Kiran Kumar; Ravuri, Rajyalakshmi; Tella, Suchita

    2014-01-01

    Aim of the Study: The purpose of the study was to determine the effect of autoclaving on the dimensional stability of three different elastomeric impression materials at three different time intervals. Materials and Methods: Standardized stainless steel master die as per ADA specification number 19 was fabricated. The impression materials used for the study were condensation silicone (GP1), addition silicone (GP2) and polyether (GP3). A total of 45 samples of the stainless steel die were made (n = 45), that is 15 samples for each group. Impression materials were mixed according to the manufacturer’s instructions and were loaded into the mold to make an impression of the die. Impressions were identified with the help of numerical coding system and measurements were made using stereomicroscope (MAGNUS MSZ-Bi) of 0.65x magnification with the help of image analysis software (IMACE PRO-INSIGHT VERSION.The results were subjected to statistical analysis using one way analysis of variance and student t-test for comparison between the groups. Results: Within the limitations of the study statistically significant dimensional changes were observed for all the three impression materials at three different time intervals but this change was not clinically significant. Conclusion: It is well-known fact that all impressions should be disinfected to avoid possible transmission of infectious diseases either by direct contact or cross contamination. Immersion and spray disinfection as well as various disinfection solutions have been tested and proven to be effective for this purpose. But for elastomeric impression materials these methods have proven to be ineffective as they do not prevent cross contamination among the dental team. So autoclaving was one of the most effective sterilization procedure for condensation silicone and addition silicone. Since polyether is hydrophilic it is better to disinfect the impressions as recommended by the manufacturer or by immersion or spray

  1. Properties of a new polyether urethane dimethacrylate photoinitiated elastomeric impression material.

    PubMed

    Craig, R G; Hare, P H

    1990-01-01

    The photoinitiated impression material is supplied premixed as a light-bodied material in a light-tight plastic syringe and as a heavy-bodied material in a tube. The impression material has excellent physical, mechanical, and clinical qualities with noteworthy long working times, short setting times, dimensional stability, accuracy, high tear strength, good wettability, biocompatibility, and ease of cold disinfection without loss of quality. The impression material is also compatible with gypsum and silver or copper metallizing baths. Accurate casts can be obtained by means of either a double-impression technique or a double-mix technique. PMID:2295985

  2. The effect of tray selection on the accuracy of elastomeric impression materials.

    PubMed

    Gordon, G E; Johnson, G H; Drennon, D G

    1990-01-01

    This study evaluated the accuracy of reproduction of stone casts made from impressions using different tray and impression materials. The tray materials used were an acrylic resin, a thermoplastic, and a plastic. The impression materials used were an additional silicone, a polyether, and a polysulfide. Impressions were made of a stainless steel master die that simulated crown preparations for a fixed partial denture and an acrylic resin model with cross-arch and anteroposterior landmarks in stainless steel that typify clinical intra-arch distances. Impressions of the fixed partial denture simulation were made with all three impression materials and all three tray types. Impressions of the cross-arch and anteroposterior landmarks were made by using all three tray types with only the addition reaction silicone impression material. Impressions were poured at 1 hour with a type IV dental stone. Data were analyzed by using ANOVA with a sample size of five. Results indicated that custom-made trays of acrylic resin and the thermoplastic material performed similarly regarding die accuracy and produced clinically acceptable casts. The stock plastic tray consistently produced casts with greater dimensional change than the two custom trays. PMID:2404101

  3. Evaluation of effectiveness of microwave irradiation for disinfection of silicone elastomeric impression material.

    PubMed

    Bhasin, Abhilasha; Vinod, V; Bhasin, Vinny; Mathew, Xavier; Sajjan, Suresh; Ahmed, Syed Tauqheer

    2013-06-01

    Use of domestic microwave oven has been suggested as a method of disinfecting a number of dental materials used in dental practice. This study was done to analyse the effect of microwave irradiation on vinyl polysiloxane putty impression material (3M ESPE, Express™ STD) contaminated with test organisms (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans. 180 square shaped specimens of addition silicon putty material were prepared and divided into 3 groups for three test organisms. The 3 groups were subdivided into 4 subgroups (n = 15) for different exposure parameters (control group 5, 6 and 7 min exposure at 650 W. The specimens were contaminated using standard inoculums of test organism and then were irradiated using domestic microwaves. Broth cultures of the control and test group specimens were plated on selective media culture plates. Colonies formed were counted. Data analyses included Kruskal-Walli's ANOVA and Mann-Whitney's tests. Nil values shows complete elimination of C. albicans and P. aeruginosa after 5, 6 and 7 min exposure. Staphylococcus aureus showed colonies with the mean value of 7.6 × 10(3) ± 2.3 × 10(3), 4.6 × 10(3) ± 2.6 × 10(3) after 5 and 6 min respectively and nil values after 7 min exposure. 5 min exposure caused complete elimination of C. albicans and P. aeruginosa strains, while 7 min exposure eliminated S. aureus completely.

  4. Influence of Custom Trays, Dual-Arch Passive, Flexed Trays and Viscosities of Elastomeric Impression Materials on Working Dies

    PubMed Central

    Kohli, Shivani; Kalsi, Rupali

    2016-01-01

    Introduction Dual arch impression technique signifies an essential improvement in fixed prosthodontics and has numerous benefits over conventional impression techniques. The accuracy of working dies fabricated from dual arch impression technique remains in question because there is little information available in the literature. Aim This study was conducted to compare the accuracy of working dies fabricated from impressions made from two different viscosities of impression materials using metal, plastic dual arch trays and custom made acrylic trays. Materials and Methods The study samples were grouped into two groups based on the viscosity of impression material used i.e. Group I (monophase), whereas Group II consisted of Dual Mix technique using a combination of light and heavy body material. These were further divided into three subgroups A, B and C depending on the type of impression tray used (metal dual arch tray, plastic dual arch tray and custom made tray). Measurements of the master cast were made using profile projector. Descriptive statistics like mean, Standard Deviation (SD) were calculated for all the groups. One way analysis of variance (ANOVA) was used for multiple group comparisons. A p-value of 0.05 or less was considered statistically significant. Results The gypsum dies obtained with the three types of impression trays using two groups of impression materials were smaller than the master models in dimensions. Conclusion The plastic dual arch trays produced dies which were the least accurate of the three groups. There was no significant difference in the die dimensions obtained using the two viscosities of impression materials. PMID:27437342

  5. Fluorinated elastomeric materials

    DOEpatents

    Lagow, Richard J.; Dumitru, Earl T.

    1990-02-13

    This invention relates to a method of making perfluorinated elastomeric materials, and to materials made by such methods. In the full synthetic scheme, a partially fluorinated polymeric compound, with moieties to prevent crystallization, is created. It is then crosslinked to a desired degree, then perfluorinated. Various intermediate materials, such as partially fluorinated crosslinked polymers, have useful properties, and are or may become commercially available. One embodiment of this invention therefore relates to perfluorination of a selected partially fluorinated, crosslinked material, which is one step of the full synthetic scheme.

  6. Fluorinated elastomeric materials

    DOEpatents

    Lagow, Richard J.; Dumitru, Earl T.

    1986-11-04

    This invention relates to a method of making perfluorinated elastomeric materials, and to materials made by such methods. In the full synthetic scheme, a partially fluorinated polymeric compound, with moieties to prevent crystallization, is created. It is then crosslinked to a desired degree, then perfluorinated. Various intermediate materials, such as partially fluorinated crosslinked polymers, have useful properties, and are or may become commercially available. One embodiment of this invention therefore relates to perfluorination of a selected partially fluorinated, crosslinked material, which is one step of the full synthetic scheme.

  7. A comparative evaluation of disinfection effect of exposures to ultra-violet light and direct current glow discharge on Candida Albicans colonies coated over elastomeric impression material: An in vitro study

    PubMed Central

    Anand, Vijay

    2013-01-01

    Aim: The aim of our study is to compare the efficacy of ultra-violet light (U-V light) and direct current glow discharge in disinfecting Candida Albicans coated elastomeric impression material. Materials and Methods: Two hundred and forty samples of addition silicone material in the form of circular discs measuring (diameter-30 mm, thickness-3 mm) were prepared. Samples were divided into four groups namely A, B, C, D, with each group containing 60 samples. All samples in each group were sub grouped as follows for exposure time 15, 30, 60, 90, 120 and 180 s respectively. Group A samples were exposed to U-V light with 8 watts. Group B samples were exposed to U-V light with 16 watts. Group C samples were exposed to U-V light with 24 watts. Group D samples were exposed to direct current glow discharge. After exposure, the impression material was swabbed on sabourauds dextrose agar (SDA) plates and incubated at 37°C for 48 h. The total number of colonies indicating the number of C. Albicans that survived the direct current glow discharge and U-V light treatment was then determined using a microscope. Results and Conclusion: Group A samples exhibited proportionate decrease in the number of colonies with each greater time of exposure. Group B samples exhibited proportionate decrease in the number of colonies with each greater time of exposure. Group C samples exhibited total absence of C. Albicans colonies at 90 s exposure. In Group D samples there was a proportionate decrease in number of C. Albicans colonies with exposure to direct current glow discharge for more seconds. Hence, this study reveals that exposure to U-V light drastically reduced the C. Albicans colonies compared with exposure to direct current glow discharge. It was observed that with greater wattage of U-V light tube in U-V light unit chamber, greater decrease in colony count was observed in lesser time of exposure. PMID:23946583

  8. Dental impression materials.

    PubMed

    Perry, Rachel

    2013-01-01

    It is clear that many impression materials are available to the veterinary dentist. They each have different inherent properties, handling characteristics, and indications for use. A thorough understanding of these concepts is essential if the veterinarian and laboratory technician are to produce meaningful and accurate reproductions of oral structures. New products are constantly being introduced to the dental market, with fantastic claims for ease of use and reproduction of detail. The reader is urged to seek independent research findings when assessing such claims, and make decisions founded in the highest possible levels of evidence.

  9. Dental impression materials.

    PubMed

    Perry, Rachel

    2013-01-01

    It is clear that many impression materials are available to the veterinary dentist. They each have different inherent properties, handling characteristics, and indications for use. A thorough understanding of these concepts is essential if the veterinarian and laboratory technician are to produce meaningful and accurate reproductions of oral structures. New products are constantly being introduced to the dental market, with fantastic claims for ease of use and reproduction of detail. The reader is urged to seek independent research findings when assessing such claims, and make decisions founded in the highest possible levels of evidence. PMID:24006720

  10. Drug and dental impression materials.

    PubMed

    Maller, Sudhakara V; Karthik, K S; Maller, Udita S; Abraham, Mathew C; Kumar, Rachuri Narendra; Manikandan, R

    2012-08-01

    Guidelines to prevent cross contamination with infectious agents have been instituted for dental clinical and laboratory procedures. However, compliance by dental offices and clinics in disinfecting impression material has not been universal. Techniques for disinfecting impression materials are spraying or immersing impression materials. These techniques can reduce the surface detail and dimensional accuracy of impressions; most disinfectants are irritants. This study reviewed whether antimicrobial activity can be achieved by mixing certain drugs with the impression material and their effects on the disinfection are achieved through such additions.

  11. Evaluation of surface detail reproduction, dimensional stability and gypsum compatibility of monophase polyvinyl-siloxane and polyether elastomeric impression materials under dry and moist conditions

    PubMed Central

    Vadapalli, Sriharsha Babu; Atluri, Kaleswararao; Putcha, Madhu Sudhan; Kondreddi, Sirisha; Kumar, N. Suman; Tadi, Durga Prasad

    2016-01-01

    Objectives: This in vitro study was designed to compare polyvinyl-siloxane (PVS) monophase and polyether (PE) monophase materials under dry and moist conditions for properties such as surface detail reproduction, dimensional stability, and gypsum compatibility. Materials and Methods: Surface detail reproduction was evaluated using two criteria. Dimensional stability was evaluated according to American Dental Association (ADA) specification no. 19. Gypsum compatibility was assessed by two criteria. All the samples were evaluated, and the data obtained were analyzed by a two-way analysis of variance (ANOVA) and Pearson's Chi-square tests. Results: When surface detail reproduction was evaluated with modification of ADA specification no. 19, both the groups under the two conditions showed no significant difference statistically. When evaluated macroscopically both the groups showed statistically significant difference. Results for dimensional stability showed that the deviation from standard was significant among the two groups, where Aquasil group showed significantly more deviation compared to Impregum group (P < 0.001). Two conditions also showed significant difference, with moist conditions showing significantly more deviation compared to dry condition (P < 0.001). The results of gypsum compatibility when evaluated with modification of ADA specification no. 19 and by giving grades to the casts for both the groups and under two conditions showed no significant difference statistically. Conclusion: Regarding dimensional stability, both impregum and aquasil performed better in dry condition than in moist; impregum performed better than aquasil in both the conditions. When tested for surface detail reproduction according to ADA specification, under dry and moist conditions both of them performed almost equally. When tested according to macroscopic evaluation, impregum and aquasil performed significantly better in dry condition compared to moist condition. In dry

  12. Friction and abrasion of elastomeric materials

    NASA Technical Reports Server (NTRS)

    Gent, A. N.

    1975-01-01

    An abrasion apparatus is described. Experimental measurements are reported for four representative elastomeric materials, including a typical high-quality tire tread material and a possible replacement material for aircraft tire treads based on transpolypentenamer (TPPR). Measurements are carried out at different levels of frictional work input, corresponding to different severities of wear, and at both ambient temperature and at 100 C. Results indicate the marked superiority in abrasion resistance of the material based on TPPR, especially at 100 C, in comparison with the other materials examined.

  13. Light-polymerized materials for custom impression trays.

    PubMed

    Wirz, J; Jaeger, K; Schmidli, F

    1990-01-01

    Custom trays are indispensable for making impressions with elastomeric products. Previous studies have demonstrated that certain autopolymerized materials are particularly suitable, but had some limitations. The recently introduced halogen-light-polymerized resins permit fabrication of custom trays that have the needed physical properties for accuracy and strength. No storage period is necessary for completion of polymerization, and the trays are not subject to distortion in moisture, making them suitable for use in the electroforming of casts.

  14. Dimensional Accuracy of Hydrophilic and Hydrophobic VPS Impression Materials Using Different Impression Techniques - An Invitro Study

    PubMed Central

    Pilla, Ajai; Pathipaka, Suman

    2016-01-01

    Introduction The dimensional stability of the impression material could have an influence on the accuracy of the final restoration. Vinyl Polysiloxane Impression materials (VPS) are most frequently used as the impression material in fixed prosthodontics. As VPS is hydrophobic when it is poured with gypsum products, manufacturers added intrinsic surfactants and marketed as hydrophilic VPS. These hydrophilic VPS have shown increased wettability with gypsum slurries. VPS are available in different viscosities ranging from very low to very high for usage under different impression techniques. Aim To compare the dimensional accuracy of hydrophilic VPS and hydrophobic VPS using monophase, one step and two step putty wash impression techniques. Materials and Methods To test the dimensional accuracy of the impression materials a stainless steel die was fabricated as prescribed by ADA specification no. 19 for elastomeric impression materials. A total of 60 impressions were made. The materials were divided into two groups, Group1 hydrophilic VPS (Aquasil) and Group 2 hydrophobic VPS (Variotime). These were further divided into three subgroups A, B, C for monophase, one-step and two-step putty wash technique with 10 samples in each subgroup. The dimensional accuracy of the impressions was evaluated after 24 hours using vertical profile projector with lens magnification range of 20X-125X illumination. The study was analyzed through one-way ANOVA, post-hoc Tukey HSD test and unpaired t-test for mean comparison between groups. Results Results showed that the three different impression techniques (monophase, 1-step, 2-step putty wash techniques) did cause significant change in dimensional accuracy between hydrophilic VPS and hydrophobic VPS impression materials. One-way ANOVA disclosed, mean dimensional change and SD for hydrophilic VPS varied between 0.56% and 0.16%, which were low, suggesting hydrophilic VPS was satisfactory with all three impression techniques. However, mean

  15. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3660 Impression material. (a) Identification. Impression material is a device composed of materials such as alginate or polysulfide intended to be placed... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impression material. 872.3660 Section...

  16. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impression material. 872.3660 Section 872.3660...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3660 Impression material. (a) Identification. Impression material is a device composed of materials such as alginate or polysulfide intended to be...

  17. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impression material. 872.3660 Section 872.3660...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3660 Impression material. (a) Identification. Impression material is a device composed of materials such as alginate or polysulfide intended to be...

  18. Resistance to disinfection of a polymicrobial association contaminating the surface of elastomeric dental impressions.

    PubMed

    Giammanco, Giovanni M; Melilli, Dario; Rallo, Antonio; Pecorella, Sonia; Mammina, Caterina; Pizzo, Giuseppe

    2009-04-01

    The aim of this study was to evaluate the ability to resist disinfection of a polymicrobial association contaminating the surface of dental impressions obtained with two different elastomers: a polyether (Impregum) and an addition-polymerized silicone (Elite). Impressions were contaminated with a mixture of three biofilm-forming microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans) and disinfected immediately after contamination, or after microbial layers were allowed to develop during a six-hour storage. Two commercial disinfectants were tested: MD 520 containing 0.5% glutaraldehyde and Sterigum Powder without glutaraldehyde. Residual contamination was recovered by mechanical rinsing immediately after disinfection and after a six-hour storage of disinfected impressions, and assessed by colony counting. Both disinfectants tested were shown to be effective in reducing the microbial presence on the impression materials, achieving at least a 102 reduction of microbial counts compared to water rinsing. However, Sterigum was generally less effective on the Elite elastomer and could not grant disinfection on six-hour aged P. aeruginosa and C. albicans microbial layers. The results of this study suggest that the materials used for the impressions influence the efficacy of disinfection. Disinfectants should be tested according to conditions encountered in everyday clinical practice and the need for immediate disinfection of impressions should be clearly indicated by manufacturers. PMID:19579694

  19. Resistance to disinfection of a polymicrobial association contaminating the surface of elastomeric dental impressions.

    PubMed

    Giammanco, Giovanni M; Melilli, Dario; Rallo, Antonio; Pecorella, Sonia; Mammina, Caterina; Pizzo, Giuseppe

    2009-04-01

    The aim of this study was to evaluate the ability to resist disinfection of a polymicrobial association contaminating the surface of dental impressions obtained with two different elastomers: a polyether (Impregum) and an addition-polymerized silicone (Elite). Impressions were contaminated with a mixture of three biofilm-forming microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans) and disinfected immediately after contamination, or after microbial layers were allowed to develop during a six-hour storage. Two commercial disinfectants were tested: MD 520 containing 0.5% glutaraldehyde and Sterigum Powder without glutaraldehyde. Residual contamination was recovered by mechanical rinsing immediately after disinfection and after a six-hour storage of disinfected impressions, and assessed by colony counting. Both disinfectants tested were shown to be effective in reducing the microbial presence on the impression materials, achieving at least a 102 reduction of microbial counts compared to water rinsing. However, Sterigum was generally less effective on the Elite elastomer and could not grant disinfection on six-hour aged P. aeruginosa and C. albicans microbial layers. The results of this study suggest that the materials used for the impressions influence the efficacy of disinfection. Disinfectants should be tested according to conditions encountered in everyday clinical practice and the need for immediate disinfection of impressions should be clearly indicated by manufacturers.

  20. Survey of Impression Materials and Techniques in Fixed Partial Dentures among the Practitioners in India.

    PubMed

    Moldi, Arvind; Gala, Vimal; Puranik, Shivakumar; Karan, Smita; Deshpande, Sumit; Neela, Neelima

    2013-01-01

    Objective. Anecdotal evidence suggests that impression materials and techniques used in general dental practice for fixed partial dentures vary from those taught in dental schools. The aim of this survey was to integrate impression techniques evolved all over the years for fixed partial dentures and to know the techniques and materials which are used in the present day by the practitioners. Materials and Methods. A total of 1000 questionnaires were sent to various practitioners in India, out of which 807 questionnaires were filled. Results. The results showed that 84.8% of prosthodontists (65.56%, urban areas) use elastomeric impression materials as well as irreversible hydrocolloids and 15.2% use irreversible hydrocolloid only. Amongst other practitioners, 55.46% use irreversible hydrocolloid (45%, rural and semiurban areas) and 44.54% use elastomeric impression materials. Elastomeric impression technique practiced most commonly is putty reline with/without spacer (77.2%); other techniques are multiple-mix and monophase techniques. Conclusion. The ideal materials, technique, and armamentarium are required for the long-term success of the treatment for fixed partial denture. Also, if the ideal procedure is not followed, it will lead to a compromised fit of the final prosthesis and failure of the treatment.

  1. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3660 Impression material. (a) Identification... device is intended to provide models for study and for production of restorative prosthetic devices,...

  2. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3660 Impression material. (a) Identification... device is intended to provide models for study and for production of restorative prosthetic devices,...

  3. Soft hydrogel materials from elastomeric gluten-mimetic proteins

    NASA Astrophysics Data System (ADS)

    Bagheri, Mehran; Scott, Shane; Wan, Fan; Dick, Scott; Harden, James; Biomolecular Assemblies Team

    2014-03-01

    Elastomeric proteins are ubiquitous in both animal and plant tissues, where they are responsible for the elastic response and mechanical resilience of tissues. In addition to fundamental interest in the molecular origins of their elastic behaviour, this class of proteins has great potential for use in biomaterial applications. The structural and elastomeric properties of these proteins are thought to be controlled by a subtle balance between hydrophobic interactions and entropic effects, and in many cases their characteristic properties can be recapitulated by multi-block protein polymers formed from repeats of short, characteristic polypeptide motifs. We have developed biomimetic multi-block protein polymers based on variants of several elastomeric gluten consensus sequences. These proteins include constituents designed to maximize their solubility in aqueous solution and minimize the formation of extended secondary structure. Thus, they are examples of elastic intrinsically disordered proteins. In addition, the proteins have distributed tyrosine residues which allow for inter-molecular crosslinking to form hydrogel networks. In this talk, we present experimental and simulation studies of the molecular and materials properties of these proteins and their assemblies.

  4. Building the edentulous impression--a layering technique using multiple viscosities of impression material.

    PubMed

    Massad, Joseph; Lobel, William; Garcia, Lily T; Monarres, Alfonso; Hammesfahr, Paul D

    2006-08-01

    The purpose of this article is to introduce a novel impression technique. The procedure demonstrates a building, or layering, method of impression making that maintains the integrity between layers of the impression materials of varying viscosities and controls the path of insertion, minimizing the incidence of overextension. To build a detailed impression of the tissue-bearing surfaces, the clinician selects the proper viscosity of impression material based on the diagnosed tissue condition.

  5. [Influence of the type of impression material, impression tray and making impression technology on the dimensional accuracy and depth of impression material penetration into "gingival sulcus". In vitro study].

    PubMed

    Riakhovskiĭ, A N; Muradov, M A

    2005-01-01

    Results of the profound study of influence of the type of impression material, impression tray and making impression technology upon main quality characteristics of the precise impression (dimensional accuracy and depth of impression material penetration into gingival sulcus) are reviewed. Original method to investigate depth of impression material penetration into gingival sulcus on experimental model is described. The impression technology exercises more influence on quality characteristics of the precise impression than type of the used material and impression tray. Optimal combination of different viscosity impression materials with technology of making impression has been defined.

  6. [Effect of the viscosity of alginate impression materials on the preliminary impression for complete dentures].

    PubMed

    Aoyama, Natsumi; Akiba, Norihisa; Uchida, Tatsuro

    2007-03-01

    The purpose of this study was to clarify the effect of the viscosity of alginate impression materials on the results of the preliminary impressions for complete dentures. Five experimental alginate impression materials with different viscosity were prepared based on a conventional material. Fifteen complete denture wearers were selected and impressions on using the experimental materials were taken. Impressions were evaluated by the success rates at the mylohyoid ridge area (MR), buccal area (BL) and retromolar pad area (RP). The success rates had a tendency to increase as the viscosity rose at MR and RP. The success rates at BL were not significantly different among the materials. Our results indicate that the viscosity of alginate impression materials has a great effect on the results of preliminary impression for complete dentures, especially at MR. Impression materials with high viscosity may be suitable for recording the anatomical form of the alveolar ridge better than those with low viscosity.

  7. Vinyl polysiloxane impression material in removable prosthodontics. Part 1: edentulous impressions.

    PubMed

    Massad, Joseph J; Cagna, David R

    2007-08-01

    Recent advances in impression materials and stock edentulous impression trays have resulted in simplified approaches to impression making in removable prosthodontics. Once considered an absolute necessity, it is now possible to avoid the need for custom impression trays. In an effort to achieve reliable master casts in a single appointment, new and innovative procedures are now available. This article, the first in a 3-part series, will review historical information, basic concepts, materials considerations, and philosophic approaches to impression making in complete-denture therapy. A modem technique using readily available impression materials will be described and illustrated so readers can consider the benefits of incorporation into their daily management of edentulous patients.

  8. Vinyl polysiloxane impression material in removable prosthodontics. Part 1: Edentulous impressions.

    PubMed

    Massad, Joseph J; Cagna, David R

    2009-02-01

    Recent advances in impression materials and stock edentulous impression trays have resulted in simplified approaches to impression making in removable prosthodontics. Once considered an absolute necessity, it is now possible to avoid the need for custom impression trays. In an effort to achieve reliable master casts in a single appointment, new and innovative procedures are now available. This article, the first in a 3-part series, will review historical information, basic concepts, materials considerations, and philosophic approaches to impression making in complete-denture therapy. A modern technique using readily available impression materials will be described and illustrated so readers can consider the benefits of incorporation into their daily management of edentulous patients.

  9. Performance testing of elastomeric seal materials under low and high temperature conditions: Final report

    SciTech Connect

    BRONOWSKI,DAVID R.

    2000-06-01

    The US Department of Energy Offices of Defense Programs and Civilian Radioactive Waste Management jointly sponsored a program to evaluate elastomeric O-ring seal materials for radioactive material shipping containers. The report presents the results of low- and high-temperature tests conducted on 27 common elastomeric compounds.

  10. A Comparative Evaluation of the Linear Dimensional Accuracy of Four Impression Techniques using Polyether Impression Material.

    PubMed

    Manoj, Smita Sara; Cherian, K P; Chitre, Vidya; Aras, Meena

    2013-12-01

    There is much discussion in the dental literature regarding the superiority of one impression technique over the other using addition silicone impression material. However, there is inadequate information available on the accuracy of different impression techniques using polyether. The purpose of this study was to assess the linear dimensional accuracy of four impression techniques using polyether on a laboratory model that simulates clinical practice. The impression material used was Impregum Soft™, 3 M ESPE and the four impression techniques used were (1) Monophase impression technique using medium body impression material. (2) One step double mix impression technique using heavy body and light body impression materials simultaneously. (3) Two step double mix impression technique using a cellophane spacer (heavy body material used as a preliminary impression to create a wash space with a cellophane spacer, followed by the use of light body material). (4) Matrix impression using a matrix of polyether occlusal registration material. The matrix is loaded with heavy body material followed by a pick-up impression in medium body material. For each technique, thirty impressions were made of a stainless steel master model that contained three complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring eight dimensions (mesiodistal, faciolingual and inter-abutment) on stone dies poured from impressions of the master model. A two-tailed t test was carried out to test the significance in difference of the distances between the master model and the stone models. One way analysis of variance (ANOVA) was used for multiple group comparison followed by the Bonferroni's test for pair wise comparison. The accuracy was tested at α = 0.05. In general, polyether impression material produced stone dies that were smaller except for the dies produced from the one step double mix impression technique. The ANOVA revealed a highly

  11. A Comparative Evaluation of the Linear Dimensional Accuracy of Four Impression Techniques using Polyether Impression Material.

    PubMed

    Manoj, Smita Sara; Cherian, K P; Chitre, Vidya; Aras, Meena

    2013-12-01

    There is much discussion in the dental literature regarding the superiority of one impression technique over the other using addition silicone impression material. However, there is inadequate information available on the accuracy of different impression techniques using polyether. The purpose of this study was to assess the linear dimensional accuracy of four impression techniques using polyether on a laboratory model that simulates clinical practice. The impression material used was Impregum Soft™, 3 M ESPE and the four impression techniques used were (1) Monophase impression technique using medium body impression material. (2) One step double mix impression technique using heavy body and light body impression materials simultaneously. (3) Two step double mix impression technique using a cellophane spacer (heavy body material used as a preliminary impression to create a wash space with a cellophane spacer, followed by the use of light body material). (4) Matrix impression using a matrix of polyether occlusal registration material. The matrix is loaded with heavy body material followed by a pick-up impression in medium body material. For each technique, thirty impressions were made of a stainless steel master model that contained three complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring eight dimensions (mesiodistal, faciolingual and inter-abutment) on stone dies poured from impressions of the master model. A two-tailed t test was carried out to test the significance in difference of the distances between the master model and the stone models. One way analysis of variance (ANOVA) was used for multiple group comparison followed by the Bonferroni's test for pair wise comparison. The accuracy was tested at α = 0.05. In general, polyether impression material produced stone dies that were smaller except for the dies produced from the one step double mix impression technique. The ANOVA revealed a highly

  12. Vinyl polysiloxane impression material in removable prosthodontics. Part 2: Immediate denture and reline impressions.

    PubMed

    Cagna, David R; Massad, Joseph J

    2007-09-01

    Accurate impressions are important elements in both the fabrication and maintenance phases of complete denture therapy. For patients possessing nonrestorable, periodontally hopeless residual dentitions, immediate denture therapy is often the treatment of choice. An impression procedure capable of accurately registering functional vestibular anatomy facilitates successful therapy. For complete dentures currently in function, periodic assessment and correction of fit extends long-term prosthesis performance. To maintain optimal tissue-base relationships, use of specialized impressions, and subsequent laboratory reline procedures is often indicated. For both of these impression procedures (ie, immediate denture impressions and denture reline impressions), vinyl polysiloxane (VPS) impression material offers distinct advantages. Part 2 of this article series reports on the use of VPS for immediate denture and reline impression procedures.

  13. Vinyl polysiloxane impression material in removable prosthodontics. Part 2: immediate denture and reline impressions.

    PubMed

    Cagna, David R; Massad, Joseph J

    2009-01-01

    Accurate impressions are important elements in both the fabrication and maintenance phases of complete denture therapy. For patients possessing nonrestorable, periodontally hopeless residual dentitions, immediate denture therapy is often the treatment of choice. An impression procedure capable of accurately registering functional vestibular anatomy facilitates successful therapy. For complete dentures currently in function, periodic assessment and correction of fit extends long-term prosthesis performance. To maintain optimal tissue-base relationships, use of specialized impressions, and subsequent laboratory reline procedures is often indicated. For both of these impression procedures (i.e., immediate denture impressions and denture reline impressions), vinyl polysiloxane (VPS) impression material offers distinct advantages. Part 2 of this article series reports on the use of VPS for immediate denture and reline impression procedures.

  14. Otologic complications caused by hearing aid mold impression material.

    PubMed

    Lee, Dong Hoon; Cho, Hyong-Ho

    2012-08-01

    We report two extremely rare cases of otologic complications caused by hearing aid mold impression material. The symptoms of patients with retained impression material are characteristic of the length of time the impression material is retained. In case 1 had a chronic discharge and granulation tissue of the middle ear, while case 2 presented with acute pain and dizziness. The management for retained impression material may require surgical interventions, which can be safely accomplished by standard otologic techniques.

  15. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3670 Resin impression tray material. (a) Identification. Resin impression tray material is a device intended for use in a two-step dental mold fabricating... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Resin impression tray material. 872.3670...

  16. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3670 Resin impression tray material. (a) Identification. Resin impression tray material is a device intended for use in a two-step dental mold fabricating... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Resin impression tray material. 872.3670...

  17. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Resin impression tray material. 872.3670 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3670 Resin impression tray material. (a) Identification. Resin impression tray material is a device intended for use in a two-step dental mold...

  18. Development and Evaluation of Elastomeric Materials for Geothermal Applications

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Kalfayan, S. H.; Reilly, W. W.; Yavrouian, A. H.; Mosesman, I. D.; Ingham, J. D.

    1979-01-01

    A material was formulated having about 250-350 psi tensile strength and 30-80 percent elongation at 260 C for at least 24 hours in simulated brine. The relationship between these laboratory test results and sealing performance in actual or simulated test conditions is not entirely clear; however, it is believed that no conventional formation or casing packer design is likely to perform well using these materials. The synthetic effort focused on high temperature block copolymers and development of curable polystyrene. Procedures were worked out for synthesizing these new materials. Initial results with heat-cured unfilled polystyrene 'gum' at 260 C indicate a tensile strength of about 50 psi. Cast films of the first sample of polyphenyl quinoxaline-polystyrene block copolymer, which has 'graft-block' structure consisting of a polystyrene chain with pendant polyphenyl quinoxaline groups, show elastomeric behavior in the required temperature range. Its tensile strength and elongation at 260 C were 220-350 psi and 18-36 percent, respectively. All of these materials also showed satisfactory hydrolytic stability.

  19. Effects of implant angulation, material selection, and impression technique on impression accuracy: a preliminary laboratory study.

    PubMed

    Rutkunas, Vygandas; Sveikata, Kestutis; Savickas, Raimondas

    2012-01-01

    The aim of this preliminary laboratory study was to evaluate the effects of 5- and 25-degree implant angulations in simulated clinical casts on an impression's accuracy when using different impression materials and tray selections. A convenience sample of each implant angulation group was selected for both open and closed trays in combination with one polyether and two polyvinyl siloxane impression materials. The influence of material and technique appeared to be significant for both 5- and 25-degree angulations (P < .05), and increased angulation tended to decrease impression accuracy. The open-tray technique was more accurate with highly nonaxially oriented implants for the small sample size investigated.

  20. Accuracy of three implant impression techniques with different impression materials and stones.

    PubMed

    Chang, Won-Gun; Vahidi, Farhad; Bae, Kwang-Hak; Lim, Bum-Soon

    2012-01-01

    The purpose of this study was to compare the accuracy of casts made using three different impression techniques to obtain an accurate definitive cast for fabrication of multiple-implant prostheses. Twelve experimental groups were formed combining the following conditions: three impression techniques, two impression materials, and two cast materials. The main effects of the three factors were analyzed by three-way analysis of variance using the full factorial general linear model between factors. The results showed that there were no significant differences in mean values for the transferred dimensions between the control and experimental groups. None of the measurements in the horizontal plane of the definitive casts demonstrated significant differences among the impression techniques with different impression and cast materials (P > .01).

  1. Comparative study of dimensional accuracy of different impression techniques using addition silicone impression material.

    PubMed

    Penaflor, C F; Semacio, R C; De Las Alas, L T; Uy, H G

    1998-01-01

    This study compared dimensional accuracy of the single, double with spacer, double with cut-out and double mix impression technique using addition silicone impression material. A typhodont containing Ivorine teeth model with six (6) full-crown tooth preparations were used as the positive control. Two stone replication models for each impression technique were made as test materials. Accuracy of the techniques were assessed by measuring four dimensions on the stone dies poured from the impression of the Ivorine teeth model. Results indicated that most of the measurements for the height, width and diameter slightly decreased and a few increased compared with the Ivorine teeth model. The double with cut-out and double mix technique presents the least difference from the master model as compared to the two latter impression techniques. PMID:10202524

  2. A new generation of sterile and radiopaque impression materials: an in vitro cytotoxicity study.

    PubMed

    Coppi, Chiara; Paolinelli Devincenzi, Chiara; Bortolini, Sergio; Consolo, Ugo; Tiozzo, Roberta

    2007-07-01

    Impression materials are largely used to record the geometry of dental tissue. Hence, the assessment of their possible cytotoxicity is a necessary step in the evaluation of their biocompatibility. The present study is carried out to evaluate the cytotoxicity of a new elastomeric sterile and radiopaque impression material. Human gingival fibroblasts, cultured in vitro are exposed directly to Elite Implant in three different viscosities, heavy, medium, and light. At 3, 9, 24, 48, and 72 h, the cellular proliferation is evaluated. In parallel, human gingival fibroblasts are exposed indirectly by means of fluid extracts of Elite Implant. The cellular viability is evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide, (MTT) assay (Sigma, St Louis, Mo). The gingival fibroblasts proliferation and viability are unaffected by the presence of Elite Implant. This new impression material may represent a safe medical device for clinical and surgical applications. In addition, this material is radiopaque and, thus, can be identified radiographically. PMID:17065163

  3. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Resin impression tray material. 872.3670 Section 872.3670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3670 Resin impression tray material....

  4. Visual observation of the dynamic flow of elastomer rubber impression material between the impression tray and oral mucosa while seating the impression tray.

    PubMed

    Nishigawa, G; Natsuaki, N; Maruo, Y; Okamoto, M; Minagi, S

    2003-06-01

    The purpose of this study was to inspect visually, the dynamics of the impression flow at seating of the impression tray. The effects of the relief and the escape hole of the impression tray on the impression flow were also examined. Three types of the transparent impression tray (flat tray, relief tray and escape hole tray) were prepared. Transparent silicone polymer was put on the impression tray surface. Four drops of the dark blue silicone impression material was injected into the transparent silicone polymer on the impression tray. The impression tray was seated on the model of the denture-supporting mucosa. The movement of the four drops caused by the impression flow was visually recorded with the video camera and examined. The result for the flat tray showed that the impression material moved from inside to the outside. It was also shown that the speed of the moved impression material increased as the seating of the impression tray advanced. The results for the relief tray and the escape hole tray showed the effect of the relief and the escape hole prepared to the impression tray on the speed and the direction of the flow of the impression material.

  5. An in vitro study of the bond strength of five adhesives used for vinyl polysiloxane impression materials and tray materials.

    PubMed

    Kumar, Surender; Gandhi, Udey Vir; Banerjee, Saurav

    2014-03-01

    Although stock trays often provide mechanical retention for elastomeric impression materials, manufacturers typically recommend the use of an adhesive, whether a stock or custom tray is used. The mention of the bond strength on the adhesive packaging is not available, therefore the clinician has no idea whatsoever of the ideal adhesive. The aim of this study was to evaluate the bond strength of three vinyl polysiloxane (VPS) materials, one with a poly(methyl methacrylate) autopolymerizing (PMMA) specimen and another with a light-polymerizing tray material (VLC), using the adhesive recommended by the manufacturer of the impression material, and two universal adhesives. A total of ninety specimens (15 × 15 × 20 mm) were used, 45 specimens were made in PMMA and rest 45 was made in VLC. Five paint-on adhesives (Coltene, Caulk, 3M, universal Zhermack and universal GC) were applied. Three impression materials, Affinis, Reprosil, and 3M, were mixed and injected into a perforated poly vinyl chloride cylinder. Tray specimens were positioned against the open cylinder end in contact with the VPS material. Tensile strength tests were conducted until adhesive separation failure. Mean values and standard errors of the adhesive strength were recorded in MPa for each material combination. GC paint-on universal adhesive provided significantly higher adhesive strength values.

  6. Vinyl polysiloxane impression material in removable prosthodontics. Part 3: implant and external impressions.

    PubMed

    Massad, Joseph J; Cagna, David R

    2009-06-01

    Today, dental implant therapy is considered a valuable asset of mainstream dental therapeutics by both patients and clinicians. In many ways, the availability of implant therapy to facilitate the support, stability, and retention of dental prostheses has revolutionized the profession and the procedures dentists accomplish on a daily basis. From another perspective, the procedures used to fabricate dental implant restorations are but modifications of previously existing, proven, and reliable techniques. This is particularly true when considering impression making for implant overdentures. Part 3 of this article series looks at the use of vinyl polysiloxane impression material systems for making definitive impressions for implant overdentures. Once constructed, it is critical that all removable dental prostheses possess external contours that are geometrically compatible with the anatomic and functional requirements of the oral tissues. Therefore, this article also will address a technique for diagnostically assessing external denture contours using vinyl polysiloxane external impression procedures.

  7. Vinyl polysiloxane impression material in removable prosthodontics part 3: implant and external impressions.

    PubMed

    Massad, Joseph J; Cagna, David R

    2007-10-01

    Today, dental implant therapy is considered a valuable asset of mainstream dental therapeutics by both patients and clinicians. In many ways, the availability of implant therapy to facilitate the support, stability, and retention of dental prostheses has revolutionized the profession and the procedures dentists accomplish on a daily basis. From another perspective, the procedures used to fabricate dental implant restorations are but modifications of previously existing, proven, and reliable techniques. This is particularly true when considering impression making for implant overdentures. Part 3 of this article series looks at the use of vinyl polysiloxane impression material systems for making definitive impressions for implant overdentures. Once constructed, it is critical that all removable dental prostheses possess external contours that are geometrically compatible with the anatomic and functional requirements of the oral tissues. Therefore, this article also will address a technique for diagnostically assessing external denture contours using vinyl polysiloxane external impression procedures.

  8. A rare allergy to a polyether dental impression material.

    PubMed

    Mittermüller, Pauline; Szeimies, Rolf-Markus; Landthaler, Michael; Schmalz, Gottfried

    2012-08-01

    Polyether impression materials have been used in dentistry for more than 40 years. Allergic reactions to these materials such as reported in the 1970s ceased after replacement of a catalyst. Very recently, however, patients have started to report symptoms that suggest a new allergic reaction from polyether impression materials. Here, we report on the results of allergy testing with polyether impression materials as well as with its components. Eight patients with clinical symptoms of a contact allergy (swelling, redness or blisters) after exposure to a polyether impression material were subjected to patch tests, two of them additionally to a prick test. A further patient with atypical symptoms of an allergy (nausea and vomiting after contact with a polyether impression material in the oral cavity) but with a history of other allergic reaction was also patch tested. The prick tests showed no immediate reactions in the two patients tested. In the patch tests, all eight patients with typical clinical symptoms showed positive reactions to the mixed polyether impression materials, to the base paste or to a base paste component. The patient with the atypical clinical symptoms did not show any positive patch test reactions. Polyether impression materials may evoke type IV allergic reactions. The causative agent was a component of the base paste. In consideration of the widespread use of this impression material (millions of applications per year) and in comparison to the number of adverse reactions from other dental materials, the number of such allergic reactions is very low. In very scarce cases, positive allergic reactions to polyether impression materials are possible.

  9. Fatal anaphylactic shock due to a dental impression material.

    PubMed

    Gangemi, Sebastiano; Spagnolo, Elvira Ventura; Cardia, Giulio; Minciullo, Paola L

    2009-01-01

    Materials used for dental impressions are usually safe. This study describes a case of fatal anaphylaxis that appeared immediately after the oral mucosa came into contact with an alginate paste used for dental impressions. The cadaveric examination and the postmortem toxicology report confirmed that the cause of death was anaphylactic shock. The patient was affected by both cardiovascular and lung diseases that worsened the condition and forbade the use of epinephrine. To the authors' knowledge, dental impression materials, and alginate in particular, have not been reported previously as being a cause of anaphylaxis.

  10. Effect of reactive adhesives on the tensile bond strength of polyvinyl siloxane impression materials to methyl methacrylate tray material.

    PubMed

    Ona, Masahiro; Takahashi, Hidekazu; Sato, Masayuki; Igarashi, Yoshimasa; Wakabayashi, Noriyuki

    2010-05-01

    The effect of new adhesives on the bond strength of elastomeric impression materials to acrylic trays was evaluated. Two polyvinyl siloxane impression materials (Fusion and Imprinsis) with reactive adhesives and one (Examix) with a conventional adhesive were tested. Flat, double-sided plates of auto-polymerizing methyl methacrylate (10 x 10 x 2.5 mm) were prepared with one of the adhesives. Five specimens were prepared by injecting each impression material into a 2-mm gap between the two plates. Tensile tests were conducted until separation failure occurred. The mean bond strengths of Fusion (1.0 MPa) and Imprinsis (0.8 MPa) were significantly greater than that of Examix (0.2 MPa). On the contrary, one of five Fusion showed adhesive failure mode while all the Imprinsis exhibited mixed failure. The conflicting results were presumably attributed to the mean tear strength of Fusion (0.8 N/mm) being higher than that of Imprinsis (0.5 N/mm).

  11. Elastomeric Polypeptides

    PubMed Central

    van Eldijk, Mark B.; McGann, Christopher L.

    2013-01-01

    Elastomeric polypeptides are very interesting biopolymers and are characterized by rubber-like elasticity, large extensibility before rupture, reversible deformation without loss of energy, and high resilience upon stretching. Their useful properties have motivated their use in a wide variety of materials and biological applications. This chapter focuses on elastin and resilin – two elastomeric biopolymers – and the recombinant polypeptides derived from them (elastin-like polypeptides and resilin-like polypeptides). This chapter also discusses the applications of these recombinant polypeptides in the fields of purification, drug delivery, and tissue engineering. PMID:21826606

  12. A coupled theory of fluid permeation and large deformations for elastomeric materials

    NASA Astrophysics Data System (ADS)

    Chester, Shawn A.; Anand, Lallit

    2010-11-01

    An elastomeric gel is a cross-linked polymer network swollen with a solvent (fluid). A continuum-mechanical theory to describe the various coupled aspects of fluid permeation and large deformations (e.g., swelling and squeezing) of elastomeric gels is formulated. The basic mechanical force balance laws and the balance law for the fluid content are reviewed, and the constitutive theory that we develop is consistent with modern treatments of continuum thermodynamics, and material frame-indifference. In discussing special constitutive equations we limit our attention to isotropic materials, and consider a model for the free energy based on a Flory-Huggins model for the free energy change due to mixing of the fluid with the polymer network, coupled with a non-Gaussian statistical-mechanical model for the change in configurational entropy—a model which accounts for the limited extensibility of polymer chains. As representative examples of application of the theory, we study (a) three-dimensional swelling-equilibrium of an elastomeric gel in an unconstrained, stress-free state; and (b) the following one-dimensional transient problems: (i) free-swelling of a gel; (ii) consolidation of an already swollen gel; and (iii) pressure-difference-driven diffusion of organic solvents across elastomeric membranes.

  13. Development of an impact noise reduction method by the adding of a small thickness elastomeric material

    NASA Astrophysics Data System (ADS)

    Arz, Jean-Pierre

    The starting point of this Ph.D. is the industrial issue submitted to the ETS by the company Bombardier Recreational Products (BRP) of the noise reduction of the tracked drive mechanism of snowmobiles. The overall goal of is to develop a method to predict the impact noise reduction obtained by the adding of an elastomeric layer specimen of small thickness between the impacting body and the impacted structure which is a complex structure (i.e. a structure whose geometry is complex and whose composition involves several materials). To reach this overall goal, three specific goals have been fixed: (1) characterize the behavior under impact of different small thickness elastomeric layers; (2) predict the impact force generated when an elastomeric layer is added on a complex vibrating structure; and (3) validate experimentally the whole method by applying it to the impact noise reduction of a bar of the snowmobile track. To reach the first specific goal (characterize the behavior under impact of different small thickness elastomeric layers), a specific experimental characterization method has been developed. Firstly, an experimental device has been realized to submit the elastomeric layer specimens to the reproducible impact conditions of an impact hammer. The measurement of the penetration depth of the hammer into the elastomeric layer is achieved by recording its motion with a high-speed camera and by detecting its position by further analysis on the individual images. Secondly, the experimental curves obtained are analyzed to point out their main characteristics and choose an appropriate impact model. Thirdly, the contact force parameters are estimated from the experimental results and from the impact model. Using this method, eight impacted elastomeric specimens have been characterized. The results show that a more precise characterization than hardness is obtained. To reach the second specific goal (predict the impact force generated when an elastomeric layer is

  14. Evaluation of effect of tray space on the accuracy of condensation silicone, addition silicone and polyether impression materials: an in vitro study.

    PubMed

    Kumar, Varun; Aeran, Himanshu

    2012-09-01

    Optimal thickness of impression materials in the custom tray in order to get the most accurate impression. To investigate the effect of different tray spacer thickness on the accuracy and the dimensional stability of impressions made from monophasic condensation silicone, addition silicone and polyether impression materials. Three different types of elastomeric monophasic impression materials were used for making the impression of a master die with tray having tray spacer thickness of 2, 4 and 6 mm. Each type of impression was poured in die stone after 1 h. Each cast was analyzed by a travelling microscope and compared with the master die. The data was tabulated and subjected to statistical evaluation. The results of the study indicated that the impressions made from 2 to 4 mm spaced trays produced more accurate stone casts when compared to 6 mm spaced tray. No statistical significant differences were observed between the accuracy and dimensional stability of the three materials tested. Minimum changes were observed when the cast was poured after 1 h and the tray space was 2 mm for all the materials tested. It is therefore advisable not to exceed tray space of 2 mm.

  15. Developments in new aircraft tire tread materials. [fatigue life of elastomeric materials

    NASA Technical Reports Server (NTRS)

    Yager, T. J.; Mccarty, J. L.; Riccitiello, S. R.; Golub, M. A.

    1976-01-01

    Comparative laboratory and field tests were conducted on experimental and state-of-the-art aircraft tire tread materials in a program aimed at seeking new elastomeric materials which would provide improved aircraft tire tread wear, traction, and blowout resistance in the interests of operational safety and economy. The experimental stock was formulated of natural rubber and amorphous vinyl polybutadiene to provide high thermal-oxidative resistance, a characteristic pursued on the premise that thermal oxidation is involved both in the normal abrasion or wear of tire treads and probably in the chain of events leading to blowout failures. Results from the tests demonstrate that the experimental stock provided better heat buildup (hysteresis) and fatigue properties, at least equal wet and dry traction, and greater wear resistance than the state-of-the-art stock.

  16. Impression material thickness in stock and custom trays.

    PubMed

    Bomberg, T J; Hatch, R A; Hoffman, W

    1985-08-01

    This study did not examine the accuracy of the resultant impressions. Rather, the impression material thickness in impressions made using both the highly advocated custom acrylic resin tray and in the highly used manufactured stock tray was examined. Comparison between the material thickness at the prepared tooth area revealed a mean difference in material thickness of less than 1 mm. The question of the significance of this difference remains to be answered. If the difference is not significant in the success of the impression and the resultant casting, then there are several advantages in using the manufactured stock tray; the first is economy. The average cost of a custom acrylic full arch impression tray is $3.65, compared with an average cost of slightly over $0.30 for the stock tray. The second advantage is the convenience factor. Making a custom tray requires planning, study models, laboratory time, curing interval, and finishing time. In contrast, the stock tray can be selected, adapted, and used in a single visit for both anticipated and unanticipated situations. If the difference in material thickness is significant, the custom tray is indicated. However, attention to detail in making and inserting the tray in the mouth must be observed to maximize the benefits of the custom tray.

  17. The dimensional accuracy of polyvinyl siloxane impression materials using two different impression techniques: An in vitro study

    PubMed Central

    Kumari, Nirmala; Nandeeshwar, D. B.

    2015-01-01

    Aim of the Study: To evaluate and compare the linear dimensional changes of the three representative polyvinyl siloxane (PVS) impression materials and to compare the accuracy of single mix with double mix impression technique. Methodology: A study mold was prepared according to revised American Dental Association specification number 19 for nonaqueous elastic dental impression materials. Three PVS impression materials selected were Elite-HD, Imprint™ II Garant, Aquasil Ultra Heavy. Two impression techniques used were single mix and double mix impression technique. A total of 60 specimens were made and after 24 h the specimens were measured using profile projector. Statistical Analysis: The data were analyzed using one-way analyses of variance analysis and significant differences were separated using Student's Newman–Keul's test. Results: When all the three study group impression materials were compared for double mix technique, the statistically significant difference was found only between Imprint™ II Garantand Elite-HD (P < 0.05). Similarly, using single mix technique, statistically significant difference were found between Elite-HD and Imprint™ II Garant (P < 0.05) and also between Aquasil Ultra Heavy and Elite-HD (P < 0.05). When the linear dimensional accuracy of all three impression material in double mix impression technique and single mix impression technique were compared with the control group, Imprint™ II Garant showed the values more nearing to the values of master die, followed by Aquasil Ultra Heavy and Elite-HD respectively. Conclusion: Among the impression materials Imprint™ II Garant showed least dimensional change. Among the impression techniques, double mix impression technique showed the better results. PMID:26929515

  18. Methodology for Evaluating Raw Material Changes to RSRM Elastomeric Insulation Materials

    NASA Technical Reports Server (NTRS)

    Mildenhall, Scott D.; McCool, Alex (Technical Monitor)

    2001-01-01

    The Reusable Solid Rocket Motor (RSRM) uses asbestos and silicon dioxide filled acrylonitrile butadiene rubber (AS-NBR) as the primary internal insulation to protect the case from heat. During the course of the RSRM Program, several changes have been made to the raw materials and processing of the AS-NBR elastomeric insulation material. These changes have been primarily caused by raw materials becoming obsolete. In addition, some process changes have been implemented that were deemed necessary to improve the quality and consistency of the AS-NBR insulation material. Each change has been evaluated using unique test efforts customized to determine the potential impacts of the specific raw material or process change. Following the evaluations, the various raw material and process changes were successfully implemented with no detectable effect on the performance of the AS-NBR insulation. This paper will discuss some of the raw material and process changes evaluated, the methodology used in designing the unique test plans, and the general evaluation results. A summary of the change history of RSRM AS-NBR internal insulation is also presented.

  19. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Resin impression tray material. 872.3670 Section 872.3670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... fabrication of crowns, bridges, or full dentures. A preliminary plaster or stone model of the patient's...

  20. Accuracy of different impression materials in parallel and nonparallel implants

    PubMed Central

    Vojdani, Mahroo; Torabi, Kianoosh; Ansarifard, Elham

    2015-01-01

    Background: A precise impression is mandatory to obtain passive fit in implant-supported prostheses. The aim of this study was to compare the accuracy of three impression materials in both parallel and nonparallel implant positions. Materials and Methods: In this experimental study, two partial dentate maxillary acrylic models with four implant analogues in canines and lateral incisors areas were used. One model was simulating the parallel condition and the other nonparallel one, in which implants were tilted 30° bucally and 20° in either mesial or distal directions. Thirty stone casts were made from each model using polyether (Impregum), additional silicone (Monopren) and vinyl siloxanether (Identium), with open tray technique. The distortion values in three-dimensions (X, Y and Z-axis) were measured by coordinate measuring machine. Two-way analysis of variance (ANOVA), one-way ANOVA and Tukey tests were used for data analysis (α = 0.05). Results: Under parallel condition, all the materials showed comparable, accurate casts (P = 0.74). In the presence of angulated implants, while Monopren showed more accurate results compared to Impregum (P = 0.01), Identium yielded almost similar results to those produced by Impregum (P = 0.27) and Monopren (P = 0.26). Conclusion: Within the limitations of this study, in parallel conditions, the type of impression material cannot affect the accuracy of the implant impressions; however, in nonparallel conditions, polyvinyl siloxane is shown to be a better choice, followed by vinyl siloxanether and polyether respectively. PMID:26288620

  1. An implant-transfer technique without impression material.

    PubMed

    Assunção, Wirley Gonçalves; Gomes, Erica Alves; Aparecida Delben, Juliana; dos-Santos, Paulo Henrique; Ricardo Barão, Valentim Adelino; Tabata, Lucas Fernando

    2010-07-01

    Different transfer impression techniques for implant-supported prostheses have been suggested to obtain a working cast. This article describes and illustrates clinical and laboratory prosthodontic procedures to transfer implant positions with splinted transfer copings and without impression material to form a laboratory analog transfer template. With this technique, a preliminary cast is modified to place the analogs according to a corrected position and obtain the master cast. Although this technique does not record adjacent tissues, it is a simple procedure, less time consuming, and easily performed.

  2. Viscoelastic properties of elastomeric materials for O-ring applications

    NASA Technical Reports Server (NTRS)

    Bower, Mark V.

    1989-01-01

    Redesign of the Space Shuttle Solid Rocket Booster necessitated re-evaluation of the material used in the field joint O-ring seals. This research project was established to determine the viscoelastic characteristics of five candidate materials. The five materials are: two fluorocarbon compounds, two nitrile compounds, and a silicon compound. The materials were tested in a uniaxial compression test to determine the characteristic relaxation functions. These tests were performed at five different temperatures. A master material curve was developed for each material from the experimental data. The results of this study are compared to tensile relaxation tests. Application of these results to the design analysis is discussed in detail.

  3. Characterization of elastomeric materials with application to design

    NASA Technical Reports Server (NTRS)

    Bower, Mark V.

    1986-01-01

    Redesign of the Space Shuttle Solid Booster has necessitated re-evaluation of the material used in the field joint O-ring seals. The viscoelastic characteristics of five candidate materials were determined. The five materials are: two fluorocarbon compounds, two nitrile compounds, and a silicon compound. The materials were tested in a uniaxial compression test to determine the characteristic relaxation functions. These tests were performed at five different temperatures. A master material curve was developed for each material from the experimental data. The results are compared to tensile relaxation tests. Application of these results to the design analysis is discussed in detail.

  4. Impression material mass retained in the mucobuccal fold.

    PubMed

    Karam Genno, N; Assaf, A

    2014-01-01

    Trapped foreign bodies and tissue reactions to foreign materials are commonly encountered in the oral cavity. Traumatically introduced dental materials, instruments, or needles are the most common materials referred to in the dental literature. This paper describes an iatrogenic foreign body encapsulation in the oral mucosa, clinically appearing as 5 × 10 mm tumor-like swelling with an intact overlying epithelium and diagnosed as a polymeric impression material. Detailed case history and, clinical and radiographic examinations including CBCT and spectrometric analysis of the retrieved sample were necessary to determine accurately the nature, size, and location of the foreign body. It is suggested that the origin of the material relates to an impression made 2 years ago, leaving a mass trapped in a traumatized mucosal tissue.

  5. Effect of Time on Gypsum-Impression Material Compatibility

    NASA Astrophysics Data System (ADS)

    Won, John Boram

    The purpose of this study was to evaluate the compatibility of dental gypsum with three recently introduced irreversible hydrocolloid (alginate) alternatives. The test materials were Alginot® (Kerr™), Position Penta Quick® (3M ESPE™) and Silgimix ® (Sultan Dental™). The irreversible hydrocolloid impression material, Jeltrate Plus antimicrobial® (Dentsply Caulk™) served as the control. Materials and Methods: Testing of materials was conducted in accordance with ANSI/ADA Specification No. 18 for Alginate Impression Materials. Statistical Analysis: The 3-Way ANOVA test was used to analyze measurements between different time points at a significance level of (p < 0.05). Outcome: It was found that there was greater compatibility between gypsum and the alternative materials over time than the traditional irreversible hydrocolloid material that was tested. A statistically significant amount of surface change/incompatibility was found over time with the combination of the dental gypsum products and the control impression material (Jeltrate Plus antimicrobial®).

  6. Development and evaluation of elastomeric materials for geothermal applications

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Kalfayan, S. H.; Reilly, W. W.; Ingham, J. D.

    1978-01-01

    A material for a casing packer for service for 24 hours in a geothermal environment was developed by synthesis of new elastomers and formulation of available materials. Formulation included use of commercial elastomer gumstocks and also crosslinking of plastic (high Tg) materials. Fibrous reinforcement of fluorocarbon rubbers was emphasized. Organic fiber reinforcement did not increase hot properties significantly. Glass fiber reinforcement gave significant increase in tensile properties. Elongation was reduced, and the glass-reinforced composition examined so far did not hold up well in the geothermal environment. Colloidal asbestos fibers were also investigated. A few experiments with polyphenyl ether gave material with low tensile and high compression set. Available high styrene SBR compositions were studied. Work to date suggests that new synthetic polymers will be required for service in geothermal environments.

  7. High k dielectric elastomeric materials for low voltage applications

    NASA Astrophysics Data System (ADS)

    Walder, C.; Molberg, M.; Opris, D. M.; Nüesch, F. A.; Löwe, C.; Plummer, C. J. G.; Leterrier, Y.; Månson, J.-A. E.

    2009-03-01

    In principle EAP technology could potentially replace common motion-generating mechanisms in positioning, valve control, pump and sensor applications, where designers are seeking quieter, power efficient devices to replace conventional electrical motors and drive trains. Their use as artificial muscles is of special interest due to their similar properties in terms of stress and strain, energy and power densities or efficiency. A broad application of dielectric elastomer actuators (DEA) is limited by the high voltage necessary to drive such devices. The development of novel elastomers offering better intrinsic electromechanical properties is one way to solve the problem. We prepared composites from cross-linked silicone elastomers or thermoplastic elastomers (TPE) by blending them with organic fillers exhibiting a high dielectric constant. Well characterized monomeric phthalocyanines and modified doped polyaniline (PANI) were used as filler materials. In addition, blends of TPE and an inorganic filler material PZT were characterized as well. We studied the influence of the filler materials onto the mechanical and electromechanical properties of the resulting mixtures. A hundredfold increase of the dielectric constant was already observed for blends of an olefin based thermoplastic elastomer and PANI.

  8. [The viscosity of Thiokol impression material during gelation (author's transl)].

    PubMed

    Araki, Y; Kawakami, M

    1976-09-01

    Viscosity behavior of the impression materials is important property which determines the pressure and its distribution to be exerted on oral soft tissues in relation to the tray design and impression technique. The impression material, however, react to gel so fast to measure the viscosity during the reaction that it is still not completely elucidated. It would be able to seize the viscosity behavior of Thiokol impression material during the gelation unequivocally by retarding the oxidative condensation reaction using weak oxidative, lead monoxide. Based on the equal reactivity of SH groups of Thiokol liquid polymer there is no difference in statistic molecular weight distribution at any degree of the reaction between with lead monoxide and with the other oxidatives now in practical use. The viscosity measurement of the mixture of Thiokol LP-2, lead monoxide, and di-butyl phthalate was performed at the rates of shear ranged from 10(1.5) to 10(3.9) sec-1 at 20 degrees C. The viscosity of the mixture progressively increases after spatulation of the materials but yield value does not appear for the time being before setting, that is, the infinite network forming via the pendant SH groups could not take place until the most of SH groups were consumed, attributed to low concentration of poly-functional prepolymer in the liquid polymer. At early stages of the reaciton the viscosity behavior is approximately Newtonian at lower rates of shear and pseudplastic at higher rates of shear. As the reaction proceeds it becomes pseudplastic even at lower rates of shear. PMID:1069036

  9. [The viscosity of Thiokol impression material during gelation (author's transl)].

    PubMed

    Araki, Y; Kawakami, M

    1976-09-01

    Viscosity behavior of the impression materials is important property which determines the pressure and its distribution to be exerted on oral soft tissues in relation to the tray design and impression technique. The impression material, however, react to gel so fast to measure the viscosity during the reaction that it is still not completely elucidated. It would be able to seize the viscosity behavior of Thiokol impression material during the gelation unequivocally by retarding the oxidative condensation reaction using weak oxidative, lead monoxide. Based on the equal reactivity of SH groups of Thiokol liquid polymer there is no difference in statistic molecular weight distribution at any degree of the reaction between with lead monoxide and with the other oxidatives now in practical use. The viscosity measurement of the mixture of Thiokol LP-2, lead monoxide, and di-butyl phthalate was performed at the rates of shear ranged from 10(1.5) to 10(3.9) sec-1 at 20 degrees C. The viscosity of the mixture progressively increases after spatulation of the materials but yield value does not appear for the time being before setting, that is, the infinite network forming via the pendant SH groups could not take place until the most of SH groups were consumed, attributed to low concentration of poly-functional prepolymer in the liquid polymer. At early stages of the reaciton the viscosity behavior is approximately Newtonian at lower rates of shear and pseudplastic at higher rates of shear. As the reaction proceeds it becomes pseudplastic even at lower rates of shear.

  10. Polyvinyl siloxane impression materials: an update on clinical use.

    PubMed

    Mandikos, M N

    1998-12-01

    Polyvinyl siloxane impression materials have applications in a variety of indirect procedures in prosthodontics and restorative dentistry. Favourable handling properties, good patient acceptance and excellent physical properties have resulted in their popularity in today's practice. In this review, the chemistry and important physical properties of polyvinyl siloxanes are summarized, and recent clinical questions of improved hydrophilics, tray adhesives, disinfection, and glove-induced polymerization inhibition are addressed.

  11. Effects of atomic oxygen and ultraviolet radiation on candidate elastomeric materials for long duration missions. Test series no.1

    NASA Technical Reports Server (NTRS)

    Linton, R. C.; Finckenor, M. M.; Kamenetzky, R. R.; Gray, P.

    1993-01-01

    Research was conducted at MSFC on the behavior of elastomeric materials after exposure to simulated space environment. Silicone S383 and Viton V747 samples were exposed to thermal vacuum, ultraviolet radiation, and atomic oxygen and then evaluated for changes in material properties. Characterization of the elastomeric materials included weight, hardness, optical inspection under normal and black light, spectrofluorescence, solar absorptance and emittance, Fourier transform infrared spectroscopy, and permeability. These results indicate a degree of sensitivity to exposure and provided some evidence of UV and atomic oxygen synergism.

  12. Wettability changes in polyether impression materials subjected to immersion disinfection

    PubMed Central

    Shetty, Shweta; Kamat, Giridhar; Shetty, Rajesh

    2013-01-01

    Background: Disinfection of impression materials prevents cross-contamination; however, the disinfectants may alter the wettability property. The purpose of this investigation was to evaluate the wettability changes of polyether impression material after immersing in four different chemical disinfectant solutions for a period of 10 min and 30 min, respectively. Materials and Methods: A total of 45 samples of polyether dental impression material (Impregum soft, 3MESPE, St. Paul, MN, USA) were randomly divided into nine groups with five specimens each. Each specimen was disc shaped, flat of 32 mm diameter and 3 mm thickness. The samples were immersed in four disinfectant solutions: 2% Glutaraldehyde, 5% sodium hypochlorite, 0.05% iodophor, and 5.25% phenol for 10 min and 30 min, respectively. The control was without disinfection. Wettability of the samples was assessed by measuring the contact angle by using the Telescopic Goniometer. Data were subjected to analysis of variance (Fisher's test) and Tukey's post hoc test for multiple comparisons at 5% level of significance. Results: The contact angle of 20.21° ± 0.22° were recorded in the control samples. After 10 min, the samples that were immersed in 5% sodium hypochlorite and 5.25% phenol showed significant statistical increase in the contact angle as compared to the control (P < 0.001). After 30 min of disinfection, only the samples immersed in 0.05% iodophor showed there were no significant changes in the contact angle, whereas the other disinfectants significantly increased the contact angle and decreased the wettability of the polyether material. Conclusion: Within the limitations of the study, 2% glutaraldehyde proved safe for 10 min of immersion disinfection while 0.05% iodophor holds promise as an effective disinfectant without affecting the wettability of the material. PMID:24130593

  13. Maxillomandibular relationship record for implant complete mouth rehabilitation with elastomeric material and facial surface index of existing denture

    PubMed Central

    Patil, Pravinkumar G.; Nimbalkar-Patil, Smita

    2015-01-01

    Introduction: The maxillomandibular relationship (MMR) record is a critical step to establish the new occlusion in implant supported complete mouth rehabilitation. Using patients existing denture for recording the MMR requires implant definitive cast to be modified extensively to completely seat the denture (with unaltered flanges) on it. This may influence the correct seating of the denture on the implant definitive cast causing faulty recording of the MMR. Materials and Method: Elastomeric record bases, reinforced with the resin framework, are fabricated and relined with the light body elastomeric material when all the healing abutments are in place. The MMR is recorded with these elastomeric record bases using vacuum formed facial surface index of the occluded existing dentures as a guideline. Results: The elastomeric record bases with facial surface index of the existing dentures can allow clinicians to record MMR records without removing the healing abutments from the mouth with acceptable accuracy. This can save chair-side time of the procedure. The record of facial surfaces of existing complete denture in the form of vacuum formed sheet helps to set the occlusal vertical dimension. Conclusion: Use of facial surface index together with the elastomeric record bases can be the useful alternative technique to record the MMR in patients with implant supported full mouth rehabilitation. Further study is required to prove its routine clinical utility. PMID:26929537

  14. The thermal and mechanical properties of a low density elastomeric ablation material

    NASA Technical Reports Server (NTRS)

    Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

    1973-01-01

    Thermal and mechanical properties data were obtained for a low density elastomeric resin based ablation material with phenolic-glass honeycomb reinforcement. Data were obtained for the material in the charred and uncharred state. Ablation material specimens were charred in a laboratory furnace at temperatures in the range from 600 K to 1700 K to obtain char specimens representative of the ablation char layer formed during reentry. These specimens were then used to obtain effective thermal conductivity, heat capacity, porosity, and permeability data at the char formation temperature. This provided a boxing of the data which enables the prediction of the transient response of the material during ablation. Limited comparisons were made between the furnace charred specimens and specimens which had been exposed to simulated reentry conditions.

  15. Utilizing stretch-tunable thermochromic elastomeric opal films as novel reversible switchable photonic materials.

    PubMed

    Schäfer, Christian G; Lederle, Christina; Zentel, Kristina; Stühn, Bernd; Gallei, Markus

    2014-11-01

    In this work, the preparation of highly thermoresponsive and fully reversible stretch-tunable elastomeric opal films featuring switchable structural colors is reported. Novel particle architectures based on poly(diethylene glycol methylether methacrylate-co-ethyl acrylate) (PDEGMEMA-co-PEA) as shell polymer are synthesized via seeded and stepwise emulsion polymerization protocols. The use of DEGMEMA as comonomer and herein established synthetic strategies leads to monodisperse soft shell particles, which can be directly processed to opal films by using the feasible melt-shear organization technique. Subsequent UV crosslinking strategies open access to mechanically stable and homogeneous elastomeric opal films. The structural colors of the opal films feature mechano- and thermoresponsiveness, which is found to be fully reversible. Optical characterization shows that the combination of both stimuli provokes a photonic bandgap shift of more than 50 nm from 560 nm in the stretched state to 611 nm in the fully swollen state. In addition, versatile colorful patterns onto the colloidal crystal structure are produced by spatial UV-induced crosslinking by using a photomask. This facile approach enables the generation of spatially cross-linked switchable opal films with fascinating optical properties. Herein described strategies for the preparation of PDEGMEMA-containing colloidal architectures, application of the melt-shear ordering technique, and patterned crosslinking of the final opal films open access to novel stimuli-responsive colloidal crystal films, which are expected to be promising materials in the field of security and sensing applications. PMID:25243892

  16. Utilizing stretch-tunable thermochromic elastomeric opal films as novel reversible switchable photonic materials.

    PubMed

    Schäfer, Christian G; Lederle, Christina; Zentel, Kristina; Stühn, Bernd; Gallei, Markus

    2014-11-01

    In this work, the preparation of highly thermoresponsive and fully reversible stretch-tunable elastomeric opal films featuring switchable structural colors is reported. Novel particle architectures based on poly(diethylene glycol methylether methacrylate-co-ethyl acrylate) (PDEGMEMA-co-PEA) as shell polymer are synthesized via seeded and stepwise emulsion polymerization protocols. The use of DEGMEMA as comonomer and herein established synthetic strategies leads to monodisperse soft shell particles, which can be directly processed to opal films by using the feasible melt-shear organization technique. Subsequent UV crosslinking strategies open access to mechanically stable and homogeneous elastomeric opal films. The structural colors of the opal films feature mechano- and thermoresponsiveness, which is found to be fully reversible. Optical characterization shows that the combination of both stimuli provokes a photonic bandgap shift of more than 50 nm from 560 nm in the stretched state to 611 nm in the fully swollen state. In addition, versatile colorful patterns onto the colloidal crystal structure are produced by spatial UV-induced crosslinking by using a photomask. This facile approach enables the generation of spatially cross-linked switchable opal films with fascinating optical properties. Herein described strategies for the preparation of PDEGMEMA-containing colloidal architectures, application of the melt-shear ordering technique, and patterned crosslinking of the final opal films open access to novel stimuli-responsive colloidal crystal films, which are expected to be promising materials in the field of security and sensing applications.

  17. Production of a calcium silicate cement material from alginate impression material.

    PubMed

    Washizawa, Norimasa; Narusawa, Hideaki; Tamaki, Yukimichi; Miyazaki, Takashi

    2012-01-01

    The purpose of this study was to synthesize biomaterials from daily dental waste. Since alginate impression material contains silica and calcium salts, we aimed to synthesize calcium silicate cement from alginate impression material. Gypsum-based investment material was also investigated as control. X-ray diffraction analyses revealed that although firing the set gypsum-based and modified investment materials at 1,200°C produced calcium silicates, firing the set alginate impression material did not. However, we succeeded when firing the set blend of pre-fired set alginate impression material and gypsum at 1,200°C. SEM observations of the powder revealed that the featured porous structures of diatomite as an alginate impression material component appeared useful for synthesizing calcium silicates. Experimentally fabricated calcium silicate powder was successfully mixed with phosphoric acid solution and set by depositing the brushite. Therefore, we conclude that the production of calcium silicate cement material is possible from waste alginate impression material.

  18. Elastomeric optical fiber sensors and method for detecting and measuring events occurring in elastic materials

    DOEpatents

    Muhs, Jeffrey D.; Capps, Gary J.; Smith, David B.; White, Clifford P.

    1994-01-01

    Fiber optic sensing means for the detection and measurement of events such as dynamic loadings imposed upon elastic materials including cementitious materials, elastomers, and animal body components and/or the attrition of such elastic materials are provided. One or more optical fibers each having a deformable core and cladding formed of an elastomeric material such as silicone rubber are embedded in the elastic material. Changes in light transmission through any of the optical fibers due the deformation of the optical fiber by the application of dynamic loads such as compression, tension, or bending loadings imposed on the elastic material or by the attrition of the elastic material such as by cracking, deterioration, aggregate break-up, and muscle, tendon, or organ atrophy provide a measurement of the dynamic loadings and attrition. The fiber optic sensors can be embedded in elastomers subject to dynamic loadings and attrition such as commonly used automobiles and in shoes for determining the amount and frequency of the dynamic loadings and the extent of attrition. The fiber optic sensors are also useable in cementitious material for determining the maturation thereof.

  19. A technique for using short term soft liners as complete dentures final impression material.

    PubMed

    Baslas, Varun; Singh, Saumyendra V; Aggarwal, Himanshi; Kaur, Simranjeet; Singh, Kamleshwar; Agarwal, Kaushal K

    2014-01-01

    Tissue conditioners can be used to condition abused tissues, record functional impressions, make temporary relining for surgical splints and obturators, and for other clinical applications, mainly because of their specific viscoelasticity. Their function in complete denture fabrication is debatable but their use as a functional impression material has been proved. The present article describes a technique for using tissue conditioners as functional impression materials. Correct method of usage, manipulation, specific properties as impression materials and precautions in different situations for obtaining accurate impressions has been highlightened.

  20. A comparison of dimensional accuracy between three different addition cured silicone impression materials.

    PubMed

    Forrester-Baker, L; Seymour, K G; Samarawickrama, D; Zou, L; Cherukara, G; Patel, M

    2005-06-01

    Ten impressions of a metal implant abutment were made with each of three addition-cured silicone impression materials. Using the technique of co-ordinate metrology, the shoulder region of the abutment and corresponding regions of both impressions and dies made from these impressions were scanned and measured. Comparison of these measurements indicated that the mean dimension measured from the shoulder region for each group of impression materials was significantly different from those taken from the original metal implant abutment. However, when these impressions were cast in a gypsum based die material, none of the measured dimensions taken from the casts were significantly different from those taken from the original metal implant abutment. Thus, any change in measured dimensions occurring during impression making, was compensated for in some way by the casting process. PMID:16011234

  1. Effect of impression material on surface reactive layer when casting pure titanium in phosphate investment.

    PubMed

    Komasa, Y; Moriguchi, A; Asai, M; Nezumi, M; Kakimoto, K; Gonda, Y

    1998-10-01

    We evaluated the effect of impression materials used in preparation of pure titanium castings on the surface reactive layer. Surface roughness of the refractory models before and after firing was smaller when silicone rather than agar impression material was used. The surface roughness of castings prepared with T-invest varied little with the impression material. However, the surface roughness of the castings prepared with CD Titaninvest was less when silicone impression material was used. Surface hardness of the castings was slightly greater when agar impression material was used, and metallic texture analysis of the surface of the castings showed a chill layer and a columnar crystal layer extending from the surface toward the interior. A relatively non-corroded white layer and a markedly corroded black layer were observed in the chill layer, and their thickness was smaller when silicone impression material was used. Use of the Electron Probe Micro Analyzer (EPMA) to determine distribution of various elements in the superficial layer of the casting plates showed that the reactive layer contained less P and Si when silicone impression material was used rather than agar. NH4H2 PO4, which is a component of the bonding material in the investment, was present at a high concentration in the superficial layer of the agar impression material. This shows the importance of preparing refractory models with a non-water-absorbing impression material to obtain pure titanium casting plates with a smaller reactive layer.

  2. Accuracy of complete dental arch impressions and stone casts using a three-dimensional measurement system. Effects on accuracy of rubber impression materials and trays.

    PubMed

    Ishida, K

    1990-01-01

    The purpose of this study was to investigate and compare the accuracy of complete dental arch impressions and stone casts made with two kinds of impression materials (addition-type silicone and polysulfide rubber) and trays (custom tray and modified custom tray). In addition, the effect of the quantity of stone was examined. Impressions were made from a metallic model of a simplified maxillary dentition. Impressions and stone casts were measured respectively with a three-dimensional measuring microscope. The results were as follows: 1. Distortions of impressions were so small that the reproducibilities of impressions were superior three-dimensionally. These kinds of impressions and trays did not influence the accuracy of impressions. 2. The setting expansion of the stone in the impression occurred in the outward direction and was affected by the kinds of impressions and trays. 3. The arch widths and lengths of the stone casts tended to increase in number. 4. Stone casts made with addition-type silicone impression material and a custom tray were the most accurate because the combination of the impression material and tray effectively suppressed the setting expansion of stone. 5. The accuracy of stone casts could be improved by controlling the quantity of stone.

  3. Application times for the single-step/double-mix technique for impression materials in clinical practice.

    PubMed

    Rupp, Frank; Saker, Odie; Axmann, Detlef; Geis-Gerstorfer, Jurgen; Engel, Eva

    2011-01-01

    Hydrophilicity of unset impression materials underlies changes occurring during working time. Hence, the clinical application time when impression materials contact oral tissues after mixing may play a critical role in successful impressions. The aim of this study was to analyze the clinical time course of impression taking applying the single-step/double-mix technique. Application times of 86 impressions, comprising 265 prepared teeth and 46 implants, taken by 14 different clinicians at a university dental clinic were analyzed. The mean time from loading the impression tray until its final position in the patient's mouth (total application time) was 51.2 seconds; confidence intervals were 46.9 (lower limit) and 55.5 (upper limit). The number of registered teeth and implants did not influence the duration of impression taking. Related to wettability data, several polyvinyl siloxane impression materials show decreased hydrophilicity with respect to estimated application times. The authors suggest considering clinically relevant application times for impression taking in future in vitro studies on physicochemical characteristics of impression materials.

  4. Effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts

    PubMed Central

    Ebadian, Behnaz; Rismanchian, Mansor; Dastgheib, Badrosadat; Bajoghli, Farshad

    2015-01-01

    Background: Different factors such as impression techniques and materials can affect the passive fit between the superstructure and implant. The aim of this study was to determine the effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts. Materials and Methods: Four internal hex implants (Biohorizons Ø4 mm) were placed on a metal maxillary model perpendicular to the horizontal plane in maxillary lateral incisors, right canine and left first premolar areas. Three impression techniques including open tray, closed tray using ball top screw abutments and closed tray using short impression copings and two impression materials (polyether and polyvinyl siloxane) were evaluated (n = 60). The changes in distances between implant analogues in mediolateral (x) and anteroposterior (y) directions and analogue angles in x/z and y/z directions in the horizontal plane on the definitive casts were measured by coordinate measuring machine. The data were analyzed by multivariate two-way analysis of variance and one sample t-test (α = 0.05). Results: No statistical significant differences were observed between different impression techniques and materials. However, deviation and distortion of definitive casts had a significant difference with the master model when short impression copings and polyvinyl siloxane impression material were used (P < 0.05). In open tray technique, there was a significant difference in the rotation of analogs compared with the master model with both impression materials (P < 0.05). Conclusion: There was no difference between open and closed tray impression techniques; however, less distortion and deviation were observed in the open tray technique. In the closed tray impression technique, ball top screw was more accurate than short impression copings. PMID:25878678

  5. [Accuracy of complete dental arch impressions and stone casts using a three-dimensional measurement system. Effect on accuracy of rubber impression materials and trays].

    PubMed

    Ishida, K

    1989-08-01

    The purpose of this study was to investigate and compare the accuracy of complete dental arch impressions and stone casts made from two kinds of impression materials (addition type silicone and polysulfide rubber) and trays (custom tray and modified custom tray). In addition, the effect of quantity of gypsum was examined. Impressions were made from a metallic model of a simplified maxillary dentition. Impressions and stone casts were measured respectively using the three-dimensional measuring microscope. The results were as follows: 1. Distortion of impressions was so small that the reproducibility of impressions was superior three-dimensionally. 2. These kinds of impressions and trays did not influence the accuracy of impressions but had an effect on the accuracy of the stone casts. 3. Generally, the setting expansion of gypsum in the impression occurred in all directions. 4. Arch widths and lengths on the stone casts tended to increase in number. 5. Stone casts made from an addition/type silicone impression material and a custom tray were the most accurate because the combination of the impression material and tray effectively suppressed the setting expansion of gypsum. 6. By controlling the quantity of gypsum, the accuracy of stone casts could be improved.

  6. Biodegradable and Elastomeric Poly(glycerol sebacate) as a Coating Material for Nitinol Bare Stent

    PubMed Central

    Kim, Min Ji; Hwang, Moon Young; Kim, JiHeung; Chung, Dong June

    2014-01-01

    We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28 ± 0.004 MPa, and Young's modulus was 0.122 ± 0.0003 MPa. Elongation was as high as 237.8 ± 0.64%, and repeated elongation behavior was also observed to at least three times the original length without rupture. The water-in-air contact angles of the PGS surfaces were about 60°. We also analyzed the properties of an electrospray coating of biodegradable PGS on a nitinol stent for the purpose of enhancing long-term patency for the therapeutic treatment of varicose veins disease. The surface morphology and thickness of coating layer could be controlled by adjusting the electrospraying conditions and solution parameters. PMID:24955369

  7. Biodegradable and elastomeric poly(glycerol sebacate) as a coating material for nitinol bare stent.

    PubMed

    Kim, Min Ji; Hwang, Moon Young; Kim, JiHeung; Chung, Dong June

    2014-01-01

    We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28 ± 0.004 MPa, and Young's modulus was 0.122 ± 0.0003 MPa. Elongation was as high as 237.8 ± 0.64%, and repeated elongation behavior was also observed to at least three times the original length without rupture. The water-in-air contact angles of the PGS surfaces were about 60°. We also analyzed the properties of an electrospray coating of biodegradable PGS on a nitinol stent for the purpose of enhancing long-term patency for the therapeutic treatment of varicose veins disease. The surface morphology and thickness of coating layer could be controlled by adjusting the electrospraying conditions and solution parameters.

  8. Dermal and mucosal reactions to an antimicrobial irreversible hydrocolloid impression material: a clinical report.

    PubMed

    Baker, Philip S; Plummer, Kevin D; Parr, Gregory R; Parker, M Harry

    2006-03-01

    As an adjunct to infection control in dental impression procedures, several manufacturers have incorporated disinfectants into irreversible hydrocolloid impression materials. However, these compounds have been shown to be tissue irritants and capable of producing allergic reactions. An anonymous, self-administered questionnaire was distributed to 56 second-year dental students who had used an irreversible hydrocolloid containing a quaternary ammonium compound as an antimicrobial (Jeltrate Plus) to make impressions during a summer preclinical occlusion course. Within the limitations of this report, the incorporation of a quaternary ammonium compound into an irreversible hydrocolloid impression material resulted in a greater incidence of dermal and mucosal irritation.

  9. A Single Step Impression Technique of Flabby Ridges Using Monophase Polyvinylsiloxane Material: A Case Report

    PubMed Central

    Pai, Umesh Y.; Reddy, Vikram Simha; Hosi, Rushad Nariman

    2014-01-01

    Complete denture fabrication in clinically compromised situations such as flabby ridges is a challenging task for the clinician. Accurate impressioning of these tissues plays a major role in ensuring a well-fitting prosthesis. In this paper, the authors have proposed a newer technique of impression making of the flabby tissues using a combination of readily available newer and older materials to ensure an accurate and easy impression of these tissues. PMID:24872897

  10. The thermal and mechanical properties of a low-density glass-fiber-reinforced elastomeric ablation material

    NASA Technical Reports Server (NTRS)

    Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

    1974-01-01

    An evaluation of the thermal and mechanical properties was performed on a molded low-density elastomeric ablation material designated as Material B. Both the virgin and charred states were examined to provide meaningful inputs to the design of a thermal protection system. Chars representative of the flight chars formed during ablation were prepared in a laboratory furnace from 600 K to 1700 K and properties of effective thermal conductivity, heat capacity, porosity and permeability were determined on the furnace chars formed at various temperature levels within the range. This provided a boxing of the data which will enable the prediction of the transient response of the material during flight ablation.

  11. Accuracy and stability of impression materials subjected to chemical disinfection - a literature review.

    PubMed

    Kotsiomiti, E; Tzialla, A; Hatjivasiliou, K

    2008-04-01

    Disinfection of impressions by immersion or spraying with disinfecting solutions is considered nowadays mandatory for effective infection control. The purpose of this review was to examine existing evidence on the effects that chemical disinfection may have on critical qualities of impressions, namely dimensional accuracy and stability over time. A PubMed search was conducted to include original laboratory research articles written in English, published between 1980 and 2005 in peer-reviewed journals and investigating the effect of chemical disinfection, by immersion or spraying, on the dimensional changes that the impression materials experience after setting. Studies were also sought manually, by tracing the references cited in the retrieved articles. The reports on dimensional changes of disinfected impression materials, although rather numerous, are difficult to compare and analyze because of variations of the experimental design. The investigations broadly agree that the disinfection process does not generally affect the dimensional integrity of the impressions, in spite of the statistically significant differences occasionally found. However, the immersion in the disinfecting solution encourages water absorption phenomena in the case of the so-called hydrophilic impression materials, especially after the long-term immersion. Chemical interactions between impressions and disinfectants may occur, but they do not appear to influence the dimensional behaviour of the former. The overall effect of the disinfection is influenced not only by the changes experienced by the impression per se, but also by the alterations of the acrylic tray containing the impression and of the gypsum product poured in it.

  12. Dimensional Changes of Alginate Dental Impression Materials-An Invitro Study

    PubMed Central

    Thombare, Ram U

    2015-01-01

    Background Dentists are always looking ahead for more dimensionally stable material for accurate and successful fabrication of prosthesis in this competitive world. Arrival of newer materials and increased material market puts dentists in dilemma for selection of material. Aim The study evaluated the effect of variations in time of pour and temperature on dimensional stability of three brands of commercially available alginates. Materials and Methods Velplast, Marieflex & Zelgan alginate impression materials were evaluated by measuring dimensional accuracy of the master cast. A die was prepared and mounted on the apparatus for the ease of impression making. The prepared casts were categorized into five groups and made up of three brands of alginate impression material with variation in time of pour viz: immediate, 20&40 minutes interval and with varying temperature of 250C, 300C & 400C. Results Impressions showed least distortion at varying degrees of temperature for 20 minutes, but the values obtained by storing of alginate impressions for 20 minutes at 300C were found to be nearly accurate than the values obtained by storing of impression at 400C. However, storing showed shrinkage of impressions. Conclusion Marieflex showed better accuracy in comparison with other two materials. Maintenance of temperature and humidity play key role during storage & transport to prevent distortion. But the study suggests immediate pouring which will minimize the distortion. The manipulation instructions, temperature of mixing water, environment & water powder ratio also plays key role in minimizing the distortion. PMID:26436059

  13. Study of the interocclusal distortion in impressions taken with different types of closed-mouth trays and two types of impression materials.

    PubMed

    Mañes-Ferrer, José-Félix; Selva-Otaolaurruchi, Eduardo-José; Parra-Arenós, Carmina; Selfa-Bas, Isabel

    2010-01-01

    The aim of this study was to compare different types of impression trays for the closed-mouth impression technique, using two different types of impression material. For this study, five different types of impression trays were used with two different types of impression materials, one of addition silicone and the other of polyether. We designed a model used for taking the impressions and for measuring interocclusal distortion. The results obtained show that the impression trays COE (GC (R) GC America INC. Alsip) and Premier (Premier (R), Premier Dental Products Co. Canada) show a lesser degree of interocclusal distortion when taking closed-mouth impressions. In terms of impression materials, the polyether was the one that produced the best results. From a clinical point of view, our study shows that the use of these types of trays is absolutely recommendable when used according to the clinical indications for which they have been designed; that said, we must not fail to consider that selecting the proper type of tray is also important.

  14. Dental impression material: a rare cause of small-bowel obstruction.

    PubMed

    Dent, Lemuel; Peterson, Analeta; Pruett, Danica; Beech, Derrick

    2009-12-01

    Small-bowel obstruction due to foreign bodies is unusual in adults. Intestinal obstruction is occasionally caused by pits, bezoars, endoscopy capsules, and gastrostomy tube buttons. We report a rare case of distal small-bowel obstruction due to dental impression material. Avoidance of this potentially life-threatening complication may be achieved by increased vigilance in accounting for all impression material when dental impression trays are removed. Early detection of swallowed dental material may afford endoscopic removal from the stomach, thus preventing intestinal obstruction.

  15. Effect of mixing techniques on bacterial attachment and disinfection time of polyether impression material

    PubMed Central

    Guler, Umut; Budak, Yasemin; Ruh, Emrah; Ocal, Yesim; Canay, Senay; Akyon, Yakut

    2013-01-01

    Objective: The aim of this study was 2-fold. The first aim was to evaluate the effects of mixing technique (hand-mixing or auto-mixing) on bacterial attachment to polyether impression materials. The second aim was to determine whether bacterial attachment to these materials was affected by length of exposure to disinfection solutions. Materials and Methods: Polyether impression material samples (n = 144) were prepared by hand-mixing or auto-mixing. Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were used in testing. After incubation, the bacterial colonies were counted and then disinfectant solution was applied. The effect of disinfection solution was evaluated just after the polymerization of impression material and 30 min after polymerization. Differences in adherence of bacteria to the samples prepared by hand-mixing and to those prepared by auto-mixing were assessed by Kruskal-Wallis and Mann-Whitney U-tests. For evaluating the efficiency of the disinfectant, Kruskal-Wallis multiple comparisons test was used. Results: E. coli counts were higher in hand-mixed materials (P < 0.05); no other statistically significant differences were found between hand- and auto-mixed materials. According to the Kruskal-Wallis test, significant differences were found between the disinfection procedures (Z > 2.394). Conclusion: The methods used for mixing polyether impression material did not affect bacterial attachment to impression surfaces. In contrast, the disinfection procedure greatly affects decontamination of the impression surface. PMID:24966729

  16. Elastomeric member

    DOEpatents

    Hoppie, Lyle O.

    1985-01-01

    An energy storage device (10) is disclosed consisting of a stretched elongated elastomeric member (16) disposed within a tubular housing (14), which elastomeric member (16) is adapted to be torsionally stressed to store energy. The elastomeric member (16) is configured in the relaxed state with a uniform diameter body section (74), and transition end sections (76, 78), attached to rigid end piece assemblies (22, 24) of a lesser diameter. The profile and deflection characteristic of the transition sections (76, 78) are such that upon stretching of the elastomeric member (16), a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing (14). Each of the transition sections (76, 78) are received within and bonded to a woven wire mesh sleeve (26, 28) having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve (26, 28) also contracts with the contraction of the associated transition section to maintain the bond therebetween. During manufacture, the sleeves (26, 28) are forced against a forming surface and bonded to the associated transition section (76, 78) to provide the correct profile and helix angle.

  17. Elastomeric member

    DOEpatents

    Hoppie, L.O.

    1985-07-30

    An energy storage device is disclosed consisting of a stretched elongated elastomeric member disposed within a tubular housing, which elastomeric member is adapted to be torsionally stressed to store energy. The elastomeric member is configured in the relaxed state with a uniform diameter body section, and transition end sections, attached to rigid end piece assemblies of a lesser diameter. The profile and deflection characteristic of the transition sections are such that upon stretching of the elastomeric member, a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing. Each of the transition sections are received within and bonded to a woven wire mesh sleeve having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve also contracts with the contraction of the associated transition section to maintain the bond there between. During manufacture, the sleeves are forced against a forming surface and bonded to the associated transition section to provide the correct profile and helix angle. 12 figs.

  18. Impression materials in fixed prosthodontics: influence of choice on clinical procedure.

    PubMed

    Hamalian, Techkouhie A; Nasr, Elie; Chidiac, José J

    2011-02-01

    The purpose of this article is to review impression materials used for fabricating fixed restorations in dentistry. Their compositions, properties, advantages, and disadvantages are presented and compared. How these properties influence clinical decisions is also described. This review helps the clinician choose which material is more suitable for a specific case. A broad search of the published literature was performed using Medline to identify pertinent current articles. Textbooks, the Internet, and manufacturers' literature were also used to supplement this information. It is limited to impression materials used in fixed prosthodontics. The review gives basic knowledge of ideal impression material properties and discusses traditional and, primarily, more recently developed products, such as polyethers, poly(vinyl siloxane), polysulfides, and condensation silicone materials. Clear advantages and disadvantages for these impression materials are provided along with the role that compositional variations have on the outcome of the impression. This should enable clinicians and technicians to easily identify the important physical properties of each type of impression material and their primary clinical indications.

  19. Extrusion-mixing compared with hand-mixing of polyether impression materials?

    PubMed

    McMahon, Caroline; Kinsella, Daniel; Fleming, Garry J P

    2010-12-01

    The hypotheses tested were two-fold (a) whether altering the base:catalyst ratio influences working time, elastic recovery and strain in compression properties of a hand-mixed polyether impression material and (b) whether an extrusion-mixed polyether impression material would have a significant advantage over a hand-mixed polyether impression material mixed to the optimum base:catalyst ratio. The polyether was hand-mixed at the optimum (manufacturers recommended) base:catalyst ratios (7:1) and further groups were made by increasing or decreasing the catalyst length by 25%. Additionally specimens were also made from an extrusion-mixed polyether impression material and compared with the optimum hand-mixed base:catalyst ratio. A penetrometer assembly was used to measure the working time (n=5). Five cylindrical specimens for each hand-mixed and extrusion mixed group investigated were employed for elastic recovery and strain in compression testing. Hand-mixing polyether impression materials with 25% more catalyst than that recommended significantly decreased the working time while hand-mixing with 25% less catalyst than that recommended significantly increased the strain in compression. The extrusion-mixed polyether impression material provided similar working time, elastic recovery and strain in compression to the hand-mixed polyether mixed at the optimum base:catalyst ratio.

  20. Flame resistant elastic elastomeric fibers

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Massucco, A. A.

    1972-01-01

    Development of materials to improve flame resistance of elastic elastomeric fibers is discussed. Two approaches, synthesis of polyether based urethanes and modification of synthesized urethanes with flame ratardant additives, are described. Specific applications of both techniques are presented.

  1. Evaluation of dimensional stability and accuracy of autoclavable polyvinyl siloxane impression material.

    PubMed

    Reddy, Subash M; Vijitha, D; Karthikeyan, S; Balasubramanian, R; Satish, A

    2013-12-01

    Dimensionally stable autoclavable impressions will be effective in controlling the cross-infection and contamination caused by patient's saliva and other oral secretions. The accuracy of newly introduced autoclavable polyvinyl siloxane impression material was assessed for its dimensional stability and accuracy. A standard metal model (Dentoform, U-501, Columbia) was customised for impression making. The impressions were made using the newly introduced polyvinyl siloxane impression materials (AFFINIS, Coltene/Whaledent AG, 9450 Alstalten, Switzerland). Fifty impressions were made and were divided into two groups A and B of 25 each. Group A was the control sample (non-autoclaved impressions) and group B was the test sample (autoclaved impressions), which was subjected to the steam autoclave procedure at 134 °C for 18 min, casts were poured in type IV gypsum products. The customised metal model, casts obtained from control and test group were subjected to laboratory evaluation with help of a travelling microscope (×10 magnification), and digital vernier calliper (0.01 mm/10 μm accuracy). Data analysis was done using one-way ANOVA and One-Sample t test to evaluate the overall accuracy (P < 0.005). As a result, there was an average reduction of 0.016 μm in overall dimension between the test and the control group when compared with the master model, which is not statistically or clinically significant. The newly introduced polyvinyl siloxane impression material is accurate and dimensional stable for clinical use when steam autoclaved at 134 °C for 18 min.

  2. Effect of two different disinfectants on dimensional stability of newer alginate impression materials over five days.

    PubMed

    Ambrose, Prem Kumar; Juszczyk, Andrzej S; Clark, Robert K F; Radford, David R

    2011-12-01

    The effect of two different disinfectants on the dimensional stability of two alginate impression materials over five days was investigated. 60 impressions were made under standardised conditions, 30 with each alginate, of which ten were disinfected in each disinfectant and ten were controls. Impressions were stored over a period of five days in a container with 100% humidity. Measurements were made between four points. Two-way analysis of variance indicated no differences in the change from baseline to day 5 between any of the combinations of alginate and disinfectant. Only two of the changes between baseline and day 5 reached statistical significance at the p < 0.01 level. Therefore it can be concluded that within the limitations of this study when newer alginate impression materials are disinfected they remain stable over 5 days.

  3. Using silicone impression material and acrylic resin to fabricate remount casts for removable partial dentures.

    PubMed

    Hsu, Yung-tsung; Farmer, John B

    2005-06-01

    A technique is described for fabrication of a remount cast for a removable partial denture. This procedure consists of filling the occlusal/incisal third with acrylic resin and injecting polyvinylsiloxane impression material into the irreversible hydrocolloid impression. This technique provides a simple method for making a remount cast and enables the clinician to remove and easily place the partial denture on the cast during occlusal refinement procedures without damage to the removable partial denture or the remount cast.

  4. A Paradigm shift in the concept for making dental impressions

    PubMed Central

    Nayar, Sanjna; Mahadevan, R.

    2015-01-01

    Digital dental impression is a revolutionary technological advancement that so surpasses the accuracy and efficiency of former techniques for obtaining replicas of prepared teeth for the purpose of fabricating restorations that its adoption by dentists is rapidly eclipsing the use of elastomeric impression materials. The ultimate goals of dentists dedicated to quality restorative dentistry are to make their treatment of patients as accurate, stressless, and efficient as possible. By elimination of the everyday problems described above, there is no question that the significant advantages of digital impressions will make intraoral digital scanning standard procedure in most dental offices within the next several years. Furthermore, digital impressions have proven to reduce remakes and returns, as well as increase overall efficiency. The patient also benefits by being provided a far more positive experience. Finally, through the use of digital impression making, it has been determined that laboratory products become more consistent and require less chair time at insertion. PMID:26015714

  5. Rheological properties of polyvinylsiloxane impression materials before mixing and during setting related to handling characteristics

    NASA Astrophysics Data System (ADS)

    Lee, Hyang-Ok; Lee, In-Bog

    2012-09-01

    The purpose of this study is to determine and compare the handling and rheological properties of polyvinylsiloxane impression pastes before mixing and during setting, and to investigate the effect of its constituents on the properties of the materials. Five polyvinylsiloxane impression materials (Examixfine, Extrude, Honigum, Imprint II, and Express) were used. A flow test and a drip test were performed to determine the handling characteristics. The rheological properties of each impression material prior to mixing (shear stress, viscosity) and during setting (storage modulus G'), loss modulus G″), loss tangent tanδ) were measured with a stress-controlled rheometer at 25°C and 32°C, respectively. Inorganic filler content of each impression material was measured and observed with a SEM. The molecular weight distribution of polymer matrix was determined with a gel permeation chromatography (GPC). Express and Honigum display lower flow compared to the other materials, due to their high yield-stress values. Examixfine exhibits the greatest flow. All materials display pseudoplastic behavior, excluding the Examixfine catalyst. The viscosities at low shear rate are greatest for Express and Honigum; however, under high shear conditions, the viscosities of Extrude and Honigum are the lowest. Following mixing, each material show an increase in G', finally reaching a plateau, and the tanδ rapidly decreases with time. Imprint II shows the highest final G' as well as the most rapid decrease in tanδ. Express and Imprint II present the highest filler content and rough filler surface, while Honigum shows the lowest filler content and small filler particles. Most products are composed of polymers over 30 kDa and oligomers less than 1 kDa. Each impression material possesses different rheological properties, which significantly affect the handling characteristics. The yield stress of the impression material minimizes unnecessary flow prior to and after seating. Viscoelastic

  6. Pressure produced on the residual maxillary alveolar ridge by different impression materials and tray design: an in vivo study.

    PubMed

    Reddy, Subash M; Mohan, Chenthil Arun; Vijitha, D; Balasubramanian, R; Satish, A; Kumar, Mahendira

    2013-12-01

    Increased ridge resorption may occur due to inappropriate pressure applied during final impression making phase of complete denture fabrication. This study was done to evaluate the pressure applied on the residual ridge while making impressions with two tray designs (with and without spacer) using, zinc oxide eugenol and light body polyvinyl siloxane impression material. Five edentulous subjects were randomly selected. For each of the five subjects four maxillary final impressions were made and were labelled as, Group A-Impression made with tray without spacer using zinc oxide eugenol impression, Group B-Impression made with tray with spacer using zinc oxide eugenol impression material, Group C-Impression made with tray without spacer using light body polyvinyl siloxane impression material, Group D-Impression made with tray with spacer using light body polyvinyl siloxane impression material. During the impression procedure a closed hydraulic system was used to remotely measure the pressures produced in three areas. The pressure produced were calibrated according to the micro strain record. Statistical comparisons of readings were done using t test and ANOVA. The acquired data revealed that ZOE produced an average pressures value of 26.534 and 72.05 microstrain, while light body PVS produced 11.430 and 37.584 microstrain value with and without spacer respectively. Significantly high values were recorded on the vault of the palate when using trays without spacer. The use of light body polyvinyl siloxane and zinc oxide eugenol impression material showed insignificant difference. Within the limitations of this study, tray design has a significantly effected on the pressures produced, while the impression materials does not have any significant difference.

  7. Silicone impression material foreign body in the middle ear: Two case reports and literature review.

    PubMed

    Suzuki, Nobuyoshi; Okamura, Koji; Yano, Takuya; Moteki, Hideaki; Kitoh, Ryosuke; Takumi, Yutaka; Usami, Shin-ichi

    2015-10-01

    We report two cases of impression material foreign body in the middle ear. The first case had been affected with chronic otitis media. The silicone flowed into the middle ear through a tympanic membrane perforation during the process of making an ear mold. About 4 years and 8 months after, the patient had severe vertigo and deafness. We found bone erosion of the prominence of the lateral semicircular canal and diagnosed labyrinthitis caused by silicone impression material. In the second case silicone flowed into the canal wall down mastoid cavity. Both cases required surgery to remove the foreign body. The clinical courses in such cases are variable and timing of surgery is sometimes difficult. In addition to reporting these two cases, we present here a review of the literature regarding impression material foreign bodies.

  8. A new method for training of ear framework creation by silicon dental impression material.

    PubMed

    Thadani, Sandeep M; Ladani, Parit S

    2012-01-01

    This article presents the novel method of training of creating cartilage framework for total ear reconstruction in microtia. Replica of costal cartilage harvested for real surgery was simulated by silicon dental impression material. Carving of framework was done with wood carving instruments. Silicon dental impression material gives the consistency and texture almost comparable to real costal cartilage. Sequential steps similar to actual surgery were simulated to create the three-dimensional framework.By using this novel technique, novice surgeons can practice creating ear framework and improvise their results in the actual surgery.

  9. A new method for training of ear framework creation by silicon dental impression material

    PubMed Central

    Thadani, Sandeep M.; Ladani, Parit S.

    2012-01-01

    This article presents the novel method of training of creating cartilage framework for total ear reconstruction in microtia. Replica of costal cartilage harvested for real surgery was simulated by silicon dental impression material. Carving of framework was done with wood carving instruments. Silicon dental impression material gives the consistency and texture almost comparable to real costal cartilage. Sequential steps similar to actual surgery were simulated to create the three-dimensional framework. By using this novel technique, novice surgeons can practice creating ear framework and improvise their results in the actual surgery. PMID:22754170

  10. Stigmatizing materialism: on stereotypes and impressions of materialistic and experiential pursuits.

    PubMed

    Van Boven, Leaf; Campbell, Margaret C; Gilovich, Thomas

    2010-04-01

    Five studies examined the stigmatization of materialism. Participants expressed negative stereotypes of materialistic people, considering them to be more selfish and self-centered than experiential people (Study 1). Participants also viewed materialistic pursuits as more extrinsically motivated than experiential pursuits (Study 2). These stereotypes led respondents from varied demographic backgrounds to form less favorable impressions of individuals who were associated with prototypically materialistic versus experiential purchases, a result that was statistically mediated by impressions that materialistic purchases were more extrinsically motivated (Study 3). These differential impressions are primarily attributable to the denigration of materialistic people rather than the admiration of experiential people (Study 4). The stigmatization of materialism led participants to like less and enjoy interacting less with their conversation partners when discussing materialistic rather than experiential purchases (Study 5). The authors discuss these findings' implications for self-perception, accurate social perception, and well-being.

  11. An evaluation of dimensional accuracy of one-step and two-step impression technique using addition silicone impression material: an in vitro study.

    PubMed

    Pande, Neelam A; Parkhedkar, R D

    2013-09-01

    The study is aimed to evaluate the dimensional accuracy, the effect of undercut of two different configurations and the elastic recovery of addition silicone impression material assessed indirectly, by measuring the dimensions on stone models recorded from the impression of the master model, using one-step and two-step impression technique, for addition silicone impression materials. Measurements are taken to evaluate horizontal or linear and vertical dimensional changes, of the abutment V and abutment C from the stainless steel model. Heavy body/light body material is used for making one-step impression technique in a custom tray. Putty/light body is used for taking two-step technique in a stock metal tray. Improved die stone is used for pouring the impression. The different 11 locations on the dies produced by two different techniques are measured microscopically on image analyzer and compared with those of stainless steel model. Anova test was applied to test the differences of mean values of inter and intra abutment measurements, to calculate p value. Unpaired t test was applied to calculate t value. Results showed less deviation of stone models produced by one-step technique from stainless steel model, whereas the deviation of stone models produced by two-step is comparatively more. (p < 0.01). This difference of deviation is significantly less in one-step as compared to two-step technique. One-step is sufficiently dimensionally accurate than two-step technique in conjunction with addition silicone impression material. They have the best elastic recovery from the two undercut configurations.

  12. Case series of undetected intranasal impression material in patients with clefts.

    PubMed

    Jones, Simon D; Drake, David J

    2013-04-01

    We report the cases of two female patients in their twenties who had had corrective surgery for bilateral cleft lip and palate as babies. They had both had residual palatal fistulas and had had further treatment that required repeated dental impressions. Several years later both had complained of persistent nasal discomfort and discharge, and routine clinical examination and investigations had failed to identify the cause. Full examination of the whole nasal cavity under general anaesthesia, in both cases, showed the presence of displaced dental impression material in the nasal floor. Removal resulted in complete resolution of symptoms.

  13. [A comparative study of mechanical properties of materials for custom-made impression trays used by implant-fixed restorations].

    PubMed

    Gvetadze, R Sh; Abramian, S V; Rusanov, F S; Nubarian, A P; Ivanov, A A

    2012-01-01

    Materials for custom-made impression trays used for impression by implant fixed restorations were compared in the study. The analysis included such values as flexural strength and elasticity modulus, impression material adhesion strength with the use of adhesive and without it. Light-cured plastic Elite LC Tray had the best rates of bending strength and elasticity modulus and the Protakril M had the highest adhesion strength both with and without adhesive.

  14. Effect of adding impression material to mandibular denture space in Piezography.

    PubMed

    Ikebe, K; Okuno, I; Nokubi, T

    2006-06-01

    The purpose of the study was to examine the effect of adding impression material on denture space using a piezographical record. Subjects were ten voluntary edentulous patients, aged from 61 to 84 years old. A maxillary trial denture with anterior artificial teeth and a mandibular base plate with a keel were inserted into the oral cavity. Three ml of tissue-conditioning materials was injected on the base plate for each trial. Afterwards, the patients were instructed to pronounce various phonemes, so that tongue, cheeks and lips conformed to the denture space. The impression complexes were cut at the level of the estimated occlusal plane. Occlusal analogues were made by duplicating the impression complexes. Measurements were performed for five analogues from the first to fifth additions for each subject. The data were compared using analysis of variance (ANOVA), and a Friedman's test followed by a Bonferroni test for multiple comparisons with a level of significance at 5%. At the molar and premolar positions, the bucco-lingual widths of the occlusal table increased significantly at incremental injection of impression materials from P1 to P4. The midpoints of the analogues were located at a distance of 1.5 mm buccally at the molar position and at a distance of 1.9 mm buccally at the premolar position from the top of the alveolar crest, independent of the addition of impression material. It was concluded that denture space was regulated by volume of material and was located slightly on the buccal side from the crest of the residual alveolar ridge.

  15. Dimensional stability of polyvinyl siloxane impression material reproducing the sulcular area.

    PubMed

    Levartovsky, Shifra; Levy, Guy; Brosh, Tamar; Harel, Noga; Ganor, Yehuda; Pilo, Raphael

    2013-01-01

    The dimensional stability of a thin intra sulcular impression material reproducing the preparation finish line was evaluated. Impressions were taken of a stainless-steel master model of a simulated abutment with a 'gingival sulcus' using Express regular, Express fast and Aquasil. The putty-wash two-step technique was applied with spacer thicknesses of 0.5, 1 and 1.5 mm. Mid mesiodistal and bucco-lingual measurements were taken directly from the sulcular impression material after 0.5, 2, 24, 48 and 72 h via a Toolmaker's microscope. The discrepancies between the measurements of the impression material and the master model were calculated. The discrepancies changed significantly over time (p<0.001). The use of a 0.5 mm spacer resulted in a negative deviation from the model (2-46 µm), minimally after 2 h. The use of 1 and 1.5 mm spacers showed a positive deviation from the model (21-52 µm) and both are equally recommended. Investment can be postponed until 72 h.

  16. Accuracy of Implant Position Transfer and Surface Detail Reproduction with Different Impression Materials and Techniques

    PubMed Central

    Alikhasi, Marzieh; Siadat, Hakimeh; Kharazifard, Mohammad Javad

    2015-01-01

    Objectives: The purpose of this study was to compare the accuracy of implant position transfer and surface detail reproduction using two impression techniques and materials. Materials and Methods: A metal model with two implants and three grooves of 0.25, 0.50 and 0.75 mm in depth on the flat superior surface of a die was fabricated. Ten regular-body polyether (PE) and 10 regular-body polyvinyl siloxane (PVS) impressions with square and conical transfer copings using open tray and closed tray techniques were made for each group. Impressions were poured with type IV stone, and linear and angular displacements of the replica heads were evaluated using a coordinate measuring machine (CMM). Also, accurate reproduction of the grooves was evaluated by a video measuring machine (VMM). These measurements were compared with the measurements calculated on the reference model that served as control, and the data were analyzed with two-way ANOVA and t-test at P= 0.05. Results: There was less linear displacement for PVS and less angular displacement for PE in closed-tray technique, and less linear displacement for PE in open tray technique (P<0.001). Also, the open tray technique showed less angular displacement with the use of PVS impression material. Detail reproduction accuracy was the same in all the groups (P>0.05). Conclusion: The open tray technique was more accurate using PE, and also both closed tray and open tray techniques had acceptable results with the use of PVS. The choice of impression material and technique made no significant difference in surface detail reproduction. PMID:27252761

  17. Method and apparatus for non-destructive evaluation of composite materials with cloth surface impressions

    NASA Technical Reports Server (NTRS)

    Madras, Eric I. (Inventor)

    1995-01-01

    A method and related apparatus for nondestructive evaluation of composite materials by determination of the quantity known as Integrated Polar Backscatter, which avoids errors caused by surface texture left by cloth impressions by identifying frequency ranges associated with peaks in a power spectrum for the backscattered signal, and removing such frequency ranges from the calculation of Integrated Polar Backscatter for all scan sites on the composite material is presented.

  18. Three-dimensional assessment of dental casts' occlusal surfaces using two impression materials.

    PubMed

    Tarawneh, F M; Panos, P G; Athanasiou, A E

    2008-11-01

    The aim of this study was to assess by means of a three-dimensional computed tomography scanning system the occlusal surface characteristics of dental casts made using two different impression materials. Alginate and polyvinyl siloxane impressions were taken of 20 dental students resulting in 40 dental casts. The casts were paired for each student separately so that each pair consisted of an alginate poured cast and a polyvinyl siloxane poured out cast. The casts were scanned using FlashCT scanner and for each cast, a three-dimensional digital image was obtained. The digitized casts were processed using the three-dimensional imaging software Geomagic Studio 9. A total of 464 paired teeth were digitally separated and superimposed. For each tooth, two measurements were obtained corresponding to the two different impression materials used. The two sets of volumes for all digitally separated teeth were compared and analysed using the Wilcoxon signed test. Larger volume measurements were obtained for teeth separated from alginate poured out casts than from their corresponding ones from polyvinyl siloxane casts (P = 0.005). When the teeth were divided into the groups of incisors, canines and premolars/molars, only the last one exhibited significant difference (P = 0.00). The mean difference between the volumes measured for all 464 teeth separated was 0.041 mm(3) (+/-0.33). The occlusal surfaces of teeth appear differently in dental casts depending on the impression materials used. Impressions of dental casts should be utilized with caution in relation to their research application and in reference with dental wear studies.

  19. Elastomeric polypeptide-based biomaterials

    PubMed Central

    Li, Linqing; Charati, Manoj B.; Kiick, Kristi L.

    2011-01-01

    Elastomeric proteins are characterized by their large extensibility before rupture, reversible deformation without loss of energy, and high resilience upon stretching. Motivated by their unique mechanical properties, there has been tremendous research in understanding and manipulating elastomeric polypeptides, with most work conducted on the elastins but more recent work on an expanded set of polypeptide elastomers. Facilitated by biosynthetic strategies, it has been possible to manipulate the physical properties, conformation, and mechanical properties of these materials. Detailed understanding of the roles and organization of the natural structural proteins has permitted the design of elastomeric materials with engineered properties, and has thus expanded the scope of applications from elucidation of the mechanisms of elasticity to the development of advanced drug delivery systems and tissue engineering substrates. PMID:21637725

  20. An in vitro study of the antiviral properties of an alginate impression material impregnated with disinfectant.

    PubMed

    Tyler, R; Tobias, R S; Ayliffe, G A; Browne, R M

    1989-06-01

    The antiviral properties of a new alginate impression material impregnated with a disinfectant (didecyldimethyl ammonium chloride) were evaluated in vitro against herpes simplex virus type I and poliovirus type I. The material was exposed to the virus suspension for periods of up to 60 min. The impregnated alginate material showed no clinically acceptable effect against either virus, although log reductions of 1.0 and 1.7 plaque-forming units of herpes virus were obtained after exposure to the material containing the disinfectant for 5 and 60 min, respectively. PMID:2549107

  1. An in vitro study of the antiviral properties of an alginate impression material impregnated with disinfectant.

    PubMed

    Tyler, R; Tobias, R S; Ayliffe, G A; Browne, R M

    1989-06-01

    The antiviral properties of a new alginate impression material impregnated with a disinfectant (didecyldimethyl ammonium chloride) were evaluated in vitro against herpes simplex virus type I and poliovirus type I. The material was exposed to the virus suspension for periods of up to 60 min. The impregnated alginate material showed no clinically acceptable effect against either virus, although log reductions of 1.0 and 1.7 plaque-forming units of herpes virus were obtained after exposure to the material containing the disinfectant for 5 and 60 min, respectively.

  2. Biometric Denture Space- Concept of Neutral Zone Revisited Using A Hydrocolloid Impression Material.

    PubMed

    Shanker, Shyam Sundar; Umamaheswaran, Aruna; Nayar, Sanjna

    2015-11-01

    Though the concept of neutral zone in making complete denture and its significance are well known, the material of choice has always been experimented to achieve better results. Recording of neutral zone using irreversible hydrocolloid (Alginate) as a material of choice would make the way of recording the neutral zone easier, as well as comfortable for the patient, when compared with other materials used for the purpose. This article describes the method of recording the biometric denture space (neutral zone) using hydrocolloid impression material which is most commonly used in everyday dental practice.

  3. Biometric Denture Space- Concept of Neutral Zone Revisited Using A Hydrocolloid Impression Material

    PubMed Central

    Umamaheswaran, Aruna; Nayar, Sanjna

    2015-01-01

    Though the concept of neutral zone in making complete denture and its significance are well known, the material of choice has always been experimented to achieve better results. Recording of neutral zone using irreversible hydrocolloid (Alginate) as a material of choice would make the way of recording the neutral zone easier, as well as comfortable for the patient, when compared with other materials used for the purpose. This article describes the method of recording the biometric denture space (neutral zone) using hydrocolloid impression material which is most commonly used in everyday dental practice. PMID:26673250

  4. Comparing the Accuracy of Three Different Impression Materials in Making Duplicate Dies

    PubMed Central

    Bajoghli, Farshad; Sabouhi, Mahmoud; Nosouhian, Saeid; Davoudi, Amin; Behnamnia, Zeynab

    2015-01-01

    Background: Marginal adaptation is very important in cast restorations. Maladaptation leads to plaque retention, reduction of mechanical and esthetic properties. The aim of this study was to evaluate the precision of three different impression materials (including: Additional silicone [AS] and condensational silicone [CS] and polyether [PE]) for duplicating master dies. Materials and Methods: Three master dies from an acrylic tooth model-with supragingival and shoulder finishing line was made by using PE: Impergum, CS: Speedex, and AS: Panasil separately. The Ni-Cr copings were prepared from master dies separately. They were placed on the acrylic model and the mean marginal difference was recorded by using a stereomicroscope. Then 30 duplicate test dies were made by using the same impression materials and the marginal gaps were recorded. The comparison was done by one-way ANOVA and SPSS software (Version 13) at a significant level of 0.05. Results: The mean marginal difference of four walls from Impergum (38.56 um) was the lowest than Speedex (38.92 um) and Panasil (38.24 um). The Impergum had the highest capability in making duplicate dies (P > 0.05). Conclusion: The Impergum impression material manifested the highest capability in making a better marginal adaptation of duplicate dies but further studies are needed to make a precise decision. PMID:26229364

  5. Bite force measurement system using pressure-sensitive sheet and silicone impression material.

    PubMed

    Ando, Katsuya; Fuwa, Yuji; Kurosawa, Masahiro; Kondo, Takamasa; Goto, Shigemi

    2009-03-01

    This study was conducted to reduce the bias in measured values caused by the thickness of materials used in occlusal examinations. To this end, a silicone impression material for bite force measurement and an experimental model of a simplified stomatognathic system were employed in this study. By means of this experimental model, results showed that the effect of bias toward the posterior arch could be reduced in the anterior-posterior distribution of bite forces and in the occlusal contact areas due to the thickness of the materials used in occlusal examinations.

  6. Two- and three-dimensional accuracy of dental impression materials: effects of storage time and moisture contamination.

    PubMed

    Chandran, Deepa T; Jagger, Daryll C; Jagger, Robert G; Barbour, Michele E

    2010-01-01

    Dental impression materials are used to create an inverse replica of the dental hard and soft tissues, and are used in processes such as the fabrication of crowns and bridges. The accuracy and dimensional stability of impression materials are of paramount importance to the accuracy of fit of the resultant prosthesis. Conventional methods for assessing the dimensional stability of impression materials are two-dimensional (2D), and assess shrinkage or expansion between selected fixed points on the impression. In this study, dimensional changes in four impression materials were assessed using an established 2D and an experimental three-dimensional (3D) technique. The former involved measurement of the distance between reference points on the impression; the latter a contact scanning method for producing a computer map of the impression surface showing localised expansion, contraction and warpage. Dimensional changes were assessed as a function of storage times and moisture contamination comparable to that found in clinical situations. It was evident that dimensional changes observed using the 3D technique were not always apparent using the 2D technique, and that the former offers certain advantages in terms of assessing dimensional accuracy and predictability of impression methods. There are, however, drawbacks associated with 3D techniques such as the more time-consuming nature of the data acquisition and difficulty in statistically analysing the data.

  7. A New Method for Evaluating Elastomeric Materials for Use in High Pressure Oxygen

    NASA Technical Reports Server (NTRS)

    Jordan, Scott M.

    2001-01-01

    The seal configuration tester (SCT) developed at the Stennis Space Center (SSC) was designed to replicate the intended application of different seat and seal materials in a high pressure oxygen system and assess the wearibility of those materials. Statistical models were used to test the reliability of the SCT in its intended application, and the tests showed very consistent measurements over time, indicating that the device was working as intended. Other statistical designs were used to test different O-ring materials in a high-pressure oxygen system. Those tests indicated that the SCT could be used to rank the performance of O-ring materials in certain environments. The results indicated that some cheaper materials performed as well as, if not better than, other more expensive materials. Different lubrications were integrated in the testing as well and had a significant impact on the performance of the materials. Testing of seat materials is the next stage of this project. An augmentation grant (JAG) was obtained to further this experimental testing at the Stennis Space Center. This part of the project is ongoing at this time and therefore there are no significant accomplishments with respect to seat materials as of yet.

  8. A summary of laboratory testing performed to characterize and select an elastomeric O-ring material to be used in the redesigned solid rocket motors of the space transportation system

    NASA Technical Reports Server (NTRS)

    Turner, J. E.

    1993-01-01

    An elastomeric O-ring material is used in the joints of the redesigned solid motors (RSRM's) of the National Space Transportation System (NSTS). The selection of the O-ring material used in the RSRM's was a very thorough process that included efforts by NASA's Marshall Space Flight Center and the Langley Research Center, and the Thiokol Corporation. One of the efforts performed at MSFC was an extensive in-house laboratory test regime to screen potential O-ring materials and ultimately to characterize the elastomeric material that was chosen to be used in the RSRM's. The laboratory tests performed at MSFC are summarized.

  9. Flight and ground tests of a very low density elastomeric ablative material

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.; Chapman, A. J., III

    1972-01-01

    A very low density ablative material, a silicone-phenolic composite, was flight tested on a recoverable spacecraft launched by a Pacemaker vehicle system; and, in addition, it was tested in an arc heated wind tunnel at three conditions which encompassed most of the reentry heating conditions of the flight tests. The material was composed, by weight, of 71 percent phenolic spheres, 22.8 percent silicone resin, 2.2 percent catalyst, and 4 percent silica fibers. The tests were conducted to evaluate the ablator performance in both arc tunnel and flight tests and to determine the predictability of the albator performance by using computed results from an existing one-dimensional numerical analysis. The flight tested ablator experienced only moderate surface recession and retained a smooth surface except for isolated areas where the char was completely removed, probably following reentry and prior to or during recovery. Analytical results show good agreement between arc tunnel and flight test results. The thermophysical properties used in the analysis are tabulated.

  10. Influence of filler on bite impression material in transillumination method for occlusal examination.

    PubMed

    Kihara, Takuya; Shigeta, Yuko; Hirabayashi, Rio; Ikawa, Tomoko; Ando, Eriko; Hirai, Shinya; Nikawa, Hiroki; Ogawa, Takumi

    2013-01-01

    The purpose of this present study was to investigate the influence of material filler and RGB values' fluctuation on creating a calibration curve, which indicates the relationship between material thickness and transmitted light brightness using the transillumination method. Creating the calibration curves were carried out through the following three methods; 1) the conventional method creates the calibration curve with a formula of thickness, 2) the maximum value method, with samples of a specified thickness, and 3) the actual value method, with a microscope. Furthermore, the reliability of each curve was verified via scanned artificial tooth data. In addition, the characteristics of light decrement were investigated. From our results, it was suggested that the filler diameter must be considered when the calibration curve is created using the bite impression material with a filler. In addition, it was suggested that the RGB values' fluctuation did not influence the calibration curve.

  11. Effects of mixing technique on bubble formation in alginate impression material.

    PubMed

    McDaniel, Thomas F; Kramer, Robert T; Im, Francis; Snow, Dallin

    2013-01-01

    Previous studies have found that variations in mixing technique can influence the porosity content of alginate impression material. The aim of this study was twofold: determine whether bubble formation in alginate is influenced by the sequence of water/powder addition prior to mixing, and to compare 4 different mixing techniques. Manual spatulation, an automated spinning bowl, a centrifugal mixer and a vacuum mixer were evaluated for the resulting porosity in the set alginate. It was found that adding powder first, versus water first, made no difference in the bubble content using the 3 automated mixing techniques (P = 0.714). However, porosity was significantly less for powder-first trials using manual spatulation (P < 0.05). It was also found that surface porosity in the resulting impressions was significantly less for centrifugal and vacuum mixing when compared to manual spatulation, while internal porosity was significantly less for centrifugal mixing compared to all other mixing techniques (P < 0.05). The centrifugal mixing and vacuum mixing techniques required the least amount of mixing time.

  12. Effects of mixing technique on bubble formation in alginate impression material.

    PubMed

    McDaniel, Thomas F; Kramer, Robert T; Im, Francis; Snow, Dallin

    2013-01-01

    Previous studies have found that variations in mixing technique can influence the porosity content of alginate impression material. The aim of this study was twofold: determine whether bubble formation in alginate is influenced by the sequence of water/powder addition prior to mixing, and to compare 4 different mixing techniques. Manual spatulation, an automated spinning bowl, a centrifugal mixer and a vacuum mixer were evaluated for the resulting porosity in the set alginate. It was found that adding powder first, versus water first, made no difference in the bubble content using the 3 automated mixing techniques (P = 0.714). However, porosity was significantly less for powder-first trials using manual spatulation (P < 0.05). It was also found that surface porosity in the resulting impressions was significantly less for centrifugal and vacuum mixing when compared to manual spatulation, while internal porosity was significantly less for centrifugal mixing compared to all other mixing techniques (P < 0.05). The centrifugal mixing and vacuum mixing techniques required the least amount of mixing time. PMID:24064161

  13. Efficacy of different disinfectant systems on alginate and addition silicone impression materials of Indian and international origin: a comparative evaluation.

    PubMed

    Samra, R K; Bhide, S V

    2010-09-01

    Study was planned to evaluate the efficacy of commonly used disinfectants and to study qualitatively and quantitatively the persistence of microflora on the untreated (control group) and the disinfected impression surface after 24 h. Disinfectant systems used were immersion systems like glutaraldehyde, sodium hypochlorite and the ultraviolet chamber. The effect of disinfectant on most commonly used Indian impression materials was carried out in this study and results compared with the most commonly used foreign brands for irreversible hydrocolloid and addition silicone. Impressions were made of 25 healthy volunteers. These were disinfected and incubated in an incubator for 24 h at 37°C for aerobic organisms. The inoculation in nutrient media was done to test the viability of microorganisms that can persist after rinsing and disinfection of the impression surface. The colony forming units were counted and compared with that of control group. Control group of all the impression material samples showed growth of Streptococcus viridans, Diphtheroids, Streptococcus pneumoniae to a greater extent. The growth of Candida albicans, Pseudomonas aerugenosa and Staphyloccus albus was present in all the groups but to a lesser extent. The persistence of the microflora on the impression surface of both the studied brands was similar but the concentration of organisms in the alginate control group was two folds as compared to addition silicone group. Use of ultraviolet chamber gave better results compared to the studied immersion systems. All the disinfection systems were effective in reducing the microbial load with ultraviolet chamber as the most effective.

  14. Evaluation of accuracy of casts of multiple internal connection implant prosthesis obtained from different impression materials and techniques: an in vitro study.

    PubMed

    Pujari, Malesh; Garg, Pooja; Prithviraj, D R

    2014-04-01

    Movement of impression copings inside the impression material using a direct (open tray) impression technique during clinical and laboratory phases may cause inaccuracy in transferring the 3-dimensional spatial orientation of implants intraorally to the cast. Consequently, the prosthesis may require corrective procedures. This in vitro study evaluated the accuracy of 3 different impression techniques using polyether and vinyl polysiloxane (VPS) impression material to obtain a precise cast for multiple internal connection implants. A reference acrylic resin model with 4 internal connection implants was fabricated. Impressions of the reference model were made using 3 different techniques and 2 different impression materials. The study consisted of 24 specimens divided into 6 groups of 4 each. Impressions were poured with ADA type IV stone (Kalrock, Kalabhai Karson Pvt Ltd, Mumbai, India). All casts were evaluated for the positional accuracy (mm) of the implant replica heads using a profile projector. These measurements were compared to the measurements calculated on the reference resin model, which served as a control. Data were analyzed with 2-way analysis of variance (ANOVA) followed by Bonferroni multiple comparison procedures to evaluate group means. The results revealed significant difference for anterior implant distance between the 2 impression materials (P < .01) and also among the 3 different techniques (P < .05). The lowest mean variation was found with the polyether impression material and the splinted technique. For posterior implants, the results suggested no significant difference between the 2 impression materials (P ≥ .05). Although results were not statistically significant, the polyether impression material showed the lowest mean variation as compared to the VPS impression material. However, there was a significant difference among the 3 different techniques (P < .05). Among the 3 different techniques, the lowest mean variation between 2 posterior

  15. Bacterial, fungal and yeast contamination in six brands of irreversible hydrocolloid impression materials.

    PubMed

    Casemiro, Luciana Assirati; Martins, Carlos Henrique Gomes; de Souza, Fernanda de Carvalho Panzeri Pires; Panzeri, Heitor; Ito, Isabel Yoko

    2007-01-01

    This study assessed the level of contamination of six commercially available irreversible hydrocolloids (two containing chlorhexidine) and identified the contamination present in the materials. Petri dishes containing selective and enriched culture media were inoculated with alginate powder (0.06 g), in triplicate. After incubation (37 degrees C/7 days), the colony-forming units (CFU) were counted and Gram stained. Biochemical identification of the different morphotypes was also performed. The contamination levels for the materials were: Jeltrate--389 CFU/g; Jeltrate Plus--516 CFU/g; Jeltrate Chromatic--135 CFU/g; Hydrogum--1,455 CFU/g; Kromopan--840 CFU/g; and Greengel--59 CFU/g. Gram staining revealed the presence of Gram-positive bacillus and Gram-positive cocci. The bacteria Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus, and Nocardia sp.; the filamentous fungi Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; and the yeast Candida sp. were isolated. The contamination detected in the impression materials points out the need for adopting measures to improve the microbiological quality of these materials. The use of contaminated materials in the oral cavity goes against the basic principles for controlling cross-contamination and may represent a risk for debilitated or immunocompromised patients. PMID:17589644

  16. Bacterial, fungal and yeast contamination in six brands of irreversible hydrocolloid impression materials.

    PubMed

    Casemiro, Luciana Assirati; Martins, Carlos Henrique Gomes; de Souza, Fernanda de Carvalho Panzeri Pires; Panzeri, Heitor; Ito, Isabel Yoko

    2007-01-01

    This study assessed the level of contamination of six commercially available irreversible hydrocolloids (two containing chlorhexidine) and identified the contamination present in the materials. Petri dishes containing selective and enriched culture media were inoculated with alginate powder (0.06 g), in triplicate. After incubation (37 degrees C/7 days), the colony-forming units (CFU) were counted and Gram stained. Biochemical identification of the different morphotypes was also performed. The contamination levels for the materials were: Jeltrate--389 CFU/g; Jeltrate Plus--516 CFU/g; Jeltrate Chromatic--135 CFU/g; Hydrogum--1,455 CFU/g; Kromopan--840 CFU/g; and Greengel--59 CFU/g. Gram staining revealed the presence of Gram-positive bacillus and Gram-positive cocci. The bacteria Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus, and Nocardia sp.; the filamentous fungi Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; and the yeast Candida sp. were isolated. The contamination detected in the impression materials points out the need for adopting measures to improve the microbiological quality of these materials. The use of contaminated materials in the oral cavity goes against the basic principles for controlling cross-contamination and may represent a risk for debilitated or immunocompromised patients.

  17. An unusual foreign body in the maxillary sinus: Dental impression material.

    PubMed

    Deniz, Y; Zengin, A Z; Karli, R

    2016-01-01

    Foreign bodies in paranasal sinuses are very rare and most of them are encountered in the maxillary sinus. These foreign bodies may be organic or inorganic and can enter the maxillary sinus through an oro-antral fistula. The oro-antral fistula is formed by a break in the bony segment of the maxillary sinus floor and usually arises subsequent to maxillary premolar and molar extractions. A 63-year-old female patient evaluated for a nonhealing, left, toothless palate lesion and chronic headache occurring over 4 years. Radiography and computed tomography revealed bone discontinuity in the left floor of the maxillary sinus and calcifications within the antrum. A blue foreign body, later identified as dental impression material, was removed by intranasal endoscopy. A careful oral examination is recommended prior to prosthetic restorations. In addition, paranasal sinus foreign bodies should be surgically removed to prevent secondary soft tissue reactions.

  18. Fibre-optic sensors for partial discharge-generated ultrasound in elastomeric high-voltage insulation materials

    NASA Astrophysics Data System (ADS)

    Rohwetter, P.; Habel, W.

    2013-05-01

    Recent progress in the development of ultrasonic fibre-optic sensors for detecting acoustic emission from partial discharge in elastomeric insulations is presented. These sensors are an important part of a proposed comprehensive scheme for the fibre-optic monitoring of cable accessories. After specifying the underlying design goals the improved fibre-optic sensor design is outlined. It is experimentally shown that it offers about ten-fold improvement over a previously investigated resonant cantilever-type design in terms of detection limit, making it competitive with conventional piezoelectric transducers, however with the added compatibility with strong electrical fields and electromagnetically noisy environments.

  19. Trouble-shooting dual arch impressions II.

    PubMed

    Kaplowitz, G J

    1997-09-01

    Dual arch impression procedures can produce accurate impressions and bite registrations for the fabrication of single crowns. To accomplish this, the dentist must select an appropriately sized and shaped tray, appropriate impression material and a dual arch impression procedure suitable for each case. Dual arch impression procedures can save impression material and chair time.

  20. Investigation of dental alginate and agar impression materials as a brain simulant for ballistic testing.

    PubMed

    Falland-Cheung, Lisa; Piccione, Neil; Zhao, Tianqi; Lazarjan, Milad Soltanipour; Hanlin, Suzanne; Jermy, Mark; Waddell, J Neil

    2016-06-01

    Routine forensic research into in vitro skin/skull/brain ballistic blood backspatter behavior has traditionally used gelatin at a 1:10 Water:Powder (W:P) ratio by volume as a brain simulant. A limitation of gelatin is its high elasticity compared to brain tissue. Therefore this study investigated the use of dental alginate and agar impression materials as a brain simulant for ballistic testing. Fresh deer brain, alginate (W:P ratio 91.5:8.5) and agar (W:P ratio 81:19) specimens (n=10) (11×22×33mm) were placed in transparent Perspex boxes of the same internal dimensions prior to shooting with a 0.22inch caliber high velocity air gun. Quantitative analysis to establish kinetic energy loss, vertical displacement elastic behavior and qualitative analysis to establish elasticity behavior was done via high-speed camera footage (SA5, Photron, Japan) using Photron Fastcam Viewer software (Version 3.5.1, Photron, Japan) and visual observation. Damage mechanisms and behavior were qualitatively established by observation of the materials during and after shooting. The qualitative analysis found that of the two simulant materials tested, agar behaved more like brain in terms of damage and showed similar mechanical response to brain during the passage of the projectile, in terms of energy absorption and vertical velocity displacement. In conclusion agar showed a mechanical and subsequent damage response that was similar to brain compared to alginate.

  1. Investigation of dental alginate and agar impression materials as a brain simulant for ballistic testing.

    PubMed

    Falland-Cheung, Lisa; Piccione, Neil; Zhao, Tianqi; Lazarjan, Milad Soltanipour; Hanlin, Suzanne; Jermy, Mark; Waddell, J Neil

    2016-06-01

    Routine forensic research into in vitro skin/skull/brain ballistic blood backspatter behavior has traditionally used gelatin at a 1:10 Water:Powder (W:P) ratio by volume as a brain simulant. A limitation of gelatin is its high elasticity compared to brain tissue. Therefore this study investigated the use of dental alginate and agar impression materials as a brain simulant for ballistic testing. Fresh deer brain, alginate (W:P ratio 91.5:8.5) and agar (W:P ratio 81:19) specimens (n=10) (11×22×33mm) were placed in transparent Perspex boxes of the same internal dimensions prior to shooting with a 0.22inch caliber high velocity air gun. Quantitative analysis to establish kinetic energy loss, vertical displacement elastic behavior and qualitative analysis to establish elasticity behavior was done via high-speed camera footage (SA5, Photron, Japan) using Photron Fastcam Viewer software (Version 3.5.1, Photron, Japan) and visual observation. Damage mechanisms and behavior were qualitatively established by observation of the materials during and after shooting. The qualitative analysis found that of the two simulant materials tested, agar behaved more like brain in terms of damage and showed similar mechanical response to brain during the passage of the projectile, in terms of energy absorption and vertical velocity displacement. In conclusion agar showed a mechanical and subsequent damage response that was similar to brain compared to alginate. PMID:27131216

  2. Evaluation of Force Degradation Pattern of Elastomeric Ligatures and Elastomeric Separators in Active Tieback State.

    PubMed

    Mohammadi, Amir; Mahmoodi, Farhang

    2015-01-01

    Background and aims. The purpose of this study was to evaluate initial force and force decay of commercially available elastomeric ligatures and elastomeric separators in active tieback state in a simulated oral environment. Materials and methods. A total of 288 elastomeric ligatures and elastomeric separators from three manufacturers (Dentaurum, RMO, 3M Unitek) were stretched to 100% and 150% of their original inner diameter. Force levels were measured initially and at 3-minute, 24-hour, and 1-, 2-, 3- and 4-week intervals. Data were analyzed by univariate analysis of variance and a post hoc Tukey test. Results. The means of initial forces of elastomeric ligatures and separators from three above-mentioned companies, when stretched to 100% of their inner diameters, were 199, 305 and 284 g, and 330, 416, 330 g; when they were stretched to 150% of their inner diameters the values were 286, 422 and 375 g, and 433, 540 and 504 g, respectively. In active tieback state, 11-18% of the initial force of the specimens was lost within the first 3 minutes and 29-63% of the force decay occurred in the first 24 hours; then force decay rate decreased. 62-81% of the initial force was lost in 4 weeks. Although force decay pattern was identical in all the products, the initial force and force decay of Dentaurum elastomeric products were less than the similar products of other companies (P<0.05). Under the same conditions, the force of elastomeric separators was greater than elastomeric ligatures of the same company. Conclusion. Regarding the force pattern of elastomeric ligatures and separators and optimal force for tooth movement, many of these products can be selected for applying orthodontic forces in active tieback state.

  3. Evaluation of Force Degradation Pattern of Elastomeric Ligatures and Elastomeric Separators in Active Tieback State

    PubMed Central

    Mohammadi, Amir; Mahmoodi, Farhang

    2015-01-01

    Background and aims. The purpose of this study was to evaluate initial force and force decay of commercially available elastomeric ligatures and elastomeric separators in active tieback state in a simulated oral environment. Materials and methods. A total of 288 elastomeric ligatures and elastomeric separators from three manufacturers (Dentaurum, RMO, 3M Unitek) were stretched to 100% and 150% of their original inner diameter. Force levels were measured initially and at 3-minute, 24-hour, and 1-, 2-, 3- and 4-week intervals. Data were analyzed by univariate analysis of variance and a post hoc Tukey test. Results. The means of initial forces of elastomeric ligatures and separators from three above-mentioned companies, when stretched to 100% of their inner diameters, were 199, 305 and 284 g, and 330, 416, 330 g; when they were stretched to 150% of their inner diameters the values were 286, 422 and 375 g, and 433, 540 and 504 g, respectively. In active tieback state, 11-18% of the initial force of the specimens was lost within the first 3 minutes and 29-63% of the force decay occurred in the first 24 hours; then force decay rate decreased. 62-81% of the initial force was lost in 4 weeks. Although force decay pattern was identical in all the products, the initial force and force decay of Dentaurum elastomeric products were less than the similar products of other companies (P<0.05). Under the same conditions, the force of elastomeric separators was greater than elastomeric ligatures of the same company. Conclusion. Regarding the force pattern of elastomeric ligatures and separators and optimal force for tooth movement, many of these products can be selected for applying orthodontic forces in active tieback state. PMID:26889363

  4. A pilot study to determine the effects of skin contact on two commonly used dental impression materials.

    PubMed

    Steyn, N; Botha, S J; Brand, P D; Bernitz, H

    2006-12-01

    Impression materials used in the analysis of bite marks are required to maintain their stability and integrity for extended periods. It has been observed that certain impressions taken of skin lose their properties with time, becoming sticky and unusable as evidence. The objective of this study was to investigate the onset of "stickiness" in two commonly used dental impression materials when brought into contact with skin. The two materials tested were Impregum and President. They were syringed into glass rings positioned on the upper arms of 28 volunteers. Changes in stickiness were monitored over a four-month period using a tensile testing machine. A metal plunger was lowered onto the impression material and then retracted measuring the adhesive force of the material to the lower surface of the plunger. Over the research period 17 of the 28 rings of Impregum became sticky and changed colour from purple to turquoise. The remaining 11 Impregum samples, all the President samples and all control samples remained unchanged over the 120 day period. The results of this study show that certain factors present in or on skin are responsible for the loss of surface integrity of Impregum. The factors responsible for these changes have not been established.

  5. The influence of mixing methods and disinfectant on the physical properties of alginate impression materials.

    PubMed

    Dreesen, Karoline; Kellens, Annelies; Wevers, Martine; Thilakarathne, Pushpike J; Willems, Guy

    2013-06-01

    The aims of this in vitro study were to quantify the effect of manual versus automatic mixing and of using a disinfectant on mechanical properties of three different alginate impression materials. Two of the three alginates tested were especially developed for orthodontic use: Orthotrace® and Orthofine® while the third was a conventional alginate CA37FS®. Alginates were mixed by hand or automatically using a Cavex alginate mixer II®. Mixing was performed at room temperature using tap water. The material was allowed to set in a water bath at 35°C (±1°C), simulating intra-oral setting conditions, and half of the samples were disinfected before testing. For each tested material, 10 standardized samples were used. The disinfectant used was the CavexImpreSafe® that has a bactericide, virucide, and fungicide function. The specimens were exposed for 3 minutes in a 3% solution and were then tested according to the ISO 1563: 1990 (E) standard specifications. Descriptive statistics and three-way analysis of variance were performed, and a 5% significance level was used for statistical analysis. Evaluation of tensile strength and elastic recovery of different alginate samples, hand versus automatical mixing or disinfected versus not disinfected, resulted in significant differences for all materials except for Orthofine®. Considering detail reproduction, all three alginates evaluated reproduced the 50-μm line successfully without interruption. The mixing method can significantly affect the elastic recovery and tensile strength of the alginates tested while the effect of using a disinfectant is less explicit.

  6. Single Stage Silicone Border Molded Closed Mouth Impression Technique-Part II.

    PubMed

    Solomon, E G R

    2011-09-01

    Functioning of a complete denture depends to a great extent on the impression technique. Several impression techniques have been described in the literature since the turn of this century when Greene [Clinical courses in dental prothesis, 1916] brothers introduced the first scientific system of recording dental impression. Advocates of each technique have their own claim of superiority over the other. The introduction of elastomeric impression materials [Skinner and Cooper, J Am Dent Assoc 51:523-536, 1955] has made possible new techniques of recording impression for complete denture construction. These rubber like materials are of two types; one has a polysulfide base and is popularily known as polysulfide rubber (Thiokol and Mercaptan). The other variety has a silicone base known as silicone rubber or silicone elastomer. Silicone elastomers are available in four different consistencies; a thin easy flowing light bodied material,a creamy medium bodied material, a highly viscous heavy bodied material and a kneadable putty material. This paper describes an active closed mouth impression technique with one stage border molding using putty silicone material as a substitute for low fusing compound. PMID:22942578

  7. Effect of five brands of latex gloves on the setting time of polyvinyl siloxane putty impression materials.

    PubMed

    Ravikumar, C M; Sangur, Rajashekar

    2012-01-01

    Addition silicone impression materials have been used as impression material for more than 20 years. Although they are among the most expensive impression materials, they became popular during the past decade as they have excellent physical properties. Prevention of infection is an important aspect in dental treatment since dental professionals are routinely exposed to the wide variety of microorganisms present in saliva. Gloves are the most common protective measure used during dental treatment. The gloves are mostly made of latex. In this study, we examine how the setting time of three types polyvinyl putty materials were affected by the use of five different brands of latex gloves and one brand of vinyl gloves. Each material was first mixed without wearing gloves according to the manufacturer's instructions. After the stipulated mixing time, the setting time was measured using the Vicat needle. The setting time is measured from the time of mixing till the time that the needle does not produce any indentation on the surface of the material. The putty material was then mixed with gloved hands (using the five different brands of latex gloves in turn) and the setting time was measured. Then the material was mixed with washed gloved hands, and the setting time was measured again. Finally, the material was mixed with vinyl gloved hands and the setting time was measured. The following conclusions were drawn from the study: Reprosil and Express showed significant variation in the setting time with the latex gloved hands.There was no significant variation in the setting time when material was mixed with unwashed vs washed gloved hands.Vinyl gloves did not significantly affect the setting time of any of the putty impression materials.

  8. Efficacy of different disinfectant systems on alginate and addition silicone impression materials of Indian and international origin: a comparative evaluation.

    PubMed

    Samra, R K; Bhide, S V

    2010-09-01

    Study was planned to evaluate the efficacy of commonly used disinfectants and to study qualitatively and quantitatively the persistence of microflora on the untreated (control group) and the disinfected impression surface after 24 h. Disinfectant systems used were immersion systems like glutaraldehyde, sodium hypochlorite and the ultraviolet chamber. The effect of disinfectant on most commonly used Indian impression materials was carried out in this study and results compared with the most commonly used foreign brands for irreversible hydrocolloid and addition silicone. Impressions were made of 25 healthy volunteers. These were disinfected and incubated in an incubator for 24 h at 37°C for aerobic organisms. The inoculation in nutrient media was done to test the viability of microorganisms that can persist after rinsing and disinfection of the impression surface. The colony forming units were counted and compared with that of control group. Control group of all the impression material samples showed growth of Streptococcus viridans, Diphtheroids, Streptococcus pneumoniae to a greater extent. The growth of Candida albicans, Pseudomonas aerugenosa and Staphyloccus albus was present in all the groups but to a lesser extent. The persistence of the microflora on the impression surface of both the studied brands was similar but the concentration of organisms in the alginate control group was two folds as compared to addition silicone group. Use of ultraviolet chamber gave better results compared to the studied immersion systems. All the disinfection systems were effective in reducing the microbial load with ultraviolet chamber as the most effective. PMID:21886411

  9. To study the flow property of seven commercially available zinc oxide eugenol impression material at various time intervals after mixing.

    PubMed

    Katna, Vishal; Suresh, S; Vivek, Sharma; Meenakshi, Khandelwal; Ankita, Gaur

    2014-12-01

    Aims and objective of the study was to evaluate the flow property of seven commercially available zinc oxide eugenol impression materials at various time intervals, after mixing 49 samples (seven groups) were fabricated for flow property of the material. The sample were fabricated as equal length of base and accelerator paste of the test materials was taken on the glass slab and mixed with a rigid stainless steel spatula as per manufacturers recommendation till the homogenous mix was obtained. The mix material was loaded in glass syringe and 0.5 ml material was injected on a cellophane sheet placed on marked glass plate. A cellophane sheet and glass plate 70 and 500 g weight was carefully placed on freshly dispensed zinc oxide eugenol impression paste sequentially. The diameter of the mix was noted after 30 s and 1 min of load application and also after the final set of material. The diameter gives the flow of material. The samples were stored at the room temperature. The data of the flow property was analyzed with analysis of variance, Post hoc test and t test. The flow of the zinc oxide eugenol impression paste after 30 s, 1 min and final set of load application for Group A to Group G was noted. Maximum flow was seen for Group G zinc oxide eugenol impression material followed by Group F, D, E, B, C and A in descending order respectively after 30 s, where as the flow property changed after 1 min in the sequence of maximum for Group G followed by Group E, D, B, A, C, and F. Lastly after final set of the impression material the flow maximum for Group G followed by Group E, D, C, F, A and B in descending order. Based on statistical analysis of the results and within in the limitations of this in-vitro study, the following conclusions were drawn that; the flow of zinc oxide eugenol impression material after 30 s, 1 min and that after the final set was maximum for P.S.P. (Group G) and the flow for PYREX (Group A) was minimum.

  10. An ideal material for the preparation of known toolmark test impressions.

    PubMed

    Petraco, Nicholas; Petraco, Nicholas D; Pizzola, Peter A

    2005-11-01

    Traditionally, toolmark test exemplars are produced by applying a tool's working surface to a piece of soft metal such as lead. Soft, pliable metals are primarily used for this purpose because they will replicate the microscopic grooves present on a tool's working surface without damaging the tool. In this paper the authors present an alternative material for the preparation of test toolmarks. Jewelry modeling or carving waxes are utilized in this study. These waxes are designed for the jewelry modeling industry to create very fine, highly detailed wax models of jewelry pieces that will be cast in various metals utilizing the lost wax casting method. Jeweler's waxes have been found to be ideal for preparing test toolmarks from exemplar tools. The test tool's working surface is applied to a piece of the appropriate wax in a manner consistent with the tool's design. The replicas obtained are exact, highly detailed, 1:1, negative impressions of the exemplar tools working surface, have a long shelf-life, and are suitable for use in toolmark examination and comparison cases. PMID:16382836

  11. Dimensional stability of a polyvinylsiloxane impression material following ethylene oxide and steam autoclave sterilization.

    PubMed

    Holtan, J R; Olin, P S; Rudney, J D

    1991-04-01

    Polyvinlsiloxane impressions were made from a stainless steel master die machined to stimulate five full veneer crown preparations symmetrically placed in an arch form. Three groups of 10 impressions each were made. Treatment groups were sterilized using an ethylene oxide gas and a conventional steam autoclave. Casts were poured and intrapreparation, height, and diameter measurements were made using a stereomicroscope, a digital electronic caliper, and a 1-inch travel dial indicator. Analysis of dimensional changes for the two groups showed that casts made from impressions sterilized by ethylene oxide are acceptable for use in the construction of fixed or removable prostheses. Casts made from impressions sterilized in a steam autoclave can be used for the fabrication of diagnostic casts and some transitional prostheses, but not for routine construction of crowns or fixed partial dentures.

  12. Prediction of fluid behavior in elastomeric seals

    SciTech Connect

    Ho, E.; Flitney, R.K.; Nau, B.S.

    1993-12-31

    Fluids sealed under pressure dissolve in the surface of elastomeric seals and then proceed to diffuse into the interior. In the case of gases, a subsequent decompression of the sealed fluid can result in dissolved gas coming out of solution in the interior of the elastomeric material and causing structural damage, explosive decompression. As part of a broader program of work concerned with seal life prediction, software has been developed for the prediction of elastomer/fluid interactions. This computer model is briefly described and examples of results are presented for a variety of operating conditions, seal materials, seal types, and fluids.

  13. Comparative evaluation of pressure generated on a simulated maxillary oral analog by impression materials in custom trays of different spacer designs: An in vitro study

    PubMed Central

    Chopra, Sakshi; Gupta, Narendra Kumar; Tandan, Amrit; Dwivedi, Ravi; Gupta, Swati; Agarwal, Garima

    2016-01-01

    Introduction: Literature reveals that masticatory load on denture bearing tissues through complete dentures should be maximum on primary stress bearing areas and least on relief area in accordance with the histology of underlying tissues. A study to validate the existing beliefs was planned to compare the pressure on mucosa using selective pressure technique and minimal pressure technique, with the incorporation of two different impression materials utilizing the pressure sensors during secondary impression procedure. Materials and Methods: The study was performed using a maxillary analog. Three pressure sensors were imbedded in the oral analog, one in the mid palatine area and the other two in the right and left ridge crest. Custom trays of two different configurations were fabricated. The two impression materials tested were light body and zinc oxide eugenol. A total of 40 impressions were made. A constant weight of 1 kg was placed, and the pressure was recorded as initial and end pressures. Results: A significant difference in the pressure produced using different impression materials was found (P < 0.001). Light body vinyl polysiloxane produced significantly lesser pressure than zinc oxide eugenol impression materials. The presence of relief did affect the magnitude of pressure at various locations. Conclusion: All impression materials produced pressure during maxillary edentulous impression making. Tray modification is an important factor in changing the amount of pressure produced. The impression materials used also had a significant role to play on the pressures acting on the tissues during impression procedure. Clinical Implication: Light body VPS impression material may be recommended to achieve minimal pressure on the denture bearing tissues in both selective as well as minimal pressure techniques. PMID:27041902

  14. Conductive elastomeric extensometer

    NASA Technical Reports Server (NTRS)

    Gause, R. L.; Glenn, C. G. (Inventor)

    1974-01-01

    An extensometer was used for measuring surface area changes of the human body caused by expansion and contraction of the body. A relatively thin and wide strain responsive conductive elastomeric band was adapted for application to a part of the body, such as around a limb or the trunk of the body. The elastomeric band is incorporated as a resistor in a balanced bridge circuit. Expansion or contraction of the portion of the body on which the elastomeric band is applied causes a change in the resistance of the band and a resultant imbalance of the bridge circuit. The output of the amplifier in volts is suitable for proving the desired reading through a recorder, oscilloscope or voltmeter.

  15. Preservation of the negative image of tooth enamel with dental impression material enhances morphometric measurements of gingival overgrowth.

    PubMed

    Miller, Marian L; Andringa, Anastasia; Turner, Lloyd T; Dalton, Timothy P; Derkenne, Sandrine; Nebert, Daniel W

    2003-04-01

    Gingival overgrowth is a common health problem caused by genetic and environmental risk factors. Animal models for quantitative histological studies are needed to uncover genetic predisposition and dose-response data that might put individuals at increased risk for gingival disease. Gingival height, thickness, inflammation, and the degree of encroachment of gingiva over the tooth, are clinical measures of overgrowth; most of these parameters can be measured histologically, but in order to quantify gingival coverage of the tooth, the image of the crown must be present. Tooth and bone typically require decalcification for histology; thus, the tooth crown, a critical landmark, is lost. We describe a method for imaging the crown histologically, using impression materials applied to dissected mouse mandibles. Four dental alginates, three polyvinyl siloxanes, and one polyether and gelatin were used. The impression-material/mandibular tissue blocks were processed routinely. Polyvinyl siloxanes were incompatible with embedding resin; alginates, polyether and gelatin could be fixed, decalcified, embedded, and sectioned. Alginates and gelatin could be stained. Success in imaging the tooth crown varied with the preparation, but the alginates, polyether, and gelatin permitted a useful degree of measurement of exposed crown and enamel thickness, along with other morphometric parameters such as thickness of the dentin, lateral mandibular ramus, rete pegs, height of the gingiva, and volume density of vessels and inflammatory cells in the lamina propria. In conclusion, this new application for impression materials allows gingival coverage of tooth crown, as well as numerous other parameters to be measured for comparison with clinical data.

  16. Influence of alginate impression materials and storage time on surface detail reproduction and dimensional accuracy of stone models.

    PubMed

    Guiraldo, Ricardo D; Moreti, Ana F F; Martinelli, Julia; Berger, Sandrine B; Meneghel, Luciana L; Caixeta, Rodrigo V; Sinhoreti, Mário A C

    2015-01-01

    This study compared the surface detail reproduction and dimensional accuracy of stone models obtained from molds prepared using different alginate impression materials (Cavex ColorChange, Hydrogum 5, or Jeltrate Plus) and with different storage times (1, 3, and 5 days) to models from molds that were filled immediately with no storage time. The molds were prepared over a matrix containing 50-μm line, (ISO 1563 standard) under pressure with a perforated metal tray. The molds were removed 2 minutes after loss of sticky consistency and either filled immediately or stored in closed jars at 100% relative humidity and 37°C for 1, 3, or 5 days. The molds were filled with dental plaster (Durone IV). Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy on the 50-μm wide line, which was 25 mm in length, according to ISO 1563 standard. The dimensional accuracy results (%) were subjected to analysis of variance. The 50-μm wide line (ISO 1563 standard) was completely reproduced by all alginate impression materials regardless of the storage time. There was no statistically significant difference in the mean dimensional accuracy values of stone models made from molds composed of different alginate impression materials and with different storage times (p = 0.989). In conclusion, storing the mold for five days prior to filling did not change the surface detail reproduction or dimensional accuracy of the alginates examined in this study.

  17. Highly tunable elastomeric silk biomaterials

    PubMed Central

    Partlow, Benjamin P.; Hanna, Craig W.; Rnjak-Kovacina, Jelena; Moreau, Jodie E.; Applegate, Matthew B.; Burke, Kelly A.; Marelli, Benedetto; Mitropoulos, Alexander N.; Omenetto, Fiorenzo G.

    2014-01-01

    Elastomeric, fully degradable and biocompatible biomaterials are rare, with current options presenting significant limitations in terms of ease of functionalization and tunable mechanical and degradation properties. We report a new method for covalently crosslinking tyrosine residues in silk proteins, via horseradish peroxidase and hydrogen peroxide, to generate highly elastic hydrogels with tunable properties. The tunable mechanical properties, gelation kinetics and swelling properties of these new protein polymers, in addition to their ability to withstand shear strains on the order of 100%, compressive strains greater than 70% and display stiffness between 200 – 10,000 Pa, covering a significant portion of the properties of native soft tissues. Molecular weight and solvent composition allowed control of material mechanical properties over several orders of magnitude while maintaining high resilience and resistance to fatigue. Encapsulation of human bone marrow derived mesenchymal stem cells (hMSC) showed long term survival and exhibited cell-matrix interactions reflective of both silk concentration and gelation conditions. Further biocompatibility of these materials were demonstrated with in vivo evaluation. These new protein-based elastomeric and degradable hydrogels represent an exciting new biomaterials option, with a unique combination of properties, for tissue engineering and regenerative medicine. PMID:25395921

  18. Friction of orthodontic elastomeric ligatures with different dimensions.

    PubMed

    Chimenti, Claudio; Franchi, Lorenzo; Di Giuseppe, Maria Grazia; Lucci, Maria

    2005-05-01

    The aim of this study was to evaluate in vitro the effect of variations in the size of elastomeric ligatures on the static frictional resistance generated by orthodontic sliding mechanics under dry condition. Frictional forces generated by elastomeric ligatures treated with a lubricating material (silicone) were analyzed as well. An Instron testing machine was used to assess the static frictional forces of a 0.019 x 0.025-inch stainless steel rectangular wire that was ligated to a molar convertible tube and to three stainless steel 0.022-inch pre-adjusted brackets with elastomeric ligatures with different dimensions: small, medium, and large. The static friction produced by two prototypes of silicone-lubricated elastomeric ligatures was also measured. The small and medium elastomeric ligatures produced significantly less friction than the large ligatures. No statistically significant difference was found between small and medium ligatures. The decrease in frictional forces of small and medium modules had to be ascribed mainly to the smaller thickness of both ligatures with respect to large ligatures. The lubricated elastomeric ligatures generated significantly smaller frictional forces than nonlubricated elastomeric ligatures with different dimensions. The variation in the dimensions of the elastomeric ligatures is able to influence the static frictional resistance generated by orthodontic sliding mechanics in the buccal segments. The use of small and medium elastomeric ligatures determines a 13-17% decrease in static friction compared with large ligatures. Silicone-lubricated modules can reduce static friction by 23-34% with respect to the small and medium nonlubricated elastomeric ligatures and by 36-43% compared with nonlubricated large ligatures.

  19. Inadvertent insertion of hearing aid impression material into the middle ear: Case report and implications for future community hearing services☆

    PubMed Central

    Algudkar, Ashwin; Maden, Belma; Singh, Arvind; Tatla, Taran

    2013-01-01

    INTRODUCTION The creation of ear moulds for hearing aids is generally considered a safe and routine procedure for trained professionals. In the literature there are reports of otological complications caused by hearing aid mould impression material in the middle ear cavity but such complications are considered rare. PRESENTATION OF CASE We present the case of a patient in whom impression material entered the middle ear through a perforation of the tympanic membrane during the process of making a hearing aid mould and review how this was managed. DISCUSSION We discuss how many aspects of the British Society of Audiology guidelines were not followed during this procedure and make recommendations as to how independent community practitioners need to be closely supervised with regular review to minimise the risks of such complications. CONCLUSION Our report demonstrates how a serious otological complication from the creation of a hearing aid impression in a community based private hearing clinic was managed. The reporting of such complications is rare but the incidence is likely to be much higher than the literature would suggest. We recommend and advise how these adverse incidents may be minimised and managed through competency reviews and formal referral links from community centres to hospital otolaryngology/audiology departments. PMID:24262374

  20. [Studies on the cytotoxic action of various silicone rubber impression materials by means of cell culture (author's transl)].

    PubMed

    Watanabe, H

    1977-07-01

    Biological test of the silicone rubber impression materials was done by utilizing tissue cultures of L strain cells. Criteria for cytotoxicity were based upon response index in agar diffusion method which was determined by zone index and lysis index, and morphological observations of the cells. The materials used were chosen among those which were commercially available. Base material, catalyst, unset and set mixes of both materials were tested respectively. X-ray fluorescence analysis of the material was also performed. Following results were obtained. 1) Base material of all the materials showed zone index of a range between 11.8 mm and 18.6 mm. On the otherhand, lysis index was relatively small and minimum response index was 11.8 mm/8.6 mm. The cells appeared normal after cultivation with the base materials, though tissue culture medium became opaque due to dissolution of the base materials. It is revealed that the above results mean little cytotoxicity to the cells. 2) Catalyst, on the otherhand, yielded intense cytotoxicity. Minimum response index for the catalyst was 13.4 mm/14.8 mm. Morphological observation was parallel to the results of agar diffusion method. 3) Unset mixes also yielded intense to moderate cytotoxicity. 4) Set mixes showed a similar in level of cytotoxicity to the unset mixes. 5) X-ray fluorescence analysis of the materials revealed existence of such elements as Si, Sr, Sn, S, Cu and Fe. Moreover, Zn was found in materials A, B, C, D and E; P in materials A and B, and Pb in materials E and F. However, it was unable to show what compound was formed by these elements. It is expected that the present results could give a clue on animal experiments or clinical use from the view point of biocompatibility of silicone rubber impression materials. PMID:282367

  1. Trouble-shooting dual arch impressions.

    PubMed

    Kaplowitz, G J

    1996-02-01

    Dual arch impression techniques enable the dentist to capture an impression of the prepared tooth, the opposing teeth and the occlusal registration in one procedure. This saves chair time and impression material.

  2. An Investigation into the Accuracy of Two Currently Available Dental Impression Materials in the Construction of Cobalt-Chromium Frameworks for Removable Partial Dentures.

    PubMed

    Dubal, Rajesh Kumar; Friel, Tim; Taylor, Philip D

    2015-03-01

    This study investigated the suitability of irreversible hydrocolloid as an impression material for cobalt-chromium framework construction. Scans of casts derived from (1) alginate and (2) addition-cured polyvinylsiloxane impressions were superposed on to a control. The differences within and between groups were compared at fixed landmarks. The investigation revealed a high degree of scan coincidence within and between groups. However, certain features, such as undercuts, resulted in a lower degree of scan coincidence. Irreversible hydrocolloid appears to be a viable alternative to addition-cured polyvinyl-siloxane as an impression material for cobalt-chromium framework construction.

  3. Surface detail reproduction and dimensional accuracy of stone models: influence of disinfectant solutions and alginate impression materials.

    PubMed

    Guiraldo, Ricardo Danil; Borsato, Thaís Teixeira; Berger, Sandrine Bittencourt; Lopes, Murilo Baena; Gonini-Jr, Alcides; Sinhoreti, Mário Alexandre Coelho

    2012-01-01

    This study compared the surface detail reproduction and dimensional accuracy of stone models obtained from molds disinfected with 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to models produced using molds which were not disinfected, with 3 alginate materials (Cavex ColorChange, Hydrogum 5 and Jeltrate Plus). The molds were prepared over matrix containing 20-, 50-, and 75-µm lines, performed under pressure with perforated metal tray. The molds were removed following gelation and either disinfected (using one of the solutions by spraying followed by storage in closed jars for 15 min) or not disinfected. The samples were divided into 12 groups (n=5). Molds were filled with dental gypsum Durone IV and 1 h after the start of the stone mixing the models were separated from the tray. Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy on the 50-µm line with 25 mm in length, in accordance with the ISO 1563 standard. The dimensional accuracy results (%) were subjected to ANOVA. The 50 µm-line was completely reproduced by all alginate impression materials regardless of the disinfection procedure. There was no statistically significant difference in the mean values of dimensional accuracy in combinations between disinfectant procedure and alginate impression material (p=0.2130) or for independent factors. The disinfectant solutions and alginate materials used in this study are no factors of choice regarding the surface detail reproduction and dimensional accuracy of stone models.

  4. Elastomeric actuator devices for magnetic resonance imaging

    NASA Technical Reports Server (NTRS)

    Dubowsky, Steven (Inventor); Hafez, Moustapha (Inventor); Jolesz, Ferenc A. (Inventor); Kacher, Daniel F. (Inventor); Lichter, Matthew (Inventor); Weiss, Peter (Inventor); Wingert, Andreas (Inventor)

    2008-01-01

    The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as .+-.20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex.

  5. Method for making an elastomeric member with end pieces

    DOEpatents

    Hoppie, L.O.; McNinch, J.H. Jr.; Nowell, G.C.

    1984-10-23

    A molding process is described for molding an elongated elastomeric member with wire mesh sleeves bonded to the ends. A molding preform of elastomeric material is positioned within a seamless mold cylinder, and the open ends of the wire mesh sleeves are mounted to end plug assemblies slidably received into the mold cylinder and positioned against the ends of the preform. A specialized profile is formed into surfaces of the respective end plug assemblies and by heating of the mold, the ends of the elastomeric preform are molded to the profile, as well as bonded to the reinforcing wire mesh sleeves. Vacuum is applied to the interior of the mold to draw outgassing vapors through relief spaces there through. The completed elastomeric member is removed from the mold cylinder by stretching, the consequent reduction in diameter enabling ready separation from the mold cylinder and removal thereof. 9 figs.

  6. Method for making an elastomeric member with end pieces

    DOEpatents

    Hoppie, Lyle O.; McNinch, Jr., Joseph H.; Nowell, Gregory C.

    1984-01-01

    A molding process for molding an elongated elastomeric member (60) with wire mesh sleeves (16) bonded to the ends (14). A molding preform (10) of elastomeric material is positioned within a seamless mold cylinder (26), and the open ends of the wire mesh sleeves (16) are mounted to end plug assemblies (30) slidably received into the mold cylinder (26) and positioned against the ends (14) of the preform (10). A specialized profile is formed into surfaces (44) of the respective end plug assemblies (30) and by heating of the mold (26), the ends (14) of the elastomeric preform (10) are molded to the profile, as well as bonded to the reinforcing wire mesh sleeves (16). Vacuum is applied to the interior of the mold to draw outgassing vapors through relief spaces therethrough. The completed elastomeric member (60) is removed from the mold cylinder (26) by stretching, the consequent reduction in diameter enabling ready separation from the mold cylinder (26) and removal thereof.

  7. The release of fluoride from two products of alginate impression materials.

    PubMed

    Hattab, F; Frostell, G

    1980-01-01

    The purpose of this study was to determine the fluoride content of two products of alginate and the possible fluoride transfer to the teeth, saliva and blood. The total fluoride content of Zelgan normal-set and Kerr alginate fastset powder was assayed by direct diffusion and diffusion of the ash. The soluble fluoride leaching out in water over 24 hour was also determined. The results show that the fluoride contents of Zelgan and Kerr alginate powders are about 1.9% and 1.5% fluoride, respectively. Of the fluoride present in Zelgan and Kerr approximately 6.5% and 5.8%, respectively, leached out in 400 ml deionized water. The fluoride uptake was estimated in two adjacent enamel layers each approximately 7 micrometers thick, using 10 teeth exposed for 5 minutes and 18 h to the alginate gel (Zelgan). The results of acid etch microsamplings indicate a significant increase in the fluoride concentration of the first enamel layer after both 5 min and 18 h exposure. Fluoride uptake within the second enamel layer was insignificant, however. Fluoride transfer to the oral saliva and to the blood was evident after impression taking.

  8. Comparison of the transfer precision of three different impression materials in combination with transfer caps for the Frialit-2 system.

    PubMed

    Lorenzoni, M; Pertl, C; Penkner, K; Polansky, R; Sedaj, B; Wegscheider, W A

    2000-07-01

    Transfer of the precise position of implants to a master cast is a prerequisite for accurate and passive fit of the superstructure. Implants lack the mobility of natural teeth and, therefore, inaccurate frameworks result in stress within the mechanical parts and the implant-bone interface. Various impression methods have been described to achieve accurate reproduction of the intra-oral relation of the implants. The aim of this experimental study was to compare three different impression materials (polyether, polyvinyl siloxane, hydrocolloid) with the Frialit(R)-2 system and with the indirect technique. In addition, the use of transfer caps (TCs) to improve transfer precision was tested with all three materials. All measurements were performed using a three-dimensional (3D) co-ordinate measuring machine that is capable of locating points in space and calculating the relative distortions as angles of tilt (rot-XY, rot-XZ, rot-YZ) and 3D displacement. The results suggest that addition-silicone (a-silicone) and polyether are the materials of choice for implant transfer procedures. The use of TCs resulted in a significantly reduced rotation in the XY-plane but did not improve the absolute 3D displacement. A-silicone with the use of TCs proved to be most precise. Comparison between polyether and polyvinyl siloxane showed significant differences in the XY-rotation and the 3D displacement in favour of the silicone. Because the mean distortions between the original model and the master casts were about 100 microm, absolutely precise fit may be unattainable owing to the physical properties of the materials. Further studies will have to evaluate the amount of tolerable stress at the implant-bone interface. PMID:10931257

  9. Compatibility Study for Plastic, Elastomeric, and Metallic Fueling Infrastructure Materials Exposed to Aggressive Formulations of Ethanol-blended Gasoline

    SciTech Connect

    Kass, Michael D; Pawel, Steven J; Theiss, Timothy J; Janke, Christopher James

    2012-07-01

    In 2008 Oak Ridge National Laboratory began a series of experiments to evaluate the compatibility of fueling infrastructure materials with intermediate levels of ethanol-blended gasoline. Initially, the focus was elastomers, metals, and sealants, and the test fuels were Fuel C, CE10a, CE17a and CE25a. The results of these studies were published in 2010. Follow-on studies were performed with an emphasis on plastic (thermoplastic and thermoset) materials used in underground storage and dispenser systems. These materials were exposed to test fuels of Fuel C and CE25a. Upon completion of this effort, it was felt that additional compatibility data with higher ethanol blends was needed and another round of experimentation was performed on elastomers, metals, and plastics with CE50a and CE85a test fuels. Compatibility of polymers typically relates to the solubility of the solid polymer with a solvent. It can also mean susceptibility to chemical attack, but the polymers and test fuels evaluated in this study are not considered to be chemically reactive with each other. Solubility in polymers is typically assessed by measuring the volume swell of the polymer exposed to the solvent of interest. Elastomers are a class of polymers that are predominantly used as seals, and most o-ring and seal manufacturers provide compatibility tables of their products with various solvents including ethanol, toluene, and isooctane, which are components of aggressive oxygenated gasoline as described by the Society of Automotive Engineers (SAE) J1681. These tables include a ranking based on the level of volume swell in the elastomer associated with exposure to a particular solvent. Swell is usually accompanied by a decrease in hardness (softening) that also affects performance. For seal applications, shrinkage of the elastomer upon drying is also a critical parameter since a contraction of volume can conceivably enable leakage to occur. Shrinkage is also indicative of the removal of one or more

  10. Adhesiveless Transfer Printing of Ultrathin Microscale Semiconductor Materials by Controlling the Bending Radius of an Elastomeric Stamp.

    PubMed

    Cho, Sungbum; Kim, Namyun; Song, Kwangsun; Lee, Jongho

    2016-08-01

    High-performance electronic devices integrated onto unconventional substrates provide opportunities for use in diverse applications, such as wearable or implantable forms of electronic devices. However, the interlayer adhesives between the electronic devices and substrates often limit processing temperature or cause electrical or thermal resistance at the interface. This paper introduces a very simple but effective transfer printing method that does not require an interlayer adhesive. Controlling the bending radius of a simple flat stamp enables picking up or printing of microscale semiconductor materials onto rigid, curvilinear, or flexible surfaces without the aid of a liquid adhesive. Theoretical and experimental studies reveal the underlying mechanism of the suggested approach. Adhesiveless printing of thin Si plates onto diverse substrates demonstrates the capability of this method. PMID:27458878

  11. First Impressions.

    ERIC Educational Resources Information Center

    Coen, Frank

    1969-01-01

    The unreliability of first impressions and subjective judgments is the subject of both Jane Austen's "Pride and Prejudice" and Lionel Trilling's "Of This Time, Of That Place"; consequently, the works are worthwhile parallel studies for high school students. Austen, by means of irony and subtle characterization, dramatizes the need for constant…

  12. Modification of chemical additives to elastomeric compositions

    NASA Astrophysics Data System (ADS)

    Mukhutdinov, A. A.; Grishin, B. S.

    1994-08-01

    The physicochemical principles of the modification of crystalline chemical additives to elastomeric compositions are examined. A classification of various types of modifications based on scientific principles is given. The modifications are subdivided into physical and physicochemical depending on the configuration of the molecules in the crystals, the defectiveness and dispersity of the crystalline particles, the melting points of the crystals, and the presence of necleophilic and electrophylic centres in the molecules of the components of binary and complex eutectic mixtures. The effectiveness of the modification of the chemical additives is determined by the manifestation in binary systems of these components in elastomeric compositions of physical and chemical synergism due to the occurrence of the relevant processes in such systems. A relation has been discovered between the physical and chemical phenomena accompanying the modification of the chemical additives in binary and complex eutectic mixtures, their influence on the properties of the elastomeric composition is examined, the ecological problems associated with the processing of such materials are discussed, and the relation between the structure and properties of the molecules of the additives is analysed using quantum-chemical calculations. The bibliography includes 92 references.

  13. Ghana. Part One-Class Materials. Development Studies No. 1, Third Impression.

    ERIC Educational Resources Information Center

    Jones, Paula; Bourne, Fay

    Background readings and classroom materials dealing with Ghana for use with secondary and college students are provided in this publication. The major historical, social, geographical, and political aspects which have contributed to the present day development of Ghana are examined. The background readings for teachers which comprise section one…

  14. Reproducibility of sterilized rubber impressions.

    PubMed

    Abdelaziz, Khalid M; Hassan, Ahmed M; Hodges, J S

    2004-01-01

    Impressions, dentures and other dental appliances may be contaminated with oral micro-flora or other organisms of varying pathogenicity from patient's saliva and blood. Several approaches have been tried to control the transmission of infectious organisms via dental impressions and because disinfection is less effective and has several drawbacks for impression characterization, several sterilization methods have been suggested. This study evaluated the reproducibility of rubber impressions after sterilization by different methods. Dimensional accuracy and wettability of two rubber impression materials (vinyl polysiloxane and polyether) were evaluated after sterilization by each of three well-known methods (immersion in 2% glutaraldehyde for 10 h, autoclaving and microwave radiation). Non-sterilized impressions served as control. The effect of the tray material on impression accuracy and the effect of topical surfactant on the wettability were also evaluated. One-way ANOVA with Dunnett's method was used for statistical analysis. All sterilizing methods reduced the reproducibility of rubber impressions, although not always significantly. Microwave sterilization had a small effect on both accuracy and wettability. The greater effects of the other methods could usually be overcome by using ceramic trays and by spraying impression surfaces with surfactant before pouring the gypsum mix. There was one exception: glutaraldehyde still degraded dimensional accuracy even with ceramic trays and surfactant. We conclude that a) sterilization of rubber impressions made on acrylic trays was usually associated with a degree of dimensional change; b) microwave energy seems to be a suitable technique for sterilizing rubber impressions; c) topical surfactant application helped restore wettability of sterilized impressions. PMID:15798825

  15. Sterilizing elastomeric chains without losing mechanical properties. Is it possible?

    PubMed Central

    Pithon, Matheus Melo; Ferraz, Caio Souza; Rosa, Francine Cristina Silva; Rosa, Luciano Pereira

    2015-01-01

    OBJECTIVE: To investigate the effects of different sterilization/disinfection methods on the mechanical properties of orthodontic elastomeric chains. METHODS: Segments of elastomeric chains with 5 links each were sent for sterilization by cobalt 60 (Co60) (20 KGy) gamma ray technology. After the procedure, the elastomeric chains were contaminated with clinical samples of Streptococcus mutans. Subsequently, the elastomeric chains were submitted to sterilization/disinfection tests carried out by means of different methods, forming six study groups, as follows: Group 1 (control - without contamination), Group 2 (70°GL alcohol), Group 3 (autoclave), Group 4 (ultraviolet), Group 5 (peracetic acid) and Group 6 (glutaraldehyde). After sterilization/disinfection, the effectiveness of these methods, by Colony forming units per mL (CFU/mL), and the mechanical properties of the material were assessed. Student's t-test was used to assess the number of CFUs while ANOVA and Tukey's test were used to assess elastic strength. RESULTS: Ultraviolet treatment was not completely effective for sterilization. No loss of mechanical properties occurred with the use of the different sterilization methods (p > 0.05). CONCLUSION: Biological control of elastomeric chains does not affect their mechanical properties. PMID:26154462

  16. Robust and Soft Elastomeric Electronics Tolerant to Our Daily Lives.

    PubMed

    Sekiguchi, Atsuko; Tanaka, Fumiaki; Saito, Takeshi; Kuwahara, Yuki; Sakurai, Shunsuke; Futaba, Don N; Yamada, Takeo; Hata, Kenji

    2015-09-01

    Clothes represent a unique textile, as they simultaneously provide robustness against our daily activities and comfort (i.e., softness). For electronic devices to be fully integrated into clothes, the devices themselves must be as robust and soft as the clothes themselves. However, to date, no electronic device has ever possessed these properties, because all contain components fabricated from brittle materials, such as metals. Here, we demonstrate robust and soft elastomeric devices where every component possesses elastomeric characteristics with two types of single-walled carbon nanotubes added to provide the necessary electronic properties. Our elastomeric field effect transistors could tolerate every punishment our clothes experience, such as being stretched (elasticity: ∼ 110%), bent, compressed (>4.0 MPa, by a car and heels), impacted (>6.26 kg m/s, by a hammer), and laundered. Our electronic device provides a novel design principle for electronics and wide range applications even in research fields where devices cannot be used.

  17. Actuating dielectric elastomers in pure shear deformation by elastomeric conductors

    SciTech Connect

    Wang, Yin; Chen, Baohong; Zhou, Jinxiong; Bai, Yuanyuan; Wang, Hong

    2014-02-10

    Pure shear experiments are commonly used to characterize dielectric elastomer (DE) material properties and to evaluate DE actuator/generator performance. It is increasingly important for many applications to replace conventional carbon grease electrodes with stretchable elastomeric conductors. We formulate a theory for DE with elastomeric conductors, synthesize transparent hydrogel as ionic conductors, and measure actuation of DE in pure shear deformation. Maximum 67% actuation strain is demonstrated. The theory agrees well with our measurement and also correlates well with reported experiments on DE with electronic conductors.

  18. Elastomeric Seal Development for Advanced Docking/Berthing System

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher; Oswald, Jay; Dunlap, Patrick; Steinetz, Bruce

    2006-01-01

    Elastomeric seals ar Elastomeric seals are being considered for application to the Advanced Docking / Berthing System. Currently, three candidate elastomers are being evaluated. To meet the unique requirements of the ADBS, several test fixtures have been built to determine each elastomer s Environmental and operating temperature compatibility Material stability when exposed to Atomic Oxygen and Ultraviolet radiation Adhesion force required to separate Compression set Leak rate These results will be compared with those from the metallic seal development to determine the final seal design

  19. Elastomeric Cellular Structure Enhanced by Compressible Liquid Filler

    PubMed Central

    Sun, Yueting; Xu, Xiaoqing; Xu, Chengliang; Qiao, Yu; Li, Yibing

    2016-01-01

    Elastomeric cellular structures provide a promising solution for energy absorption. Their flexible and resilient nature is particularly relevant to protection of human bodies. Herein we develop an elastomeric cellular structure filled with nanoporous material functionalized (NMF) liquid. Due to the nanoscale infiltration in NMF liquid and its interaction with cell walls, the cellular structure has a much enhanced mechanical performance, in terms of loading capacity and energy absorption density. Moreover, it is validated that the structure is highly compressible and self-restoring. Its hyper-viscoelastic characteristics are elucidated. PMID:27221079

  20. Elastomeric Cellular Structure Enhanced by Compressible Liquid Filler

    NASA Astrophysics Data System (ADS)

    Sun, Yueting; Xu, Xiaoqing; Xu, Chengliang; Qiao, Yu; Li, Yibing

    2016-05-01

    Elastomeric cellular structures provide a promising solution for energy absorption. Their flexible and resilient nature is particularly relevant to protection of human bodies. Herein we develop an elastomeric cellular structure filled with nanoporous material functionalized (NMF) liquid. Due to the nanoscale infiltration in NMF liquid and its interaction with cell walls, the cellular structure has a much enhanced mechanical performance, in terms of loading capacity and energy absorption density. Moreover, it is validated that the structure is highly compressible and self-restoring. Its hyper-viscoelastic characteristics are elucidated.

  1. Elastomeric Cellular Structure Enhanced by Compressible Liquid Filler.

    PubMed

    Sun, Yueting; Xu, Xiaoqing; Xu, Chengliang; Qiao, Yu; Li, Yibing

    2016-01-01

    Elastomeric cellular structures provide a promising solution for energy absorption. Their flexible and resilient nature is particularly relevant to protection of human bodies. Herein we develop an elastomeric cellular structure filled with nanoporous material functionalized (NMF) liquid. Due to the nanoscale infiltration in NMF liquid and its interaction with cell walls, the cellular structure has a much enhanced mechanical performance, in terms of loading capacity and energy absorption density. Moreover, it is validated that the structure is highly compressible and self-restoring. Its hyper-viscoelastic characteristics are elucidated. PMID:27221079

  2. Adhesive, elastomeric gel impregnating composition

    DOEpatents

    Shaw, David Glenn; Pollard, John Randolph; Brooks, Robert Aubrey

    2002-01-01

    An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

  3. Stiffness and damping of elastomeric O-rings

    NASA Technical Reports Server (NTRS)

    Darlow, M. S.; Mehta, R. K.; Smalley, A. J.

    1979-01-01

    Report presents perameterpreturbation test program (using nineteen combinations of Test perameters) for elastomeric O-rings conducting for range of materials, temperatures, amplitudes, squeeze valves, stretch valves, cross-sectional diameters, and groove widths. Tests data were plotted and Power law lines fitted to sets of data.

  4. Mechanical regulation of cell function with geometrically modulated elastomeric substrates

    PubMed Central

    Fu, Jianping; Wang, Yang-Kao; Yang, Michael T.; Desai, Ravi A.; Yu, Xiang; Liu, Zhijun; Chen, Christopher S.

    2011-01-01

    We report the establishment of a library of micromolded elastomeric micropost arrays to modulate substrate rigidity independently of effects on adhesive and other material surface properties. We demonstrate that micropost rigidity impacts cell morphology, focal adhesions, cytoskeletal contractility, and stem cell differentiation. Furthermore, early changes in cytoskeletal contractility predicted later stem cell fate decisions at the single cell level. PMID:20676108

  5. Effect of cervical relining of acrylic resin copings on the accuracy of stone dies obtained using a polyether impression material.

    PubMed

    de Sá, André Tomazini Gomes; de Freitas, César Antunes; de Sá, Fátima Cristina; Ursi, Wagner José Silva; Simões, Tânia Christina; de Freitas, Márcia Furtado Antunes

    2008-01-01

    The purpose of this study was to evaluate the accuracy of the respective dies after polyether elastomeric procedure in the presence or absence of cervical contact of the acrylic resin shell with the cervical region, establishing a comparison to dies obtained with stock trays. This study consisted of three groups with 10 specimens each: 1) acrylic copings without cervical contact, (cn); 2) acrylic copings with cervical contact (cc); 3) perforated stock tray, (st). The accuracy of the resulting dies was verified with the aid of a master crown, precisely fit to the master steel die. ANOVA test found statistically significant differences among groups (p<0.001). Tukey's test found that the smallest discrepancy occurred in group cn, followed by cc, while the st group presented the highest difference (cc x cn: p=0.007; st x cn: p<0.001; st x cc: p<0.001).

  6. Utilization of iTero digital impression unit for resin composite inlay.

    PubMed

    Laman, Stephen A; Frey, Gary N; Patel, Shalizeh A; Quock, Ryan L

    2014-01-01

    Historically, traditional elastomeric impression techniques for indirect fixed procedures have presented challenges for the operator, laboratory, and patient. Recent digital impression unit technology offers a compelling alternative to elastomeric impressions. The iTero system applies parallel confocal imaging to create a virtual impression that can be easily captured, edited, and uploaded electronically to the dental laboratory. Computer-aided design/computer-aided manufacturing technology is applied to the virtual impression to create an unlimited number of identical polyurethane models. This case report is presented from the perspectives of the clinicians and the laboratory technician using an iTero system to treat a left mandibular second premolar with a resin composite inlay.

  7. Non-flammable elastomeric fiber from a fluorinated elastomer and containing an halogenated flame retardant

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Sheth, S. G.; Sidman, K. R.; Massucco, A. A. (Inventor)

    1976-01-01

    Flame retardant elastomeric compositions are described comprised of either spandex type polyurethane having incorporated into the polymer chain halogen containing polyols, conventional spandex type polyurethanes in physical admixture with flame retardant additives, or fluoroelastomeric resins in physical admixture with flame retardant additives. Methods are described for preparing fibers of the flame retardant elastomeric materials and articles of manufacture comprised of the flame retardant clastomeric materials and non elastic materials such as polybenzimidazoles, fiberglass, nylons, etc.

  8. Technique for making flexible impression trays for the microstomic patient.

    PubMed

    Whitsitt, J A; Battle, L W

    1984-10-01

    This impression technique can be used for patients in whom routine use of stock impression trays is hindered by microstomia. Putty wash material can be manipulated with minimal effort and time. Placing the completed preliminary impression in a free-flowing mix of dental stone stabilizes the impression material and facilitates boxing and pouring of the impression. The resultant preliminary casts can then be used for diagnostic purposes and for making rigid sectional trays for final impressions.

  9. A prospective clinical evaluation of electronically mixed polyvinyl siloxane impression materials: results from the prosthetic "SuperStudy"--a consumer evaluation.

    PubMed

    Kugel, G; Swift, E J; Sorensen, J A; Tucker, J H; Dunne, J T

    1999-01-01

    Polyvinyl siloxane (PVS) impression materials incorporating a polyether carbosilane wetting agent and mixed with an electronic mixing system (Pentamix) were clinically compared with traditionally delivered (i.e., automixed) PVS impression materials during routine use by 1,505 general and specialized dental practitioners evaluating more than 30,000 impressions. Each study participant selected 20 patients and used standard tooth-preparation procedures appropriate to the therapy required, supplied specific data on each case, and ultimately evaluated the marginal detail, fit, and success of the final restorations. The areas requiring evaluation upon completion of the final restorations were ranked between "excellent," "good," "poor," and "remake needed," among users of the PVS materials with the electronic mixing system. About 80% of the respondents rated the Pentamix system as easier to mix and deliver than the gun or hand-mixed systems and two thirds said it was faster to mix. The system also received high scores for hygienic delivery, ease of mixing, and clean-up.

  10. Process for spinning flame retardant elastomeric compositions. [fabricating synthetic fibers for high oxygen environments

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Sheth, S.; Sidman, K. R.; Massucco, A. A. (Inventor)

    1978-01-01

    Flame retardant elastomeric compositions comprised of either spandex type polyurethane having halogen containing polyols incorporated into the polymer chain, conventional spandex type polyurethanes in physical admixture with flame retardant additives, or fluoroelastomeric resins in physical admixture with flame retardant additives were developed. Methods are described for preparing fibers of the flame retardant elastomeric materials and manufactured articles as well as nonelastic materials such as polybenzimidazoles, fiberglass, and nylons, for high oxygen environments.

  11. Thermo-cross-linked elastomeric opal films.

    PubMed

    Schäfer, Christian G; Viel, Benjamin; Hellmann, Goetz P; Rehahn, Matthias; Gallei, Markus

    2013-11-13

    An efficient and convenient thermal cross-linking protocol in elastomeric opal films leading to fully reversible and stretch-tunable optical materials is reported. In this study, functional monodisperse core-shell particles were arranged in a face-centered cubic (fcc) lattice structure by a melt flow process. A problem up to now was that un-cross-linked films could not be drawn fully reversibly and hence lost their optical and mechanical performance. After thermal cross-linking reaction, the obtained films can be drawn like rubbers and the color of their Bragg reflection changes because of controlled lattice deformation, which makes the cross-linked films mechanochromic sensors. Different techniques were developed for the cross-linking of the films a posteriori, after their preparation in the melt flow process. A photo-cross-linking approach was reported earlier. This study now deals with a very efficient thermo-cross-linking approach based on the chemistry of hydroxyl- and isocyanate-functionalities that form urethane bridges. The focus of the present work is the mechanism and efficiency of this cross-linking process for elastomeric opal films with excellent mechanical and optical properties. PMID:24134322

  12. Dimensional accuracy of 2-stage putty-wash impressions: influence of impression trays and viscosity.

    PubMed

    Balkenhol, Markus; Ferger, Paul; Wöstmann, Bernd

    2007-01-01

    The aim of this in vitro study was to evaluate the influence of the impression tray and viscosity of the wash material on the dimensional accuracy of impressions taken using a 2-stage putty-wash technique. Identically shaped metal stock trays (MeTs) and disposable plastic stock trays (DiTs) were used for taking impressions (n = 10) of a mandibular cast (4 abutments) with 2 different impression materials. Dies were poured and the relative diameter deviation was calculated after measurement. Zero viscosity of the materials was determined. Dimensional accuracy was significantly affected when DiTs were used. Lower-viscosity wash materials led to more precise impressions.

  13. The effect upon friction of the degradation of orthodontic elastomeric modules.

    PubMed

    Edwards, Ian Robert; Spary, David John; Rock, William Peter

    2012-10-01

    Orthodontic elastomeric modules are susceptible to degradation and deformation after time in the mouth. The aims of this study were to determine whether degradation of elastomeric modules significantly affects friction during sliding mechanics and to investigate whether there is a difference in the behaviour of elastomeric modules after storage in both in vivo and in vitro environments. An Instron testing machine was used to determine the friction generated by elastomeric modules on 0.019 × 0.025 inch stainless steel archwires at 4 degrees of bracket tip. Four brands of modules were tested straight from the packet (n = 15), after storage in artificial saliva (n = 15), and after being in patients' mouths (n = 32). Modules were tested after 24 hours, 1 week, and 6 weeks after storage in both in vivo and in vitro. Analysis of variance revealed that the degradation of elastomeric modules had a variable affect upon friction and that each storage medium produced a distinct pattern of frictional resistance. Modules stored in artificial saliva experienced a significant reduction in friction (P < 0.001) while modules collected from patients' mouths produced similar friction to modules tested straight from the packet. TP Super Slick® modules under dry test conditions produced significantly greater friction than the other three types of test modules (P < 0.001). The structure and surface characteristics of elastomeric modules may affect frictional resistance when a bracket slides along an archwire. These effects vary according to time, storage medium, and brand of elastomeric material.

  14. Lasting Impression

    ERIC Educational Resources Information Center

    Kennedy, Mike

    2006-01-01

    Many schools and universities thought they were getting a good deal when they were building education facilities in the 1950s and 1960s. However, the K-12 and higher-education spaces constructed to accommodate the millions of baby-boomer students no longer look like the quick-fix bargain they did years ago. Low-quality materials and construction,…

  15. Thermomechanical behavior of shape memory elastomeric composites

    NASA Astrophysics Data System (ADS)

    Ge, Qi; Luo, Xiaofan; Rodriguez, Erika D.; Zhang, Xiao; Mather, Patrick T.; Dunn, Martin L.; Qi, H. Jerry

    2012-01-01

    Shape memory polymers (SMPs) can fix a temporary shape and recover their permanent shape in response to environmental stimuli such as heat, electricity, or irradiation. Most thermally activated SMPs use the macromolecular chain mobility change around the glass transition temperature ( Tg) to achieve the shape memory (SM) effects. During this process, the stiffness of the material typically changes by three orders of magnitude. Recently, a composite materials approach was developed to achieve thermally activated shape memory effect where the material exhibits elastomeric response in both the temporary and the recovered configurations. These shape memory elastomeric composites (SMECs) consist of an elastomeric matrix reinforced by a semicrystalline polymer fiber network. The matrix provides background rubber elasticity while the fiber network can transform between solid crystals and melt phases over the operative temperature range. As such it serves as a reversible "switching phase" that enables shape fixing and recovery. Shape memory elastomeric composites provide a new paradigm for the development of a wide array of active polymer composites that utilize the melt-crystal transition to achieve the shape memory effect. This potentially allows for material systems with much simpler chemistries than most shape memory polymers and thus can facilitate more rapid material development and insertion. It is therefore important to understand the thermomechanical behavior and to develop corresponding material models. In this paper, a 3D finite-deformation constitutive modeling framework was developed to describe the thermomechanical behavior of SMEC. The model is phenomenological, although inspired by micromechanical considerations of load transfer between the matrix and fiber phases of a composite system. It treats the matrix as an elastomer and the fibers as a complex solid that itself is an aggregate of melt and crystal phases that evolve from one to the other during a

  16. Comparison of Contamination of Low-Frictional Elastomeric Rings with That of Conventional Elastomeric Rings by Streptococcus mutans - An In-vivo Study

    PubMed Central

    Mogra, Subraya; Shetty, V. Surendra; Shetty, Siddarth; Jose, Nidhin Philip

    2015-01-01

    Introduction: The presence of brackets and ligatures has been shown to be related to an increase in gingival inflammation and increased risk of decalcification. The various measures were taken to reduce the plaque accumulation and also lot of efforts were made by manufacturers that reduced the binding friction between the ligature rings and arch wire that facilitated easy sliding of the tooth through the wire. The low frictional ligatures rings manufactured by different manufacturers presumed to attract fewer bacteria due to greater reduction in surface roughness. Our study aimed to evaluate whether the low frictional elastomeric rings accumulate fewer bacteria than conventional ligature rings. Materials and Methods: Thirty patients (15 males and 15 females) who underwent fixed appliance therapy were selected. The study was done using split-mouth design. In each volunteer, synergy low frictional elastomeric rings were tied to brackets bonded to the maxillary premolar on the right side and mandibular premolar on the left side. Conventional elastomeric rings that served as control group were tied to the contralateral teeth, with the same design. Samples were collected after four weeks (28 days) and cultured for bacteria Streptococcus mutans. Results: There was no statistical difference between Streptococcus mutans count in low frictional elastomeric rings with that of conventional rings. Conclusion: We concluded that adherence of Streptococcus mutans is similar in both synergy low frictional elastomeric rings and conventional clear elastomeric rings and thus the manufacturer’s claim of minimal bacterial adherence was discarded. PMID:26023638

  17. Effects of sulfur-based hemostatic agents and gingival retraction cords handled with latex gloves on the polymerization of polyvinyl siloxane impression materials

    PubMed Central

    MACHADO, Carlos Eduardo Palhares; GUEDES, Carlos Gramani

    2011-01-01

    Objectives This study investigated the possible interactions between three addition silicone materials (Express®, Aquasil Ultra® and Adsil®), three hemostatic agents (ferric sulfate, StatGel FS®; aluminum sulfate, GelCord®; and aluminum chloride, Hemostop®) and gingival retraction cords previously handled with latex gloves to determine whether direct contact with medicaments or indirect contamination by latex in conditions similar to those found in clinical practice inhibit or affect the setting of the impression materials. Material and Methods A portable device for the simultaneous test of several specimens was specifically developed for this study. Polymerization inhibition was analyzed by examination of the impressions and the molded surface. Ten trials were performed for each addition silicone material used in the study, at a total of 240 study samples. Results All the samples tested (N=240) were nonreactive regardless of the type of combination used. Conclusions Aluminum sulfate, ferric sulfate and aluminum chloride hemostatic solutions did not show any inhibitory potential on the addition silicone samples under study, and there were no changes in polymerization as a result of contact between addition silicone and retraction cords handled with latex gloves. PMID:22230998

  18. A laboratory investigation of orthodontic elastomeric chains.

    PubMed

    Rock, W P; Wilson, H J; Fisher, S E

    1985-10-01

    The dimensions and force/extension characteristics of 13 commercially available orthodontic chain elastomeric materials are reported. The relationship between force and extension was not linear over the range investigated and there were two definite transition points in the curves. Over the first linear part of the curve the two-loop specimens had stiffness values from 0.9 to 1.6 N/mm. Stiffness fell as the number of loops increased so that four-loop chains produced 0.6-1.1 N/mm. One hundred per cent extension produced forces in the 4-5 N range for most specimens. It is suggested that an extension of between 50 and 70 per cent would provide the most satisfactory orthodontic force.

  19. Development of ultra-hydrophilic and non-cytotoxic dental vinyl polysiloxane impression materials using a non-thermal atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Kwon, Jae-Sung; Kim, Yong Hee; Choi, Eun Ha; Kim, Kyoung-Nam

    2013-05-01

    Dental vinyl polysiloxane (VPS) impression materials are widely used for the replication of intraoral tissue where hydrophilicity is important as the oral tissues are surrounded by wet saliva. Recent attempts to improve the wettability of VPS using a ‘surfactant’, however, have resulted in a high level of cytotoxicity. Hence, in this study, application of a non-thermal atmospheric-pressure plasma jet (NTAPPJ) on VPS and its effects in terms of both hydrophilicity and cytotoxicity were investigated. The results showed that the application of the plasma jet resulted in significant improvement of hydrophilicity of VPS that had no surfactant, whereby the results were similar to commercially available products with the surfactant. The surface chemical analysis results indicated that this was due to the oxidation and decreased amount of hydrocarbon on the surface following NTAPPJ exposure. Meanwhile, an NTAPPJ-treated sample was shown to be non-cytotoxic. Therefore, the use of dental VPS impression materials without any surfactant, in conjunction with an NTAPPJ treatment, is a promising method for ultra-hydrophilic but yet non-cytotoxic materials.

  20. Use of elastomeric elements in control of rotor instability

    NASA Technical Reports Server (NTRS)

    Smalley, A. J.

    1980-01-01

    The dynamic characteristics of elastomeric supports are discussed. Stiffness and damping characteristics for elastomers of various geometries including O-rings, buttons loaded in compression, and rectangular elements loaded in shear are presented. The effects of frequency, temperature, and amplitude are illustrated, as well as the effects of material and geometry. Empirical design methods are illustrated, and several examples are presented where elastomers have successfully controlled both synchronous and nonsynchronous vibrations.

  1. Analysis of the Influence of Food Colorings in Esthetic Orthodontic Elastomeric Ligatures

    PubMed Central

    Dias da Silva, Vanessa; de Lima, Eduardo Martinelli S; Dias, Caroline; Osório, Leandro Berni

    2016-01-01

    Proposition: The purpose of this study was to evaluate in vitro the color changes of esthetic orthodontic elastomeric ligatures of different shades when exposed to four food colorings commonly found in the diet of patients. Materials and Methods: The sample consisted of esthetic orthodontic elastomeric ligatures in the colors pearl, pearl blue, pearl white and colorless, which were immersed for 72 hours in five different solutions: distilled water (control group), coffee, tea, Coca-Cola ® and wine. The color changes of the esthetic orthodontic elastomeric ligatures were measured with the aid of a spectrophotometer, at T1 - as provided by the manufacturer; and T2 - after colorings process. Results: The results indicated that the esthetic orthodontic elastomeric ligatures of all initial hues are susceptible to pigmentation. Among the evaluated colors, all changed the finished look and the color of the samples tested. In ascending order, the color of the samples was as follows: distilled water, Coca-Cola®, black tea, wine and coffee. Conclusion: The substances that have a greater potential for pigmentation in esthetic orthodontic elastomeric ligatures were black tea, wine and coffee, respectively. All shades of esthetic orthodontic elastomeric ligatures are susceptible to color change. PMID:27733878

  2. A Comparative Evaluation of Dimensional Accuracy and Surface Detail Reproduction of Four Hydrophilic Vinyl Polysiloxane Impression Materials Tested Under Dry, Moist, and Wet Conditions-An In Vitro Study.

    PubMed

    Nagrath, Rahul; Lahori, Manesh; Agrawal, Manjari

    2014-12-01

    Vinyl polysiloxane (VPS) impression materials have application in a wide variety of situations in both fixed and removable prosthodontics. A major limitation of VPS impression materials is their hydrophobicity. There are two aspects of this problem, the wettability of the polymerized impression by dental gypsum materials and the ability of the unpolymerized material to wet intraoral tissues. To address this problem, manufacturers have added surfactants and labelled these new products as "hydrophilic vinyl polysiloxane." The purpose of this study was to evaluate and compare dimensional accuracy and surface detail reproduction of four hydrophilic VPS impression materials, when used under dry, moist, and wet conditions. A total of 180 samples were made of stainless steel die similar to as described in ADA sp. no. 19. The die was scored with three horizontal and two vertical lines. Impressions were made under dry, moist and wet conditions. Dimensional accuracy was measured by comparing the length of the middle horizontal line in each impression to the same line on the metal die, by using Universal Length Measuring machine. A 2-way ANOVA was performed on the percentage change data for measured lengths of the 4 impression materials under the 3 conditions to evaluate dimensional accuracy. Surface detail was evaluated in two ways: (1) by use of criteria similar to ADA sp. no. 19 for detail reproduction, and (2) by use of a method that categorized the impressions as satisfactory or unsatisfactory based on their surface characteristics: presence of pits, voids, or roughness. Pearson X2 (α = 0.05) was used to compare surface detail reproduction results. Conditions (dry, moist, and wet) did not cause significant adverse effects on the dimensional accuracy of all the four material. With both surface detail analyses, dry, moist, and wet conditions had a significant effect on the detail reproduction of all the four materials (P < 0.05). The study concluded that the

  3. Clinical success rates for polyether crown impressions when mixed dynamically and statically.

    PubMed

    Schmitter, Marc; Johnson, Glen H; Faggion, Clovis; Klose, Christina; Mitov, Gergo; Nothdurft, Frank P; Pospiech, Peter R; Rammelsberg, Peter; Ohlmann, Brigitte; Schwarz, Stefanie; Stober, Thomas; Schiller, Petra; Pritsch, Maria

    2012-06-01

    The purpose of this study is to compare success rates of dual-viscosity impressions for two types of mixing techniques of the polyether elastomeric impression material. Additionally, influencing parameters on the success rates should be evaluated. The expectation was that there would be no difference between the success rates for the two mixing techniques. Two centres enrolled 290 subjects (727 teeth) into the trial. Patients were randomized for the two types of mixing techniques. One step, dual-viscosity impressions were made with either statically mixed Impregum Soft tray material (SAM) or dynamically mixed Impregum Penta H DuoSoft (DMM). Low viscosity Impregum Garant L DuoSoft was used for both groups. Gingival displacement involved the use of two braided cords. Full-arch trays were used exclusively. Both critical defects and operator errors were assessed for the first impression taken by trained dentists. The primary outcome was impression success. For comparison of the two mixing techniques, the odds ratio for success and the corresponding one-sided 95% confidence interval was calculated by a logistic regression model. To account for the dependence between several teeth within one patient, the method of general estimating equations was used. The overall impression success rate was 35.4%. Both mixing techniques showed equal success rates indicated by an OR of 1.0 and a lower limit of the one-sided 95% confidence interval of 0.71. Using this result to develop the corresponding interval for the difference, it could be shown that the success rate using SAM was at most 8.2% lower than that when using DMM with a probability of 95%. Multivariate logistic regression analysis of other potential influencing factors showed position of finish line (p = 0.008, supra compared to mixed), blood coagulation disorder (p = 0.021) and the level of training of the clinician (student vs dentist, p=0.008) to have an independent influence on the success rate. Dynamic mechanical

  4. Hybrid magnetorheological fluid elastomeric lag dampers for helicopter stability augmentation

    NASA Astrophysics Data System (ADS)

    Hu, Wei; Wereley, Norman M.

    2008-08-01

    A laboratory demonstration of a hybrid magnetorheological fluid-elastomeric (MRFE) damper is investigated for adjustable or programmable lag mode damping in helicopters, so that damping requirements can be varied as a function of different flight conditions. The laboratory demonstration of this hybrid MRFE lag damper consists of a double lap shear elastomeric damper in parallel with two magnetorheological (MR) flow mode dampers. This is compared to a damper where only elastomeric materials are implemented, i.e., a double lap shear specimen. The relationship between the output force and the quasi-steady harmonic displacement input to a flow mode MR damper is exploited, where the output force can be adjusted as a function of applied magnetic field. Equivalent viscous damping is used to compare the damping characteristics of the hybrid damper to a conventional elastomeric damper under steady-state sinusoidal displacement excitation. To demonstrate feasibility, a hybrid MRFE damper test setup is designed, and single frequency (lag frequency or rotor in-plane bending frequency) and dual frequency (lag frequency and rotor frequency) tests are conducted under different magnetic fields. The hybrid MRFE damper exhibits amplitude-dependent damping behavior. However, with application of a magnetic field, the damping level is controlled to a specific damping level objective as a function of displacement amplitude. Similarly, under dual frequency conditions, damping degradation at the lag frequency, because of lag motion at the rotor frequency, can also be recovered by increasing magnetic field. A time-domain analysis is developed to study the nonlinear dynamic behavior of the hybrid MRFE damper. Using rate-dependent elasto-slides, the amplitude-dependent behavior of the hybrid MRFE damper is accurately reconstructed using both constant and current-dependent (i.e. controllable) parameters. The analysis is physically motivated and can be applied to the elastomer and MR fluid

  5. Chemical Stability of Telavancin in Elastomeric Pumps☆

    PubMed Central

    Sand, Patrick; Aladeen, Traci; Kirkegaard, Paul; LaChance, Dennis; Slover, Christine

    2015-01-01

    solutions examined. All decreases in telavancin concentration were ≤2.7%. Comparison of each test sample solution to the corresponding glass control indicated no loss of active drug due to absorption by the elastomeric material of the pumps. The greatest increase in the amount of total degradants observed over the 8-day period was ~0.7 w/w%. Conclusions The results of this study indicate that telavancin remains chemically stable when diluted in the Intermate Infusion System and the Homepump Eclipse elastomeric pumps and stored at 2°C to 8°C for up to 8 days protected from light at the concentration range and dilution schemes evaluated. PMID:26649079

  6. Complete denture impression techniques practiced by private dental practitioners: a survey.

    PubMed

    Kakatkar, Vinay R

    2013-09-01

    Impression making is an important step in fabricating complete dentures. A survey to know the materials used and techniques practiced while recording complete denture impressions was conducted. It is disheartening to know that 33 % practitioners still use base plate custom trays to record final impressions. 8 % still use alginate for making final impressions. An acceptable technique for recording CD impressions is suggested.

  7. Understanding Mechanical Response of Elastomeric Graphene Networks

    PubMed Central

    Ni, Na; Barg, Suelen; Garcia-Tunon, Esther; Macul Perez, Felipe; Miranda, Miriam; Lu, Cong; Mattevi, Cecilia; Saiz, Eduardo

    2015-01-01

    Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls. PMID:26348898

  8. Elastomeric Photopolymers: Shaping Polymer Gels with Light

    NASA Astrophysics Data System (ADS)

    Kornfield, Julia

    2008-03-01

    Polymer gels that possess a latent ability to change shape, which can be triggered in a spatially resolved manner using light---``elastomeric photopolymers''---have been developed to meet the need for materials that can be reshaped without direct contact, e.g., to non-invasively adjust an implanted lens in the human eye. The physics of diffusion and swelling in elastomers are applied to create a transparent silicone suitable for making a foldable intraocular lens that can be reshaped using near ultraviolet light. A crosslinked silicone matrix dictates the initial shape of the lens, while ``macromers''--short silicone chains with polymerizable end groups—and photoinitiator enable shape adjustment using light: polymerization of the macromer in the irradiated regions, followed by diffusion of free macromer causes local swelling. To predict shape change directly from irradiation profile, a theoretical treatment is presented that captures 1. shape change with no external forces, 2. coupling between diffusion and deformation, and 3. connection between thermodynamics, constitutive equations and equations of motion. Using continuum mechanics complemented with thermodynamics within the auspices of the finite element method, we develop a steady-state model which successfully captures the coupling between diffusion and deformation. Parameter values are drawn from our prior experimental studies of the mechanical properties, equilibrium swelling, penetrant diffusivities and interaction parameters in systematically varied polydimethylsiloxane (PDMS) networks and acrylate endcapped PDMS macromers. Preliminary computational studies show qualitative agreement with experimentally observed phenomena.

  9. Strain-induced crystallization in elastomeric polymer networks prepared in solution and sol-gel derived high-temperature organic-inorganic hybrid materials

    NASA Astrophysics Data System (ADS)

    Premachandra, Jagath Kumara

    Cross-linking polymer chains in solution should bring about fewer inter-chain entanglements in the resulting network. The subsequent drying of this network should compress the chains into a "super-contracted" state. The opposing effects of these changes on strain-induced crystallization in cis-1,4-polyisoprene networks formed in solution were investigated. Higher elongations were required to achieve strain-induced crystallinity in the networks prepared at higher dilutions, suggesting that in this regard the compressed states of the chains was more important than their reduced entangling. The constrained-junction theory was applied to strain-induced crystallization in the above networks. The stress-strain isotherms generated from this theory were in satisfactory agreement with experiment. It was found that the constraint parameter kappa decreases with increase in dilution during cross-linking mainly due to the fact that cross-linking in solution decreases chain interpenetration. The dependence of hydrolysis and condensation of gamma-ureidopropyltrimethoxysilane on pH in the water-methanol system at 23sp°C was investigated by FTIR spectroscopy. Quantitative analysis of rates of hydrolysis showed that gamma-ureidopropyltrimethoxysilane is most stable in the water-methanol system at pH 7.7. The rate of overall condensation of silanols produced by the hydrolysis was qualitatively analyzed. These silanol groups are relatively more stable around pH 4.87. The mechanical properties, thermal stability and water absorption of high-temperature sulfopolybenzobisthiazole-silica hybrid materials were investigated. The use of a bonding agent N,N-diethylaminopropyltrimethoxysilane facilitated the interfacial bonding between the organic and inorganic phases in these materials prepared through the sol-gel process. Tensile modulus, thermal stability and the resistant to water absorption were increased with increase in silica content in the resulting composites

  10. ETI: Our first impressions

    NASA Astrophysics Data System (ADS)

    Harrison, Albert A.; Johnson, Joel T.

    2000-06-01

    Despite scant or ambiguous information, people are capable of developing comprehensive and detailed impressions. Consequently, if the detection of an electromagnetically-active civilization is announced, many people will rapidly form impressions of what the extraterrestrials and their civilization are "like". First impressions are crucial, not only because of their immediate psychological, social, and political consequences on Earth, but because they can influence the future of interstellar communication. Initial impressions will rest less on hard data than on the nature and tone of the "evidence" that is gleaned from the transmission; the interpretation and dissemination of this evidence; and the hard wiring, psychological programming, cultural conditioning, and social influence processes that shape human perception. We consider how dispositional inferences, implicit theories of personality, negatively toned or adverse information, physical appearance, prior expectations, the confirmation bias, and thinking and unthinking approaches to attitude formation are likely to affect human impressions of ETI.

  11. Mechanically programmed shape change in laminated elastomeric composites.

    PubMed

    Robertson, Jaimee M; Torbati, Amir H; Rodriguez, Erika D; Mao, Yiqi; Baker, Richard M; Qi, H Jerry; Mather, Patrick T

    2015-07-28

    Soft, anisotropic materials, such as myocardium in the heart and the extracellular matrix surrounding cells, are commonly found in nature. This anisotropy leads to specialized responses and is imperative to material functionality, yet few soft materials exhibiting similar anisotropy have been developed. Our group introduced an anisotropic shape memory elastomeric composite (A-SMEC) composed of non-woven, aligned polymer fibers embedded in an elastomeric matrix. The composite exhibited shape memory (SM) behavior with significant anisotropy in room-temperature shape fixing. Here, we exploit this anisotropy by bonding together laminates with oblique anisotropy such that tensile deformation at room temperature - mechanical programming - results in coiling. This response is a breakthrough in mechanical programming, since non-affine shape change is achieved by simply stretching the layered A-SMECs at room temperature. We will show that pitch and curvature of curled geometries depend on fiber orientations and the degree of strain programmed into the material. To validate experimental results, a model was developed that captures the viscoplastic response of A-SMECs. Theoretical results correlated well with experimental data, supporting our conclusions and ensuring attainability of predictable curling geometries. We envision these smart, soft, shape changing materials will have aerospace and medical applications.

  12. Photocrosslinkable and elastomeric hydrogels for bone regeneration.

    PubMed

    Thakur, Teena; Xavier, Janet R; Cross, Lauren; Jaiswal, Manish K; Mondragon, Eli; Kaunas, Roland; Gaharwar, Akhilesh K

    2016-04-01

    Nanocomposite biomaterials are extensively investigated for cell and tissue engineering applications due their unique physical, chemical and biological characteristics. Here, we investigated the mechanical, rheological, and degradation properties of photocrosslinkable and elastomeric nanocomposite hydrogels from nanohydroxyapatite (nHAp) and gelatin methacryloyl (GelMA). The addition of nHAp resulted in a significant increase in mechanical stiffness and physiological stability. Cells readily adhere and proliferate on the nanocomposite surfaces. Cyclic stretching of cells on the elastomeric nanocomposites revealed that nHAp elicited a stronger alignment response in the direction of strain. In vitro studies highlight enhanced bioactivity of nanocomposites as determined by alkaline phosphate (ALP) activity. Overall, the elastomeric and photocrosslinkable nanocomposite hydrogels can be used for minimally invasive therapy for bone regeneration.

  13. Elastomeric member for energy storage device

    DOEpatents

    Hoppie, Lyle O.; Chute, Richard

    1985-01-01

    An energy storage device (10) is disclosed consisting of a stretched elongated elastomeric member (16), disposed within a tubular housing (14), which elastomeric member (16) is adapted to be torsionally stressed to store energy. The elastomeric member (16) is configured in the relaxed state with a uniform diameter body section, transition end sections, and is attached to rigid end piece assemblies (22, 24) of a lesser diameter. The profile and deflection characteristic of the transition sections (76, 78) are such that upon stretching of the member, a substantially uniform diameter assembly results to minimize the required volume of the surrounding housing (14). During manufacture, woven wire mesh sleeves (26, 28) are forced against a forming surface and bonded to the associated transition section (76, 78) to provide the correct profile and helix angle. Each sleeve (26, 28) contracts with the contraction of the associated transition section to maintain the bond therebetween.

  14. Improved fibre optic acoustic sensors for partial discharge in elastomeric insulations

    NASA Astrophysics Data System (ADS)

    Rohwetter, Philipp; Lothongkam, Chaiyaporn; Habel, Wolfgang; Heidmann, Gerd; Pepper, Daniel

    2014-05-01

    Partial discharge in elastomeric high voltage insulations is a major reason for device failure. The special challenges of the high voltage environment limit the use of conventional acoustic emission sensors. Fibre-optic sensors can cope with these challenges thanks to their optical sensing principle and the use of all-dielectric materials. In this contribution, improvements to a previously introduced design of ultrasonic fibre-optic acoustic partial discharge sensors for elastomeric insulations are presented. The improved performance of fibre-optic acoustic sensors in detecting AC partial discharge is demonstrated. Furthermore, their ability to detect low-level damage processes in elastomeric insulation under DC dielectric stress is shown to outperform the highly sensitive electrical detection method.

  15. Elastomeric organic material for switching application

    SciTech Connect

    Shiju, K. E-mail: pravymon@gmail.com Praveen, T. E-mail: pravymon@gmail.com Preedep, P. E-mail: pravymon@gmail.com

    2014-10-15

    Organic Electronic devices like OLED, Organic Solar Cells etc are promising as, cost effective alternatives to their inorganic counterparts due to various reasons. However the organic semiconductors currently available are not attractive with respect to their high cost and intricate synthesis protocols. Here we demonstrate that Natural Rubber has the potential to become a cost effective solution to this. Here an attempt has been made to fabricate iodine doped poly isoprene based switching device. In this work Poly methyl methacrylate is used as dielectric layer and Aluminium are employed as electrodes.

  16. Elastomeric organic material for switching application

    NASA Astrophysics Data System (ADS)

    Shiju, K.; Praveen, T.; Preedep, P.

    2014-10-01

    Organic Electronic devices like OLED, Organic Solar Cells etc are promising as, cost effective alternatives to their inorganic counterparts due to various reasons. However the organic semiconductors currently available are not attractive with respect to their high cost and intricate synthesis protocols. Here we demonstrate that Natural Rubber has the potential to become a cost effective solution to this. Here an attempt has been made to fabricate iodine doped poly isoprene based switching device. In this work Poly methyl methacrylate is used as dielectric layer and Aluminium are employed as electrodes.

  17. Recombinant Exon-Encoded Resilins for Elastomeric Biomaterials

    PubMed Central

    Qin, Guokui; Rivkin, Amit; Lapidot, Shaul; Hu, Xiao; Arinus, Shira B.; Dgany, Or; Shoseyov, Oded; Kaplan, David L.

    2011-01-01

    Resilin is an elastomeric protein found in specialized regions of the cuticle of most insects, providing outstanding material properties including high resilience and fatigue lifetime for insect flight and jumping needs. Two exons (1 and 3) from the resilin gene in Drosophila melanogaster were cloned and the encoded proteins expressed as soluble products in Escherichia coli. A heat and salt precipitation method was used for efficient purification of the recombinant proteins. The proteins were solution cast from water and formed into rubber-like biomaterials via horseradish peroxidase-mediated cross-linking. Comparative studies of the two proteins expressed from the two different exons were investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Circular Dichrosim (CD) for structural features. Little structural organization was found, suggesting structural order was not induced by the enzyme-mediateed dityrosine cross-links. Atomic Force Microscopy (AFM) was used to study the elastomeric properties of the uncross-linked and cross-linked proteins. The protein from exon 1 exhibited 90% resilience in comparison to 63% for the protein from exon 3, and therefore may be the more critical domain for functional materials to mimic native resilin. Further, the cross-linking of the recombinant exon 1 via the citrate-modified photo-Fenton reaction was explored as an alternative dityrosine mediated polymerization method and resulted in both highly elastic and adhesive materials. The citrate-modified photo-Fenton system may be suitable for in-vivo applications of resilin biomaterials. PMID:21963157

  18. Elastomeric member and method of manufacture therefor

    DOEpatents

    Hoppie, L.O.

    1985-12-10

    An energy storage device is disclosed consisting of a stretched elongated elastomeric member disposed within a tubular housing, which elastomeric member is adapted to be torsionally stressed to store energy. The elastomeric member is configured in the relaxed state with a uniform diameter body section, and transition end sections, attached to rigid end piece assemblies of a lesser diameter. The profile and deflection characteristic of the transition sections are such that upon stretching of the elastomeric member, a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing. Each of the transition sections are received within and bonded to a woven wire mesh sleeve having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve also contracts with the contraction of the associated transition section to maintain the bond therebetween. During manufacture, the sleeves are forced against a forming surface and bonded to the associated transition section to provide the correct profile and helix angle. 12 figs.

  19. Elastomeric member and method of manufacture therefor

    DOEpatents

    Hoppie, Lyle O.

    1985-01-01

    An energy storage device (10) is disclosed consisting of a stretched elongated elastomeric member (16) disposed within a tubular housing (14), which elastomeric member (16) is adapted to be torsionally stressed to store energy. The elastomeric member (16) is configured in the relaxed state with a uniform diameter body section (74), and transition end sections (76, 78), attached to rigid end piece assemblies (22, 24) of a lesser diameter. The profile and deflection characteristic of the transition sections (76, 78) are such that upon stretching of the elastomeric member (16), a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing (14). Each of the transition sections (76, 78) are received within and bonded to a woven wire mesh sleeve (26, 28) having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve (26, 28) also contracts with the contraction of the associated transition section to maintain the bond therebetween. During manufacture, the sleeves (26, 28) are forced against a forming surface and bonded to the associated transition section (76, 78) to provide the correct profile and helix angle.

  20. Airbag Impressions in Soil

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken by the Mars Exploration Rover Opportunity's panoramic camera shows where the rover's airbags left impressions in the martian soil. The drag marks were made after the rover successfully landed at Meridiani Planum and its airbags were retracted. The rover can be seen in the foreground.

  1. Virtual First Impressions

    ERIC Educational Resources Information Center

    Bergren, Martha Dewey

    2005-01-01

    Frequently, a nurse's first and only contact with a graduate school, legislator, public health official, professional organization, or school nursing colleague is made through e-mail. The format, the content, and the appearance of the e-mail create a virtual first impression. Nurses can manage their image and the image of the profession by…

  2. Impressions of Leadership

    ERIC Educational Resources Information Center

    Smith, Agnes

    2005-01-01

    I was early arriving for an appointment with the superintendent at the school where I would begin my first year as an elementary school principal. While I waited, I reflected on my first teaching job, where I had formed my first and most lasting impressions of leadership from the principal. Now it was my turn to be a principal, and I aspired to…

  3. Elastomeric Recombinant Protein-based Biomaterials

    PubMed Central

    Annabi, Nasim; Mithieux, Suzanne M.; Camci-Unal, Gulden; Dokmeci, Mehmet R.; Weiss, Anthony S.; Khademhosseini, Ali

    2013-01-01

    Elastomeric protein-based biomaterials, produced from elastin derivatives, are widely investigated as promising tissue engineering scaffolds due to their remarkable properties including substantial extensibility, long-term stability, self-assembly, high resilience upon stretching, low energy loss, and excellent biological activity. These elastomers are processed from different sources of soluble elastin such as animal-derived soluble elastin, recombinant human tropoelastin, and elastin-like polypeptides into various forms including three dimensional (3D) porous hydrogels, elastomeric films, and fibrous electrospun scaffolds. Elastin-based biomaterials have shown great potential for the engineering of elastic tissues such as skin, lung and vasculature. In this review, the synthesis and properties of various elastin-based elastomers with their applications in tissue engineering are described. PMID:23935392

  4. Elastomeric binders for electrodes. [in secondary lithium cells

    NASA Technical Reports Server (NTRS)

    Yen, S. P. S.; Shen, D. H.; Somoano, R. B.

    1983-01-01

    The poor mechanical integrity of the cathode represents an important problem which affects the performance of ambient temperature secondary lithium cells. Repeated charge of a TiS2 cathode may give rise to stresses which disturb the electrode structure and can contribute to capacity loss. An investigation indicates that the use of an inelastic binder material, such as Teflon, aggravates the problem, and can lead to electrode disruption and poor TiS2 particle-particle contact. The feasibility of a use of elastomers as TiS2 binder materials has, therefore, been explored. It was found that elastomeric binders provide an effective approach for simplifying rechargeable cathode fabrication. A pronounced improvement in the mechanical integrity of the cathode structure contributes to a prolonged cycle life.

  5. Prediction of macroscopic properties of elastomeric networks

    SciTech Connect

    Al-ghamdi, A.M.S.; Rayes, T.B.; Galiatsatos, V.

    1993-12-31

    Monte Carlo simulations of amorphous elastomeric networks of polyisoprene and polybutadiene cured with sulfur have been prepared. The effect of molecular weight of the prepolymer, and the concentration and type of cross-links is studied. The affine modulus as a function of the extent of reaction is reported. Comparisons between the two polymers and reasons for their differing behavior are being attributed to their molecular characteristics.

  6. Impression Testing of Self-Healing Polymers

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Huber, Amy

    2005-01-01

    As part of the BIOSANT program (biologically-inspired smart nanotechnology), scientists at NASA-Langley have identified a "self-healing" plastic that spontaneously closes the hole left by the passage of a bullet. To understand and generalize the phenomenon in question, the mechanical properties responsible for this ability are being explored. Low-rate impression testing was chosen to characterize post-yield material properties, and it turned out that materials that heal following ballistic puncture also show up to 80% healing of the low-rate impression. Preliminary results on the effects of temperature and rate of puncture are presented.

  7. Tool for Taking Clay Impressions

    NASA Technical Reports Server (NTRS)

    Duncan, R. S.

    1984-01-01

    Clay impression of small parts taken with tool consisting of hollow tube closed at one end. Slots at other end admit part short distance into tube. Impression used to make silicone rubber mold for examination.

  8. A new method for making casts from irreversible hydrocolloid impressions.

    PubMed

    Steas, A

    1991-03-01

    This method of making casts from alginate (irreversible hydrocolloid) edentulous impressions is a departure from the usual procedures. It consists of recognizing the weaknesses of the materials being used and handling them to the best advantage to minimize deleterious effects. A proper dental stone mixed with an accelerator is painted over the entire anatomic surface of the impression. A base is added only after the first application of stone sets. This method protects against volume change of the irreversible hydrocolloid impression material and distortion of the unsupported portions of the impression.

  9. Substance Use as Impression Management.

    ERIC Educational Resources Information Center

    Sharp, Mark J.; Getz, J. Greg

    1996-01-01

    Examines the function of substance use as an impression management tactic. Introductory psychology students (n=377) responded to a survey instrument measuring self-monitoring, perceived success in impression management, interaction anxiety, and self-esteem. Results suggest that alcohol use may serve an impression management function. (JPS)

  10. The effects of disposable and custom-made impression trays on the accuracy of impressions.

    PubMed

    Burton, J F; Hood, J A; Plunkett, D J; Johnson, S S

    1989-06-01

    This study indicates that some non-rigid impression trays, including disposable plastic trays and custom-made acrylic resin trays, may produce unreliable results when used with some medium-bodied elastomers. The study does not question the well-documented clinical accuracy of these elastomers when they are used with rigid trays. Disposable plastic trays are found to be acceptable when used with a combination of reversible and non-reversible hydrocolloid impression materials.

  11. Using double-poured alginate impressions to fabricate bleaching trays.

    PubMed

    Haywood, V B; Powe, A

    1998-01-01

    Esthetic and diagnostic treatment often requires two casts of one arch, one for baseline and one for alterations (diagnostic wax-up, bleaching tray, occlusal analysis). The purpose of this study was to compare the accuracy of stone casts generated from a second pour of a properly handled alginate impression with first-poured casts. A maxillary dentoform was indexed with six reference spaces (#8-15, 9-2, 2-15, and incisal-to-gingival of #3, 9, 14). Irreversible hydrocolloid (Jeltrate) impressions were made in perforated steel trays by a single investigator. Impression material was spatulated for 1 minute. The seated impression and dentoform were wrapped in a damp paper towel to simulate intraoral conditions, and allowed to set for 2 minutes. Upon separation, the impression was stored in a damp towel for 5 minutes. The impression was poured in cast stone (Microstone) according to the manufacturer's instructions. The stone-filled impression was immediately rewrapped in a damp paper towel and allowed to set for 45 minutes at room temperature. Upon removal of the stone, the impression was rinsed with cold water, shaken dry, and repoured in the same manner. Ten impressions were made: the first five impressions were poured to make casts for Group A, then repoured as described above for casts for Group B. The remaining five impressions were poured once to make casts for Group C. The six spaces of each cast were measured three times in random order using a dial caliper and the space average calculated for the cast. At each space, analysis of variance showed no significant difference among Groups A, B, or C (P < 0.05). When alginate impressions that have been poured with cast stone are kept moist during stone setting and repoured within 45 minutes, two casts can be generated from one impression with the same degree of accuracy as two casts made from taking two separate impressions, providing the alginate does not tear during first cast removal.

  12. Joint custody: preliminary impressions.

    PubMed

    Awad, G A

    1983-02-01

    Joint custody is currently a popular and debatable issue. It is felt that some of the controversy is due to the lack of agreement on a definition. Following some examples of the differences in personal and judicial definitions of joint custody, a classification of custody is offered. Four types of custody arrangements are described: Absolute Sole Custody, Sole Custody, Non-Alternating Joint Custody (disputed and undisputed) and Alternating Joint Custody (disputed and undisputed). A critical review of the literature follows. Finally, clinical impressions about the two types of joint custody are discussed. PMID:6839267

  13. Accuracy and consistency of modern elastomeric pumps.

    PubMed

    Weisman, Robyn S; Missair, Andres; Pham, Phung; Gutierrez, Juan F; Gebhard, Ralf E

    2014-01-01

    Continuous peripheral nerve blockade has become a popular method of achieving postoperative analgesia for many surgical procedures. The safety and reliability of infusion pumps are dependent on their flow rate accuracy and consistency. Knowledge of pump rate profiles can help physicians determine which infusion pump is best suited for their clinical applications and specific patient population. Several studies have investigated the accuracy of portable infusion pumps. Using methodology similar to that used by Ilfeld et al, we investigated the accuracy and consistency of several current elastomeric pumps. PMID:25140510

  14. Method of making hollow elastomeric bodies

    NASA Technical Reports Server (NTRS)

    Broyles, H. F.; Moacanin, J.; Cuddihy, E. F. (Inventor)

    1976-01-01

    Annular elastomeric bodies having intricate shapes are cast by dipping a heated, rotating mandrel into a solution of the elastomer, permitting the elastomer to creep into sharp recesses, drying the coated mandrel and repeating the operation until the desired thickness has been achieved. A bladder for a heart assist pump in which a cylindrical body terminating in flat, sharp horizontal flanges fabricated by this procedure has been subjected to over 2,500 hours of simulated life conditions with no visible signs of degradation.

  15. Dimensional stability of autopolymerizing acrylic resin impression trays.

    PubMed

    Fehling, A W; Hesby, R A; Pelleu, G B

    1986-05-01

    A study was undertaken to determine the optimal interval between fabrication of an autopolymerizing acrylic resin custom impression tray and making a final impression. Twenty mandibular arch-shaped trays, 10 each of Fastray and Formatray resin, were evaluated for dimensional change. Both materials behaved similarly. Cross-arch contraction of the borders of buccal flanges and unilateral expansion of the borders of buccal-to-lingual flanges were observed. These changes indicate distortion. Linear dimensional changes occurred throughout 6 hours, which suggests that any impression made in a methyl methacrylate acrylic resin custom impression tray should be poured as soon as is conveniently possible. Significant linear dimensional changes were observed for only 40 minutes from the initiation of tray fabrication. This study concludes that while an aged tray is preferred, it is acceptable to make an impression in an autopolymerizing resin custom impression tray after 40 minutes.

  16. Dimensional stability ofautoclave sterilised addition cured impressions and trays.

    PubMed

    Deb, S; Etemad-Shahidi, S; Millar, B J

    2014-03-01

    The aim of this study was to investigate the dimensional accuracy of impressions following sterilisation by autoclaving. Dental impressions (75) were of a dentoform containing 6 reference points. The impressions were split into 5 groups of 15, each group used a different impression technique. Groups were divided into 3 subgroups with 5 impressions as control, 5 for disinfection by Perform-ID and 5 being autoclaved. Measurements were made using a travelling light microscope. A minimal significant dimensional difference (0.01impression method. No significant dimensional differences were observed for all other groups (P>0.05). The trays and materials tested were suitable for the autoclave sterilisation.

  17. Custom impression trays. Part II: Removal forces.

    PubMed

    Dixon, D L; Breeding, L C; Moseley, J P

    1994-03-01

    When choosing a material for making custom impression trays, it is important to understand the forces to which the tray will be subjected during removal of the completed impression from the oral cavity. Such forces have not been recorded in the dental literature. The purpose of Part II of this three-part series was to record these forces in vitro, using two different tray-removal methods. A polymethyl methacrylate custom tray was used during this study. Results from this investigation indicated that it is easier to remove a completed impression, made with a custom tray, by a single point of anterior force application (224 N) than by force application evenly around the tray (514 N). The recorded force values from this investigation will be used in Part III of this series.

  18. Force reduction of orthodontic elastomeric chains after one month in the mouth.

    PubMed

    Rock, W P; Wilson, H J; Fisher, S E

    1986-07-01

    The effect of ageing activated orthodontic elastomeric chains for one month in the mouth is reported. Over this period the mean value of exerted force fell by about 50 per cent of the original value. All the materials tested underwent a decrease in stiffness which contributed to a reduction in the force exerted. After a four week treatment period space closures in the range 0-5 mm were produced by the specimens tested.

  19. Reactions in elastomeric nanoreactors reveal the role of force on the kinetics of the Huisgen reaction on surfaces.

    PubMed

    Han, Xu; Bian, Shudan; Liang, Yong; Houk, K N; Braunschweig, Adam B

    2014-07-30

    The force dependence of the copper-free Huisgen cycloaddition between an alkyne and a surface-bound azide was examined in elastomeric nanoreactors. These studies revealed that pressure and chain length are critical factors that determine the reaction rate. These experiments demonstrate the central role of pressure and surface structure on interfacial processes that are increasingly important in biology, materials science, and nanotechnology.

  20. Effect of impression technique on bond strength.

    PubMed

    Su, Jiaping; Hobson, Ross S; McCabe, John F

    2004-01-01

    If the effects of surface preparation (eg, acid etching, laser preparation, crystal growth) are to be investigated on the same tooth from which the bond strength is recorded, a method of surface replication is required that does not affect the subsequent bond. This study investigated the effect of 2 different methods of taking impressions on bond strength. Three groups of 11 mandibular incisors were used. The labial enamel was etched with 37% phosphoric acid for 30 seconds. Group A (control) had no impression taken; in group B (silicone), impressions were taken with silicone impression material before bonding; in group C (polyether), an impression was taken with polyether before bonding. After the impressions were taken, GAC brackets (A Company, San Diego, Calif) were bonded to the labial surfaces of the etched enamel with Transbond XT light-cured composite (3M Unitek, Monrovia, Calif). Teeth with bonded brackets were stored in water at 37 degrees C for 24 hours, and then bond strength was measured on a testing machine. The adhesive remnant index (ARI) was also recorded. The lowest bond strength was found after silicone replication (mean [standard deviation]: 8.6 [1.7] MPa) and the highest in the control group (21.2 [4.0] MPa). There was no significant difference between the control group and the polyether replication group (19.1 [4.7] MPa). The surface detail replications of polyether and silicone were found to be identical. It was concluded that polyether had no significant effect on bond strength and was suitable for surface replication before bonding. Polyether allows replication of the enamel surface without a significant effect on bond strength, and this technique could be used to examine the relationship between enamel preparation techniques and subsequent bond strength between composite and enamel.

  1. Implant overdenture impressions using a dynamic impression concept

    PubMed Central

    Lee, Byung-Kil; Park, Sang-Hun; Lee, Cheong-Hee

    2014-01-01

    A dynamic impression is a functional impression that records the functional movement of the patient's own muscle and muscle attachment. This process reduces the number of random factors. This article describes a method for making a special tray using a dynamic impression concept that was made from provisional dentures used for implant healing. The individual tray is used to make a wash-impression to record the features of the mucosa in detail. The main advantage of this technique is that it provides a functional relationship of the implant components to the supporting tissues without overextension because provisional denture had been used for 2 months and the border length of individual tray was nearly the same as that of provisional denture. The delivery of the prosthesis constructed using this impression technique is time-saving because there is no need for border molding and there are fewer post-insertion appliance adjustments. PMID:24605209

  2. Making a Great First Impression

    ERIC Educational Resources Information Center

    Evenson, Renee

    2007-01-01

    Managers and business owners often base hiring decisions on first impressions. That is why it is so important to teach students to make a great first impression--before they go on that first job interview. Managers do not have unrealistic expectations, they just want to hire people who they believe can develop into valuable employees. A nice…

  3. Friction of soft elastomeric wrinkled surfaces

    NASA Astrophysics Data System (ADS)

    Rand, Charles J.; Crosby, Alfred J.

    2009-09-01

    We evaluate the sliding of a rigid spherical lens over a surface-wrinkled, elastomeric substrate. Sliding is conducted both parallel and perpendicular to the aligned surface wrinkles, and the sliding force is compared to the required sliding forces on nonwrinkled surfaces. We evaluate the effects of wrinkle dimensions and applied normal force on the sliding resistance. A simple Bowden-Tabor friction model can describe the dependence of the sliding force on normal load, with different coefficients of friction associated with the nonwrinkled and wrinkled surfaces both perpendicular and parallel. The aspect ratio of the wrinkles has a secondary effect on the sliding force. We associate the changes in friction to changes in the tangential stiffness and fracture angle caused by the surface wrinkles.

  4. Elastomeric Conducting Polyaniline Formed Through Topological Control of Molecular Templates.

    PubMed

    Ding, Hangjun; Zhong, Mingjiang; Wu, Haosheng; Park, Sangwoo; Mohin, Jacob W; Klosterman, Luke; Yang, Zhou; Yang, Huai; Matyjaszewski, Krzysztof; Bettinger, Christopher John

    2016-06-28

    A strategy for creating elastomeric conducting polyaniline networks is described. Simultaneous elastomeric mechanical properties (E < 10 MPa) and electronic conductivities (σ > 10 S cm(-1)) are achieved via molecular templating of conjugated polymer networks. Diblock copolymers with star topologies processed into self-assembled elastomeric thin films reduce the percolation threshold of polyaniline synthesized via in situ polymerization. Block copolymer templates with star topologies produce elastomeric conjugated polymer composites with Young's moduli ranging from 4 to 12 MPa, maximum elongations up to 90 ± 10%, and electrical conductivities of 30 ± 10 S cm(-1). Templated polyaniline films exhibit Young's moduli up to 3 orders of magnitude smaller compared to bulk polyaniline films while preserving comparable bulk electronic conductivity. Flexible conducting polymers have prospective applications in devices for energy storage and conversion, consumer electronics, and bioelectronics. PMID:27175931

  5. Elastomeric Conducting Polyaniline Formed Through Topological Control of Molecular Templates.

    PubMed

    Ding, Hangjun; Zhong, Mingjiang; Wu, Haosheng; Park, Sangwoo; Mohin, Jacob W; Klosterman, Luke; Yang, Zhou; Yang, Huai; Matyjaszewski, Krzysztof; Bettinger, Christopher John

    2016-06-28

    A strategy for creating elastomeric conducting polyaniline networks is described. Simultaneous elastomeric mechanical properties (E < 10 MPa) and electronic conductivities (σ > 10 S cm(-1)) are achieved via molecular templating of conjugated polymer networks. Diblock copolymers with star topologies processed into self-assembled elastomeric thin films reduce the percolation threshold of polyaniline synthesized via in situ polymerization. Block copolymer templates with star topologies produce elastomeric conjugated polymer composites with Young's moduli ranging from 4 to 12 MPa, maximum elongations up to 90 ± 10%, and electrical conductivities of 30 ± 10 S cm(-1). Templated polyaniline films exhibit Young's moduli up to 3 orders of magnitude smaller compared to bulk polyaniline films while preserving comparable bulk electronic conductivity. Flexible conducting polymers have prospective applications in devices for energy storage and conversion, consumer electronics, and bioelectronics.

  6. The effect of dietary pigmentation on the esthetic appearance of clear orthodontic elastomeric modules

    PubMed Central

    Talic, Nabeel F; Almudhi, Abdullazez A

    2016-01-01

    Objective: To compare the stain resistance of three types of clear elastomeric modules exposed to several common dietary substances through the assessment of the perception of a group of dentists to discoloration using visual analog scale (VAS). Materials and Methods: Elastomeric modules from Unitek (AU), Ormco (OR), and dentaurum (DE) were immersed in the following food substances: Coffee, black tea, chocolate, energy drink, ketchup, and Coca-Cola for 72 h. VAS was used to reflect the module staining severity. Results: Significant difference was found among the three types of modules examined in this study. OR modules showed the least mean staining ratings by the examiners. There was no statistical difference in the staining properties between AU and DE modules. Coffee and tea showed higher staining potential as compared to all staining media. Furthermore, there was no difference in the staining characteristics of coffee and black tea. Conclusions: Coffee and tea are strong staining media that should be avoided by patients who opted to have esthetic appliances for their orthodontic treatment. Elastomeric modules manufactured by AU showed higher staining optical properties as compared to the other two companies, which could be related to the manufacturing processing of these modules. PMID:27127754

  7. Long-term compression effects on elastomeric O-ring behavior

    NASA Technical Reports Server (NTRS)

    Clinton, R. G.; Turner, J. E.

    1990-01-01

    This paper discusses the results of testing performed on elastomeric seal materials that had been under compression for extended periods of time. Elastomeric seals used in the Space Shuttle redesigned solid rocket motors can experience compression times of up to six months. These seals must be capable of sealing internal motor pressure upon ignition. The tests described herein were performed in order to verify that the seals, which had experienced long-term compression could seal throughout motor operation. Testing was divided into two phases: (1) dynamic high pressure testing, and (2) resiliency testing. Dynamic testing was performed using specialized test fixtures that allowed simulation of the field joint movements during initial motor operation along with high pressure gas. Resiliency testing was performed using specialized test fixtures that also simulated field joint movements and also had the ability to measure the sealing force of the O-ring. Results from all testing indicated that the current elastomeric seals used in the redesigned solid rocket motors will seal during motor operations in the currently defined launch environments.

  8. The application of elastomeric connector for multi-channel electrophysiological recordings.

    PubMed

    Szabó, Imre; Máthé, Kálmán; Tóth, Attila; Hernádi, István; Czurkó, András

    2002-02-15

    Interest in recording multi-channel electrophysiological data from behaving animals is rapidly growing, and many laboratories tend to record a large number of EEG and/or multi-unit channels, despite the limitation of the size of the headpiece that a small behaving animal can carry. A common drawback of these experiments, therefore, is the relatively large size of even the smallest, commercially available, high-density micro-connectors for the headset. To overcome this problem, we suggest the application of elastomeric or silicone inter-rubber connectors, that are widely used in electronics. The elastomeric or "zebra" connector consists of alternating thin strips of layered electrically conductive and non-conductive materials. The conductive strips provide electrical connections between uninsulated contact surfaces of printed circuit boards such as the connector plate of the micro-drive, that holds the brain electrode wires, and the preamplifier board of the recording system. In the present paper, we provide technical details of the design of this type of connector-sets and discuss common issues arising from their use. By comparing the applicability of two designs, we aim to demonstrate the simplicity, reliability and durability of the elastomeric inter-rubber connectors in electrophysiological experiments on freely moving laboratory animals.

  9. Dewetting of thin liquid films near soft elastomeric layers.

    PubMed

    Kumar, Satish; Matar, Omar K

    2004-05-15

    Thin liquid film instabilities driven by van der Waals forces and in the proximity of soft elastomeric layers are considered in this work through two model problems: (i) a liquid film resting on an elastomeric layer and (ii) a liquid film bounded from one side by a rigid substrate and from the other side by an elastomeric layer. The elastomeric layers are modeled as linear viscoelastic solids, van der Waals forces are assumed to act only in the liquid, and lubrication theory and linear stability analysis are applied. For a liquid film resting on an elastomeric layer, substrate deformability has a destabilizing effect, as evidenced by an increase in the maximum growth rate and range of unstable wavenumbers. The destabilization worsens for thicker solid layers and is due to a lowering of the effective liquid-air interfacial tension. For an elastomeric layer resting on a liquid film, layer deformability has a stabilizing effect for thin layers but a destabilizing effect for thicker layers, with the former due to an enhancement and the latter due to a reduction of the effective solid-air interfacial tension. The results presented here suggest the possibility of exploiting the dewetting of thin liquid films to create topographically patterned surfaces on soft polymeric solids.

  10. Solvent-resistant elastomeric microfluidic devices and applications

    NASA Astrophysics Data System (ADS)

    van Dam, Robert Michael

    Microfluidics is increasingly being used in many areas of biotechnology and chemistry to achieve reduced reagent volumes, improved performance, integration, and parallelism, among other advantages. Though early devices were based on rigid materials such as glass and silicon, elastomeric materials such as polydiznethylsiloxane (PDMS) are rapidly emerging as a ubiquitous platform for applications in biotechnology. This is due, in part, to simpler fabrication procedures and to the ability to integrate mechanical microvalves at vastly greater densities. For many applications in the areas of chemical synthesis and analysis, however, PDMS cannot replace glass and silicon due to its incompatibility with many solvents and reagents. Such areas could benefit tremendously from the development of an elastomeric microfluidic device technology that combines the advantages of PDMS with the property of solvent resistance. Simplified fabrication could increase the accessibility of microfluidics, and the possibility of dense valve integration could lead to significant advances in device sophistication. Applications could be more rapidly developed by design re-use due to the independence of mechanical valves on fluid properties (unlike electrokinetic pumping), and the property of permeability could enable novel fluidic functions for accessing a broader range of reactions than is possible in glass and silicon. The first half of this thesis describes our strategies and efforts to develop this new enabling technology. Several approaches are presented in Chapter 3, and two particularly successful ones, based on new elastomers (FNB and PFPE), are described in Chapters 4 and 5. Chapter 6 describes a novel method of fabricating devices from 3D molds that could expand the range of useful clastomers. The second half of this thesis discusses microfluidic combinatorial synthesis and high throughput screening-applications that take particular advantage of the ability to integrate thousands of

  11. Use of Clinical UV Chamber to Disinfect Dental Impressions: A Comparative Study

    PubMed Central

    Sharma, Sakshi; Kumar, Varun; Gupta, Neelu

    2015-01-01

    Introduction Dental impressions are potential source of infection in a prosthodontic practice. Risk of transmission of infection through saliva, blood etc is considered as hazard for both dentist as well as dental auxiliary staff. A number of methods are currently employed for disinfecting the impressions which are technique sensitive and time consuming. This study focuses on disinfecting impression using dental UV chamber which is commonly employed for storing sterilized instruments. Aim The aim of this invitro study was to evaluate the use of clinical UV chamber to disinfect various impression materials at different time intervals and its comparison with 2% glutaraldehyde using standard immersion technique. Materials and Methods Total sample size of 180 specimens was taken from three different impression materials. The impressions were made from 30 dentulous subjects. A total of ten impressions were made for each impression material i.e. alginate, addition silicone and polyether impression material. Six punch samples were taken from each impression. Out of 6 punch sample, one was kept as control, second was disinfected by immersing in freshly prepared 2% glutaraldehyde solution for 10 minutes and remaining four were exposed to UV rays for 3 minutes, 6 minutes, 10 minutes and 15 minutes using dental UV chamber. Amount of disinfection achieved was evaluated by counting the colonies over the culture plates with the help of digital colony. Results The results showed that the mean CFUs for alginate were found to be i.e. 11797.40 ± 5989.73 (mean ± SD). The mean CFUs for addition silicone impression material was found 7095.40 with a standard deviation of 4268.83 and the mean CFUs for polyether impression material was found to be 2168.92 ± 1676 (mean ± SD). Conclusion For alginate and addition silicone impression material, disinfection was achieved on exposure to UV rays for a period of 10 minutes. However, for polyether impression material 3 minutes of exposure to

  12. Elastomeric and soft conducting microwires for implantable neural interfaces.

    PubMed

    Kolarcik, Christi L; Luebben, Silvia D; Sapp, Shawn A; Hanner, Jenna; Snyder, Noah; Kozai, Takashi D Y; Chang, Emily; Nabity, James A; Nabity, Shawn T; Lagenaur, Carl F; Cui, X Tracy

    2015-06-28

    Current designs for microelectrodes used for interfacing with the nervous system elicit a characteristic inflammatory response that leads to scar tissue encapsulation, electrical insulation of the electrode from the tissue and ultimately failure. Traditionally, relatively stiff materials like tungsten and silicon are employed which have mechanical properties several orders of magnitude different from neural tissue. This mechanical mismatch is thought to be a major cause of chronic inflammation and degeneration around the device. In an effort to minimize the disparity between neural interface devices and the brain, novel soft electrodes consisting of elastomers and intrinsically conducting polymers were fabricated. The physical, mechanical and electrochemical properties of these materials were extensively characterized to identify the formulations with the optimal combination of parameters including Young's modulus, elongation at break, ultimate tensile strength, conductivity, impedance and surface charge injection. Our final electrode has a Young's modulus of 974 kPa which is five orders of magnitude lower than tungsten and significantly lower than other polymer-based neural electrode materials. In vitro cell culture experiments demonstrated the favorable interaction between these soft materials and neurons, astrocytes and microglia, with higher neuronal attachment and a two-fold reduction in inflammatory microglia attachment on soft devices compared to stiff controls. Surface immobilization of neuronal adhesion proteins on these microwires further improved the cellular response. Finally, in vivo electrophysiology demonstrated the functionality of the elastomeric electrodes in recording single unit activity in the rodent visual cortex. The results presented provide initial evidence in support of the use of soft materials in neural interface applications.

  13. Elastomeric and soft conducting microwires for implantable neural interfaces

    PubMed Central

    Kolarcik, Christi L.; Luebben, Silvia D.; Sapp, Shawn A.; Hanner, Jenna; Snyder, Noah; Kozai, Takashi D.Y.; Chang, Emily; Nabity, James A.; Nabity, Shawn T.; Lagenaur, Carl F.; Cui, X. Tracy

    2015-01-01

    Current designs for microelectrodes used for interfacing with the nervous system elicit a characteristic inflammatory response that leads to scar tissue encapsulation, electrical insulation of the electrode from the tissue and ultimately failure. Traditionally, relatively stiff materials like tungsten and silicon are employed which have mechanical properties several orders of magnitude different from neural tissue. This mechanical mismatch is thought to be a major cause of chronic inflammation and degeneration around the device. In an effort to minimize the disparity between neural interface devices and the brain, novel soft electrodes consisting of elastomers and intrinsically conducting polymers were fabricated. The physical, mechanical and electrochemical properties of these materials were extensively characterized to identify the formulations with the optimal combination of parameters including Young’s modulus, elongation at break, ultimate tensile strength, conductivity, impedance and surface charge injection. Our final electrode has a Young’s modulus of 974 kPa which is five orders of magnitude lower than tungsten and significantly lower than other polymer-based neural electrode materials. In vitro cell culture experiments demonstrated the favorable interaction between these soft materials and neurons, astrocytes and microglia, with higher neuronal attachment and a two-fold reduction in inflammatory microglia attachment on soft devices compared to stiff controls. Surface immobilization of neuronal adhesion proteins on these microwires further improved the cellular response. Finally, in vivo electrophysiology demonstrated the functionality of the elastomeric electrodes in recording single unit activity in the rodent visual cortex. The results presented provide initial evidence in support of the use of soft materials in neural interface applications. PMID:25993261

  14. Using double-poured alginate impressions to fabricate bleaching trays.

    PubMed

    Haywood, V B; Powe, A

    1998-01-01

    Esthetic and diagnostic treatment often requires two casts of one arch, one for baseline and one for alterations (diagnostic wax-up, bleaching tray, occlusal analysis). The purpose of this study was to compare the accuracy of stone casts generated from a second pour of a properly handled alginate impression with first-poured casts. A maxillary dentoform was indexed with six reference spaces (#8-15, 9-2, 2-15, and incisal-to-gingival of #3, 9, 14). Irreversible hydrocolloid (Jeltrate) impressions were made in perforated steel trays by a single investigator. Impression material was spatulated for 1 minute. The seated impression and dentoform were wrapped in a damp paper towel to simulate intraoral conditions, and allowed to set for 2 minutes. Upon separation, the impression was stored in a damp towel for 5 minutes. The impression was poured in cast stone (Microstone) according to the manufacturer's instructions. The stone-filled impression was immediately rewrapped in a damp paper towel and allowed to set for 45 minutes at room temperature. Upon removal of the stone, the impression was rinsed with cold water, shaken dry, and repoured in the same manner. Ten impressions were made: the first five impressions were poured to make casts for Group A, then repoured as described above for casts for Group B. The remaining five impressions were poured once to make casts for Group C. The six spaces of each cast were measured three times in random order using a dial caliper and the space average calculated for the cast. At each space, analysis of variance showed no significant difference among Groups A, B, or C (P < 0.05). When alginate impressions that have been poured with cast stone are kept moist during stone setting and repoured within 45 minutes, two casts can be generated from one impression with the same degree of accuracy as two casts made from taking two separate impressions, providing the alginate does not tear during first cast removal. PMID:9656923

  15. Functional Impressions in Complete Denture and Overdenture Treatment

    PubMed Central

    Kršek, Hrvoje

    2015-01-01

    Tooth loss can cause loss of occlusal, masticatory, esthetic, physiognomic, phonetic and psychosocial function of patients. The most frequently used treatment method of completely edentulous patients and patients with a small number of remaining teeth are complete dentures or overdentures. One of the most important clinical and laboratory procedures in their fabrication is functional impression taking. The aim of this paper was to present procedures of taking functional impressions in fabrication of complete dentures and overdentures, using standardized techniques and materials. An accurate functional impression together with other correctly performed clinical and laboratory procedures ensure good retention and stability of dentures, which is a precondition for restoring patients’ lost functions. PMID:27688385

  16. Functional Impressions in Complete Denture and Overdenture Treatment.

    PubMed

    Kršek, Hrvoje; Dulčić, Nikša

    2015-03-01

    Tooth loss can cause loss of occlusal, masticatory, esthetic, physiognomic, phonetic and psychosocial function of patients. The most frequently used treatment method of completely edentulous patients and patients with a small number of remaining teeth are complete dentures or overdentures. One of the most important clinical and laboratory procedures in their fabrication is functional impression taking. The aim of this paper was to present procedures of taking functional impressions in fabrication of complete dentures and overdentures, using standardized techniques and materials. An accurate functional impression together with other correctly performed clinical and laboratory procedures ensure good retention and stability of dentures, which is a precondition for restoring patients' lost functions.

  17. Functional Impressions in Complete Denture and Overdenture Treatment

    PubMed Central

    Kršek, Hrvoje

    2015-01-01

    Tooth loss can cause loss of occlusal, masticatory, esthetic, physiognomic, phonetic and psychosocial function of patients. The most frequently used treatment method of completely edentulous patients and patients with a small number of remaining teeth are complete dentures or overdentures. One of the most important clinical and laboratory procedures in their fabrication is functional impression taking. The aim of this paper was to present procedures of taking functional impressions in fabrication of complete dentures and overdentures, using standardized techniques and materials. An accurate functional impression together with other correctly performed clinical and laboratory procedures ensure good retention and stability of dentures, which is a precondition for restoring patients’ lost functions.

  18. Nonthrombogenic, biodegradable elastomeric polyurethanes with variable sulfobetaine content.

    PubMed

    Ye, Sang-Ho; Hong, Yi; Sakaguchi, Hirokazu; Shankarraman, Venkat; Luketich, Samuel K; D'Amore, Antonio; Wagner, William R

    2014-12-24

    For applications where degradable polymers are likely to have extended blood contact, it is often important for these materials to exhibit high levels of thromboresistance. This can be achieved with surface modification approaches, but such modifications may be transient with degradation. Alternatively, polymer design can be altered such that the bulk polymer is thromboresistant and this is maintained with degradation. Toward this end a series of biodegradable, elastic polyurethanes (PESBUUs) containing different zwitterionic sulfobetaine (SB) content were synthesized from a polycaprolactone-diol (PCL-diol):SB-diol mixture (100:0, 75:25, 50:50, 25:75 and 0:100) reacted with diisocyanatobutane and chain extended with putrescine. The chemical structure, tensile mechanical properties, thermal properties, hydrophilicity, biodegradability, fibrinogen adsorption and thrombogenicity of the resulting polymers was characterized. With increased SB content some weakening in tensile properties occurred in wet conditions and enzymatic degradation also decreased. However, at higher zwitterionic molar ratios (50% and 75%) wet tensile strength exceeded 15 MPa and breaking strain was >500%. Markedly reduced thrombotic deposition was observed both before and after substantial degradation for both of these PESBUUs and they could be processed by electrospinning into a vascular conduit format with appropriate compliance properties. The mechanical and degradation properties as well as the acute in vitro thrombogenicity assessment suggest that these tunable polyurethanes could provide options appropriate for use in blood contacting applications where a degradable, elastomeric component with enduring thromboresistance is desired. PMID:25415875

  19. Nonthrombogenic, biodegradable elastomeric polyurethanes with variable sulfobetaine content.

    PubMed

    Ye, Sang-Ho; Hong, Yi; Sakaguchi, Hirokazu; Shankarraman, Venkat; Luketich, Samuel K; D'Amore, Antonio; Wagner, William R

    2014-12-24

    For applications where degradable polymers are likely to have extended blood contact, it is often important for these materials to exhibit high levels of thromboresistance. This can be achieved with surface modification approaches, but such modifications may be transient with degradation. Alternatively, polymer design can be altered such that the bulk polymer is thromboresistant and this is maintained with degradation. Toward this end a series of biodegradable, elastic polyurethanes (PESBUUs) containing different zwitterionic sulfobetaine (SB) content were synthesized from a polycaprolactone-diol (PCL-diol):SB-diol mixture (100:0, 75:25, 50:50, 25:75 and 0:100) reacted with diisocyanatobutane and chain extended with putrescine. The chemical structure, tensile mechanical properties, thermal properties, hydrophilicity, biodegradability, fibrinogen adsorption and thrombogenicity of the resulting polymers was characterized. With increased SB content some weakening in tensile properties occurred in wet conditions and enzymatic degradation also decreased. However, at higher zwitterionic molar ratios (50% and 75%) wet tensile strength exceeded 15 MPa and breaking strain was >500%. Markedly reduced thrombotic deposition was observed both before and after substantial degradation for both of these PESBUUs and they could be processed by electrospinning into a vascular conduit format with appropriate compliance properties. The mechanical and degradation properties as well as the acute in vitro thrombogenicity assessment suggest that these tunable polyurethanes could provide options appropriate for use in blood contacting applications where a degradable, elastomeric component with enduring thromboresistance is desired.

  20. Elastomeric gradients: a hedge against stress concentration in marine holdfasts?

    PubMed Central

    Waite, J Herbert; Vaccaro, Eleonora; Sun, Chengjun; Lucas, Jared M

    2002-01-01

    The byssal threads of marine mussels are elastomeric fibres with a great capacity for absorbing and dissipating energy. Up to 70% of the total absorbed energy can be dissipated in the byssus. Because byssal threads attach the mussel to hard inert surfaces in its habitat, they must combine the need to be good shock absorbers with appropriate matching of Young's modulus between living tissue and a hard sub-stratum such as stone - stiffnesses that can differ by five orders of magnitude. Recent data suggest that improved modulus matching and decreased stress concentration between different portions of the byssus is achieved by the use of protein gradients. Protein gradients in byssal threads are constructed using natural macromolecular chimeras having a central collagenous domain, variable flanking modules and histidine-rich amino and carboxy termini. Stiff silk-like flanking modules prevail distally, while at the animal end, rubbery modules resembling elastin predominate. In between the two thread ends there is a mix of both module types. The histidine-rich termini provide metal binding/cross-linking sites, while collagen domains may confer self-assembly on all parts of the structure. A graded axial distribution of flanking modules is expected to moderate stress concentration in joined materials having disparate moduli. PMID:11911771

  1. Development of a snubber type magnetorheological fluid elastomeric lag damper for helicopter stability augmentation

    NASA Astrophysics Data System (ADS)

    Ngatu, Grum T.

    Most advanced helicopter rotors are typically fitted with lag dampers, such as elastomeric or hybrid fluid-elastomeric (FE) lag dampers, which have lower parts counts, are lighter in weight, easier to maintain, and more reliable than conventional hydraulic dampers. However, the damping and stiffness properties of elastomeric and fluid elastomeric lag dampers are non-linear functions of lag/rev frequency, dynamic lag amplitude, and operating temperature. It has been shown that elastomeric damping and stiffness levels diminish markedly as amplitude of damper motion increases. Further, passive dampers tend to present severe damping losses as damper operating temperature increases either due to in-service self-heating or hot atmospheric conditions. Magnetorheological (MR) dampers have also been considered for application to helicopter rotor lag dampers to mitigate amplitude and frequency dependent damping behaviors. MR dampers present a controllable damping with little or no stiffness. Conventional MR dampers are similar in configuration to linear stroke hydraulic type dampers, which are heavier, occupy a larger space envelope, and are unidirectional. Hydraulic type dampers require dynamic seal to prevent leakage, and consequently, frequent inspections and maintenance are necessary to ensure the reliability of these dampers. Thus, to evaluate the potential of combining the simplicity and reliability of FE and smart MR technologies in augmenting helicopter lag mode stability, an adaptive magnetorheological fluid-elastomeric (MRFE) lag damper is developed in this thesis as a retrofit to an actual fluid-elastomeric (FE) lag damper. Consistent with the loading condition of a helicopter rotor system, single frequency (lag/rev) and dual frequency (lag/rev at 1/rev) sinusoidal loading were applied to the MRFE damper at varying temperature conditions. The complex modulus method was employed to linearly characterize and compare the performance of the MRFE damper with the

  2. Impression Procedures for Metal Frame Removable Partial Dentures as Applied by General Dental Practitioners.

    PubMed

    Fokkinga, Wietske A; van Uchelen, Judith; Witter, Dick J; Mulder, Jan; Creugers, Nico H J

    2016-01-01

    This pilot study analyzed impression procedures for conventional metal frame removable partial dentures (RPDs). Heads of RPD departments of three dental laboratories were asked to record features of all incoming impressions for RPDs during a 2-month period. Records included: (1) impression procedure, tray type (stock/custom), impression material (elastomer/alginate), use of border-molding material (yes/no); and (2) RPD type requested (distal-extension/tooth-bounded/combination). Of the 132 total RPD impressions, 111 (84%) involved custom trays, of which 73 (55%) were combined with an elastomer. Impression border-molding material was used in 4% of the cases. Associations between impression procedure and RPD type or dentists' year/university of graduation were not found.

  3. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40 Applicability; description...

  4. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40 Applicability; description...

  5. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40...

  6. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40...

  7. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40...

  8. Social relevance enhances memory for impressions in older adults.

    PubMed

    Cassidy, Brittany S; Gutchess, Angela H

    2012-01-01

    Previous research has demonstrated that older adults have difficulty retrieving contextual material over items alone. Recent research suggests this deficit can be reduced by adding emotional context, allowing for the possibility that memory for social impressions may show less age-related decline than memory for other types of contextual information. Two studies investigated how orienting to social or self-relevant aspects of information contributed to the learning and retrieval of impressions in young and older adults. Participants encoded impressions of others in conditions varying in the use of self-reference (Experiment 1) and interpersonal meaningfulness (Experiment 2), and completed memory tasks requiring the retrieval of specific traits. For both experiments, age groups remembered similar numbers of impressions. In Experiment 1 using more self-relevant encoding contexts increased memory for impressions over orienting to stimuli in a non-social way, regardless of age. In Experiment 2 older adults had enhanced memory for impressions presented in an interpersonally meaningful relative to a personally irrelevant way, whereas young adults were unaffected by this manipulation. The results provide evidence that increasing social relevance ameliorates age differences in memory for impressions, and enhances older adults' ability to successfully retrieve contextual information.

  9. Simulated Body Fluid Nucleation of Three-Dimensional Printed Elastomeric Scaffolds for Enhanced Osteogenesis.

    PubMed

    Castro, Nathan J; Tan, Wilhelmina Nanrui; Shen, Charlie; Zhang, Lijie Grace

    2016-07-01

    Osseous tissue defects caused by trauma present a common clinical problem. Although traditional clinical procedures have been successfully employed, several limitations persist with regards to insufficient donor tissue, disease transmission, and inadequate host-implant integration. Therefore, this work aims to address current limitations regarding inadequate host tissue integration through the use of a novel elastomeric material for three-dimensional (3D) printing biomimetic and bioactive scaffolds. A novel thermoplastic polyurethane-based elastomeric composite filament (Gel-Lay) was used to manufacture porous scaffolds. In an effort to render the scaffolds more bioactive, the flexible scaffolds were subsequently incubated in simulated body fluid at various time points and evaluated for enhanced mechanical properties along with the effects on cell adhesion, proliferation, and 3-week osteogenesis. This work is the first reported use of a novel class of flexible elastomeric materials for the manufacture of 3D printed bioactive scaffold fabrication allowing efficient and effective nucleation of hydroxyapatite (HA) leading to increased nanoscale surface roughness while retaining the bulk geometry of the predesigned structure. Scaffolds with interconnected microfibrous filaments of ∼260 μm were created and nucleated in simulated body fluid that facilitated cell adhesion and spreading after only 24 h in culture. The porous structure further allowed efficient nucleation, exchange of nutrients, and metabolic waste removal during new tissue formation. Through the incorporation of osteoconductive HA, human fetal osteoblast adhesion and differentiation were greatly enhanced thus setting the tone for further exploration of this novel material for biomedical and tissue regenerative applications. PMID:27298115

  10. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  11. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  12. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  13. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  14. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  15. A review on the cords & plies reinforcement of elastomeric polymer matrix

    NASA Astrophysics Data System (ADS)

    Mahmood, S. S.; Husin, H.; Mat-Shayuti, M. S.; Hassan, Z.

    2016-06-01

    Steel, polyester, nylon and rayon are the main materials of cords & plies that have been reinforced in the natural rubber to produce quality tyres but there is few research reported on cord and plies reinforcement in silicone rubber. Taking the innovation of tyres as inspiration, this review's first objective is to compile the comprehensive studies about the cords & plies reinforcement in elastomeric polymer matrix. The second objective is to gather information about silicone rubber that has a high potential as a matrix phase for cords and plies reinforcement. All the tests and findings are gathered and compiled in sections namely processing preparation, curing, physical and mechanical properties, and adhesion between cords-polymer.

  16. [Complications Resulting from Taking Ear Impressions].

    PubMed

    Sugiuchi, Tomoko; Kodera, Kazuoki; Zusho, Hiroyuki; Asano, Yoshikazu; Kanesada, Keiko; Hayashida, Mitsuhiro; Kanaya, Koichiro; Tokumaru, Takeshi

    2015-08-01

    In 2012, we carried out a study in a large sample to understand the secondary injuries caused during the taking ear impressions for hearing aids. This study is a follow-up of previous research conducted in 1986 (285 medical institutions) and 1999 (98 medical institutions). We posted a questionnaire survey to the otolaryngology departments of 3,257 medical institutions. The response rate to the questionnaire was 62.9% (2,050 of the 3,257 institutions), and the results indicated that 301 of the 2050 institutions (14.7%) had experience with secondary injuries, with a total of 460 cases reported. In 342 of the 460 cases (74.3%), the secondary injuries occurred at hearing-aid dealerships, followed by 67 cases (14.6%) at affiliated medical institutions, and 51 cases (11.1%) in other locations, including other medical institutions, rehabilitation counseling centers, and educational institutions. The most common type of secondary injury (298 cases, 64.8%) was caused by the presence of foreign bodies in the ear, which in turn was a result of complications occurring during the removal of residual ear impression material. Of these 298 cases, 32 required excision of the foreign bodies and surgical intervention under general anesthesia. The remaining 10 cases exhibited isolated tympanic membrane perforation without foreign body-related complications. Furthermore, 146 cases (31.7%) developed bleeding and otitis externa following removal of the ear impression, and there were reports of cases with bleeding that required long-term outpatient care and treatment. Therefore, since retention of a foreign body in the ear and tympanic membrane perforation can occur even in patients without a history of surgery or prior otologic history, adjustment of hearing aids requires prior otorhinolaryngological examination. Furthermore, because of the risk of secondary injury when taking ear impressions, this procedure must be performed with caution under the guidance of an otolaryngologist.

  17. Plaque retention on elastomeric ligatures. An in vivo study

    PubMed Central

    CONDÒ, R.; CASAGLIA, A.; CONDÒ, S.G.; CERRONI, L.

    2013-01-01

    SUMMARY Fixed orthodontic appliances make it difficult to maintain the oral hygiene, resulting in plaque accumulation. Retention of bacterial plaque, represents a risk for white spot lesions and development of periodontal disease. Aim Purpose of this study was to determine in vivo the retention of plaque on three different elastic ligatures, in comparison with stainless steel ligature, to determine a possible association between type of ligatures and accumulation of microorganisms. Material and Methods three elastic ligation systems were analyzed for plaque retention: ring-shape, clear, latex ligatures (Leone® Spa), ring-shape, grey, polyurethane ligatures (Micerium® Spa) and grey, polyurethane, Slide low-friction ligatures (Leone® Spa), compared with stainless steel ligatures (Leone® Spa) used as control. Forthy orthodontic patients undergoing fixed orthodontic therapy were selected. A sample for each type of ligature were applied inside the oral cavity of each subject. Samples were kept in the oral cavity for 28 days, ligating 0.16 X 0.22 stainless steel archwire to stainless steel orthodontic premolars brackets. The presence of bacterical slime was quantified by spectrophotometric method (crystal violet-Bouin’s fixative) and morphological observations was evaluated by Scanning Electron Microscopy (SEM). Results From analysis of bacterical slime emerges that all the elastics showed a low plaque retention, especially if compared to the group of steinless steel ligatures, that presented a greater plaque adhesion, statistically significant compared to the Slide group (r<0.0002) and the two elastic groups (r<0.0001). This study reported no significant difference between the Slide ligatures and the traditional elastic ligatures as regards the retention of plaque. SEM images showed presence of cocci, rods and few filamentous organisms and an interbacterial matrix in all observed samples. Conclusion Elastomeric ligatures showed a significant lower susceptibility

  18. Stability of colistimethate sodium in a disposable elastomeric infusion device.

    PubMed

    Abdulla, Alan; van Leeuwen, Roelof W F; de Vries Schultink, Aurelia H M; Koch, Birgit C P

    2015-01-01

    Infections of the respiratory tract with Pseudomonas aeruginosa in cystic fibrosis patients are frequently treated with colistimethate sodium (CMS). For the intravenous administration of CMS a disposable elastomeric pump is a convenient option. To date, there are no data available on the chemical stability of CMS solutions stored in elastomeric pumps. We evaluated the chemical stability of 0.8 mg/mL solutions of CMS by measuring the degradation over a period of 7 days. Test samples were prepared by diluting CMS with saline solution (0.9%). The preparations were transferred to 100-mL elastomeric pumps and stored at 4 °C. The chemical stability was measured by a high-performance liquid chromatography method with UV detection. There was no degradation of CMS (<0.5% of CMS present as colistin) for at least 3 day at 4 °C, and after 7 days all test samples remained chemically stable (<5% of CMS present as colistin). Since colistin formed in pharmacy-compounded CMS solutions prior to administration may cause toxicity, we advise that the solution should be used before the hydrolysis of CMS occurs. Therefore, we recommend that the 0.8 mg/mL solution of CMS can be stored for up to 3 days at 4 °C in an elastomeric pump. PMID:25863116

  19. Rotary Actuators Based on Pneumatically Driven Elastomeric Structures.

    PubMed

    Gong, Xiangyu; Yang, Ke; Xie, Jingjin; Wang, Yanjun; Kulkarni, Parth; Hobbs, Alexander S; Mazzeo, Aaron D

    2016-09-01

    Unique elastomeric rotary actuators based on pneumatically driven peristaltic motion are demonstrated. Using silicone-based wheels, these motors enable a new class of soft locomotion not found in nature, which is capable of withstanding impact, traversing irregular terrain, and operating in water. For soft robotics, this work marks progress toward providing torque without bending actuators. PMID:27348794

  20. Voltage-controlled surface wrinkling of elastomeric coatings.

    PubMed

    van den Ende, Daan; Kamminga, Jan-Dirk; Boersma, Arjen; Andritsch, Thomas; Steeneken, Peter G

    2013-07-01

    Wrinkling of elastomeric coatings by an electric field is reported. The associated changes in the coating's optical properties yield switchable mirrors and windows. The field Ec needed to induce wrinkling is a factor of 4.4 lower than the theoretically predicted value, which is attributed to space-charge injection. PMID:23703838

  1. Maxillomandibular relationship record for complete arch/mouth implant restorations using putty-elastomeric occlusion rim at healing abutment level

    PubMed Central

    Patil, Pravinkumar G.; Nimbalkar-Patil, Smita

    2015-01-01

    Introduction: Recording of the maxillomandibular relationship (MMR) in implant complete arch restorations usually necessitates removal of the healing abutments to attach the record bases, which makes the procedures tedious and time-consuming. Materials and Methods: This article describes the procedure of recording of MMR for complete mouth rehabilitation with the help of the putty elastomeric record base cum occlusion rim reinforced with the acrylic resin framework. This technique records the MMR without removing the healing abutments from mouth and without attaching the acrylic-resin record base with wax occlusion rim. Results: The use of putty-elastomeric occlusion rim provides stable interocclusal records for implant supported complete arch (or mouth) rehabilitation. Conclusion: Maxillomandibular relationship records made with the present technique is less time-consuming and accurate with less chances of distortion of the MMR records. PMID:26321828

  2. Impression creep characterization of TiAl weldments

    SciTech Connect

    Gibbs, W.S.; Aikin, R.M. Sr.; Martin, P.L.; Patterson, R.A.

    1990-01-01

    The Impression Creep technique has been applied to XD{trademark} TiAl weldments to evaluate the local creep resistance of the fusion zone and the heat affected zone. The material used in this study was TiAl produced by Martin Marietta Research Laboratories, using their patented ingot processing which incorporates 1 to 10 {mu}m diameter particles of carbide, nitride or boride compounds. The impression creep technique uses a small indenter to locally evaluate the creep resistance of the heterogeneous microstructure developed during the welding process. The indenters used in this investigation were 1 mm in diameter. Results obtained from the impression creep tests are compared to results obtained from constant stress tensile creep tests on the base material. Creep resistance of the heat affected zone and the fusion zone are compared to and contrasted with the base material strength. 19 refs., 2 figs., 2 tabs.

  3. Resilin-PEG Hybrid Hydrogels Yield Degradable Elastomeric Scaffolds with Heterogeneous Microstructure.

    PubMed

    McGann, Christopher L; Akins, Robert E; Kiick, Kristi L

    2016-01-11

    Hydrogels derived from resilin-like polypeptides (RLPs) have shown outstanding mechanical resilience and cytocompatibility; expanding the versatility of RLP-based materials via conjugation with other polypeptides and polymers would offer great promise in the design of a range of materials. Here, we present an investigation of the biochemical and mechanical properties of hybrid hydrogels composed of a recombinant RLP and a multiarm PEG macromer. These hybrid hydrogels can be rapidly cross-linked through a Michael-type addition reaction between the thiols of cysteine residues on the RLP and vinyl sulfone groups on the multiarm PEG. Oscillatory rheology and tensile testing confirmed the formation of elastomeric hydrogels with mechanical resilience comparable to aortic elastin; hydrogel stiffness was easily modulated through the cross-linking ratio. Macromolecular phase separation of the RLP-PEG hydrogels offers the unique advantage of imparting a heterogeneous microstructure, which can be used to localize cells, through simple mixing and cross-linking. Assessment of degradation of the RLP by matrix metalloproteinases (MMPs) illustrated the specific proteolysis of the polypeptide in both its soluble form and when cross-linked into hydrogels. Finally, the successful encapsulation and viable three-dimensional culture of human mesenchymal stem cells (hMSCs) demonstrated the cytocompatibility of the RLP-PEG gels. Overall, the cytocompatibility, elastomeric mechanical properties, microheterogeneity, and degradability of the RLP-PEG hybrid hydrogels offer a suite of promising properties for the development of cell-instructive, structured tissue engineering scaffolds.

  4. Resilin-PEG Hybrid Hydrogels Yield Degradable Elastomeric Scaffolds with Heterogeneous Microstructure.

    PubMed

    McGann, Christopher L; Akins, Robert E; Kiick, Kristi L

    2016-01-11

    Hydrogels derived from resilin-like polypeptides (RLPs) have shown outstanding mechanical resilience and cytocompatibility; expanding the versatility of RLP-based materials via conjugation with other polypeptides and polymers would offer great promise in the design of a range of materials. Here, we present an investigation of the biochemical and mechanical properties of hybrid hydrogels composed of a recombinant RLP and a multiarm PEG macromer. These hybrid hydrogels can be rapidly cross-linked through a Michael-type addition reaction between the thiols of cysteine residues on the RLP and vinyl sulfone groups on the multiarm PEG. Oscillatory rheology and tensile testing confirmed the formation of elastomeric hydrogels with mechanical resilience comparable to aortic elastin; hydrogel stiffness was easily modulated through the cross-linking ratio. Macromolecular phase separation of the RLP-PEG hydrogels offers the unique advantage of imparting a heterogeneous microstructure, which can be used to localize cells, through simple mixing and cross-linking. Assessment of degradation of the RLP by matrix metalloproteinases (MMPs) illustrated the specific proteolysis of the polypeptide in both its soluble form and when cross-linked into hydrogels. Finally, the successful encapsulation and viable three-dimensional culture of human mesenchymal stem cells (hMSCs) demonstrated the cytocompatibility of the RLP-PEG gels. Overall, the cytocompatibility, elastomeric mechanical properties, microheterogeneity, and degradability of the RLP-PEG hybrid hydrogels offer a suite of promising properties for the development of cell-instructive, structured tissue engineering scaffolds. PMID:26646060

  5. Eyeblinks in formation of impressions.

    PubMed

    Omori, Y; Miyata, Y

    1996-10-01

    The purpose of this study was to investigate the influence of frequency of one's eyeblinks on creating a personal impression. The subjects, 102 males and 127 females, ages 15 to 60 years, rated on a 7-point semantic differential scale a rarely blinking person or a frequently blinking person described on a question-sheet. A factor analysis of the ratings yielded three factors, interpreted as Nervousness, Unfriendliness, and Lack of intelligence. The frequently blinking person was rated as more nervous and less intelligent than the rarely blinking person. Present results provided evidence that frequency of eyeblinks may play an important role on the formation of impressions. Further implications of the findings are discussed. PMID:8902035

  6. Forming impressions from incongruent traits.

    PubMed

    Casselden, P A; Hampson, S E

    1990-08-01

    The factors that affect the ease with which impressions are formed from incongruent trait pairs are investigated. In Experiments 1 and 2, trait pairs that were both descriptively and evaluatively congruent, as well as ones that were only evaluatively congruent, were found to be more imaginable and to be perceived as more frequently co-occurring than incongruent trait pairs. In Experiment 3, response latency provided a converging measure of ease of imaginability. Experiment 4 examined written descriptions of targets described by these trait pairs, and found more attempts to integrate the congruent than the incongruent pairs. These findings are discussed in terms of the relation between laypersons' impressions of personality and formal personality assessment.

  7. Forming impressions from incongruent traits.

    PubMed

    Casselden, P A; Hampson, S E

    1990-08-01

    The factors that affect the ease with which impressions are formed from incongruent trait pairs are investigated. In Experiments 1 and 2, trait pairs that were both descriptively and evaluatively congruent, as well as ones that were only evaluatively congruent, were found to be more imaginable and to be perceived as more frequently co-occurring than incongruent trait pairs. In Experiment 3, response latency provided a converging measure of ease of imaginability. Experiment 4 examined written descriptions of targets described by these trait pairs, and found more attempts to integrate the congruent than the incongruent pairs. These findings are discussed in terms of the relation between laypersons' impressions of personality and formal personality assessment. PMID:2213498

  8. An Improved Correlation between Impression and Uniaxial Creep

    SciTech Connect

    Hsueh, Chun-Hway; Miranda, Pedro; Becher, Paul F

    2006-01-01

    A semiempirical correlation between impression and uniaxial creep has been established by Hyde et al. [Int. J. Mech. Sci. 35, 451 (1993) ] using finite element results for materials exhibiting general power-law creep with the stress exponent n in the range 2 {<=} n {<=} 15. Here, we derive the closed-form solution for a special case of viscoelastic materials, i.e., n = 1, subjected to impression creep and obtain the exact correlation between impression and uniaxial creep. This analytical solution serves as a checkpoint for the finite element results. We then perform finite element analyses for the general case to derive a semiempirical correlation, which agrees well with both analytical viscoelastic results and the existing experimental data. Our improved correlation agrees with the correlation of Hyde et al. for n {>=} 4, and the difference increases with decreasing n for n<4.

  9. Soft materials with recoverable shape factors from extreme distortion states

    DOE PAGES

    Goff, Jonathan; Sulaiman, Santy; Arkles, Barry; Lewicki, James P.

    2016-01-20

    We present elastomeric polysiloxane nanocomposites with elongations of >5000% (more than 3× greater than any previously reported material) with excellent shape recovery. Highly deformable materials are desirable for the fabrication of stretchable implants and microfluidic devices. No crosslinking or domain formation is observed by a variety of analytical techniques, suggesting that their elastomeric behavior is caused by polymer chain entanglements.

  10. Ultraviolet light crosslinking of poly(trimethylene carbonate) for elastomeric tissue engineering scaffolds.

    PubMed

    Bat, Erhan; Kothman, Bas H M; Higuera, Gustavo A; van Blitterswijk, Clemens A; Feijen, Jan; Grijpma, Dirk W

    2010-11-01

    A practical method of photocrosslinking high molecular weight poly(trimethylene carbonate)(PTMC) is presented. Flexible, elastomeric and biodegradable networks could be readily prepared by UV irradiating PTMC films containing pentaerythritol triacrylate (PETA) and a photoinitiator. The network characteristics, mechanical properties, wettability, and in vitro enzymatic erosion of the photocrosslinked PTMC films were investigated. Densely crosslinked networks with gel contents up to 98% could be obtained in this manner. Upon photocrosslinking, flexible and tough networks with excellent elastomeric properties were obtained. To illustrate the ease with which the properties of the networks can be tailored, blends of PTMC with mPEG-PTMC or with PTMC-PCL-PTMC were also photocrosslinked. The wettability and the enzymatic erosion rate of the networks could be tuned by blending with block copolymers. Tissue engineering scaffolds were also fabricated using these flexible photocrosslinkable materials. After crosslinking, the fabricated PTMC-based scaffolds showed inter-connected pores and extensive microporosity. Human mesenchymal stem cell (hMSC) culturing studies showed that the photocrosslinked scaffolds prepared from PTMC and PTMC/PTMC-PCL-PTMC blends are well-suited for tissue engineering applications. PMID:20739060

  11. Antimicrobial Effect of Zataria Multiflora Extract in Comparison with Chlorhexidine Mouthwash on Experimentally Contaminated Orthodontic Elastomeric Ligatures

    PubMed Central

    Aghili, Hossein; Jafari Nadoushan, Abbas Ali; Herandi, Vahid

    2015-01-01

    Objectives: Long-term use of orthodontic appliances and fixation ligatures creates a favorable environment for the accumulation of oral normal microflora and increases the risk of enamel demineralization and periodontal disease. The aim of this study was to compare the antimicrobial effects of Zataria Multiflora extract and 0.2% chlorhexidine (CHX) mouthwash on experimentally contaminated orthodontic elastomeric ligatures. Materials and Methods: In this lab trial study, Iranian and foreign-made elastomeric ligatures were experimentally contaminated in Streptococcus mutans, Enterococcus faecalis and Candida albicans suspensions. Ligatures were then decontaminated using 0.2% CHX as the control, 0.5 mg/ml Zataria multiflora extract mouthwashes as the test and phosphate buffered saline (PBS) as the negative control for one hour. Antimicrobial properties of both solutions were evaluated by comparing the mean viable bacterial cell count on both rings after decontamination, using SPSS version 15 software. Results: The mean viable bacterial cell count on Iranian ligatures was greater than that on foreign-made ligatures before disinfection (P=0.001), however this difference for C. albicans was not statistically significant (P=0.061). Chlorhexidine mouthwash completely eliminated all tested microorganisms attached to both elastomeric rings, but Zataria extract was only capable of completely eliminating C. albicans from both ligatures. Statistically significant differences were found in viable bacterial counts on both ligatures before and after disinfection with Zataria extract (P=0.0001). Conclusion: Zataria multiflora extract has antimicrobial properties and can be used for disinfection of elastomeric ligatures. In vivo studies are required to evaluate the efficacy of the incorporation of this herbal extract in mouthwashes for orthodontic patients. PMID:26005448

  12. Bending a beam by a generalized ideal elastomeric gel

    PubMed Central

    Cai, Shengqiang

    2015-01-01

    A hybrid beam with a gel layer bonded on the top of an elastic non-swellable substrate has been commonly adopted to make various sensors and actuators. Usually, different models need to be developed for the hybrid beam when different gels are used in the system. In this article, based on the generalized ideal elastomeric gel model, we formulate a unified relationship between the swelling of hydrogels and the bending curvature of the elastic beam, which is independent of specific swelling mechanisms of gels. We further illustrate that the equations derived in the article can be used to validate the ideal elastomeric gel model and measure the elasticity of polymer networks of the gels. PMID:25792965

  13. Assessing patient preference for two types of elastomeric infusion device.

    PubMed

    Dodd, Susan

    Home administration of antibiotic therapy to cystic fibrosis patients is one of many applications for the use of elastomeric infusion devices. Patient acceptability can significantly affect adherence to complex drug regimens with concordance being a concern in this patient population. While patient acceptance is often cited as a factor in pump selection, patient preference has not been assessed within a particular class of infusion device. The objective of this study was to assess patient preference for one type of elastomeric infusion device (Baxter Intermate--hard-shelled design) or another (Fresenius Kabi Eclipse--soft-shelled design). Twenty-four patients entered the study. 20/24 (83%) patients expressed a preference for the Eclipse, while 4/24 (17%) stated no preference for either device. The Eclipse device was found to be much more favourable in terms of comfort and discreetness. Patient preference should therefore be given significant consideration in order to maximize concordance with drug regimens. PMID:18026019

  14. Generation and detection of gigahertz surface acoustic waves using an elastomeric phase-shift mask

    NASA Astrophysics Data System (ADS)

    Li, Dongyao; Zhao, Peng; Zhao, Ji-Cheng; Cahill, David G.

    2013-10-01

    We describe a convenient approach for measuring the velocity vSAW of surface acoustic waves (SAWs) of the near-surface layer of a material through optical pump-probe measurements. The method has a lateral spatial resolution of <10 μm and is sensitive to the elastic constants of the material within ≈300 nm of the surface. SAWs with a wavelength of 700 nm and 500 nm are generated and detected using an elastomeric polydimethylsiloxane phase-shift mask which is fabricated using a commercially available Si grating as a mold. Time-domain electromagnetics calculations show, in agreement with experiment, that the efficiency of the phase-shift mask for generating and detecting SAWs decreases rapidly as the periodicity of the mask decreases below the optical wavelength. We validate the experimental approach using bulk and thin film samples with known elastic constants.

  15. Elastomeric microfluidic diode and rectifier work with Newtonian fluids

    PubMed Central

    Liu, John; Chen, Yan; Taylor, Clive R.; Scherer, Axel; Kartalov, Emil P.

    2009-01-01

    We report on two microfluidic elastomeric autoregulatory devices—a diode and a rectifier. They exhibit physically interesting and complex nonlinear behaviors (saturation, bias-dependent resistance, and rectification) with a Newtonian fluid. Due to their autoregulatory properties, they operate without active external control. As a result, they enable increased microfluidic device density and overall system miniaturization. The demonstrated diode and rectifier would also be useful components in future microfluidic logic circuitry. PMID:20057932

  16. Interaction of Reinforced Elastomeric Bearings in Bridge Construction

    NASA Astrophysics Data System (ADS)

    Nittmannová, Ľubica; Magura, Martin

    2016-03-01

    The aim of this paper is to demonstrate the behavior of reinforced elastomeric bearings under various loads. They are made of special types of bearings. The experimental verification of these special bearings has been tested on various types of loading. The results of the experimental measurements are compared with the results of the numerical modeling and calculations according to the standard assumptions in STN EN 1337-3. In the conclusion, the results are summarized for the selected types of bearings.

  17. Equilibrium swelling of elastomeric materials in solvent environments

    SciTech Connect

    Green, P.F.

    1990-03-01

    The equilibrium swelling of silicones, fluorosilicones, VITON and ethylene-propylene-diene (EPDM) elastomers in an environment of the jet fuel JP4 was investigated. The volume of silicone and DPDM elastomers increased by approximately 100% when they were placed in a saturated environment of JP4. Conversely, the volume of the fluorosilicone elastomer increased by approximately 15% and that of VITON less than 1%. In acetone, a commonly used solvent, the equilibrium swelling of VITON and the fluorosilicone elastomer was excessive, on the order of 100%, wheras the silicone and EPDM elastomers exhibited small changes in dimensions. Reasons for these observations are discussed in detail. We also present a simple scheme by which one may, qualitatively, determine the dimensional stability of these elastomers in different solvents if the cohesive energy density of the solvent, which is readily available in a number of handbooks, is known. We also evaluated the vulnerability of some commonly used engineering thermoplastics to JP4. The results are tabulated. 13 refs., 6 figs., 3 tab.

  18. Disinfection of dental impressions and occlusal records by ultraviolet radiation.

    PubMed

    Larsen, T; Fiehn, N E; Peutzfeldt, A; Owall, B

    2000-06-01

    As chemical disinfection of dental impressions may cause adverse effects on materials and the dental personnel this study examined disinfection by ultraviolet radiation. Alginate, addition silicone rubber and red wax contaminated by Streptococcus salivarius, Fusobacterium nucleatum and five other bacteria in different suspension media were radiated for up to 18 min, and the number of colony forming units was compared to non-radiated controls. The effect of ultraviolet radiation differed among bacterial species and depended on the organic content in the suspension. Generally, the bacterial reduction after ultraviolet radiation was below 4 log steps and thus insufficient for disinfection of dental impressions. PMID:11307403

  19. Disinfection of dental impressions and occlusal records by ultraviolet radiation.

    PubMed

    Larsen, T; Fiehn, N E; Peutzfeldt, A; Owall, B

    2000-06-01

    As chemical disinfection of dental impressions may cause adverse effects on materials and the dental personnel this study examined disinfection by ultraviolet radiation. Alginate, addition silicone rubber and red wax contaminated by Streptococcus salivarius, Fusobacterium nucleatum and five other bacteria in different suspension media were radiated for up to 18 min, and the number of colony forming units was compared to non-radiated controls. The effect of ultraviolet radiation differed among bacterial species and depended on the organic content in the suspension. Generally, the bacterial reduction after ultraviolet radiation was below 4 log steps and thus insufficient for disinfection of dental impressions.

  20. An innovative impression technique for fabrication of a custom made ocular prosthesis

    PubMed Central

    Tripuraneni, Sunil Chandra; Vadapalli, Sriharsha Babu; Ravikiran, P; Nirupama, N

    2015-01-01

    Various impression and fitting techniques have been described in the past for restoring ocular defects. The present article describes a new direct impression technique for recording and rehabilitating ocular defects, by custom-made ocular prosthesis. All the techniques described in the history, mainly concentrated in recording the tissue surface of the defect, which made it difficult to contour the palpebral surface resulting in the poor esthetics of the prosthesis. The present impression technique uses heavy bodied polyvinyl siloxane impression material, which facilitates accurate recording of the tissue surface and the palpebral surface of the defect, resulting in the fabrication of functionally and esthetically acceptable prosthesis. PMID:26265651

  1. An innovative impression technique for fabrication of a custom made ocular prosthesis.

    PubMed

    Tripuraneni, Sunil Chandra; Vadapalli, Sriharsha Babu; Ravikiran, P; Nirupama, N

    2015-06-01

    Various impression and fitting techniques have been described in the past for restoring ocular defects. The present article describes a new direct impression technique for recording and rehabilitating ocular defects, by custom-made ocular prosthesis. All the techniques described in the history, mainly concentrated in recording the tissue surface of the defect, which made it difficult to contour the palpebral surface resulting in the poor esthetics of the prosthesis. The present impression technique uses heavy bodied polyvinyl siloxane impression material, which facilitates accurate recording of the tissue surface and the palpebral surface of the defect, resulting in the fabrication of functionally and esthetically acceptable prosthesis.

  2. Comparison of digital and conventional impression techniques: evaluation of patients’ perception, treatment comfort, effectiveness and clinical outcomes

    PubMed Central

    2014-01-01

    Background The purpose of this study was to compare two impression techniques from the perspective of patient preferences and treatment comfort. Methods Twenty-four (12 male, 12 female) subjects who had no previous experience with either conventional or digital impression participated in this study. Conventional impressions of maxillary and mandibular dental arches were taken with a polyether impression material (Impregum, 3 M ESPE), and bite registrations were made with polysiloxane bite registration material (Futar D, Kettenbach). Two weeks later, digital impressions and bite scans were performed using an intra-oral scanner (CEREC Omnicam, Sirona). Immediately after the impressions were made, the subjects’ attitudes, preferences and perceptions towards impression techniques were evaluated using a standardized questionnaire. The perceived source of stress was evaluated using the State-Trait Anxiety Scale. Processing steps of the impression techniques (tray selection, working time etc.) were recorded in seconds. Statistical analyses were performed with the Wilcoxon Rank test, and p < 0.05 was considered significant. Results There were significant differences among the groups (p < 0.05) in terms of total working time and processing steps. Patients stated that digital impressions were more comfortable than conventional techniques. Conclusions Digital impressions resulted in a more time-efficient technique than conventional impressions. Patients preferred the digital impression technique rather than conventional techniques. PMID:24479892

  3. Evaluation of oral scanning in comparison to impression using three-dimensional registration

    NASA Astrophysics Data System (ADS)

    Brogle-Kim, Yur-Chung; Deyhle, Hans; Müller, Bert; Schulz, Georg; Bormann, Therese; Beckmann, Felix; Jäger, Kurt

    2012-10-01

    Crown and bridge restorations are one of the main treatment methods in fixed prosthodontics. The fabrication requires data on the patient's denture shape. This information is generally obtained as a hard copy from an impression mold. Alternatively, one can acquire the data electronically using oral optical three-dimensional (3D) imaging techniques, which determine the surface of the denture. The aim of the study was to quantitatively compare the accuracy of three dimensional scanning with that of conventional impressions and give a statement how far the scanner provides a clinical alternative with equal or better precision. Data from 10 teeth were acquired in the dental office with a polyether impression material and an oral scanner. Data from the impressions were digitalized by means of micro computed tomography. The data were then 3D registered to identify the potential differences between impression and optical scan. We could demonstrate that the oral scanner's data and the conventional impressions are comparable.

  4. Custom impression trays: Part I--Mechanical properties.

    PubMed

    Breeding, L C; Dixon, D L; Moseley, J P

    1994-01-01

    Dimensional stability of custom impression trays is an important factor in determining the degree of accuracy achieved in forming a master cast. Such trays must remain stable over time and must not exhibit permanent deformation when a completed impression is removed from the oral cavity. Measurement of the mechanical properties allows comparison between various tray materials and is useful in interpreting data on stresses incurred during removal of the completed impression. In Part I of this three-part series, the various mechanical properties of five tray resins: one autopolymerizing polymethyl methacrylate, one light-polymerizing, and three brands of thermoplastic resins were recorded and compared. The thermoplastic resins studied in this investigation exhibited lower measured values for the strength and elastic modulus properties than the light-polymerizing resin and the autopolymerizing polymethyl methacrylate resin studied.

  5. Custom impression trays: Part I--Mechanical properties.

    PubMed

    Breeding, L C; Dixon, D L; Moseley, J P

    1994-01-01

    Dimensional stability of custom impression trays is an important factor in determining the degree of accuracy achieved in forming a master cast. Such trays must remain stable over time and must not exhibit permanent deformation when a completed impression is removed from the oral cavity. Measurement of the mechanical properties allows comparison between various tray materials and is useful in interpreting data on stresses incurred during removal of the completed impression. In Part I of this three-part series, the various mechanical properties of five tray resins: one autopolymerizing polymethyl methacrylate, one light-polymerizing, and three brands of thermoplastic resins were recorded and compared. The thermoplastic resins studied in this investigation exhibited lower measured values for the strength and elastic modulus properties than the light-polymerizing resin and the autopolymerizing polymethyl methacrylate resin studied. PMID:8120842

  6. Empirical impression technique for artificial eye fitting.

    PubMed

    LeGrand, J A; Hughes, M O

    1990-01-01

    Using an impression of the anophthalmic socket to facilitate the design of an artificial eye is common practice today. The Modified Impression technique was described in the American Journal of Ophthalmology, February 1969, by Lee Allen and Howard E. Webster. It is a highly successful method that involves taking an impression of the socket using an impression tray, then making a wax casting of the impression, and final modifications to the anterior aspect of the wax model. A different technique has been in use in our office and elsewhere for more than 15 years, also with a high degree of success. We've dubbed it the "Empirical/Impression" method. It involves similar steps to the Modified Impression system, but in different order: first a wax model of the anterior aspect of the eye is designed and modified; second, an impression is made of the socket, using this wax model as an impression tray. The primary advantage of this method is efficiency. It involves one less laboratory procedure, hence making a "one-day custom eye" a reality. Although this process can be used in almost any case, the Modified Impression technique may work better for certain highly irregular sockets where "reading" the fornices by empirical means may be difficult. Either method requires a highly skilled and experienced fitter to make appropriate modifications to the anterior aspect of the prosthesis.

  7. Surface porosity of stone casts resulting from immersion of addition silicone rubber impressions in disinfectant solutions.

    PubMed

    Hiraguchi, Hisako; Kaketani, Masahiro; Hirose, Hideharu; Kikuchi, Hisaji; Yoneyama, Takayuki

    2014-01-01

    This study investigated the effects of immersion of addition silicone rubber impressions in disinfectant solutions on the surface porosity of the resulting stone casts. Five brands of type 2 and 3 addition silicone rubber impression materials and one brand of type 4 dental stone were used. Impressions of a master die designed to simulate an abutment tooth were immersed in disinfectant for 30 minutes. The disinfectants used were 2% glutaraldehyde solution and 0.55% ortho-phthalaldehyde solution. The surface porosities of stone casts obtained from two brands of impression materials immersed in disinfectant for 30 minutes were determined. Results suggest that impression materials immersed in disinfectant solutions need sufficient time before pouring into dental stone.

  8. In-use Stability of Ceftaroline Fosamil in Elastomeric Home Infusion Systems and MINI-BAG Plus Containers.

    PubMed

    Bhattacharya, Sisir; Parekh, Satish; Dedhiya, Mahendra

    2015-01-01

    The objective of this study was to determine in-use stability of ceftaroline fosamil infusion solution of concentrations up to 12 mg/mL in elastomeric home infusion system prefilled with 0.9% Sodium Chloride Injection USP or 5% Dextrose Injection USP and MINI-BAG Plus Container delivery devices prefilled with 0.9% sodium chloride injection. In-use ceftaroline fosamil infusion solution (12 mg/mL) was prepared for elastomeric home infusion systems (Homepump Eclipse, Baxter Intermate, and AccuRx Elastomeric Pump) pre-filled with either 0.9% sodium chloride injection or 5% dextrose; or Baxter MINI-BAG Plus Containers pre-filled with 0.9% Sodium Chloride Injection USP (4 mg/mL to 12 mg/mL ceftaroline fosamil in final solution). The systems were stored refrigerated for 24 hours followed by up to 6 hours of storage at room temperature. Samples were analyzed at various time points for assay and degradation product by a validated stability-indicating high-performance liquid chromatography method. In-use ceftaroline fosamil infusion solution, ranging from 4-mg/mL to a maximum of 12-mg/mL concentration, in elastomeric home infusion systems prefilled with 0.9% sodium chloride injection or 5% dextrose, and MINI-BAG Plus Containers prefilled with 0.9% sodium chloride injection were chemically stable for up to 24 hours refrigerated at 2°C to 8°C (36°F to 46°F) and up to 6 hours at room temperature and had acceptable compatibility with material used. Ceftaroline fosamil (4 mg/mL to 12 mg/mL) maintains its potency for up to 24 hours refrigerated at 2°C to 8°C (36°F to 46°F) and up to 6 hours of storage at room temperature upon reconstitution in infusion solution with 0.9% sodium chloride or 5% dextrose when used in elastomeric home infusion system and MINI-BAG Plus Containers delivery devices prefilled with 0.9% sodium chloride injection. PMID:26775451

  9. Manikin-based performance evaluation of elastomeric respirators against combustion particles.

    PubMed

    He, Xinjian; Yermakov, Michael; Reponen, Tiina; McKay, Roy T; James, Kelley; Grinshpun, Sergey A

    2013-01-01

    This study investigated the effects of faceseal leakage, breathing flow, and combustion material on the overall (non-size-selective) penetration of combustion particles into P-100 half and full facepiece elastomeric respirators used by firefighters. Respirators were tested on a breathing manikin exposed to aerosols produced by combustion of three materials (wood, paper, and plastic) in a room-size exposure chamber. Testing was performed using a single constant flow (inspiratory flow rate = 30 L/min) and three cyclic flows (mean inspiratory flow rates = 30, 85, and 135 L/min). Four sealing conditions (unsealed, nose-only sealed, nose and chin sealed, and fully sealed) were examined to evaluate the respirator faceseal leakage. Total aerosol concentration was measured inside (C(in)) and outside (C(out)) the respirator using a condensation particle counter. The total penetration through the respirator was determined as a ratio of the two (P = C(in) / C(out)). Faceseal leakage, breathing flow type and rate, and combustion material were all significant factors affecting the performance of the half mask and full facepiece respirators. The efficiency of P-100 respirator filters met the NIOSH certification criteria (penetration ≤0.03%); it was not significantly influenced by the challenge aerosol and flow type, which supports the current NIOSH testing procedure using a single challenge aerosol and a constant airflow. However, contrary to the NIOSH total inward leakage (TIL) test protocol assuming that the result is independent on the type of the tested aerosol, this study revealed that the challenge aerosol significantly affects the particle penetration through unsealed and partially sealed half mask respirators. Increasing leak size increased total particle penetration. The findings point to some limitations of the existing TIL test in predicting protection levels offered by half mask elastomeric respirators. PMID:23442086

  10. Evaluation of digital dental models obtained from dental cone-beam computed tomography scan of alginate impressions

    PubMed Central

    Jiang, Tingting; Lee, Sang-Mi; Hou, Yanan; Chang, Xin

    2016-01-01

    Objective To investigate the dimensional accuracy of digital dental models obtained from the dental cone-beam computed tomography (CBCT) scan of alginate impressions according to the time elapse when the impressions are stored under ambient conditions. Methods Alginate impressions were obtained from 20 adults using 3 different alginate materials, 2 traditional alginate materials (Alginoplast and Cavex Impressional) and 1 extended-pour alginate material (Cavex ColorChange). The impressions were stored under ambient conditions, and scanned by CBCT immediately after the impressions were taken, and then at 1 hour intervals for 6 hours. After reconstructing three-dimensional digital dental models, the models were measured and the data were analyzed to determine dimensional changes according to the elapsed time. The changes within the measurement error were regarded as clinically acceptable in this study. Results All measurements showed a decreasing tendency with an increase in the elapsed time after the impressions. Although the extended-pour alginate exhibited a less decreasing tendency than the other 2 materials, there were no statistically significant differences between the materials. Changes above the measurement error occurred between the time points of 3 and 4 hours after the impressions. Conclusions The results of this study indicate that digital dental models can be obtained simply from a CBCT scan of alginate impressions without sending them to a remote laboratory. However, when the impressions are not stored under special conditions, they should be scanned immediately, or at least within 2 to 3 hours after the impressions are taken. PMID:27226958

  11. Response of elastomeric packaging components to a corrosive simulant mixed waste

    SciTech Connect

    Nigrey, P.J.; Dickens, T.G.

    1997-10-01

    The purpose of hazardous and radioactive materials packaging is to enable these materials to be transported without posing a threat to the health or property of the general public. To achieve this aim, regulations in the US have been written establishing general design requirements for such packagings. While no regulations have been written specifically for mixed waste packaging, regulations for the constituents of mixed wastes, i.e., hazardous and radioactive substances, have been codified by the US Department of Transportation and the US Nuclear Regulatory Commission. Based on these national requirements, a Chemical Compatibility Testing Program was developed in the Transportation Systems Department at SNL. In this paper, the authors present the results of Part B of the second phase of this testing program. The first phase screened five liner materials and six seal materials towards four simulant mixed wastes. Part A of the second phase involved the comprehensive testing of five candidate liner materials to an aqueous Hanford Tank simulant mixed waste. Part B involved similar testing on elastomeric materials, ethylene-propylene and butadiene-acrylonitrile rubber. The comprehensive testing protocol involved exposing the respective materials to a matrix of four gamma radiation doses ({approximately}1, 3, 6, and 40 kGy), three temperatures (18, 50, and 60 C), and four exposure times (7, 14, 28, and 180 days). Following their exposure to these combinations of conditions, the materials were evaluated by measuring six material properties. These properties were specific gravity, dimensional changes, hardness, vapor transport rates, compression set, and mechanical properties.

  12. Flame resistant elastomeric polymer development. [for use in space shuttle instrument packaging

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Sheth, S. G.; Sidman, K. R.

    1975-01-01

    Elastomeric products were developed for use in the space shuttle program, and investigations were conducted to improve the properties of elastomers developed in previous programs, and to evaluate the possibility of using lower-cost general purpose polymers. Products were fabricated and processed on conventional processing equipment; these products include: foams based on fluorinated rubber flame-retarded compounds with a density of 20-30 pounds/cubic foot for use as padding and in helmets; foams based on urethane for use in instrument packaging in the space shuttle; flexible and semi-rigid films of fluorinated rubber and neoprene compounds that would not burn in a 70% nitrogen, 30% oxygen atmosphere, and in a 30% nitrogen, 70% oxygen atmosphere, respectively for use in packaging or in laminates; coated fabrics which used both nylon and Kelvar fabric substrates, coated with either fluorinated or neoprene polymer compositions to meet specific levels of flame retardancy; and other flame-resistant materials.

  13. Curvilinear electronics formed using silicon membrane circuits and elastomeric transfer elements.

    PubMed

    Ko, Heung Cho; Shin, Gunchul; Wang, Shuodao; Stoykovich, Mark P; Lee, Jeong Won; Kim, Dong-Hun; Ha, Jeong Sook; Huang, Yonggang; Hwang, Keh-Chih; Rogers, John A

    2009-12-01

    Materials and methods to achieve electronics intimately integrated on the surfaces of substrates with complex, curvilinear shapes are described. The approach exploits silicon membranes in circuit mesh structures that can be deformed in controlled ways using thin, elastomeric films. Experimental and theoretical studies of the micromechanics of such curvilinear electronics demonstrate the underlying concepts. Electrical measurements illustrate the high yields that can be obtained. The results represent significant experimental and theoretical advances over recently reported concepts for creating hemispherical photodetectors in electronic eye cameras and for using printable silicon nanoribbons/membranes in flexible electronics. The results might provide practical routes to the integration of high performance electronics with biological tissues and other systems of interest for new applications.

  14. A comparison of the effects of different methods of impression build-up on earmoulds.

    PubMed

    Macrae, J H

    1991-06-01

    An investigation was carried out into effects of three types of impression build-up (patting down of impressions, special earmould-maker build-up and the multistage impression technique) on the dimensions, static pressure seal, degree of acoustic seal and the subjective tightness and comfort of earmoulds. Patting down the impression significantly improved the degree of acoustic seal provided by earmoulds without making them feel tighter or less comfortable. However, special build-up was much more effective than patting down and the multistage impression technique was slightly more effective than special build-up in improving the degree of acoustic seal. The improvement in acoustic seal provided by both multistage and specially built-up earmoulds can usually be obtained without an unacceptable level of discomfort. Patting down the impression did not improve the chance of obtaining a static pressure seal. Special build-up of the impression by the earmould-maker significantly increased the proportion of earmoulds which provided a static pressure seal but an even higher proportion of earmoulds made from multistage impressions provided a seal. Dimension results indicated that an increase in earmould-maker build-up of the minor axis at the beginning of the canal segment of the impression would improve the acoustic seal provided by specially built-up earmoulds and that earmoulds with rounder tips are more likely to provide a static pressure seal than earmoulds with more elliptical tips. The better the impression material fills the ear canal, the rounder the tip of the impression, and the rounder the tip of the earmould made from the impression.

  15. Comparison of intraoral scanning and conventional impression techniques using 3-dimensional superimposition

    PubMed Central

    Rhee, Ye-Kyu

    2015-01-01

    PURPOSE The aim of this study is to evaluate the appropriate impression technique by analyzing the superimposition of 3D digital model for evaluating accuracy of conventional impression technique and digital impression. MATERIALS AND METHODS Twenty-four patients who had no periodontitis or temporomandibular joint disease were selected for analysis. As a reference model, digital impressions with a digital impression system were performed. As a test models, for conventional impression dual-arch and full-arch, impression techniques utilizing addition type polyvinylsiloxane for fabrication of cast were applied. 3D laser scanner is used for scanning the cast. Each 3 pairs for 25 STL datasets were imported into the inspection software. The three-dimensional differences were illustrated in a color-coded map. For three-dimensional quantitative analysis, 4 specified contact locations(buccal and lingual cusps of second premolar and molar) were established. For twodimensional quantitative analysis, the sectioning from buccal cusp to lingual cusp of second premolar and molar were acquired depending on the tooth axis. RESULTS In color-coded map, the biggest difference between intraoral scanning and dual-arch impression was seen (P<.05). In three-dimensional analysis, the biggest difference was seen between intraoral scanning and dual-arch impression and the smallest difference was seen between dual-arch and full-arch impression. CONCLUSION The two- and three-dimensional deviations between intraoral scanner and dual-arch impression was bigger than full-arch and dual-arch impression (P<.05). The second premolar showed significantly bigger three-dimensional deviations than the second molar in the three-dimensional deviations (P>.05). PMID:26816576

  16. Effect of splinting in accuracy of two implant impression techniques.

    PubMed

    de Avila, Erica Dorigatti; de Matos Moraes, Fernanda; Castanharo, Sabrina Maria; Del'Acqua, Marcelo Antonialli; de Assis Mollo, Francisco

    2014-12-01

    Because there is no consensus in the literature about the need for a splint between copings, the aim of this study was to evaluate, in vitro, the accuracy of 2 impression techniques for implant-supported prostheses. A master cast was fabricated with four parallel implant abutment analogs and a passive framework. Two groups with 5 casts each were formed: Group 1 (squared impression copings with no splint: S) and Group 2 (splinted squared impression copings, using metal drill burs and Pattern resin: SS). The impression material used was polyvinyl siloxane with open trays for standard preparation of the casts. For each cast, the framework was positioned, and a titanium screw was tightened with 10 N·cm torque in analog A, after which measurements of the abutment-framework interface gaps were performed at analogs C and D. This process was repeated for analog D. These measurements were analyzed using software. A one-way analysis of variance (ANOVA) with a confidence interval of 95% was used to analyze the data. Significant differences were detected between S and SS in relation to the master cast (P ≤ 0.05). The median values of the abutment-framework interface gaps were as follows: master cast: 39.64 μm; squared impression copings with no splint: 205.86 μm; splinted squared impression copings: 99.19 μm. Under the limitations of this study, the technique presented for Group 2 produces better results compared with the technique used for Group 1.

  17. PRELIMINARY REPORT: EFFECTS OF IRRADIATION AND THERMAL EXPOSURE ON ELASTOMERIC SEALS FOR CASK TRANSPORTATION AND STORAGE

    SciTech Connect

    Verst, C.; Skidmore, E.; Daugherty, W.

    2014-05-30

    A testing and analysis approach to predict the sealing behavior of elastomeric seal materials in dry storage casks and evaluate their ability to maintain a seal under thermal and radiation exposure conditions of extended storage and beyond was developed, and initial tests have been conducted. The initial tests evaluate the aging response of EPDM elastomer O-ring seals. The thermal and radiation exposure conditions of the CASTOR® V/21 casks were selected for testing as this cask design is of interest due to its widespread use, and close proximity of the seals to the fuel compared to other cask designs leading to a relatively high temperature and dose under storage conditions. A novel test fixture was developed to enable compression stress relaxation measurements for the seal material at the thermal and radiation exposure conditions. A loss of compression stress of 90% is suggested as the threshold at which sealing ability of an elastomeric seal would be lost. Previous studies have shown this value to be conservative to actual leakage failure for most aging conditions. These initial results indicate that the seal would be expected to retain sealing ability throughout extended storage at the cask design conditions, though longer exposure times are needed to validate this assumption. The high constant dose rate used in the testing is not prototypic of the decreasingly low dose rate that would occur under extended storage. The primary degradation mechanism of oxidation of polymeric compounds is highly dependent on temperature and time of exposure, and with radiation expected to exacerbate the oxidation.

  18. Elastomer degradation sensor using a piezoelectric material

    DOEpatents

    Olness, Dolores U.; Hirschfeld, deceased, Tomas B.

    1990-01-01

    A method and apparatus for monitoring the degradation of elastomeric materials is provided. Piezoelectric oscillators are placed in contact with the elastomeric material so that a forced harmonic oscillator with damping is formed. The piezoelectric material is connected to an oscillator circuit,. A parameter such as the resonant frequency, amplitude or Q value of the oscillating system is related to the elasticity of the elastomeric material. Degradation of the elastomeric material causes changes in its elasticity which, in turn, causes the resonant frequency, amplitude or Q of the oscillator to change. These changes are monitored with a peak height monitor, frequency counter, Q-meter, spectrum analyzer, or other measurement circuit. Elasticity of elastomers can be monitored in situ, using miniaturized sensors.

  19. Clinical Evaluation of Different Pre-impression Preparation Procedures of Dental Arch

    PubMed Central

    Arora, Nitin; Arora, Monika; Gupta, Naveen; Agarwal, Manisha; Verma, Rohit; Rathod, Pankaj

    2015-01-01

    Background: Bubbles and voids on the occlusal surface impede the actual intercuspation and pre-impression preparation aims to reduce the incidence of air bubbles and voids as well as influences the quality of occlusal reproduction and actual clinical intercuspation in the articulator. The study was undertaken to determine the influence of different pre-impression preparation procedures of antagonistic dental arch on the quality of the occlusal reproduction of the teeth in irreversible hydrocolloid impressions and to determine most reliable pre-impression preparation method to reduce the incidence of air bubbles. Materials and Methods: A total of 20 subjects were selected having full complement of mandibular teeth from second molar to second molar with well demarcated cusp height. 200 impressions were made with irreversible hydrocolloid material. The impressions were divided into five groups of 40 impressions each and each group had one specific type of pre-impression preparation. All the impressions were poured in die stone. A stereomicroscope with graduated eyepiece was used to count the number of bubbles on the occlusal surface of premolars and molars. The mean and standard deviations were calculated for each group. Mann–Whitney U-test was applied to find the significant difference between different groups. Results: Least bubbles were found in the group in which oral cavity was dried by saliva ejector and fluid hydrocolloid was finger painted onto the occlusal surfaces immediately before the placement of impression tray in the mouth. Conclusion: It was found that finger painting the tooth surfaces with fluid hydrocolloid immediately before the placement of loaded impression tray in the mouth was the most reliable method. The oral cavity can be cleared more easily of excess saliva by vacuum suction rather than by use of an astringent solution. PMID:26229376

  20. Microphase Separation and Dynamics of Elastomeric Polyureas

    NASA Astrophysics Data System (ADS)

    Runt, James; Castagna, Alicia; Choi, Taeyi; Jeong, Youmi

    2012-02-01

    Polyureas, consisting of alternating polyether soft segments and urea-containing hard segments, are of interest for shock and other energy absorbing applications. The properties of these materials are strongly influenced by microphase separation of the hard and soft segments, which is rather incomplete. Bulk- and solution-polymerized polyureas based on oligomeric polytetramethylene oxide and methylene diphenyl diisocyanate were investigated, and the role of PTMO molecular weight was identified. The morphology was characterized using atomic force microscopy and quantitative degrees of phase separation were determined from small-angle X-ray scattering. Dielectric relaxation spectroscopy and dynamic mechanical analysis were used to probe the dynamics. Particular attention was paid to the segmental dynamics of the soft phase, which has been proposed to be a major contributor to shock energy absorption in these materials.

  1. Micromechanical damage and fracture in elastomeric polymers

    NASA Astrophysics Data System (ADS)

    Heyden, Stefanie

    This thesis aims at a simple one-parameter macroscopic model of distributed damage and fracture of polymers that is amenable to a straightforward and efficient numerical implementation. The failure model is motivated by post-mortem fractographic observations of void nucleation, growth and coalescence in polyurea stretched to failure, and accounts for the specific fracture energy per unit area attendant to rupture of the material. Furthermore, it is shown that the macroscopic model can be rigorously derived, in the sense of optimal scaling, from a micromechanical model of chain elasticity and failure regularized by means of fractional strain-gradient elasticity. Optimal scaling laws that supply a link between the single parameter of the macroscopic model, namely the critical energy-release rate of the material, and micromechanical parameters pertaining to the elasticity and strength of the polymer chains, and to the strain-gradient elasticity regularization, are derived. Based on optimal scaling laws, it is shown how the critical energy-release rate of specific materials can be determined from test data. In addition, the scope and fidelity of the model is demonstrated by means of an example of application, namely Taylor-impact experiments of polyurea rods. Hereby, optimal transportation meshfree approximation schemes using maximum-entropy interpolation functions are employed. Finally, a different crazing model using full derivatives of the deformation gradient and a core cut-off is presented, along with a numerical non-local regularization model. The numerical model takes into account higher-order deformation gradients in a finite element framework. It is shown how the introduction of non-locality into the model stabilizes the effect of strain localization to small volumes in materials undergoing softening. From an investigation of craze formation in the limit of large deformations, convergence studies verifying scaling properties of both local- and non-local energy

  2. Individualized impression trays from existing complete dentures.

    PubMed

    McArthur, D R

    1980-11-01

    This technique can be used to avoid the making of preliminary impressions for complete dentures in patients with abnormally small oral openings. With this method, the patient must have existing dentures, and the border extensions must be adequate to serve as individualized impression trays.

  3. Nanoscale squeezing in elastomeric nanochannels for single chromatin linearization

    PubMed Central

    Matsuoka, Toshiki; Kim, Byoung Choul; Huang, Jiexi; Douville, Nicholas Joseph; Thouless, M.D.; Takayama, Shuichi

    2012-01-01

    This paper describes a novel nanofluidic phenomenon where untethered DNA and chromatin are linearized by rapidly narrowing an elastomeric nanochannel filled with solutions of the biopolymers. This nanoscale squeezing procedure generates hydrodynamic flows while also confining the biopolymers into smaller and smaller volumes. The unique features of this technique enable full linearization then trapping of biopolymers such as DNA. The versatility of the method is also demonstrated by analysis of chromatin stretchability and mapping of histone states using single strands of chromatin. PMID:23186544

  4. Combined Technologies for Microfabricating Elastomeric Cardiac Tissue Engineering Scaffolds

    PubMed Central

    Guillemette, Maxime D.; Park, Hyoungshin; Hsiao, James C.; Jain, Saloni R.; Larson, Benjamin L.; Langer, Robert; Freed, Lisa E.

    2012-01-01

    Polymer scaffolds that direct elongation and orientation of cultured cells can enable tissue engineered muscle to act as a mechanically functional unit. We combined micromolding and microablation technologies to create muscle tissue engineering scaffolds from the biodegradable elastomer poly(glycerol sebacate). These scaffolds exhibited well defined surface patterns and pores and robust elastomeric tensile mechanical properties. Cultured C2C12 muscle cells penetrated the pores to form spatially controlled engineered tissues. Scanning electron and confocal microscopy revealed muscle cell orientation in a preferential direction, parallel to micromolded gratings and long axes of microablated anisotropic pores, with significant individual and interactive effects of gratings and pore design. PMID:20718054

  5. The neural dynamics of updating person impressions.

    PubMed

    Mende-Siedlecki, Peter; Cai, Yang; Todorov, Alexander

    2013-08-01

    Person perception is a dynamic, evolving process. Because other people are an endless source of social information, people need to update their impressions of others based upon new information. We devised an fMRI study to identify brain regions involved in updating impressions. Participants saw faces paired with valenced behavioral information and were asked to form impressions of these individuals. Each face was seen five times in a row, each time with a different behavioral description. Critically, for half of the faces the behaviors were evaluatively consistent, while for the other half they were inconsistent. In line with prior work, dorsomedial prefrontal cortex (dmPFC) was associated with forming impressions of individuals based on behavioral information. More importantly, a whole-brain analysis revealed a network of other regions associated with updating impressions of individuals who exhibited evaluatively inconsistent behaviors, including rostrolateral PFC, superior temporal sulcus, right inferior parietal lobule and posterior cingulate cortex.

  6. The neural dynamics of updating person impressions.

    PubMed

    Mende-Siedlecki, Peter; Cai, Yang; Todorov, Alexander

    2013-08-01

    Person perception is a dynamic, evolving process. Because other people are an endless source of social information, people need to update their impressions of others based upon new information. We devised an fMRI study to identify brain regions involved in updating impressions. Participants saw faces paired with valenced behavioral information and were asked to form impressions of these individuals. Each face was seen five times in a row, each time with a different behavioral description. Critically, for half of the faces the behaviors were evaluatively consistent, while for the other half they were inconsistent. In line with prior work, dorsomedial prefrontal cortex (dmPFC) was associated with forming impressions of individuals based on behavioral information. More importantly, a whole-brain analysis revealed a network of other regions associated with updating impressions of individuals who exhibited evaluatively inconsistent behaviors, including rostrolateral PFC, superior temporal sulcus, right inferior parietal lobule and posterior cingulate cortex. PMID:22490923

  7. Hierarchically UVO patterned elastomeric and thermoplastic structures

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Kulkarni, Manish; Marshall, Allan; Karim, Alamgir

    2014-03-01

    We demonstrate a simple yet versatile method to fabricate tunable hierarchical micro-nanostructures on flexible Poly(dimethylsiloxane) (PDMS) elastomer and thermoplastic polymer surface by a two-step process. Nanoscale patterned PDMS was obtained by imprinting compact disc (CD)/digital video disc (DVD) patterns. The second micro pattern was superposed by selective densification of PDMS by exposing to ultraviolet-ozone radiation (UVO) through micro-patterned TEM grid as a mask. The nanoscale patterns are preserved through UVO exposure step leading to formation of deep hierarchical patterns, so that for a 19 um square mesh, the micro pattern has a depth of 600nm with 6h PDMS UVO exposure time. This simple method can be promoted to fabricate hierarchical structures of thermoplastic materials (such as polystyrene), from which the mechanism of capillary imprinting and thermal stability of hierarchical patterns are investigated. This study is potentially important to various applications ranging from biomimetic scaffolds to solar cell.

  8. Three-Dimensional Elastomeric Scaffolds Designed with Cardiac-Mimetic Structural and Mechanical Features

    PubMed Central

    Neal, Rebekah A.; Jean, Aurélie; Park, Hyoungshin; Wu, Patrick B.; Hsiao, James; Engelmayr, George C.; Langer, Robert

    2013-01-01

    Tissue-engineered constructs, at the interface of material science, biology, engineering, and medicine, have the capacity to improve outcomes for cardiac patients by providing living cells and degradable biomaterials that can regenerate the native myocardium. With an ultimate goal of both delivering cells and providing mechanical support to the healing heart, we designed three-dimensional (3D) elastomeric scaffolds with (1) stiffnesses and anisotropy mimicking explanted myocardial specimens as predicted by finite-element (FE) modeling, (2) systematically varied combinations of rectangular pore pattern, pore aspect ratio, and strut width, and (3) structural features approaching tissue scale. Based on predicted mechanical properties, three scaffold designs were selected from eight candidates for fabrication from poly(glycerol sebacate) by micromolding from silicon wafers. Large 20×20 mm scaffolds with high aspect ratio features (5:1 strut height:strut width) were reproducibly cast, cured, and demolded at a relatively high throughput. Empirically measured mechanical properties demonstrated that scaffolds were cardiac mimetic and validated FE model predictions. Two-layered scaffolds providing fully interconnected pore networks were fabricated by layer-by-layer assembly. C2C12 myoblasts cultured on one-layered scaffolds exhibited specific patterns of cell elongation and interconnectivity that appeared to be guided by the scaffold pore pattern. Neonatal rat heart cells cultured on two-layered scaffolds for 1 week were contractile, both spontaneously and in response to electrical stimulation, and expressed sarcomeric α-actinin, a cardiac biomarker. This work not only demonstrated several scaffold designs that promoted functional assembly of rat heart cells, but also provided the foundation for further computational and empirical investigations of 3D elastomeric scaffolds for cardiac tissue engineering. PMID:23190320

  9. The elastomers for complete denture impression: A review of the literature

    PubMed Central

    Daou, Elie E.

    2010-01-01

    This article reviews the current trends in materials used for complete denture impression. Peer-reviewed articles, published in English and in French between 1954 and 2007, were identified through a MEDLINE search (Pubmed and Elsevier) and a hand search of relevant textbooks and annual publications. Emphasis was made on the characteristics of the elastomers, their manipulation, the different techniques used, and the quality of the impression obtained. The combination of excellent physical properties, handling characteristics, and unlimited dimensional stability assures the popularity of these impression materials. PMID:24151408

  10. Elastically stretchable thin film conductors on an elastomeric substrate

    NASA Astrophysics Data System (ADS)

    Jones Harris, Joyelle Elizabeth

    Imagine a large, flat screen television that can be rolled into a small cylinder after purchase in the store and then unrolled and mounted onto the wall of a home. The electronic devices within the television must be able to withstand large deformation and tensile strain. Consider a robot that is covered with an electronic skin that simulates human skin. The skin would enable the machine to lift an elderly person with care and sensitivity. The skin will endure repeated deformation with the highest tensile strains being experienced at the robot's joints. These applications and many others will benefit from stretchable electronic circuitry. While several different methods have been employed to create stretchable electronics, all methods use a common tool -- stretchable conductors. Therefore, the goal of this thesis work was to fabricate elastically stretchable conductors that can be used in stretchable electronics. We deposited Au thin films on an elastomeric substrate, and the resulting conductors remained electrically continuous when stretched by 30% and more. We developed photolithographic processes that can be used to pattern elastically stretchable conductors with a 10 mum resolution. We fabricated bi-level stretchable conductors that are separated by an elastomeric insulator and are electrically connected through via holes in the insulator. We applied our bi-level conductors to create a stretchable resistor-inductor-capacitor (RLC) circuit with a tunable resonant frequency. We also used stretchable conductors to measure action potentials in biological samples. This thesis describes the fabrication and application of our elastically stretchable conductors.

  11. Finite Element Analysis of Plastic Deformation During Impression Creep

    NASA Astrophysics Data System (ADS)

    Naveena; Ganesh Kumar, J.; Mathew, M. D.

    2015-04-01

    Finite element (FE) analysis of plastic deformation associated with impression creep deformation of 316LN stainless steel was carried out. An axisymmetric FE model of 10 × 10 × 10 mm specimen with 1-mm-diameter rigid cylindrical flat punch was developed. FE simulation of impression creep deformation was performed by assuming elastic-plastic-power-law creep deformation behavior. Evolution of the stress with time under the punch during elastic, plastic, and creep processes was analyzed. The onset of plastic deformation was found to occur at a nominal stress about 1.12 times the yield stress of the material. The size of the developed plastic zone was predicted to be about three times the radius of the punch. The material flow behavior and the pile-up on specimen surface have been modeled.

  12. The Effect of Disinfection by Spray Atomization on Dimensional Accuracy of Condensation Silicone Impressions

    PubMed Central

    Saleh Saber, Fariba; Abolfazli, Nader; Kohsoltani, Maryam

    2010-01-01

    Background and aims The condensation silicone impression materials are available, but there is little knowledge of their accuracy after disinfection. The objective of this study was to evaluate the effect of the disinfection by spray atomization on dimensional accuracy of condensation silicone impressions. Materials and methods Impressions were made on a stainless steel master model containing a simulated two complete crown preparation with an edentulous space interposed using Spidex® and Rapid® impression materials. 44 impressions were made with each material, of which 16 were disinfected with 5.25% sodium hypochlorite, 16 were disinfected with 10% iodophor and 12 were not disinfected. Three dimensional measurements of working casts, including interpreparation distance, height, and diameter, were calculated using a measuring microscope graduated at 0.001 mm. Dimensional changes (mm) between the disinfected and non-disinfected working casts were compared. One-way analysis of variance (ANOVA) was employed to analyze the data (α=0.05). Results Disinfection of each condensation silicone material by spraying atomization with two different disinfectant material resulted in significant change in interpreparation distance (p<0.05). Changes in height and diameter were only significant in Spidex® impressions (p<0.05). Conclusion Significant changes in the mean dimensions were seen as a result of disinfection by spraying; however, the dimensional changes do not seem great enough to cause critical positional distortion of teeth when fixed partial denture restorations are made. PMID:23346339

  13. Chlorhexidine gluconate mouthwashes as a surfactant for addition-reaction silicone impressions.

    PubMed

    Reshad, Mamaly; Nesbit, Michael; Petrie, Aviva; Setchell, Derrick

    2009-03-01

    Addition-reaction silicone impression (PVS) materials are hydrophobic. Hydrophobicity of the impression material may interfere with the wetting of the tooth, resulting in void formation. The study investigates whether conditioning teeth with Chlorhexidine-gluconate based mouthwashes can reduce the hydrophobicity and the number of voids on PVS impressions. Impression material contact angle specimens on bovine tooth surfaces were measured using a Reflex Microscope. PVS impressions (President) were made of untreated bovine teeth in three groups (1, 2 and 3) and fourth group used Impregum polyether impression material: Group I was used as a control group, and original and mint flavoured Corsodyl (Chlorhexidine) mouthwashes were used as clinical surfactants in Groups 2 and 3, respectively. Contact angle readings were recorded on each side of every impression in each of the four groups and compared by an analysis of variance. In the second part of the study, the numbers of air voids on impression surfaces were visually recorded. The proportions of air voids in the groups were compared using a Chi-squared test. The mean angle for Group 3 with mint flavoured Corsodyl mouthwash was significantly smaller than that of any of the other groups (P < 0.05). The only statistically significant (P < 0.01) comparisons of the proportions of air voids were between Group 4 and each of the other experimental groups, with the percentage of voids being significantly greater in Group 4. Although Corsodyl mint significantly reduced the mean contact angle it did not significantly reduce the percentage of voids on impression surfaces. PMID:19378615

  14. Characterization and impression creep testing of silicon aluminum oxynitride ceramics

    NASA Astrophysics Data System (ADS)

    Fox, Kevin M.

    2005-11-01

    Three Yb-containing SiAlON materials were studied for potential use as hot section components in advanced microturbine engines. Two of the materials consisted of equiaxed alpha-SiAlON grains, elongated beta-SiAlON grains, and an amorphous intergranular phase containing a relatively large amount of Yb. The third material consisted of alpha- and beta-SiAlON grains with equiaxed morphologies and virtually no intergranular phase. An instrument was designed and constructed for impression creep testing of the YbSiAlON materials. Uniaxial compression creep experiments were also performed for comparison. In compression creep, the SiAlON materials exhibited activation energies that were similar to those of other SiAlONs reports in the literature, and stress exponents that were approximately 1. In impression creep, the SiAlONs tested exhibited activation energies similar to those reported in the literature for SiAlONs tested in uniaxial compression and tension. However, the SiAlON composition with equiaxed beta-SiAlON grains showed an exaggerated activation energy due to a change in creep mechanism above 1340°C. The measured stress exponents in impression creep were approximately 2. The stress state present below the punch in impression creep caused dilation to occur in the grain structure. The dilation results in an increase in the volume of the multi-grain junctions, and an increased dependence of strain rate on stress. The enlarged multi-grain junctions can become filled with the intergranular glassy phase. These large pockets of the glassy phase can enable an additional creep mechanism whereby the equiaxed grains slide past each other viscously. All of the SiAlONs developed an additional volume of the intergranular glassy phase during creep testing. A microstructure containing elongated beta-SiAlON grains is most effective in enhancing creep performance of the Yb-SiAlON materials tested. The impression creep data for the Yb-SiAlON materials can be related to the

  15. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6880 Preformed impression tray. (a) Identification. A preformed impression tray is a metal or plastic device intended to hold impression...

  16. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6880 Preformed impression tray. (a) Identification. A preformed impression tray is a metal or plastic device intended to hold impression...

  17. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6880 Preformed impression tray. (a) Identification. A preformed impression tray is a metal or plastic device intended to hold impression...

  18. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6880 Preformed impression tray. (a) Identification. A preformed impression tray is a metal or plastic device intended to hold impression...

  19. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6880 Preformed impression tray. (a) Identification. A preformed impression tray is a metal or plastic device intended to hold impression...

  20. From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials.

    PubMed

    D'Amore, Antonio; Amoroso, Nicholas; Gottardi, Riccardo; Hobson, Christopher; Carruthers, Christopher; Watkins, Simon; Wagner, William R; Sacks, Michael S

    2014-11-01

    In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters adjusted to match the macro-level mechanical test data. Fiber model validation was performed at the microscopic level by individual fiber mechanical tests using AFM. Results demonstrated very good agreement to the experimental data, and revealed the formation of extended preferential fiber orientations spanning the entire model space. We speculate that these emergent structures may be responsible for the tissue-like macroscale behaviors observed in electrospun scaffolds. To conclude, the modeling approach has implications for (1) gaining insight on the intricate relationship between fabrication variables, structure, and mechanics to manufacture more functional devices/materials, (2) elucidating the effects of cell or particulate inclusions on global construct mechanics, and (3) fabricating better performing tissue surrogates that could recapitulate native tissue mechanics.

  1. From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials

    PubMed Central

    D'Amore, Antonio; Amoroso, Nicholas; Gottardi, Riccardo; Hobson, Christopher; Carruthers, Christopher; Watkins, Simon; Wagner, William R.; Sacks, Michael S.

    2014-01-01

    In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters adjusted to match the macro-level mechanical test data. Fiber model validation was performed at the microscopic level by individual fiber mechanical tests using AFM. Results demonstrated very good agreement to the experimental data, and revealed the formation of extended preferential fiber orientations spanning the entire model space. We speculate that these emergent structures may be responsible for the tissue-like macroscale behaviors observed in electrospun scaffolds. To conclude, the modeling approach has implications for (1) gaining insight on the intricate relationship between fabrication variables, structure, and mechanics to manufacture more functional devices/materials, (2) elucidating the effects of cell or particulate inclusions on global construct mechanics, and (3) fabricating better performing tissue surrogates that could recapitulate native tissue mechanics. PMID:25128869

  2. Experimental and numerical investigation of energy dissipation in elastomeric rotational joint under harmonic loading

    NASA Astrophysics Data System (ADS)

    Jrad, Hanen; Dion, Jean Luc; Renaud, Franck; Tawfiq, Imad; Haddar, Mohamed

    2016-10-01

    This paper focuses on energy losses caused by inner damping and friction in an elastomeric rotational joint. A description of the design of a new experimental device intended to characterize dynamic stiffness in rotational elastomeric joint is presented. An original method based on Lagrange's equations, which allows accurately measuring forces and torques only with accelerometers, is proposed in order to identify dissipated energy in the rotational elastomeric joint. A rheological model developed taking into account dependence of the torque and the angular displacement (rotation). Experimental results and simulations used to quantify the dissipated energy in order to evaluate the damping ratio are presented and discussed.

  3. Conjunctival impression cytology: bright hope of children.

    PubMed

    1991-01-01

    A practical method of screening for pre-clinical xerophthalmia due to vitamin A deficiency, called conjunctival impression cytology (CIC), is described as it is being used in a training stage in the Philippines. The noninvasive technic consists of touching the conjunctiva with a filter paper disc, and fixing and staining the disc on a slide for histology. Normally goblet cells with mucin spots are seen among sheets of epithelial cells. In abnormal conjunctiva from vitamin A deficient individuals, the epithelial cells are enlarged, and goblet cells are lacking. These specimens may be obtained from areas of the conjunctiva that appear clinically normal. The equipment needed is millipore paper, a hand-held suction pump with 5 feet of tubing, tissue or gauze, screw-top vials, labels, fixative, Papanicolaou stain, and a microscope. Vitamin A supplements can be given to affected children, or to the whole population at risk. With CIC training materials donated by International Center for Epidemiologic and Preventive Ophthalmology (ICEPO) at the Wilmer Institute, and the School of Hygiene and Public Health of the Johns Hopkins University, Baltimore, the 1st training class was certified by the Nutrition Center of the Philippines. Twice yearly training of physicians and technologists has been recommended.

  4. Preliminary impression techniques for microstomia patients.

    PubMed

    Kumar, K Aswini; Bhat, Vinaya; Nair, K Chandrasekheran; Suresh, Reshma

    2016-01-01

    The Prosthetic rehabilitation of microstomia patients presents difficulties at all the stages. The difficulty starts with the preliminary impression making. This is due to the tongue rigidity and the decreased oral opening. A maximum oral opening which is smaller than the size of the tray can make prosthetic treatment challenging. Due to the restricted mouth opening, insertion and removal of the impression trays is extremely cumbersome and various modifications of the trays have been used in the past. Among these are the flexible trays and the sectional trays used with different modes of reassembling the segments extra orally after the impression is made. This article reviews the literature published from 1971 to 2015 concerning preliminary impression techniques used in making impressions for patients with microstomia based on various tray designs. An electronic search was performed across three databases (PubMed, Science Direct and Google Scolar) for relevant citations. The keywords/combinations used for the search were microstomia, limited/constricted/restricted mouth opening/oral access, trismus, sectional trays, impressions and prosthetic/prosthodontic rehabilitation. The search was limited to papers written in English which resulted in a total of 45 related articles of which 17 articles were included for discussion of this review.

  5. Preliminary impression techniques for microstomia patients.

    PubMed

    Kumar, K Aswini; Bhat, Vinaya; Nair, K Chandrasekheran; Suresh, Reshma

    2016-01-01

    The Prosthetic rehabilitation of microstomia patients presents difficulties at all the stages. The difficulty starts with the preliminary impression making. This is due to the tongue rigidity and the decreased oral opening. A maximum oral opening which is smaller than the size of the tray can make prosthetic treatment challenging. Due to the restricted mouth opening, insertion and removal of the impression trays is extremely cumbersome and various modifications of the trays have been used in the past. Among these are the flexible trays and the sectional trays used with different modes of reassembling the segments extra orally after the impression is made. This article reviews the literature published from 1971 to 2015 concerning preliminary impression techniques used in making impressions for patients with microstomia based on various tray designs. An electronic search was performed across three databases (PubMed, Science Direct and Google Scolar) for relevant citations. The keywords/combinations used for the search were microstomia, limited/constricted/restricted mouth opening/oral access, trismus, sectional trays, impressions and prosthetic/prosthodontic rehabilitation. The search was limited to papers written in English which resulted in a total of 45 related articles of which 17 articles were included for discussion of this review. PMID:27621540

  6. [The need and possibility for disinfecting impressions in orthodontics (a review of the literature)].

    PubMed

    Shcherbakov, A S; Iushmanova, T N; Mokrenko, E V

    1992-01-01

    Reviews the data on a high risk of viral and bacterial infection of dentists in connection with the high prevalence of AIDS and viral hepatitis B and on the possibility of infection of dental patients and the staff by microorganisms transfer on the impressions. Presents the present-day methods and means for disinfection of the impression material. Emphasizes inadequate knowledge of the dentists about the virucidal efficacy and the possibility of the impressions changing their properties in disinfection, which fact results in inaccuracy of the ready articles.

  7. Custom impression trays. Part III: A stress distribution model.

    PubMed

    Moseley, J P; Dixon, D L; Breeding, L C

    1994-05-01

    All resins used to make custom impression trays exhibit plastic deformation at some force value; therefore it is important to compare the physical property values of such materials with the stresses to which impression trays are subjected during dental procedures. A simple mathematical model of a custom tray was developed to predict stress distributions in this final part of a three-part investigation. Experimental stress analysis of such a tray confirmed the accuracy of the model, which was then used to predict the maximum stress experienced by the tray during removal of a completed impression from the oral cavity. The results of this analysis indicated that these stresses would be significantly lower than the yield stress for a commonly used polymethyl methacrylate resin or a light-polymerized resin. The stresses were also sufficiently low for us to conclude that thermoplastic resins would not permanently deform; however, the stresses encountered in the experimental confirmation procedure were close to the yield stress values for these materials.

  8. [Dental prostheses and dental impressions from a hygienic viewpoint].

    PubMed

    Engelhardt, J P

    1986-12-01

    Dentures, dental impressions, removable orthodontic appliances and all dental technical devices, which are part of any dental treatment are parts as well of a potential crosscontamination chain in dental treatment. Most of those items do not tolerate heat as a sure sterilization medium. For disinfection, chemical disinfectant solutions may be used as far as they work properly and as they are tolerated by the materials in question. Though, one can report some progress in disinfection of dentures and impressions, there are still questions open depending on safety and/or compatibility of the particular materials. For disinfection of removable dentures chlorine-yielding preparations such as Maranon can be recommended. Peracid preparations, such as Sekusept, Sekusept steril and Dentavon may be useful for disinfection of dental impressions. To do the possible means to reduce the infection risk for all persons involved in the dental treatment, patient, dentist, dental technician and all auxiliary persons. This includes both, active hygiene provisions as sterilization and disinfection, as well as possible passive self protection.

  9. The influence of impression trays on the accuracy of stone casts poured from irreversible hydrocolloid impressions.

    PubMed

    Mendez, A J

    1985-09-01

    An investigation was conducted to determine which of four commonly used impression trays yields the best results when making irreversible hydrocolloid impressions. This objective was achieved by evaluating the comparative accuracy of stone casts obtained from irreversible hydrocolloid impressions made with trays of different characteristics. The following conclusions are drawn from this study. Some kind of distortion can be expected in irreversible hydrocolloid impressions with the use of any of the tested impression trays. The perforated trays (B and D) reproduce more accurately the distances along the length and the width of the arch than the nonperforated trays (A and C). The depth of the palatal vault (distance f-g) is reproduced most accurately by the Rim-lock nonperforated tray (A) followed closely by the stock perforated (B) and the custom nonperforated (C) trays. Under the conditions of this study, all the impressions had a tendency to be oversized except the impressions made with the stock perforated tray (B). Those impressions were slightly undersized for all but two measured distances. Clinically significant inaccuracies produced by any of the four tested impression trays were not found in this study.

  10. Complex Optical Surfaces Formed by Replica Molding Against Elastomeric Masters

    PubMed

    Xia; Kim; Zhao; Rogers; Prentiss; Whitesides

    1996-07-19

    Complex, optically functional surfaces in organic polymers can be fabricated by replicating relief structures present on the surface of an elastomeric master with an ultraviolet or thermally curable organic polymer, while the master is deformed by compression, bending, or stretching. The versatility of this procedure for fabricating surfaces with complex, micrometer- and submicrometer-scale patterns was demonstrated by the production of (i) diffraction gratings with periods smaller than the original grating; (ii) chirped, blazed diffraction gratings (where the period of a chirped grating changes continuously with position) on planar and curved surfaces; (iii) patterned microfeatures on the surfaces of approximately hemispherical objects (for example, an optical surface similar to a fly's eye); and (iv) arrays of rhombic microlenses. These topologically complex, micropatterned surfaces are difficult to fabricate with other techniques.

  11. Seismic isolation of nuclear power plants using elastomeric bearings

    NASA Astrophysics Data System (ADS)

    Kumar, Manish

    Seismic isolation using low damping rubber (LDR) and lead-rubber (LR) bearings is a viable strategy for mitigating the effects of extreme earthquake shaking on safety-related nuclear structures. Although seismic isolation has been deployed in nuclear structures in France and South Africa, it has not seen widespread use because of limited new build nuclear construction in the past 30 years and a lack of guidelines, codes and standards for the analysis, design and construction of isolation systems specific to nuclear structures. The nuclear accident at Fukushima Daiichi in March 2011 has led the nuclear community to consider seismic isolation for new large light water and small modular reactors to withstand the effects of extreme earthquakes. The mechanical properties of LDR and LR bearings are not expected to change substantially in design basis shaking. However, under shaking more intense than design basis, the properties of the lead cores in lead-rubber bearings may degrade due to heating associated with energy dissipation, some bearings in an isolation system may experience net tension, and the compression and tension stiffness may be affected by the horizontal displacement of the isolation system. The effects of intra-earthquake changes in mechanical properties on the response of base-isolated nuclear power plants (NPPs) were investigated using an advanced numerical model of a lead-rubber bearing that has been verified and validated, and implemented in OpenSees and ABAQUS. A series of experiments were conducted at University at Buffalo to characterize the behavior of elastomeric bearings in tension. The test data was used to validate a phenomenological model of an elastomeric bearing in tension. The value of three times the shear modulus of rubber in elastomeric bearing was found to be a reasonable estimate of the cavitation stress of a bearing. The sequence of loading did not change the behavior of an elastomeric bearing under cyclic tension, and there was no

  12. Gold-Tipped Elastomeric Pillars for Cellular Mechanotransduction.

    PubMed

    Ghassemi, S; Rossier, O; Sheetz, M P; Wind, S J; Hone, J

    2009-11-01

    We describe a technique for the fabrication of arrays of elastomeric pillars whose top surfaces are treated with selective chemical functionalization to promote cellular adhesion in cellular force transduction experiments. The technique involves the creation of a rigid mold consisting of arrays of circular holes into which a thin layer of Au is deposited while the top surface of the mold and the sidewalls of the holes are protected by a sacrificial layer of Cr. When an elastomer is formed in the mold, the Au adheres to the tops of the molded pillars. This can then be selectively functionalized with a protein that induces cell adhesion, while the rest of the surface is treated with a repellent substance. An additional benefit is that the tops of the pillars can be fluorescently labeled for improved accuracy in force transduction measurements. PMID:20526428

  13. Adhesion of elastomeric surfaces structured with micro-dimples

    NASA Astrophysics Data System (ADS)

    Nanni, Gabriele; Fragouli, Despina; Ceseracciu, Luca; Athanassiou, Athanassia

    2015-01-01

    Topography has a dominant role in determining the adhesion properties of a surface. In this work we explore how arrays of micron-sized dimples can alter the adhesion performance of elastomeric surfaces. We study the effect of the dimple surface coverage, showing that the dimples act both as passive suction devices, allowing to exceed the adhesion performance of untextured surfaces, and crack-like defects, generating stress concentration at the edge of the contact area between the surface of the sample and a flat surface. Interestingly, our results reveal that the suction effect generated by the negative pressure produced by the dimples can be effectively tuned by adjusting their depth. These findings have significant relevance for the fabrication of adhesive systems in which selective adhesion to objects with small difference in weight is required.

  14. Optimal elastomeric scaffold leaflet shape for pulmonary heart valve leaflet replacement.

    PubMed

    Fan, Rong; Bayoumi, Ahmed S; Chen, Peter; Hobson, Christopher M; Wagner, William R; Mayer, John E; Sacks, Michael S

    2013-02-22

    Surgical replacement of the pulmonary valve (PV) is a common treatment option for congenital pulmonary valve defects. Engineered tissue approaches to develop novel PV replacements are intrinsically complex, and will require methodical approaches for their development. Single leaflet replacement utilizing an ovine model is an attractive approach in that candidate materials can be evaluated under valve level stresses in blood contact without the confounding effects of a particular valve design. In the present study an approach for optimal leaflet shape design based on finite element (FE) simulation of a mechanically anisotropic, elastomeric scaffold for PV replacement is presented. The scaffold was modeled as an orthotropic hyperelastic material using a generalized Fung-type constitutive model. The optimal shape of the fully loaded PV replacement leaflet was systematically determined by minimizing the difference between the deformed shape obtained from FE simulation and an ex-vivo microCT scan of a native ovine PV leaflet. Effects of material anisotropy, dimensional changes of PV root, and fiber orientation on the resulting leaflet deformation were investigated. In-situ validation demonstrated that the approach could guide the design of the leaflet shape for PV replacement surgery.

  15. Shape-Memory Polymers Based on Fatty Acid-Filled Elastomeric Ionomers

    NASA Astrophysics Data System (ADS)

    Izzo, Elise; Weiss, Robert

    2009-03-01

    Shape memory polymers (SMPs) have applications as medical devices, actuators, sensors, artificial muscles, switches, smart textiles, and self-deployable structures. All previous design of SMPs has involved synthesizing new polymers or modifying existing polymers. This paper describes a new type of SMP based on blends of an elastomeric ionomer and low molar mass fatty acids or their salts (FAS). Shape memory elastomers were prepared from mixtures of a sulfonated EPDM ionomer and various amounts of a FAS (e.g., zinc stearate, zinc oleate, and various aliphalic acids). Nanophase separation of the metal sulfonate groups provided the ``permanent'' crosslinks, while sub-microscopic crystals of the low molecular weight FAS provided a physical crosslink needed for the temporary shape. The material was deformed above the melting point of the FAS and the new shape was fixed by cooling the material while under stress to below the melting point of the FAS. Polar interactions between the ionomer and the FAS stabilized the dispersion of the FAS in the polymer and provided the continuity between the phases that allowed the crystals of the FAS to provide a second network of physical crosslinks. The temporary shape was erased and the material returned to the primary shape by heating above the melting point of the FAS.

  16. Damage of Elastomeric Matrix Composites (EMC-rubbers) Under Static Loading Conditions: Experimental and Numerical Study

    SciTech Connect

    Ayari, F.

    2011-01-17

    Elastomeric matrix composites (EMC-rubbers) are considered as isotropic hyper elastic incompressible materials under static loading conditions. As a rubber material element cannot be extended to an infinite stretch ratio, a damage mechanism at large strain is considered. The phenomenon of cavitation plays an important role in the damage of EMCs and influences the toughening mechanism of rubber-modified plastics. Indeed, cavitation in elastomers is thought to be initiated from flaws, which grow primarily due to a hydrostatic tensile stress and ahead of the crack; there will not only be a high stress perpendicular to the plane of the crack but also significant stress components in the other direction. However, there exists historically much discussion on the evolution of the cavitation in elastomers under monotonic and/or static solicitation. Mainly, cavitation instability occurs when the stress levels are sufficiently high so that the void expansion rate becomes infinitely large. Many research works have been performed to understand the effects of rubber cavitation on toughening of plastics. In fact, the cavitation phenomenon is not well known in detail. The most popular idea states that the cavitation is related to the existence of the gas bubbles trapped in the material during the production stage and the growing of the cavities would then be the result of the growing gas bubbles. Further, instable failure mechanism at the end of the cavitation is not well known too.

  17. Designing an elastomeric binder for large-volume-change electrodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Chen, Zonghai

    It is of commercial importance to develop high capacity negative and positive electrode materials for lithium-ion batteries to meet the energy requirements of portable electronic devices. Excellent capacity retention has been achieved for thin sputtered films of amorphous Si, Ge and Si-Sn alloys even when cycled to 2000 mAh/g and above, which suggests that amorphous alloys are capable of extended cycling. However, PVDF-based composite electrodes incorporating a-Si0.64Sn0.36/Ag powder (10 wt% silver coating) (˜10mum) still suffer from severe capacity fading because of the huge volumetric changes of a-Si0.64Sn0.36/Ag during charge/discharge cycling. It is the objective of this thesis to understand the problem scientifically and to propose practical solutions to solve this problem. Mechanical studies of binders for lithium battery electrodes have never been reported in the literature. The mechanical properties of commonly used binders, such as poly(vinylidene fluoride) (PVDF), haven't been challenged because commercially used active materials, such as LiCoO2 and graphite, have small volumetric changes (<10%) during charge/discharge cycling. However, the recently proposed metallic alloys have huge volumetric changes (up to 250%) during cycling. In this case, the mechanical properties of the binder become critical. A tether model is proposed to qualitatively understand the capacity fading of high-volume-change electrodes, and to predict the properties of a good binder system. A crosslinking/coupling route was used to modify the binder system according to the requirements of the tether model. A poly(vinylidene fluoride-tetrafluoroethylenepropylene)-based elastomeric binder system was designed to successfully improve the capacity retention of a-Si0.64 Sn0.36/Ag composite electrodes. In this thesis, it has also proven nontrivial to maximize the capacity retention of large-volume-change electrodes even when a fixed elastomeric binder system was used. The parameters that

  18. Application of the time-temperature superposition principle to the mechanical characterization of elastomeric adhesives for crash simulation purposes

    NASA Astrophysics Data System (ADS)

    Rauh, A.; Hinterhölzl, R.; Drechsler, K.

    2012-05-01

    In the automotive industry, finite element simulation is widely used to ensure crashworthiness. Mechanical material data over wide strain rate and temperature ranges are required as a basis. This work proposes a method reducing the cost of mechanical material characterization by using the time-temperature superposition principle on elastomeric adhesives. The method is based on the time and temperature interdependence which is characteristic for mechanical properties of polymers. Based on the assumption that polymers behave similarly at high strain rates and at low temperatures, a temperature-dominated test program is suggested, which can be used to deduce strain rate dependent material behavior at different reference temperatures. The temperature shift factor is found by means of dynamic mechanical analysis according to the WLF-equation, named after Williams, Landel and Ferry. The principle is applied to the viscoelastic properties as well as to the failure properties of the polymer. The applicability is validated with high strain rate tests.

  19. Effectiveness of common healthcare disinfectants against H1N1 influenza virus on reusable elastomeric respirators.

    PubMed

    Subhash, Shobha S; Cavaiuolo, Maria; Radonovich, Lewis J; Eagan, Aaron; Lee, Martin L; Campbell, Sheldon; Martinello, Richard A

    2014-07-01

    This study evaluated the efficacy of 3 common hospital disinfectants to inactivate influenza virus on elastomeric respirators. Quaternary ammonium/isopropyl alcohol and bleach detergent wipes eliminated live virus, whereas 70% isopropyl alcohol alone was ineffective.

  20. Using "click-e-bricks" to make 3D elastomeric structures.

    PubMed

    Morin, Stephen A; Shevchenko, Yanina; Lessing, Joshua; Kwok, Sen Wai; Shepherd, Robert F; Stokes, Adam A; Whitesides, George M

    2014-09-10

    Soft, 3D elastomeric structures and composite structures are easy to fabricate using click-e-bricks, and the internal architecture of these structures together with the capabilities built into the bricks themselves provide mechanical, optical, electrical, and fluidic functions.

  1. Evaluation of factors affecting the accuracy of impressions using quantitative surface analysis.

    PubMed

    Lee, I K; DeLong, R; Pintado, M R; Malik, R

    1995-01-01

    Impression material goes from a plastic to an elastic state during setting. Movement of the impression and excessive seating pressure during this transition can cause distortion in the impressions. The purpose of this study is to determine if the impression distortion is related to movement during setting or to distortion of the putty phase in the two-step impressioning technique. A master model of a maxillary quadrant of teeth was impressed using four different procedures: 1) one-step technique without movement (1S-NM); 2) one-step technique with movement (1S-M); 3) two-step technique without movement (2S-NM); and 4) two-step technique with movement (2S-M). An artificial oral environment and surface analysis technique of the Minnesota Dental Research Center for Biomaterials and Biomechanics were used to produce the impressions and measure their accuracy. A digitized image of the first premolar of the master model was aligned with a digitized image of the first premolar of each epoxy model using AnSur. The root mean squared difference (RMS) between the aligned images is a measure of the distortion. The corresponding RMS values for the different methods were: 1S-NM = 23.7 +/- 9.21; 1S-M = 20.4 +/- 3.9; 2S-NM = 20.5 +/- 7.7; 2S-M = 21.3 +/- 4.4. Statistical analysis using a two-way analysis of variance showed no difference at the 0.05 level of significance. Pairwise comparison using the Tukey method showed that neither technique (one-step vs two-step) nor movement is a significant factor. These results showed that low seating pressure will not cause any greater distortions in the two-step impression technique than in the one-step technique, and minor movement during the setting of the impression material will no cause distortion.

  2. Elastomeric Structural Attachment Concepts for Aircraft Flap Noise Reduction - Challenges and Approaches to Hyperelastic Structural Modeling and Analysis

    NASA Technical Reports Server (NTRS)

    Sreekantamurthy, Thammaiah; Turner, Travis L.; Moore, James B.; Su, Ji

    2014-01-01

    Airframe noise is a significant part of the overall noise of transport aircraft during the approach and landing phases of flight. Airframe noise reduction is currently emphasized under the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) Project goals of NASA. A promising concept for trailing-edge-flap noise reduction is a flexible structural element or link that connects the side edges of the deployable flap to the adjacent main-wing structure. The proposed solution is distinguished by minimization of the span-wise extent of the structural link, thereby minimizing the aerodynamic load on the link structure at the expense of increased deformation requirement. Development of such a flexible structural link necessitated application of hyperelastic materials, atypical structural configurations and novel interface hardware. The resulting highly-deformable structural concept was termed the FLEXible Side Edge Link (FLEXSEL) concept. Prediction of atypical elastomeric deformation responses from detailed structural analysis was essential for evaluating feasible concepts that met the design constraints. The focus of this paper is to describe the many challenges encountered with hyperelastic finite element modeling and the nonlinear structural analysis of evolving FLEXSEL concepts. Detailed herein is the nonlinear analysis of FLEXSEL concepts that emerged during the project which include solid-section, foamcore, hollow, extended-span and pre-stressed concepts. Coupon-level analysis performed on elastomeric interface joints, which form a part of the FLEXSEL topology development, are also presented.

  3. Evaluation of the effect of different stretching patterns on force decay and tensile properties of elastomeric ligatures

    PubMed Central

    Aminian, Amin; Nakhaei, Samaneh; Agahi, Raha Habib; Rezaeizade, Masoud; Aliabadi, Hamed Mirzazadeh; Heidarpour, Majid

    2015-01-01

    Background: There have been numerous researches on elastomeric ligatures, but clinical conditions in different stages of treatment are not exactly similar to laboratory conditions. The aim of this in vitro study was to simulate clinical conditions and evaluate the effect of three stretching patterns on the amount of force, tensile strength (TS) and extension to TS of the elastomers during 8 weeks. Materials and Methods: Forces, TS and extension to TS of two different brands of elastomers were measured at initial, 24 h and 2, 4, and 8-week intervals using a testing machine. During the study period, the elastomers were stored in three different types of jig (uniform stretching, 1 and 3 mm point stretching) designed by the computer-aided design and computer-aided manufacturing technique in order to simulate the different stages of orthodontic treatment. Results: The elastomeric ligatures under study exhibited a similar force decay pattern. The maximum force decay occurred during the first 24 h (49.9% ± 15%) and the amount of force decay was 75.7% ± 8% after 8 weeks. In general, the TS decreased during the study period, and the amount of extension to TS increased. Conclusion: Although the elastic behavior of all ligatures under study was similar, the amount of residual force, TS and extension to TS increased in elastomers under point stretching pattern. PMID:26759597

  4. Accuracy of Different Putty-Wash Impression Techniques with Various Spacer Thickness

    PubMed Central

    Arora, Aman; Singh, Vijay Pratap

    2012-01-01

    ABSTRACT One of the most important steps is accurate impression making for fabrication of fixed partial denture. The two different putty-wash techniques that are commonly used are: (1) Putty-wash one-step technique, (2) putty-wash two-step technique. A uniform wash space is needed for an accurate impression. Nissan et al recommended the use of two-step technique for accurate impression making as there is uniform wash space for the light body material to polymerize. The aim of the present study was to compare the accuracy of stone casts obtained from different putty-wash impression techniques using various spacer thickness. The critical factor that influences the accuracy of putty-wash impression techniques is the controlled wash bulk which is absent in one-step putty-wash impression technique and with polyethylene spacer was used. How to cite this article: Chugh A, Arora A, Singh VP. Accuracy of Different Putty-Wash Impression Techniques with Various Spacer Thickness. Int J Clin Pediatr Dent 2012;5(1):33-38. PMID:25206132

  5. Effect of various putty-wash impression techniques on marginal fit of cast crowns.

    PubMed

    Nissan, Joseph; Rosner, Ofir; Bukhari, Mohammed Amin; Ghelfan, Oded; Pilo, Raphael

    2013-01-01

    Marginal fit is an important clinical factor that affects restoration longevity. The accuracy of three polyvinyl siloxane putty-wash impression techniques was compared by marginal fit assessment using the nondestructive method. A stainless steel master cast containing three abutments with three metal crowns matching the three preparations was used to make 45 impressions: group A = single-step technique (putty and wash impression materials used simultaneously), group B = two-step technique with a 2-mm relief (putty as a preliminary impression to create a 2-mm wash space followed by the wash stage), and group C = two-step technique with a polyethylene spacer (plastic spacer used with the putty impression followed by the wash stage). Accuracy was assessed using a toolmaker microscope to measure and compare the marginal gaps between each crown and finish line on the duplicated stone casts. Each abutment was further measured at the mesial, buccal, and distal aspects. One-way analysis of variance was used for statistical analysis. P values and Scheffe post hoc contrasts were calculated. Significance was determined at .05. One-way analysis of variance showed significant differences among the three impression techniques in all three abutments and at all three locations (P < .001). Group B yielded dies with minimal gaps compared to groups A and C. The two-step impression technique with 2-mm relief was the most accurate regarding the crucial clinical factor of marginal fit.

  6. Accuracy of different putty-wash impression techniques with various spacer thickness.

    PubMed

    Chugh, Anshul; Arora, Aman; Singh, Vijay Pratap

    2012-01-01

    One of the most important steps is accurate impression making for fabrication of fixed partial denture. The two different putty-wash techniques that are commonly used are: (1) Putty-wash one-step technique, (2) putty-wash two-step technique. A uniform wash space is needed for an accurate impression. Nissan et al recommended the use of two-step technique for accurate impression making as there is uniform wash space for the light body material to polymerize. The aim of the present study was to compare the accuracy of stone casts obtained from different putty-wash impression techniques using various spacer thickness. The critical factor that influences the accuracy of putty-wash impression techniques is the controlled wash bulk which is absent in one-step putty-wash impression technique and with polyethylene spacer was used. How to cite this article: Chugh A, Arora A, Singh VP. Accuracy of Different Putty-Wash Impression Techniques with Various Spacer Thickness. Int J Clin Pediatr Dent 2012;5(1):33-38.

  7. Thermoviscoplastic behaviors of anisotropic shape memory elastomeric composites for cold programmed non-affine shape change

    NASA Astrophysics Data System (ADS)

    Mao, Yiqi; Robertson, Jaimee M.; Mu, Xiaoming; Mather, Patrick T.; Jerry Qi, H.

    2015-12-01

    Shape memory polymers (SMPs) can fix a temporary shape and recover their permanent shape upon activation by an external stimulus. Most SMPs require programming at above their transition temperatures, normally well above the room temperature. In addition, most SMPs are programmed into shapes that are affine to the high temperature deformation. Recently, a cold-programmed anisotropic shape memory elastomeric composite was developed and showed interesting low temperature stretching induced shape memory behavior. There, simple, uniaxial stretching at low temperature transformed the composites into curled temporary shapes upon unloading. The exact geometry of the curled state depended on the microstructure of the composite, and the curled shape showed no affinity to the deformed shape. Heating the sample recovered the sample back to its original shape. This new composite consisted of an elastomeric matrix reinforced by aligned amorphous polymer fibers. By utilizing the plastic-like behavior of the amorphous polymer phase at low temperatures, a temporary shape could be fixed upon unloading since the induced plastic-like strain resists the recovery of the elastomer matrix. After heating to a high temperature, the permanent shape was recovered when the amorphous polymer softened and the elastomer matrix contracted. To set a theoretical foundation for capturing the cold-programmed shape memory effects and the dramatic non-affine shape change of this composite, a 3D anisotropic thermoviscoelastic constitutive model is developed in this paper. In this model, the matrix is modeled as a hyperelastic solid, and the amorphous phase of the fibrous mat is considered as a nonlinear thermoviscoplastic solid, whose viscous flow resistance is sensitive to both temperature and stress. The plastic-deformation like behavior demonstrated in the fiber is treated as nonlinear viscoplasticity with extremely high viscosity or long relaxation time at zero-stress state at low temperature. The

  8. Accuracy of Digital vs. Conventional Implant Impressions

    PubMed Central

    Lee, Sang J.; Betensky, Rebecca A.; Gianneschi, Grace E.; Gallucci, German O.

    2015-01-01

    The accuracy of digital impressions greatly influences the clinical viability in implant restorations. The aim of this study is to compare the accuracy of gypsum models acquired from the conventional implant impression to digitally milled models created from direct digitalization by three-dimensional analysis. Thirty gypsum and 30 digitally milled models impressed directly from a reference model were prepared. The models were scanned by a laboratory scanner and 30 STL datasets from each group were imported to an inspection software. The datasets were aligned to the reference dataset by a repeated best fit algorithm and 10 specified contact locations of interest were measured in mean volumetric deviations. The areas were pooled by cusps, fossae, interproximal contacts, horizontal and vertical axes of implant position and angulation. The pooled areas were statistically analysed by comparing each group to the reference model to investigate the mean volumetric deviations accounting for accuracy and standard deviations for precision. Milled models from digital impressions had comparable accuracy to gypsum models from conventional impressions. However, differences in fossae and vertical displacement of the implant position from the gypsum and digitally milled models compared to the reference model, exhibited statistical significance (p<0.001, p=0.020 respectively). PMID:24720423

  9. Assessing the clarity of friction ridge impressions.

    PubMed

    Hicklin, R Austin; Buscaglia, JoAnn; Roberts, Maria Antonia

    2013-03-10

    The ability of friction ridge examiners to correctly discern and make use of the ridges and associated features in finger or palm impressions is limited by clarity. The clarity of an impression relates to the examiner's confidence that the presence, absence, and attributes of features can be correctly discerned. Despite the importance of clarity in the examination process, there have not previously been standard methods for assessing clarity in friction ridge impressions. We introduce a process for annotation, analysis, and interchange of friction ridge clarity information that can be applied to latent or exemplar impressions. This paper: (1) describes a method for evaluating the clarity of friction ridge impressions by using color-coded annotations that can be used by examiners or automated systems; (2) discusses algorithms for overall clarity metrics based on manual or automated clarity annotation; and (3) defines a method of quantifying the correspondence of clarity when comparing a pair of friction ridge images, based on clarity annotation and resulting metrics. Different uses of this approach include examiner interchange of data, quality assurance, metrics, and as an aid in automated fingerprint matching. PMID:23313600

  10. Impression formation: the role of expressive behavior.

    PubMed

    Riggio, R E; Friedman, H S

    1986-02-01

    This research examined the effects of personality/social skills and individual differences in expressive style on impression formation. Particular attention was given to the role of nonverbal behaviors in the formation of initial impressions. Sixty-two subjects were measured on self-report personality and communication skill scales, on posed emotional sending ability, and on physical attractiveness. Subjects were then videotaped while giving a spontaneous "explanation." Trained coders measured five separate nonverbal cue factors displayed by the subjects in the videotapes. Groups of untrained judges viewed the tapes and rated their impressions of the subjects on scales of likability, speaking effectiveness, and expressivity-confidence. Male subjects who were nonverbally skilled and extraverted tended to display more outwardly focused and fluid expressive behaviors, and made more favorable impressions on judges, than did males who scored low on the measures of nonverbal skills and extraversion. Females who were nonverbally skilled displayed more facial expressiveness, which led to more favorable initial impressions. Sex differences may reflect basic differences in the acquisition and use of expressive nonverbal cues by males and females. PMID:3517289

  11. How To Achieve Better Impressions in Computer-Mediated Communication?

    ERIC Educational Resources Information Center

    Liu, Yuliang; Ginther, Dean

    This paper presents a review of the literature on impression formation in face-to-face (FtF) and computer-mediated communication (CMC) and provides impression management recommendations for CMC users in a variety of environments. The first section provides an introduction to impression formation. Factors affecting impression formation in FtF and…

  12. Giving the wrong impression: food and beverage brand impressions delivered to youth through popular movies

    PubMed Central

    Skatrud-Mickelson, Monica; Adachi-Mejia, Anna M.; MacKenzie, Todd A.; Sutherland, Lisa A.

    2012-01-01

    Background Marketing on television showcases less-healthful options, with emerging research suggesting movies promote similar products. Given the obesity epidemic, understanding advertising to youth should be a public health imperative. The objective of this study was to estimate youth impressions to food and beverages delivered through movies. Methods Impressions were calculated by dividing US receipts annually into average movie ticket prices, then multiplying this by the number of brand appearances. Examination by ratings, product types and ages were conducted by Spearman rank correlation coefficient tests. Results Youth in the USA saw over 3 billion food, beverage or food–retail establishment (FRE) impressions on average, annually from 1996 to 2005. Those aged 12–18 viewed over half of all impressions, with PG-13-rated movies containing 61.5% of impressions. There were no significant trends in brand appearances by food, beverage or FRE impressions over the decade, although there was a decreasing trend in R-rated impressions for both foods (P< 0.01) and beverages (P< 0.01), but not FREs (P= 0.08). Conclusions Movies promote billions of food and beverage impressions annually to youth. Given the public health crisis of obesity, future research should further investigate these trends, as well as the potential association of these unhealthy exposures in youth. PMID:22076600

  13. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch.

    PubMed

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H W

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  14. Elastomeric angled microflaps with reversible adhesion for transfer-printing semiconductor membranes onto dry surfaces.

    PubMed

    Yoo, Byungsuk; Cho, Sungbum; Seo, Seungwan; Lee, Jongho

    2014-11-12

    Recent research for unconventional types of electronics has revealed that it is necessary to transfer-print high-performance microelectronic devices onto diverse surfaces, including flexible or stretchable surfaces, to relieve mechanical constraints associated with conventional rigid electronics. Picking up and placing ultrathin microdevices without damage are critical procedures for the successful manufacture of various types of unconventional electronics. This paper introduces elastomeric angled microflaps that have reversible adhesion; i.e., they generate higher adhesion for picking up and low adhesion for printing because of their structural shapes and viscoelastic material properties. The microstructured stamp, fabricated in relatively simple ways, enables simultaneous transfer-printing of multiple silicon membranes that have irregular shapes in sizes ranging from micrometer to millimeter scales. Mechanical characterizations by experiment reveal optimal parameters for picking up and placing ultrathin membranes on a programmable custom-built microstage. Further refinement of the structures and materials should be useful for many applications requiring the microassembly of multiple semiconductor membranes in diverse shapes and sizes on dry surfaces without the aid of liquid adhesives.

  15. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch

    PubMed Central

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H. W.

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  16. Facial feedback effects on impression formation.

    PubMed

    Ohira, H; Kurono, K

    1993-12-01

    Two experiments were conducted to examine effects of facial expressions upon social cognitive processes in which the impression of another person is formed. In each experiment, 30 female college students were induced to display or conceal their facial reactions to a hypothetical target person whose behaviors were mildly hostile (Exp. 1) or mildly friendly (Exp. 2), or their facial expressions were not manipulated. Displaying the facial expressions shifted the impression into the congruent directions with hedonic values corresponding to the facial expressions. Concealing the facial expressions, however, did not influence impression formation. Also, the positive-negative asymmetry was observed in the facial feedback effects, that is, the negative facial expression had a stronger effect on social cognition than the positive one. PMID:8170774

  17. Handshaking, gender, personality, and first impressions.

    PubMed

    Chaplin, W F; Phillips, J B; Brown, J D; Clanton, N R; Stein, J L

    2000-07-01

    Although people's handshakes are thought to reflect their personality and influence our first impressions of them, these relations have seldom been formally investigated. One hundred twelve participants had their hand shaken twice by 4 trained coders (2 men and 2 women) and completed 4 personality measures. The participants' handshakes were stable and consistent across time and coders. There were also gender differences on most of the handshaking characteristics. A firm handshake was related positively to extraversion and emotional expressiveness and negatively to shyness and neuroticism; it was also positively related to openness to experience, but only for women. Finally, handshake characteristics were related to the impressions of the participants formed by the coders. These results demonstrate that personality traits, assessed through self-report, can predict specific behaviors assessed by trained observers. The pattern of relations among openness, gender, handshaking, and first impressions suggests that a firm handshake may be an effective form of self-promotion for women.

  18. The bond strength of different tray adhesives on vinyl polysiloxane to two tray materials: an in vitro study.

    PubMed

    Ashwini, B L; Manjunath, S; Mathew, K Xavier

    2014-03-01

    There has been no established chemical bonding between custom tray resin and the elastomeric impression materials without the use of manufacturer's recommended specific tray adhesive. The present study was aimed to compare the bond strength of the manufacturer recommended tray adhesives with the universal tray adhesives using the medium body consistency vinyl polysiloxane (VPS) material and custom tray made of autopolymerising resin and visible light cure (VLC) resin. A total 90 cubicle specimens of autopolymerising resin and 90 specimens of VLC resin were tested for its tensile bond strength. Effectiveness of universal tray adhesive was compared with manufactured tray adhesive. Each of these specimens was then subjected to tensile load in hounsefield universal testing machine at a cross head speed of 5 mm/min and the results were compared and evaluated using one way analysis of variance and post hoc Tuckey's test. Analysis of bond strength revealed that the universal tray adhesive showed better strength and was statiscally significant when compared to the manufacture supplied tray adhesive. Comparison between both the groups, VLC resin showed better bond strength as compared to autopolymerizing resin. Universal tray adhesive had better tensile bond strength than the manufacturers recommended tray adhesive with the medium body viscosity VPS impression material for both autopolymerising and VLC tray resin. PMID:24604995

  19. Revisiting impressions using dual-arch trays.

    PubMed

    Small, Bruce W

    2012-01-01

    Making routine perfect impressions is the goal of any restorative dentist. Using dual-arch trays is an easy, repeatable way to accomplish that goal, as long as each step is done before the next and each step is performed perfectly. This column reviewed several articles that support the metal dual-arch concept and provided some clinical tips that might help restorative dentists. The dual-arch technique does have its limits and is meant for one or two teeth in a quadrant when there are other teeth to occlude with. Also, if the case involves anterior guidance, a full-arch impression maybe advisable.

  20. Comparative evaluation of dimensional accuracy of different polyvinyl siloxane putty-wash impression techniques-in vitro study.

    PubMed Central

    Dugal, Ramandeep; Railkar, Bhargavi; Musani, Smita

    2013-01-01

    Background: Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy. The purpose of this in vitro study was to compare the dimensional accuracy of the casts obtained from one step double mix, two step double mix polyvinyl siloxane putty- wash impression techniques using three different spacer thicknesses (0.5mm, 1mm and 1.5mm), in order to determine the impression technique that displays the maximum linear dimensional accuracy. Materials & Methods: A Mild steel model with 2 abutment preparations was fabricated, and impressions were made 15 times with each technique. All impressions were made with an addition-reaction silicone impression material (Express, 3M ESPE) and customarily made perforated metal trays. The 1-step putty/light-body impressions were made with simultaneous use of putty and light-body materials. The 2-step putty/light-body impressions were made with 0.5-mm, 1mm and 1.5mm-thick metal-prefabricated spacer caps. The accuracy of the 4 different impression techniques was assessed by measuring 7 dimensions (intra- and inter abutment) (20-μm accuracy) on stone casts poured from the impressions of the mild steel model. The data were analyzed by one sample‘t’ test. Results: The stone dies obtained with all the techniques had significantly larger or smaller dimensions as compared to those of the mild steel model (P<0.05). The order for highest to lowest deviation from the mild steel model was: single step putty/light body, 2-step putty/light body with 0.5mm spacer thickness, 2-step putty/light body1.5mm spacer thickness, and 2-step putty/light body with 1mm spacer thickness. Significant differences among all of the groups for both absolute dimensions of the stone dies, and their standard deviations from the master model (P<0.05), were noted. Conclusions: The 2-step putty/light-body impression technique with 1mm spacer thickness was

  1. High-performance supercapacitors, actuators and elastomeric composites based on CNT assemblies

    NASA Astrophysics Data System (ADS)

    Kozlov, Mikhail; Oh, Jiyoung; Shin, Minkyoon; Robles, Raquel; Lima, M. Árcio; Baughman, Ray

    2009-03-01

    A number of materials ranging from carbon nanotube (CNT) yarns, sheets and CNT-based composites to shape memory alloys (SMA) have been explored for the application in the area of energy conversion and storage. Highly porous sheets comprised of Single Walled Carbon Nanotubes and doped polypyrrole (SWNT-PPy) were found to possess remarkably high specific capacitance of about 131 F/g; CNT-elastomeric polymer composites exhibited electrical conductivity of about 0.5 S/cm and can be stretched by 1400%. We found that if powered electrically, the isometric stress generated by the CNT-based actuators could be as large as 12 MPa. This approaches the stress generation capability of commercial ferroelectrics and is significantly larger than that of natural muscles. We also report several types of artificial muscles that convert the chemical energy of high--energy-density fuels to mechanical energy. Because of more than 30 times higher energy density obtainable for fuels like methanol, compared to that for the most advanced batteries, the major expected benefits are dramatic increase in energy conversion efficiency, work capacity, power performance.

  2. An Impress Method of Reading Instruction.

    ERIC Educational Resources Information Center

    Gawarkiewicz, Patricia

    The effectiveness of the impress method of reading instruction, in which the student and teacher read aloud simultaneously, was studied. The subjects were 24 fourth and fifth grade students from a New Jersey school, whose reading level was a year or more below grade placement (indicated by scores on a standardized achievement test) and who…

  3. Patterns of Vocalization and Impression Formation

    ERIC Educational Resources Information Center

    Hayes, Donald P.; Bouma, Gary D.

    1975-01-01

    This article discusses the interactive behavior that accompanies verbal exchange. It specifically describes a set of experiments designed to isolate an important subset of interactive behavior, the vocal (as opposed to the verbal) and to relate this information to a wide range of social impressions resulting from verbal exchange. (Available from…

  4. Additivity of Clothing Cues in First Impressions.

    ERIC Educational Resources Information Center

    Lennon, Sharron J.

    1986-01-01

    The theory of information integration was used to predict that in first impression situations, clothing/physical appearance cues have differential importance depending upon the type of judgment elicited. Female college students (N=104) viewed and responded to slides of colored line drawings of female stimulus persons. Multiple regression of data…

  5. Interpersonal Teaching Style and Student Impression Formation

    ERIC Educational Resources Information Center

    Coldren, Jeffrey; Hively, Jodi

    2009-01-01

    Assuming that learning is an inherently social process, this research explores interpersonal variables that affect teaching. Specifically, does the interpersonal teaching style affect student impressions of the instructor? Eighty-five undergraduates viewed one of three ten-minute videos that portrayed either an authoritarian, authoritative, or…

  6. Borescope Device Takes Impressions In Ducts

    NASA Technical Reports Server (NTRS)

    Walter, Richard F.; Turner, Laura J.

    1990-01-01

    Maneuverable device built around borescope equipped to make impression molds of welded joints in interior surfaces of ducts. Molds then examined to determine degress of mismatch in welds. Inserted in duct, and color-coded handles on ends of cables used to articulate head to maneuver around corners. Use of device fairly easy and requires little training.

  7. Elastomeric fluorescent POF for partial discharge detection: recent progress

    NASA Astrophysics Data System (ADS)

    Siebler, Daniel; Hohberg, Michaela; Rohwetter, Philipp; Brusenbach, Roy; Plath, Ronald

    2015-09-01

    We present recent progress in our development of fibre-optic sensors for the detection of partial discharge (PD) in silicone cable accessories, based on detecting related low-level optical emission. We experimentally show that the sensitive optical detection of PD can dramatically enhance the performance of conventional electrical PD measurement in electromagnetically noisy environments, and that it can yield high sensitivity and specificity even when no synchronous electrical PD measurement is conducted. This is demonstrated using a real-scale model of a high voltage cable accessory with a surface-attached conventional thermoplastic fluorescent polymer optical fibre (F-POF) sensor. In order to increase light collection efficiency, as a prerequisite for a commercially competitive implementation using cost-efficient detectors, sensing fibres will have to be integrated into the silicone rubber insulation, close to the potential origin of PD-induced damage. This is the rationale for our efforts to develop elastomeric fluorescent sensing fibres, tailored to the requirements of the application. We discuss specific challenges to be tackled and report on the successful implementation of all-silicone rubber fluorescent POF, to our best knowledge for the first time.

  8. Fabrication of biodegradable elastomeric scaffolds with sub-micron morphologies

    PubMed Central

    Stankus, John J.; Guan, Jianjun; Wagner, William R.

    2010-01-01

    The native extracellular matrix (ECM) of elastic tissues is strong and flexible and supports cell adhesion and enzymatic matrix remodeling. In an attempt to convey these ECM properties to a synthetic scaffold appropriate for soft tissue engineering applications, a biodegradable, elastomeric poly(ester urethane)urea (PEUU) was combined with type I collagen at various ratios (2.5, 5, 10, 20, 50, 60, 70, 80, and 90 wt% collagen) and electrospun to construct elastic matrices. Randomly orientated fibers in the electrospun matrices ranged in diameter from 100–900 nm, dependent on initial polymer concentration. Picrosirius red staining of matrices and CD spectroscopy of released collagen confirmed collagen incorporation and preservation of collagen structure at the higher collagen mass fractions. Matrices were strong and distensible possessing strengths of 2–13 MPa with breaking strains of 160–280% even with low PEUU content. Collagen incorporation significantly enhanced smooth muscle cell adhesion onto electrospun scaffolds. An approach has been demonstrated that mimics elastic extracellular matrices by using a synthetic component to provide mechanical function together with a biomacromolecule, collagen. Such matrices may find application in engineering soft tissue. PMID:15307165

  9. Identification of dynamic stiffness matrices of elastomeric joints using direct and inverse methods

    NASA Astrophysics Data System (ADS)

    Noll, Scott; Dreyer, Jason T.; Singh, Rajendra

    2013-08-01

    New experiments are designed to permit direct comparison between direct and inverse identification methods of the dynamic stiffness matrices of elastomeric joints, including non-diagonal terms. The joints are constructed with combinations of inclined elastomeric cylinders to control non-diagonal terms in the stiffness matrix. The inverse experiment consists of an elastic metal beam end-supported by elastomeric joints coupling the in-plane transverse and longitudinal beam motion. A prior method is extended to identify the joint dynamic stiffness matrices of dimension 3 from limited modal measurements of the beam. The dynamic stiffness and loss factors of the elastomeric cylinders are directly measured in a commercial elastomer test machine in shear, compression, and inclined configurations and a coordinate transformation is used to estimate the kinematic non-diagonal stiffness terms. Agreement is found for both dynamic stiffness and loss factors between the direct and inverse methods at small displacements. Further, the identified joint properties are employed in a model that successfully predicts the modal parameters and accelerance spectra of the inverse experiment. This article provides valuable insight on the difficulties encountered when comparing system and elastomeric component test results.

  10. Microstructured elastomeric surfaces with reversible adhesion and examples of their use in deterministic assembly by transfer printing.

    PubMed

    Kim, Seok; Wu, Jian; Carlson, Andrew; Jin, Sung Hun; Kovalsky, Anton; Glass, Paul; Liu, Zhuangjian; Ahmed, Numair; Elgan, Steven L; Chen, Weiqiu; Ferreira, Placid M; Sitti, Metin; Huang, Yonggang; Rogers, John A

    2010-10-01

    Reversible control of adhesion is an important feature of many desired, existing, and potential systems, including climbing robots, medical tapes, and stamps for transfer printing. We present experimental and theoretical studies of pressure modulated adhesion between flat, stiff objects and elastomeric surfaces with sharp features of surface relief in optimized geometries. Here, the strength of nonspecific adhesion can be switched by more than three orders of magnitude, from strong to weak, in a reversible fashion. Implementing these concepts in advanced stamps for transfer printing enables versatile modes for deterministic assembly of solid materials in micro/nanostructured forms. Demonstrations in printed two- and three-dimensional collections of silicon platelets and membranes illustrate some capabilities. An unusual type of transistor that incorporates a printed gate electrode, an air gap dielectric, and an aligned array of single walled carbon nanotubes provides a device example.

  11. You want to give a good impression? Be honest! Moral traits dominate group impression formation.

    PubMed

    Brambilla, Marco; Sacchi, Simona; Rusconi, Patrice; Cherubini, Paolo; Yzerbyt, Vincent Y

    2012-03-01

    Research has shown that warmth and competence are core dimensions on which perceivers judge others and that warmth has a primary role at various phases of impression formation. Three studies explored whether the two components of warmth (i.e., sociability and morality) have distinct roles in predicting the global impression of social groups. In Study 1 (N= 105) and Study 2 (N= 112), participants read an immigration scenario depicting an unfamiliar social group in terms of high (vs. low) morality, sociability, and competence. In both studies, participants were asked to report their global impression of the group. Results showed that global evaluations were better predicted by morality than by sociability or competence-trait ascriptions. Study 3 (N= 86) further showed that the effect of moral traits on group global evaluations was mediated by the perception of threat. The importance of these findings for the impression-formation process is discussed.

  12. You want to give a good impression? Be honest! Moral traits dominate group impression formation.

    PubMed

    Brambilla, Marco; Sacchi, Simona; Rusconi, Patrice; Cherubini, Paolo; Yzerbyt, Vincent Y

    2012-03-01

    Research has shown that warmth and competence are core dimensions on which perceivers judge others and that warmth has a primary role at various phases of impression formation. Three studies explored whether the two components of warmth (i.e., sociability and morality) have distinct roles in predicting the global impression of social groups. In Study 1 (N= 105) and Study 2 (N= 112), participants read an immigration scenario depicting an unfamiliar social group in terms of high (vs. low) morality, sociability, and competence. In both studies, participants were asked to report their global impression of the group. Results showed that global evaluations were better predicted by morality than by sociability or competence-trait ascriptions. Study 3 (N= 86) further showed that the effect of moral traits on group global evaluations was mediated by the perception of threat. The importance of these findings for the impression-formation process is discussed. PMID:22435848

  13. 75 FR 64742 - In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-20

    ... Austin, Texas (``ILF''). 75 FR 47027 (Aug. 4, 2010). The complaint alleges violations of section 337 of... COMMISSION In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of... having elastomeric gel and components thereof by reason of infringement of certain claims of U.S....

  14. A survey of the methods of disinfection of dental impressions used in dental hospitals in the United Kingdom.

    PubMed

    Blair, F M; Wassell, R W

    1996-05-25

    The potential for cross-infection from microbial contaminated dental impressions has long been recognised. This study set out to investigate impression decontamination procedures currently used in UK dental hospitals (1995) and to see how these may have changed since a previous survey, carried out in 1988. A variety of disinfection solutions and regimes were highlighted both within and between dental hospitals. Several of the disinfecting solutions currently being used have not been specifically tested for efficacy with impression materials. The laboratories were asked to highlight any adverse reactions. Five laboratories reported that some alginates resulted in casts with poor surface properties when immersed in hypochlorite (0.1 and 1%), sodium dichloroisocyanurate, and 2% glutaraldehyde solutions. This paper highlights that there is no universally recognised impression disinfection/sterilisation protocol. It is recommended that all impressions should at least undergo a disinfecting procedure by immersion in 1% sodium hypochlorite for a minimum of 10 minutes. PMID:8652299

  15. Influence of Blackness on Visual Impression of Color Images

    NASA Astrophysics Data System (ADS)

    Eda, Tetsuya; Koike, Yoshiki; Matsushima, Sakurako; Ishikawa, Tomoharu; Ozaki, Koichi; Ayama, Miyoshi

    Two experiments, using color images of Japanese lacquer objects, investigated the relation between the strength of blackness and the visual and artistic impression of digital color images presented on a display. The first experiment determined the mean RGB values of black surface areas in the test stimuli where observers began to perceive the areas as “black”, and the mean RGB values where observers perceived the areas “really black”. Results indicate that to perceive a “really black” surface, RGB values should be lower than those of the original image in some pictures. The second experiment investigated, how, and to what degree the RGB values of black areas affect the visual impression of an artistic picture. Three factors, “high-quality axis”, “mysterious axis”, and “feeling of material axis”, were extracted by factor analysis. Results indicate that the Art students seem to be more sensitive in the evaluations along the “high-quality axis” and “mysterious axis” than the Engineering students are, while the opposite tendency is observed in the evaluation along the “feeling of material axis”.

  16. ANIMAL ANALOGIES IN FIRST IMPRESSIONS OF FACES.

    PubMed

    Zebrowitz, Leslie A; Wadlinger, Heather A; Luevano, Victor X; White, Benjamin M; Xing, Cai; Zhang, Yi

    2011-08-01

    Analogies between humans and animals based on facial resemblance have a long history. We report evidence for reverse anthropomorphism and the extension of facial stereotypes to lions, foxes, and dogs. In the stereotype extension, more positive traits were attributed to animals judged more attractive than con-specifics; more childlike traits were attributed to those judged more babyfaced. In the reverse anthropomorphism, human faces with more resemblance to lions, ascertained by connectionist modeling of facial metrics, were judged more dominant, cold, and shrewd, controlling attractiveness, babyfaceness, and sex. Faces with more resemblance to Labradors were judged warmer and less shrewd. Resemblance to foxes did not predict impressions. Results for lions and dogs were consistent with trait impressions of these animals and support the species overgeneralization hypothesis that evolutionarily adaptive reactions to particular animals are overgeneralized, with people perceived to have traits associated with animals their faces resemble. Other possible explanations are discussed.

  17. ANIMAL ANALOGIES IN FIRST IMPRESSIONS OF FACES

    PubMed Central

    Zebrowitz, Leslie A.; Wadlinger, Heather A.; Luevano, Victor X.; White, Benjamin M.; Xing, Cai; Zhang, Yi

    2013-01-01

    Analogies between humans and animals based on facial resemblance have a long history. We report evidence for reverse anthropomorphism and the extension of facial stereotypes to lions, foxes, and dogs. In the stereotype extension, more positive traits were attributed to animals judged more attractive than con-specifics; more childlike traits were attributed to those judged more babyfaced. In the reverse anthropomorphism, human faces with more resemblance to lions, ascertained by connectionist modeling of facial metrics, were judged more dominant, cold, and shrewd, controlling attractiveness, babyfaceness, and sex. Faces with more resemblance to Labradors were judged warmer and less shrewd. Resemblance to foxes did not predict impressions. Results for lions and dogs were consistent with trait impressions of these animals and support the species overgeneralization hypothesis that evolutionarily adaptive reactions to particular animals are overgeneralized, with people perceived to have traits associated with animals their faces resemble. Other possible explanations are discussed. PMID:25339791

  18. Thermally tailored gradient topography surface on elastomeric thin films.

    PubMed

    Roy, Sudeshna; Bhandaru, Nandini; Das, Ritopa; Harikrishnan, G; Mukherjee, Rabibrata

    2014-05-14

    We report a simple method for creating a nanopatterned surface with continuous variation in feature height on an elastomeric thin film. The technique is based on imprinting the surface of a film of thermo-curable elastomer (Sylgard 184), which has continuous variation in cross-linking density introduced by means of differential heating. This results in variation of viscoelasticity across the length of the surface and the film exhibits differential partial relaxation after imprinting with a flexible stamp and subjecting it to an externally applied stress for a transient duration. An intrinsic perfect negative replica of the stamp pattern is initially created over the entire film surface as long as the external force remains active. After the external force is withdrawn, there is partial relaxation of the applied stresses, which is manifested as reduction in amplitude of the imprinted features. Due to the spatial viscoelasticity gradient, the extent of stress relaxation induced feature height reduction varies across the length of the film (L), resulting in a surface with a gradient topography with progressively varying feature heights (hF). The steepness of the gradient can be controlled by varying the temperature gradient as well as the duration of precuring of the film prior to imprinting. The method has also been utilized for fabricating wettability gradient surfaces using a high aspect ratio biomimetic stamp. The use of a flexible stamp allows the technique to be extended for creating a gradient topography on nonplanar surfaces as well. We also show that the gradient surfaces with regular structures can be used in combinatorial studies related to pattern directed dewetting. PMID:24697617

  19. Elastomeric Seal Performance after Terrestrial Ultraviolet Radiation Exposure

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Oravec, Heather A.; Mather, Janice L.; Taylor, Shawn C.; Dunlap, Patrick H.

    2015-01-01

    Ultraviolet radiation was evaluated to determine its negative effects on the performance of elastomeric gas pressure seals. The leak rates of the silicone elastomer S0383-70 O-ring test articles were used to quantify the degradation of the seals after exposure to vacuum-ultraviolet and/or middle-to-near-ultraviolet wavelength radiation. Three groups of seals were exposed in terrestrial facilities to 115-165 nm wavelength radiation, 230-500 nm wavelength radiation, or both spectrums, for an orbital spaceflight equivalent of 125 hours. The leak rates of the silicone elastomer S0383-70 seals were quantified and compared to samples that received no radiation. Each lot contained six samples and statistical t-tests were used to determine the separate and combined influences of exposure to the two wavelength ranges. A comparison of the mean leak rates of samples exposed to 115-165 nm wavelength radiation to the control specimens showed no difference, suggesting that spectrum was not damaging. The 230-500 nm wavelength appeared to be damaging, as the mean leak rates of the specimens exposed to that range of wavelengths, and those exposed to the combined 115-165 nm and 230-500 nm spectrums, were significantly different from the leak rates of the control specimens. Most importantly, the test articles exposed to both wavelength spectrums exhibited mean leak rates two orders of magnitude larger than any other exposed specimens, which suggested that both wavelength spectrums are important when simulating the orbital environment.

  20. Force decay and deformation of orthodontic elastomeric ligatures.

    PubMed

    Taloumis, L J; Smith, T M; Hondrum, S O; Lorton, L

    1997-01-01

    This study evaluated commercially available molded gray elastomeric ligatures from seven companies for force decay, dimensional change, and the relationship between ligature dimension and force. The initial wall thickness, inside diameter, outside diameter, and force levels of each ligature were measured. Three of four test groups of ligatures were stretched over stainless steel dowels with a circumference approximating that of a large orthodontic twin bracket. Test group 1 was kept at room temperature and humidity for 28 days and test group 2 in a synthetic saliva bath at 37 degrees C, pH 6.84 for 28 days. The residual forces and dimensional changes were measured. The third test group was placed in a synthetic saliva bath at 37 degrees C, pH 6.84, and force levels recorded at initial, 24 hours, 7 days, 14 days, and 28 days. The fourth test group of unstretched samples was placed in a synthetic saliva bath at 37 degrees C, pH 6.84 for 28 days to evaluate dimensional changes due solely to moisture sorption. The results for stretched samples in a simulated oral environment revealed the following: (1) Moisture and heat had a pronounced effect on force decay and permanent deformation, (2) a positive correlation existed between the wall thickness and force, (3) a negative correlation existed between the inside diameter and force, (4) a weak correlation existed between outside diameter and force, (5) the greatest force loss occurred in the first 24 hours and the decay pattern was similar for all ligatures tested, and (6) unstretched ligatures absorbed moisture in the range of 0.060% to 3.15%. The ligatures tested appear to be suitable for use during initial aligning and leveling. However, the rapid force loss and permanent deformation of these products may preclude their use for rotational and torque corrections. PMID:9009917

  1. Thermally tailored gradient topography surface on elastomeric thin films.

    PubMed

    Roy, Sudeshna; Bhandaru, Nandini; Das, Ritopa; Harikrishnan, G; Mukherjee, Rabibrata

    2014-05-14

    We report a simple method for creating a nanopatterned surface with continuous variation in feature height on an elastomeric thin film. The technique is based on imprinting the surface of a film of thermo-curable elastomer (Sylgard 184), which has continuous variation in cross-linking density introduced by means of differential heating. This results in variation of viscoelasticity across the length of the surface and the film exhibits differential partial relaxation after imprinting with a flexible stamp and subjecting it to an externally applied stress for a transient duration. An intrinsic perfect negative replica of the stamp pattern is initially created over the entire film surface as long as the external force remains active. After the external force is withdrawn, there is partial relaxation of the applied stresses, which is manifested as reduction in amplitude of the imprinted features. Due to the spatial viscoelasticity gradient, the extent of stress relaxation induced feature height reduction varies across the length of the film (L), resulting in a surface with a gradient topography with progressively varying feature heights (hF). The steepness of the gradient can be controlled by varying the temperature gradient as well as the duration of precuring of the film prior to imprinting. The method has also been utilized for fabricating wettability gradient surfaces using a high aspect ratio biomimetic stamp. The use of a flexible stamp allows the technique to be extended for creating a gradient topography on nonplanar surfaces as well. We also show that the gradient surfaces with regular structures can be used in combinatorial studies related to pattern directed dewetting.

  2. Marginal and Internal Fit of Cobalt-Chromium Fixed Dental Prostheses Generated from Digital and Conventional Impressions

    PubMed Central

    Skjerven, Henrik; Carlsson, Pablo; Karlsson, Stig; Örtorp, Anders

    2014-01-01

    Objectives. Digital impressions are increasingly used and have the potential to avoid the problem of inaccurate impressions. Only a few studies to verify the accuracy of digital impressions have been performed. The purpose of this study was to compare the marginal and internal fit of 3-unit tooth supported fixed dental prostheses (FDPs) fabricated from digital and conventional impressions. Methods. Ten FDPs were produced from digital impressions using the iTero system and 10 FDPs were produced using vinyl polysiloxane (VPS) impression material. A triple-scan protocol and CAD software were used for measuring and calculating discrepancies of the FDPs at 3 standard areas: mean internal discrepancy, absolute marginal gap, and cervical area discrepancy. The Mann-Whitney U test was used for analyzing the results. Results. For conventional and digital impressions, respectively, FDPs had an absolute marginal gap of 147 μm and 142 μm, cervical area discrepancy of 69 μm and 44 μm, and mean internal discrepancy of 117 μm and 93 μm. The differences were statistically significant in the cervical and internal areas (P < 0.001). Significance. The results indicated that the digital impression technique is more exact and can generate 3-unit FDPs with a significantly closer fit compared to the VPS technique. PMID:24723954

  3. Odor Impression Prediction from Mass Spectra.

    PubMed

    Nozaki, Yuji; Nakamoto, Takamichi

    2016-01-01

    The sense of smell arises from the perception of odors from chemicals. However, the relationship between the impression of odor and the numerous physicochemical parameters has yet to be understood owing to its complexity. As such, there is no established general method for predicting the impression of odor of a chemical only from its physicochemical properties. In this study, we designed a novel predictive model based on an artificial neural network with a deep structure for predicting odor impression utilizing the mass spectra of chemicals, and we conducted a series of computational analyses to evaluate its performance. Feature vectors extracted from the original high-dimensional space using two autoencoders equipped with both input and output layers in the model are used to build a mapping function from the feature space of mass spectra to the feature space of sensory data. The results of predictions obtained by the proposed new method have notable accuracy (R≅0.76) in comparison with a conventional method (R≅0.61). PMID:27326765

  4. Odor Impression Prediction from Mass Spectra

    PubMed Central

    Nakamoto, Takamichi

    2016-01-01

    The sense of smell arises from the perception of odors from chemicals. However, the relationship between the impression of odor and the numerous physicochemical parameters has yet to be understood owing to its complexity. As such, there is no established general method for predicting the impression of odor of a chemical only from its physicochemical properties. In this study, we designed a novel predictive model based on an artificial neural network with a deep structure for predicting odor impression utilizing the mass spectra of chemicals, and we conducted a series of computational analyses to evaluate its performance. Feature vectors extracted from the original high-dimensional space using two autoencoders equipped with both input and output layers in the model are used to build a mapping function from the feature space of mass spectra to the feature space of sensory data. The results of predictions obtained by the proposed new method have notable accuracy (R≅0.76) in comparison with a conventional method (R≅0.61). PMID:27326765

  5. Comparison of dimensional accuracy of digital dental models produced from scanned impressions and scanned stone casts

    NASA Astrophysics Data System (ADS)

    Subeihi, Haitham

    Introduction: Digital models of dental arches play a more and more important role in dentistry. A digital dental model can be generated by directly scanning intraoral structures, by scanning a conventional impression of oral structures or by scanning a stone cast poured from the conventional impression. An accurate digital scan model is a fundamental part for the fabrication of dental restorations. Aims: 1. To compare the dimensional accuracy of digital dental models produced by scanning of impressions versus scanning of stone casts. 2. To compare the dimensional accuracy of digital dental models produced by scanning of impressions made of three different materials (polyvinyl siloxane, polyether or vinyl polyether silicone). Methods and Materials: This laboratory study included taking addition silicone, polyether and vinyl polyether silicone impressions from an epoxy reference model that was created from an original typodont. Teeth number 28 and 30 on the typodont with a missing tooth number 29 were prepared for a metal-ceramic three-unit fixed dental prosthesis with tooth #29 being a pontic. After tooth preparation, an epoxy resin reference model was fabricated by duplicating the typodont quadrant that included the tooth preparations. From this reference model 12 polyvinyl siloxane impressions, 12 polyether impressions and 12 vinyl polyether silicone impressions were made. All 36 impressions were scanned before pouring them with dental stone. The 36 dental stone casts were, in turn, scanned to produce digital models. A reference digital model was made by scanning the reference model. Six groups of digital models were produced. Three groups were made by scanning of the impressions obtained with the three different materials, the other three groups involved the scanning of the dental casts that resulted from pouring the impressions made with the three different materials. Groups of digital models were compared using Root Mean

  6. Elastomeric Properties of Poly(glycerol sebacate) (PGS) Based Nanoparticle Composites

    NASA Astrophysics Data System (ADS)

    Chung, Hyun-Joong; Li, Xinda; Hong, Albert T.-L.

    2014-03-01

    Owing to the unique combination of biocompatible, biodegradable, and elastomeric properties, poly(glycerol sebacate) and their derivatives are an emerging class of biomaterials for soft tissue replacement, drug delivery, tissue adhesive, and hard tissue regeneration. The mechanical properties of the polyester have been tailored to match a wide range of target organs, ranging from cardiac muscle to bones, by manipulating the process parameters to modulate cross-linking density. In the present study, we applied nanoparticles and cross-linking agents to further optimize their elastomeric properties. Especially, the study aims to enhance the practically important, but less studied, property of tear resistance. Microscopic origin of the property enhancement is discussed.

  7. Antibacterial efficacy and effect of Morinda citrifolia L. mixed with irreversible hydrocolloid for dental impressions: A randomized controlled trial

    PubMed Central

    Ahmed, A. Shafath; Charles, P. David; Cholan, R.; Russia, M.; Surya, R.; Jailance, L.

    2015-01-01

    Aim: This study aimed to evaluate whether the extract of Morinda citrifolia L. mixed with irreversible hydrocolloid powder decreases microbial contamination during impression making without affecting the resulting casts. Materials and Methods: Twenty volunteers were randomly divided into two groups (n = 10). Group A 30 ml extract of M. citrifolia L diluted in 30 ml of water was mixed to make the impression with irreversible hydrocolloid material. Group B 30 ml deionized water was mixed with irreversible hydrocolloid material to make the impressions following which the surface roughness and dimensional stability of casts were evaluated. Results: Extract of M. citrifolia L. mixed with irreversible hydrocolloid decreased the percentage of microorganisms when compared with water (P < 0.001) but did not affect the surface quality or dimensional stability of the casts. Conclusion: Mixing the extract of M. citrifolia L. with irreversible hydrocolloid powder is an alternative method to prevent contamination without sacrificing impression quality. PMID:26538926

  8. Valence-based age differences in medial prefrontal activity during impression formation.

    PubMed

    Cassidy, Brittany S; Leshikar, Eric D; Shih, Joanne Y; Aizenman, Avigael; Gutchess, Angela H

    2013-01-01

    Reports of age-related changes to medial prefrontal cortex (mPFC) activity during socio-cognitive tasks have shown both age-equivalence and under recruitment. Emotion work illustrates selective mPFC response dependent on valence, such that negative emotional images evoke increased ventral mPFC activity for younger adults, while older adults recruit vmPFC more for positive material. By testing whether this differential age-related response toward valenced material is also present for the social task of forming impressions, we may begin to understand inconsistencies regarding when age differences are present vs. absent in the literature. Using fMRI, participants intentionally formed impressions of positive and negative face-behavior pairs in anticipation of a memory task. Extending previous findings to a social task, valence-based reversals were present in dorsal and ventral mPFC, and posterior cingulate cortex. Younger adults elicited increased activity when forming negative impressions, while older adults had more recruitment when forming positive impressions. This suggests an age-related shift toward emphasizing positive social information may be reflected in the recruitment of regions supporting forming impressions. Overall, the results indicate an age-related shift in neural response to socio-cognitive stimuli that is valence dependent rather than a general age-related reduction in activity, in part informing prior inconsistencies within the literature. PMID:23998453

  9. Valence-based age differences in medial prefrontal activity during impression formation.

    PubMed

    Cassidy, Brittany S; Leshikar, Eric D; Shih, Joanne Y; Aizenman, Avigael; Gutchess, Angela H

    2013-01-01

    Reports of age-related changes to medial prefrontal cortex (mPFC) activity during socio-cognitive tasks have shown both age-equivalence and under recruitment. Emotion work illustrates selective mPFC response dependent on valence, such that negative emotional images evoke increased ventral mPFC activity for younger adults, while older adults recruit vmPFC more for positive material. By testing whether this differential age-related response toward valenced material is also present for the social task of forming impressions, we may begin to understand inconsistencies regarding when age differences are present vs. absent in the literature. Using fMRI, participants intentionally formed impressions of positive and negative face-behavior pairs in anticipation of a memory task. Extending previous findings to a social task, valence-based reversals were present in dorsal and ventral mPFC, and posterior cingulate cortex. Younger adults elicited increased activity when forming negative impressions, while older adults had more recruitment when forming positive impressions. This suggests an age-related shift toward emphasizing positive social information may be reflected in the recruitment of regions supporting forming impressions. Overall, the results indicate an age-related shift in neural response to socio-cognitive stimuli that is valence dependent rather than a general age-related reduction in activity, in part informing prior inconsistencies within the literature.

  10. Effect of blackness level on visual impression of color images

    NASA Astrophysics Data System (ADS)

    Eda, Tetsuya; Koike, Yoshiki; Matsushima, Sakurako; Ayama, Miyoshi

    2008-02-01

    In this study, two experiments were conducted to clarify the relation between RGB values and perceived blackness. In the first experiment, the average RGB values of black surface areas in the test stimuli where observers begin to perceive the areas 'black', and further another average RGB values where observers perceive the areas 'really black' were determined. Results indicate that to realize a 'really black' surface, RGB values should be lower than those of the original image in some pictures. In the second experiment, how and to what degree the RGB values of black area affect the visual impression of artistic picture was investigated. Three dimensions, "high-quality axis", "mysterious axis", and "feeling of material axis", were extracted by factor analysis. Results indicate that the Art students seem to be more sensitive in the evaluations along the "high-quality axis" and "mysterious axis" than the Engineering students, while the opposite tendency is shown in the evaluation along the "feeling of material axis".

  11. The Bidimensional Impression Management Index (BIMI): measuring agentic and communal forms of impression management.

    PubMed

    Blasberg, Sabrina A; Rogers, Katherine H; Paulhus, Delroy L

    2014-01-01

    Measures of impression management have yet to incorporate two-factor models of person perception. The 2 primary factors are often labeled agency and communion. In Study 1, we assembled a new measure of impression management—the Bidimensional Impression Management Index (BIMI): It comprises 2 subscales designed specifically to tap agentic and communal content. Both subscales showed adequate alpha reliabilities under both honest and faking conditions. In Study 2, the BIMI was cross-validated in a new sample: The subscales remained relatively independent, and their reliabilities remained solid. A coherent pattern of personality correlates also supported the validities of both subscales. In Study 3, the differential sensitivity of the 2 subscales was demonstrated by manipulating the job type in simulated job applications. Implications and applications of the BIMI are discussed. PMID:24328818

  12. Three-dimensional accuracy of different impression techniques for dental implants

    PubMed Central

    Nakhaei, Mohammadreza; Madani, Azam S; Moraditalab, Azizollah; Haghi, Hamidreza Rajati

    2015-01-01

    Background: Accurate impression making is an essential prerequisite for achieving a passive fit between the implant and the superstructure. The aim of this in vitro study was to compare the three-dimensional accuracy of open-tray and three closed-tray impression techniques. Materials and Methods: Three acrylic resin mandibular master models with four parallel implants were used: Biohorizons (BIO), Straumann tissue-level (STL), and Straumann bone-level (SBL). Forty-two putty/wash polyvinyl siloxane impressions of the models were made using open-tray and closed-tray techniques. Closed-tray impressions were made using snap-on (STL model), transfer coping (TC) (BIO model) and TC plus plastic cap (TC-Cap) (SBL model). The impressions were poured with type IV stone, and the positional accuracy of the implant analog heads in each dimension (x, y and z axes), and the linear displacement (ΔR) were evaluated using a coordinate measuring machine. Data were analyzed using ANOVA and post-hoc Tukey tests (α = 0.05). Results: The ΔR values of the snap-on technique were significantly lower than those of TC and TC-Cap techniques (P < 0.001). No significant differences were found between closed and open impression techniques for STL in Δx, Δy, Δz and ΔR values (P = 0.444, P = 0.181, P = 0.835 and P = 0.911, respectively). Conclusion: Considering the limitations of this study, the snap-on implant-level impression technique resulted in more three-dimensional accuracy than TC and TC-Cap, but it was similar to the open-tray technique. PMID:26604956

  13. Effect of contaminants on the adhesion of light-bodied silicones to putty silicones in putty-wash impression technique.

    PubMed

    Tjan, A H

    1988-05-01

    This study was concerned with the adhesion of a light-bodied silicone to a putty silicone in a putty-wash impression technique when the preliminary putty impression was contaminated with human saliva or residues from acrylic resins used in the fabrication of provisional restorations by direct technique. Data indicated that condensation and addition silicones differed in their susceptibility toward the tested contaminants. Salivary contamination and chemical residues from the autopolymerizing acrylic resins weakened the bond strength and caused adhesive failure dependent upon the type of silicone impression material used.

  14. Phoenix Makes an Impression on Mars

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This view from the Surface Stereo Imager on NASA's Phoenix Mars Lander shows the first impression dubbed Yeti and looking like a wide footprint -- made on the Martian soil by the Robotic Arm scoop on Sol 6, the sixth Martian day of the mission, (May 31, 2008).

    Touching the ground is the first step toward scooping up soil and ice and delivering the samples to the lander's experiments.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  15. Observations and impressions from lunar orbit

    NASA Technical Reports Server (NTRS)

    Mattingly, T. K.; El-Baz, F.; Laidley, R. A.

    1972-01-01

    On Apollo 16, the command module pilot made observations of particular surface features and processes to complement photographic and other remotely sensed data. Emphasis was placed on geological problems that required the extreme dynamic range and color sensitivities of the human eye; repetitive observations of varying sun angles and viewing directions; and, in some cases, on-the-scene interpretations. Visual observations and impressions recorded during the mission verified the effectiveness of the hardware and techniques used. The orbiting observer functioned both as a sensor, in otherwise inaccessible areas such as earthshine and shadows, and as a designator of potentially significant data that were acquired on the photographic record.

  16. Elastomeric and mechanically stiff nanocomposites from poly(glycerol sebacate) and bioactive nanosilicates.

    PubMed

    Kerativitayanan, Punyavee; Gaharwar, Akhilesh K

    2015-10-01

    Poly(glycerol sebacate) (PGS) has been proposed for tissue engineering applications owing to its tough elastomeric mechanical properties, biocompatibility and controllable degradation. However, PGS shows limited bioactivity and thus constraining its utilization for musculoskeletal tissue engineering. To address this issue, we developed bioactive, highly elastomeric, and mechanically stiff nanocomposites by covalently reinforcing PGS network with two-dimensional (2D) nanosilicates. Nanosilicates are ultrathin nanomaterials and can induce osteogenic differentiation of human stem cells in the absence of any osteogenic factors such as dexamethasone or bone morphogenetic proteins-2 (BMP2). The addition of nanosilicate to PGS matrix significantly enhances the mechanical stiffness without affecting the elastomeric properties. Moreover, nanocomposites with higher amount of nanosilicates have higher in vitro stability as determined by degradation kinetics. The increase in mechanical stiffness and in vitro stability is mainly attributed to enhanced interactions between nanosilicates and PGS. We evaluated the in vitro bioactivity of nanocomposite using preosteoblast cells. The addition of nanosilicates significantly enhances the cell adhesion, support cell proliferation, upregulate alkaline phosphates and mineralized matrix production. Overall, the combination of high mechanically stiffness and elastomericity, tailorable degradation profile, and the ability to promote osteogenic differentiation of PGS-nanosilicate can be used for regeneration of bone. PMID:26297886

  17. [Impression Formation in the Diagnosis and Treatment of Mental Disorders].

    PubMed

    Linden, Michael; Dymke, Tina; Hüttner, Susanne; Schnaubelt, Sabine

    2016-06-01

    The first item of any psychopathological assessment is "general impression". There is some research under the heading of "impression formation" which shows that the outer appearance of a person decides about how a person is perceived by others and how others react. Impression formation is an important factor in social interaction. This is of special importance in mental disorders, which may express themselves in a distorted impression formation. As impression formation is by and large an emotional process, measurement can be done by adjective lists. An example is the bipolar MED rating scale. Such lists can be used in therapy to help patients and therapists to understand the problem and initiate modifications. A special group intervention in occupational therapy is described. Results suggest that impression formation is quite objective, that self- and observer judgments coincide and that therapy can help to adopt a less irritating outer appearance. PMID:27286526

  18. Impression Management in Survey Responding: Easier for Collectivists or Individualists?

    PubMed Central

    Riemer, Hila; Shavitt, Sharon

    2012-01-01

    Three experiments indicate that when individualists and collectivists engage in impression management on self-reports, they do so through different psychological mechanism s. Collectivists do so through a relatively automatic process. Thus, they can impression manage even when cognitively busy. Individualists impression manage through a more effortful process. Therefore, they can do so only when the situation permits effortful processing. These findings highlight distinct conditions under which social norms may influence consumer self-reports across cultures. PMID:23175618

  19. [Impression traces from firearms on cadaver skin].

    PubMed

    Püschel, K; Koops, E; Kulle, K J

    1996-01-01

    Guns may occasionally leave traces on human skin, for example by compression/impression of the tissue (esp. in the area of livores), by contact-transfer of dirt, oil, and rust, or by forming the pattern of blood-smears. The case of a 31-year-old drug-addict is presented in detail: The man committed suicide by shooting himself (entrance hole under the chin). When the dead body was found there was no weapon at the scene. By careful securing of evidence and analyzing the pattern of metallisations (identified as rust from the old pistol) it was reconstructed that the suicident held the pistol (identified as Russian Tokarew TT33-7.62 mm) in his hand for many hours postmortem until it was removed by an unknown thief. PMID:8687278

  20. [Impression traces from firearms on cadaver skin].

    PubMed

    Püschel, K; Koops, E; Kulle, K J

    1996-01-01

    Guns may occasionally leave traces on human skin, for example by compression/impression of the tissue (esp. in the area of livores), by contact-transfer of dirt, oil, and rust, or by forming the pattern of blood-smears. The case of a 31-year-old drug-addict is presented in detail: The man committed suicide by shooting himself (entrance hole under the chin). When the dead body was found there was no weapon at the scene. By careful securing of evidence and analyzing the pattern of metallisations (identified as rust from the old pistol) it was reconstructed that the suicident held the pistol (identified as Russian Tokarew TT33-7.62 mm) in his hand for many hours postmortem until it was removed by an unknown thief.

  1. Chronic maxillary sinusitis associated with dental impression material.

    PubMed

    Rodrigues, Moacyr-Tadeu V; Munhoz, Etiene-de Andrade; Cardoso, Camila-Lopes; de Freitas, César-Antunes; Damante, José-Humberto

    2009-04-01

    A 62-year-old man was referred for routine treatment of hyperplasia of the mucosa in the anterior lower jaw. An oroantral fistula was detected in the right superior alveolar ridge. The patient had no complaints. Plain radiographs showed a radiopaque foreign body in the posterior region associated with opacification of the maxillary sinus. Computed tomography showed the same hyperdense foreign body located in the posterior lower part of the sinus and an abnormal soft tissue mass in the entire right maxillary sinus. When asked about sinusitis, the patient mentioned occasional episodes of pus taste and intermittent crises of headache lasting for one week. The patient has been edentulous for 20 years. Sinus debridement was performed and the oroantral fistula was closed. The clinical suspicion of the presence of zinc oxide-eugenol paste was confirmed by microscopical and chemical analysis. After 6 months of follow-up, the fistula continued to be closed and sinusitis did not recur. This clinical case of maxillary chronic sinusitis illustrates a different odontogenic origin.

  2. A sectional-splinting technique for impressing multiple implant units by eliminating the use of an open tray

    PubMed Central

    Deogade, Suryakant C.; Dube, Gunjan

    2014-01-01

    Since the inception of root form implant dentistry by P-I Branemark in the early 1980's, so many technical advances have been put forward by several authors. However, the open tray impression technique is still performed for impressing multiple implant fixtures as it was first described in the original Branemark procedure manual. The most critical aspect for a successful implant-supported restoration is the passive and an accurate fit of superstructures to avoid preload and loading stresses. Splinting impression technique in multiple implants has gained popularity. Auto-polymerizing acrylic resin is among the most routinely practiced splinting material for multiple implant units. However, unfortunately, it exhibits shrinkage, which makes an impression quite inaccurate. This case report presents the solution to minimize the shrinkage of resin by utilizing sectional-splinting technique as advocated in the previous implant literature. PMID:24963251

  3. Removal of latex glove contaminants prior to taking poly (vinylsiloxane) impressions.

    PubMed

    Browning, G C; Bromme, J C; Murchison, D F

    1994-11-01

    Sulfur compounds found in latex gloves may be deposited on teeth and gingiva, inhibiting the setting of poly(vinylsiloxane) impression materials. The objective of this in vivo study was to screen a variety of methods to remove these contaminants. Ten patients were each tested with eight decontamination methods. Before each trial, the facial surfaces and adjacent gingiva of the maxillary central and lateral incisors were contaminated with 20 wipes of a latex glove. Decontamination methods included a 30-second rinse with mouthwash, 3% hydrogen peroxide, or air-water syringe; a 30-second toothbrush scrub with water, mouthwash, or hydrogen peroxide; a 30-second cotton pellet-Cavidry scrub; and a 30-second cleaning with a prophy cup and pumice. A 10-second water rinse followed each method except the air-water syringe and Cavidry groups. A low-viscosity poly(vinylsiloxane) impression material was then used to take an impression of the area. To test surface inhibition, the gingival, tooth, and palatal impression surfaces were wiped with cotton-tipped applicators, and the degree of inhibition was subjectively categorized by two independent investigators. Mechanical decontamination with a toothbrush or pumice was significantly more effective than was rinsing alone, regardless of the solution used.

  4. Effects of Music on Image Impression and Relationship between Impression and Physical Properties

    NASA Astrophysics Data System (ADS)

    Sato, Keiko; Mitsukura, Yasue

    Auditory information plays an integral role in AV media because even identical images are perceived differently when they are matched with different music. However, we now present a few studies in which the changes in subjective perceptions were analyzed on the basis of the physical properties of the perceived items. The purpose of this study is to investigate the effects of music on image impression in terms of the physical properties of images. In this paper, we first elucidate the changes in subjective impressions when the image is presented by itself and when it is presented with music. Secondly, to clarify the relation between the impression of an image or music and physical properties, we compare the different image or music perceptions with each other and also compare their respective physical properties, which include color information, structural information, and frequency characteristics. As a result, the color information of an image containing green or saturation colors and the power of the music were strongly correlated with adjectives expressing activity. Moreover, the entropy of saturation correlated with words expressing spatial extent.

  5. Downplaying Positive Impressions: Compensation Between Warmth and Competence in Impression Management

    PubMed Central

    Holoien, Deborah Son; Fiske, Susan T.

    2014-01-01

    The compensation effect demonstrates a negative relationship between the dimensions of warmth and competence in impression formation in comparative contexts. However, does compensation between warmth and competence extend to impression management? Two studies examined whether people actively downplay their warmth in order to appear competent and downplay their competence in order to appear warm. In Studies 1a and 1b, participants selected words pretested to be high or low in warmth and competence to include in an e-mail message to people they wanted to impress. As predicted, participants downplayed their competence when they wanted to appear warm (Study 1a) and downplayed their warmth when they wanted to appear competent (Study 1b). In Studies 2a and 2b, compensation also occurred when participants introduced themselves to another person, as evidenced by the questions they selected to answer about themselves, their self-reported goals, and their open-ended introductions. Compensation occurred uniquely between warmth and competence and not for other dimensions, such as healthiness (Study 2a) and political interest (Study 2b), which suggests that the compensation effect extends beyond a mere zero-sum exchange between dimensions. PMID:24550571

  6. Downplaying Positive Impressions: Compensation Between Warmth and Competence in Impression Management.

    PubMed

    Holoien, Deborah Son; Fiske, Susan T

    2013-01-01

    The compensation effect demonstrates a negative relationship between the dimensions of warmth and competence in impression formation in comparative contexts. However, does compensation between warmth and competence extend to impression management? Two studies examined whether people actively downplay their warmth in order to appear competent and downplay their competence in order to appear warm. In Studies 1a and 1b, participants selected words pretested to be high or low in warmth and competence to include in an e-mail message to people they wanted to impress. As predicted, participants downplayed their competence when they wanted to appear warm (Study 1a) and downplayed their warmth when they wanted to appear competent (Study 1b). In Studies 2a and 2b, compensation also occurred when participants introduced themselves to another person, as evidenced by the questions they selected to answer about themselves, their self-reported goals, and their open-ended introductions. Compensation occurred uniquely between warmth and competence and not for other dimensions, such as healthiness (Study 2a) and political interest (Study 2b), which suggests that the compensation effect extends beyond a mere zero-sum exchange between dimensions. PMID:24550571

  7. A simple scanning spectrometer based on a stretchable elastomeric reflective grating

    SciTech Connect

    Ghisleri, C.; Milani, P.; Potenza, M. A. C.; Bellacicca, A.; Ravagnan, L.

    2014-02-10

    We report a scanning optical spectrometer based on the use of a stretchable elastomeric reflective grating. The grating is obtained by supersonic cluster beam implantation of silver nanoparticles on polydimethylsiloxane previously grooved by molding to create a replica of a commercial digital versatile disk grating. The use of a stretchable grating allows the spectrometer spanning the whole optical wavelength range by solely extending the diffraction element by more than 100% of its original dimensions. The stretchable reflective optical grating shows excellent performances and stability upon thousands of stretching cycles. The use of this elastomeric element makes the optical layout and the mechanics of the spectrometer extremely simple and advantageous for those applications where spectral resolution is not a major requirement. As a proof of principle, we present the absorption spectrum of Rhodamine B in solution obtained by our spectrometer and compared to commercial instruments.

  8. Increasing pumping efficiency in a micro throttle pump by enhancing displacement amplification in an elastomeric substrate

    NASA Astrophysics Data System (ADS)

    Fujiwara, T.; Johnston, I. D.; Tracey, M. C.; Tan, C. K. L.

    2010-06-01

    Fluid transport is accomplished in a micro throttle pump (MTP) by alternating deformation of a micro channel cast into a polydimethylsiloxane (PDMS) elastomeric substrate. The active deformation is achieved using a bimorph PZT piezoelectric disc actuator bonded to a glass diaphragm. The bimorph PZT deflects the diaphragm as well as alternately pushing and pulling the elastomer layer providing displacement amplification in the PDMS directly surrounding the micro channel. In order to improve pumping rates we have embedded a polymethylmethacrylate (PMMA) ring into the PMDS substrate which increases the magnitude of the displacement amplification achieved. FEM simulation of the elastomeric substrate deformation predicts that the inclusion of the PMMA ring should increase the channel deformation. We experimentally demonstrate that inclusion of a PMMA ring, having a diameter equal to that of the circular node of the PZT/glass/PDMS composite, increases in the throttle resistance ratio by 40% and the maximum pumping rate by 90% compared to an MTP with no ring.

  9. Pattern transfer printing by kinetic control of adhesion to an elastomeric stamp

    DOEpatents

    Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang, Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao

    2011-05-17

    The present invention provides methods, systems and system components for transferring, assembling and integrating features and arrays of features having selected nanosized and/or microsized physical dimensions, shapes and spatial orientations. Methods of the present invention utilize principles of `soft adhesion` to guide the transfer, assembly and/or integration of features, such as printable semiconductor elements or other components of electronic devices. Methods of the present invention are useful for transferring features from a donor substrate to the transfer surface of an elastomeric transfer device and, optionally, from the transfer surface of an elastomeric transfer device to the receiving surface of a receiving substrate. The present methods and systems provide highly efficient, registered transfer of features and arrays of features, such as printable semiconductor element, in a concerted manner that maintains the relative spatial orientations of transferred features.

  10. A pillar-based microfilter for isolation of white blood cells on elastomeric substrate.

    PubMed

    Alvankarian, Jafar; Bahadorimehr, Alireza; Yeop Majlis, Burhanuddin

    2013-01-01

    Our goal is to design, fabricate, and characterize a pillar-based microfluidic device for size-based separation of human blood cells on an elastomeric substrate with application in the low-cost rapid prototyping of lab-chip devices. The single inlet single outlet device is using parallel U-shape arrays of pillars with cutoff size of 5.5 μm for trapping white blood cells (WBCs) in a pillar chamber with internal dead-volume of less than 1.0 μl. The microstructures are designed to limit the elastomeric deformation against fluid pressures. Numerical analysis showed that at maximum pressure loss of 15 kPa which is lower than the device conformal bonding strength, the pillar elastomeric deformation is less than 5% for flow rates of up to 1.0 ml min(-1). Molding technique was employed for device prototyping using polyurethane methacrylate (PUMA) resin and polydimethylsiloxane (PDMS) mold. Characterization of the dual-layer device with beads and blood samples is performed. Tests with blood injection showed that ∼18%-25% of WBCs are trapped and ∼84%-89% of red blood cells (RBCs) are passed at flow rates of 15-50 μl min(-1) with a slight decrease of WBCs trap and improve of the RBCs pass at higher flow rates. Similar results were obtained by separation of mixed microspheres of different size injected at flow rates of up to 400 μl min(-1). Tests with blood samples stained by fluorescent gel demonstrated that the WBCs are accumulated in the arrays of pillars that later end up to blockage of the device. Filtration results of using elastomeric substrate present a good consistency with the trend of separation efficiencies of the similar silicon-based filters. PMID:24403994

  11. Process for the preparation of fluorine containing crosslinked elastomeric polytriazine and product so produced

    NASA Technical Reports Server (NTRS)

    Rosser, R. W.; Korus, R. A. (Inventor)

    1980-01-01

    Crosslinking elastomeric polytriazines are prepared by a 4 step procedure which consists of (1) forming a poly(imidoylamidine) by the reaction, under reflux conditions, of anhydrous ammonia with certain perfluorinated alkyl or alkylether dinitriles; (2) forming a linear polytriazine by cyclizing the imidoylamidine linkages by reaction with certain perfluorinated alkyl or alkylether acid anhydrides or halides; (3) extending the linear polytriazine chain by further refluxing in anhydrous ammonia; and (4) heating to cyclize the new imidoylamidine and thereby crosslink the polymer.

  12. Prefabricated custom impression trays for the altered cast technique.

    PubMed

    Lund, P S; Aquilino, S A

    1991-12-01

    Removable partial prosthodontic treatment requires multiple patient appointments with intermediate laboratory steps. A technique is described that allows the removable partial denture framework try-in and the impression for the altered cast to be efficiently completed in a single appointment. The method uses prefabricated custom impression trays that are readily attached to the framework after the try-in.

  13. Impression Creep Behavior of 316LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Mathew, M. D.; Naveena; Vijayanand, D.

    2013-02-01

    Impression creep tests have been carried out at 923 K on 316LN SS containing 0.07, 0.14, and 0.22 wt.% nitrogen, under different applied stress levels. It was observed that the impression creep depth versus time curves were similar to the creep curves obtained from conventional uniaxial creep tests. The impression creep curves were characterized by a loading strain and primary and secondary creep stages similar to uniaxial creep curves. The tertiary stage observed in uniaxial creep curves was absent. The steady-state impression velocity was found to increase with increasing applied stress. The equivalent steady-state creep rates calculated from impression velocities were found to be in good agreement with the steady-state creep rates obtained from conventional uniaxial creep tests. Equivalence between applied stress and steady-state impression velocity with uniaxial creep stress and steady-state creep rate, respectively, has been established based on the laws of mechanics for time-dependent plasticity. It was found that impression velocity was sensitive to the variation in nitrogen content in the steel; impression velocity decreased with increasing nitrogen content, and the results obtained in this study were in agreement with those obtained from uniaxial creep tests.

  14. A Study of Peer Tutors Using the Neurological Impress Method.

    ERIC Educational Resources Information Center

    McAllister, Elizabeth A.

    A study investigated the efficacy of using the neurological impress method in peer tutoring during reading instruction. The neurological impress reading method is a unison reading procedure in which the student and teacher or tutor read aloud simultaneously and quickly, with the student placed slightly in front of the teacher so that the teacher's…

  15. Impression Management and the Control of Social Anxieties.

    ERIC Educational Resources Information Center

    Miller, Rowland S.

    Impression management refers to the concept that people engaged in interaction will attempt to control the image of themselves that others form. This provides a foundation for social interaction, giving others information about who we are and what to expect from us. A central concern of impression management is the manner in which we are evaluated…

  16. Read Two Impress: An Intervention for Disfluent Readers

    ERIC Educational Resources Information Center

    Young, Chase; Rasinski, Timothy; Mohr, Kathleen A. J.

    2016-01-01

    The authors describe a research-based method to increase students' reading fluency. The method is called Read Two Impress, which is derived from the Neurological Impress Method and the method of repeated readings. The authors provide step-by-step procedures to effectively implement the reading fluency intervention. Previous research indicates that…

  17. Impressions of College Intructors: Stability and Change in Student Ratings

    ERIC Educational Resources Information Center

    Dudley, Kari L.

    2013-01-01

    Although the topic of stability and change in classroom impressions research is not new, there remain unanswered questions about what impressions are stable, when they are likely to change, and for whom they are likely to change over the course of a semester. My research will begin to answer those questions. My research took place in four college…

  18. Impression Management: The Web Presence of College Presidents

    ERIC Educational Resources Information Center

    Morgan, Joanne Cardin

    2013-01-01

    Leadership profile pages on organizational websites have become staged opportunities for impression management. This research uses content analysis to examine the strategies of assertive impression management used to construct the leadership Web presence of the 70 presidents of national public universities, as identified in the "US News and…

  19. Impression Cytology of the Lid Wiper Area.

    PubMed

    Muntz, Alex; van Doorn, Kevin; Subbaraman, Lakshman N; Jones, Lyndon W

    2016-01-01

    Few reports on the cellular anatomy of the lid wiper (LW) area of the inner eyelid exist and only one report makes use of cytological methods. The optimization of a method of collecting, staining and imaging cells from the LW region using impression cytology (IC) is described in this study. Cells are collected from the inner surface of the upper eyelid of human subjects using hydrophilic polytetrafluoroethylene (PTFE) membranes, and stained with cytological dyes to reveal the presence of goblet cells, mucins, cell nuclei and various degrees of pre- and para-keratinization. Immunocytochemical dyes show cell esterase activity and compromised cell membranes by the use of a confocal scanning laser microscope. Up to 100 microscopic digital images are captured for each sample and stitched into a high-resolution, large scale image of the entire IC span. We demonstrate a higher sensitivity of IC than reported before, appropriate for identifying cellular morphologies and metabolic activity in the LW area. To our knowledge, this is the first time this selection of fluorescent dyes was used to image LW IC membranes. This protocol will be effective in future studies to reveal undocumented details of the LW area, such as assessing cellular particularities of contact lens wearers or patients with dry eye or lid wiper epitheliopathy. PMID:27584693

  20. Neural correlates of self-deception and impression-management.

    PubMed

    Farrow, Tom F D; Burgess, Jenny; Wilkinson, Iain D; Hunter, Michael D

    2015-01-01

    Self-deception and impression-management comprise two types of deceptive, but generally socially acceptable behaviours, which are common in everyday life as well as being present in a number of psychiatric disorders. We sought to establish and dissociate the 'normal' brain substrates of self-deception and impression-management. Twenty healthy participants underwent fMRI scanning at 3T whilst completing the 'Balanced Inventory of Desirable Responding' test under two conditions: 'fake good', giving the most desirable impression possible and 'fake bad' giving an undesirable impression. Impression-management scores were more malleable to manipulation via 'faking' than self-deception scores. Response times to self-deception questions and 'fake bad' instructions were significantly longer than to impression-management questions and 'fake good' instructions respectively. Self-deception and impression-management manipulation and 'faking bad' were associated with activation of medial prefrontal cortex (mPFC) and left ventrolateral prefrontal cortex (vlPFC). Impression-management manipulation was additionally associated with activation of left dorsolateral prefrontal cortex and left posterior middle temporal gyrus. 'Faking bad' was additionally associated with activation of right vlPFC, left temporo-parietal junction and right cerebellum. There were no supra-threshold activations associated with 'faking good'. Our neuroimaging data suggest that manipulating self-deception and impression-management and more specifically 'faking bad' engages a common network comprising mPFC and left vlPFC. Shorter response times and lack of dissociable neural activations suggests that 'faking good', particularly when it comes to impression-management, may be our most practiced 'default' mode. PMID:25527112

  1. Comparison of frictional resistance between self-ligating and conventional brackets tied with elastomeric and metal ligature in orthodontic archwires

    PubMed Central

    Leite, Vanessa Vieira; Lopes, Murilo Baena; Gonini Júnior, Alcides; de Almeida, Marcio Rodrigues; Moura, Sandra Kiss; de Almeida, Renato Rodrigues

    2014-01-01

    Objective To compare the frictional resistance between self-ligating and conventional brackets tied to different types of wire. Material and Methods Abzil Kirium Capelozza (Pattern I) and Easy Clip (Roth prescription) incisor brackets were used. An elastomeric ligature or a ligating wire 0.10-in was used to ligate the wire to the Abzil bracket. Three types of orthodontic archwire alloys were assessed: 0.016-in NiTi wire, 0.016 x 0.021-in NiTi wire and 0.019 x 0.025-in steel wire. Ten observations were carried out for each bracket-archwire angulation combination. Brackets were mounted in a special appliance, positioned at 90 degrees in relation to the wire and tested in two angulations. Frictional test was performed in a Universal Testing Machine at 5 mm/min and 10 mm of displacement. The means (MPa) were submitted to ANOVA and Tukey's test set at 5% of significance. The surfaces of wires and brackets were observed at SEM. Results Steel-tied brackets (16.48 ± 8.31) showed higher means of frictional resistance than elastomeric-tied brackets (4.29 ± 2.16 ) and self-ligating brackets (1.66 ± 1.57) (P < 0.05), which also differed from each other (P < 0.05). As for the type of wire, 0.019 x 0.025-in steel wire (5.67 ± 3.97) showed lower means (P < 0.05) than 0.16-in NiTi wire (8.26 ± 10.92) and 0.016 x 0.021-in NiTi wire (8.51 ± 7.95), which did not differ from each other (P > 0.05). No statistical differences (P > 0.05) were found between zero (7.76 ± 8.46) and five-degree (7.19 ± 7.93) angulations. Conclusions Friction was influenced not only by the type of bracket, but also by the ligating systems. Different morphological aspects were observed for the brackets and wires studied PMID:25162575

  2. Repeatability and reproducibility of individual abutment impression, assessed with a blue light scanner

    PubMed Central

    Kim, Dong-Yeon; Lee, Jae-Jun; Kim, Ji-Hwan

    2016-01-01

    PURPOSE We assessed the repeatability and reproducibility of abutment teeth dental impressions, digitized with a blue light scanner, by comparing the discrepancies in repeatability and reproducibility values for different types of abutment teeth. MATERIALS AND METHODS To evaluate repeatability, impressions of the canine, first premolar, and first molar, prepared for ceramic crowns, were repeatedly scanned to acquire 5 sets of 3-dimensional data via stereolithography (STL) files. Point clouds were compared and the error sizes were measured (n=10, per type). To evaluate reproducibility, the impressions were rotated by 10-20° on the table and scanned. These data were compared to the first STL data and the error sizes were measured (n=5, per type). One-way analysis of variance was used to assess the repeatability and reproducibility of the 3 types of teeth, and Tukey honest significant differences (HSD) multiple comparison test was used for post hoc comparisons (α=.05). RESULTS The differences with regard to repeatability were 4.5, 2.7, and 3.1 µm for the canine, premolar, and molar, indicating the poorest repeatability for the canine (P<.001). For reproducibility, the differences were 6.6, 5.8, and 11.0 µm indicating the poorest reproducibility for the molar (P=.007). CONCLUSION Our results indicated that impressions of individual abutment teeth, digitized with a blue light scanner, had good repeatability and reproducibility. PMID:27350856

  3. Numerical study of effect of elastomeric stress absorbers on stress reduction in bone-dental implant interface

    PubMed Central

    MEHDI, Ghalem; BELARBI, Abderrahmane; MANSOURI, Bensmaine; AZARI, Zitouni

    2015-01-01

    Objective This paper focused on optimal stress distribution in the mandibular bone surrounding a dental implant and is devoted to the development of a modified Osteoplant® implant type in order to minimize stress concentration in the bone-implant interface. Material and Methods This study investigated 0.4 mm thick layers of two elastomeric stress barriers incorporated into the dental implant using 3-D finite element analysis. Results Overall, this proposed implant provoked lower load transfer in bone-implant interface due to the effect of the elastomers as stress absorbers. The stress level in the bone was reduced between 28% and 42% for three load cases: 75 N, 60 N and 27 N in corono-apical, linguo-buccal and disto-mesial direction, respectively. Conclusion The proposed model provided an acceptable solution for load transfer reduction to the mandible. This investigation also permitted to choose how to incorporate two elastomers into the Osteoplant® implant system. PMID:25760271

  4. “Evaluation of the Effect of Ultraviolet Disinfection on Dimensional Stability of the Polyvinyl Silioxane Impressions.” an in-Vitro Study

    PubMed Central

    Godbole, Surekha R; Dahane, Trupti M; Nimonkar, Sharayu V

    2014-01-01

    Introduction: Infection control is an important concept in the present day practice of dentistry. The prosthodontists are at an added risk of transmission because of the infection spreading through the contaminated lab equipments while working in the lab. The purpose of this study is to evaluate the effect of UV light disinfection on dimensional stability of polyvinyl siloxane impressions. Materials and Methods : Impressions were made in perforated custom tray. After polymerization of impression, half the samples were disinfected in UV light and remaining samples were not subjected to disinfection and poured in die stone which served as control group. Linear dimensions were measured on the cast with travelling microscope of 0.001accuracy. Result : The result showed that UV light disinfectant showed no significant dimensional changes on impressions. Conclusion: Hence, it can be safely used to disinfect impressions in clinical prosthodontic procedures. PMID:25386528

  5. To improve the flame resistance of spandex elastic elastomeric fiber

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Strength characteristics of fibers were improved to pass the 70% oxygen/30% nitrogen specification. Spinning techniques and information about incorporating these fibers in fabric structures using wrapping materials of Beta Fiberglas, Nomex, and PBI were developed.

  6. Contamination level of alginate impressions arriving at a dental laboratory.

    PubMed

    Sofou, A; Larsen, T; Fiehn, N-E; Owall, B

    2002-09-01

    The contamination level of alginate impressions delivered to a large dental laboratory in Sweden was determined. One hundred and seven consecutive alginate impressions were included during 7 days. Samples were taken and transferred into sterile physiological saline and analysed microbiologically for colony-forming units (cfu) as well as nonhemolytic, alpha-hemolytic, and beta-hemolytic colonies. After sampling, the clinics were contacted and asked to fill in simple questionnaires about their routines of disinfecting impressions. The questionnaire study revealed that about half of the clinics had some kind of disinfection routine, while the others rinsed in running water only. Seventy-two percent of the impressions yielded growth of bacteria, with a median number of 1.3x10(2) cfu. Thirteen per cent of the samples yielded >10(3) cfu, with a maximum number of 3.4x10(4) cfu. The majority of isolates were non- and alpha-hemolytic bacteria. Growth was recorded in 61.3% of disinfected impressions, and the numbers of bacteria in disinfected and nondisinfected impressions were similar. These findings raise the question of whether impressions need to be disinfected or if proper handling and hygienic procedures are sufficient to block the possible route of infection. PMID:12271349

  7. Contamination level of alginate impressions arriving at a dental laboratory.

    PubMed

    Sofou, A; Larsen, T; Fiehn, N-E; Owall, B

    2002-09-01

    The contamination level of alginate impressions delivered to a large dental laboratory in Sweden was determined. One hundred and seven consecutive alginate impressions were included during 7 days. Samples were taken and transferred into sterile physiological saline and analysed microbiologically for colony-forming units (cfu) as well as nonhemolytic, alpha-hemolytic, and beta-hemolytic colonies. After sampling, the clinics were contacted and asked to fill in simple questionnaires about their routines of disinfecting impressions. The questionnaire study revealed that about half of the clinics had some kind of disinfection routine, while the others rinsed in running water only. Seventy-two percent of the impressions yielded growth of bacteria, with a median number of 1.3x10(2) cfu. Thirteen per cent of the samples yielded >10(3) cfu, with a maximum number of 3.4x10(4) cfu. The majority of isolates were non- and alpha-hemolytic bacteria. Growth was recorded in 61.3% of disinfected impressions, and the numbers of bacteria in disinfected and nondisinfected impressions were similar. These findings raise the question of whether impressions need to be disinfected or if proper handling and hygienic procedures are sufficient to block the possible route of infection.

  8. A Comparison of Accuracy of Matrix Impression System with Putty Reline Technique and Multiple Mix Technique: An In Vitro Study

    PubMed Central

    Kumar, M Praveen; Patil, Suneel G; Dheeraj, Bhandari; Reddy, Keshav; Goel, Dinker; Krishna, Gopi

    2015-01-01

    Background: The difficulty in obtaining an acceptable impression increases exponentially as the number of abutments increases. Accuracy of the impression material and the use of a suitable impression technique are of utmost importance in the fabrication of a fixed partial denture. This study compared the accuracy of the matrix impression system with conventional putty reline and multiple mix technique for individual dies by comparing the inter-abutment distance in the casts obtained from the impressions. Materials and Methods: Three groups, 10 impressions each with three impression techniques (matrix impression system, putty reline technique and multiple mix technique) were made of a master die. Typodont teeth were embedded in a maxillary frasaco model base. The left first premolar was removed to create a three-unit fixed partial denture situation and the left canine and second premolar were prepared conservatively, and hatch marks were made on the abutment teeth. The final casts obtained from the impressions were examined under a profile projector and the inter-abutment distance was calculated for all the casts and compared. Results: The results from this study showed that in the mesiodistal dimensions the percentage deviation from master model in Group I was 0.1 and 0.2, in Group II was 0.9 and 0.3, and Group III was 1.6 and 1.5, respectively. In the labio-palatal dimensions the percentage deviation from master model in Group I was 0.01 and 0.4, Group II was 1.9 and 1.3, and Group III was 2.2 and 2.0, respectively. In the cervico-incisal dimensions the percentage deviation from the master model in Group I was 1.1 and 0.2, Group II was 3.9 and 1.7, and Group III was 1.9 and 3.0, respectively. In the inter-abutment dimension of dies, percentage deviation from master model in Group I was 0.1, Group II was 0.6, and Group III was 1.0. Conclusion: The matrix impression system showed more accuracy of reproduction for individual dies when compared with putty reline

  9. Biodegradation of polyether-polyol-based polyurethane elastomeric films: influence of partial replacement of polyether polyol by biopolymers of renewable origin.

    PubMed

    Obruca, Stanislav; Marova, Ivana; Vojtova, Lucy

    2011-07-01

    In this work we investigated the degradation process ofpolyether-polyol-based polyurethane (PUR) elastomeric films in the presence of a mixed thermophilic culture as a model of a natural bacterial consortium. The presence of PUR material in cultivation medium resulted in delayed but intensive growth of the bacterial culture. The unusually long lag phase was caused by the release of unreacted polyether polyol and tin catalyst from the material. The lag phase was significantly shortened and the biodegradability of PUR materials was enhanced by partial replacement (10%) of polyether polyol with biopolymers (carboxymethyl cellulose, hydroxyethyl cellulose, acetyl cellulose and actylated starch). The process of material degradation consisted of two steps. First, the materials were mechanically disrupted and, second, the bacterial culture was able to utilize abiotic degradation products, which resulted in supported bacterial growth. Direct utilization of PUR by the bacterial culture was observed as well, but the bacterial culture contributed only slightly to the total mass losses. The only exception was PUR material modified by acetyl cellulose. In this case, direct biodegradation represented the major mechanism of material decomposition. Moreover, PUR material modified by acetyl cellulose did not tend to undergo abiotic degradation. In conclusion, the modification of PUR by proper biopolymers is a promising strategy for reducing potential negative effects of waste PUR materials on the environment and enhancing their biodegradability. PMID:21882557

  10. Strategies for managing impressions of racial identity in the workplace.

    PubMed

    Roberts, Laura Morgan; Cha, Sandra E; Kim, Sung Soo

    2014-10-01

    This article deepens understanding of the workplace experiences of racial minorities by investigating racial identity-based impression management (RIM) by Asian American journalists. Racial centrality, directly or indirectly, predicted the use of 4 RIM strategies (avoidance, enhancement, affiliation, and racial humor). Professional centrality also predicted strategy use, which was related to life satisfaction and perceived career success. By shedding light on proactive strategies that individuals use to influence colleagues' impressions of their racial identity, we contribute to research on diversity in organizations, impression management, and racial identity.

  11. Strategies for managing impressions of racial identity in the workplace.

    PubMed

    Roberts, Laura Morgan; Cha, Sandra E; Kim, Sung Soo

    2014-10-01

    This article deepens understanding of the workplace experiences of racial minorities by investigating racial identity-based impression management (RIM) by Asian American journalists. Racial centrality, directly or indirectly, predicted the use of 4 RIM strategies (avoidance, enhancement, affiliation, and racial humor). Professional centrality also predicted strategy use, which was related to life satisfaction and perceived career success. By shedding light on proactive strategies that individuals use to influence colleagues' impressions of their racial identity, we contribute to research on diversity in organizations, impression management, and racial identity. PMID:25090148

  12. Accuracy of Gypsum Casts after Different Impression Techniques and Double Pouring

    PubMed Central

    Silva, Stephania Caroline Rodolfo; Messias, Aion Mangino; Abi-Rached, Filipe de Oliveira; de Souza, Raphael Freitas; Reis, José Maurício dos Santos Nunes

    2016-01-01

    This study evaluated the accuracy of gypsum casts after different impression techniques and double pouring. Ten patients were selected and for each one it was obtained 5 partial putty/wash impressions with vinyl polysiloxane (VPS) material from teeth #13 to #16 with partial metal stock trays. The following techniques were performed: (1) one-step; two-step relief with: (2) PVC film; (3) slow-speed tungsten carbide bur and scalpel blade, (4) small movements of the tray and (5) without relief—negative control. The impressions were disinfected with 0.5% sodium hypochlorite for 10 minutes and stored during 110 and 230 minutes for the first and second pouring, respectively, with type IV gypsum. Three intra-oral lateral photographs of each patient were taken using a tripod and a customized radiographic positioner. The images were imported into ImageJ software and the total area of the buccal surface from teeth #13 to #16 was measured. A 4.0% coefficient of variance was criterion for using these measurements as Baseline values. The casts were photographed and analyzed using the same standardization for the clinical images. The area (mm2) obtained from the difference between the measurements of each gypsum cast and the Baseline value of the respective patient were calculated and analyzed by repeated-measures two way-ANOVA and Mauchly’s Sphericity test (α = 0.05). No significant effect was observed for Impression technique (P = 0.23), Second pouring (P = 0.99) and their interaction (P = 0.25). The impression techniques and double pouring did not influence the accuracy of the gypsum casts. PMID:27736967

  13. Stiffness and damping of elastomeric O-ring bearing mounts

    NASA Technical Reports Server (NTRS)

    Smalley, A. J.

    1977-01-01

    A test rig to measure the dynamic stiffness and damping of elastomer O rings was described. Test results for stiffness and loss coefficient in the frequency range from 50 Hz to 1000 Hz are presented. Results are given for three different materials, for five temperatures, for three amplitudes, for five values of squeeze for three values of stretch for three values of cross-section diameter and for three values of groove width. All test data points were plotted. In addition, trend summary plots were presented which compare the effect of material, temperature, amplitude, squeeze, stretch, cross-section diameter, and groove width. O ring deflections under a static load for different material were presented; and effective static stiffness values were compared with dynamic values.

  14. Reducing cold flow in elastomeric O-rings

    NASA Technical Reports Server (NTRS)

    Henry, R. H.; Olsen, O. K.

    1976-01-01

    Pretreatment technique accelerates compression set of O-rings: seal is pressure loaded; seal and pressure mechanisms are heated to 160 F; load is applied to heated seal, causing material to flow; parts are cooled to room temperature; and load is removed.

  15. A selective-pressure impression technique for the edentulous maxilla.

    PubMed

    Duncan, Jacqueline P; Raghavendra, Sangeetha; Taylor, Thomas D

    2004-09-01

    This article describes a selective-pressure impression technique for the edentulous maxilla that is intended to compensate for the polymerization shrinkage of heat-polymerized polymethyl methacrylate resin and provides improved palatal adaptation of the definitive denture base.

  16. Electronic evaluation for video commercials by impression index.

    PubMed

    Kong, Wanzeng; Zhao, Xinxin; Hu, Sanqing; Vecchiato, Giovanni; Babiloni, Fabio

    2013-12-01

    How to evaluate the effect of commercials is significantly important in neuromarketing. In this paper, we proposed an electronic way to evaluate the influence of video commercials on consumers by impression index. The impression index combines both the memorization and attention index during consumers observing video commercials by tracking the EEG activity. It extracts features from scalp EEG to evaluate the effectiveness of video commercials in terms of time-frequency-space domain. And, the general global field power was used as an impression index for evaluation of video commercial scenes as time series. Results of experiment demonstrate that the proposed approach is able to track variations of the cerebral activity related to cognitive task such as observing video commercials, and help to judge whether the scene in video commercials is impressive or not by EEG signals.

  17. Electronic evaluation for video commercials by impression index.

    PubMed

    Kong, Wanzeng; Zhao, Xinxin; Hu, Sanqing; Vecchiato, Giovanni; Babiloni, Fabio

    2013-12-01

    How to evaluate the effect of commercials is significantly important in neuromarketing. In this paper, we proposed an electronic way to evaluate the influence of video commercials on consumers by impression index. The impression index combines both the memorization and attention index during consumers observing video commercials by tracking the EEG activity. It extracts features from scalp EEG to evaluate the effectiveness of video commercials in terms of time-frequency-space domain. And, the general global field power was used as an impression index for evaluation of video commercial scenes as time series. Results of experiment demonstrate that the proposed approach is able to track variations of the cerebral activity related to cognitive task such as observing video commercials, and help to judge whether the scene in video commercials is impressive or not by EEG signals. PMID:24427225

  18. Baseline and Lifetime Assessments for DC745U Elastomeric Components

    SciTech Connect

    Maxwell, R S; Chinn, S C; Herberg, J; Harvey, C; Alviso, C; Vance, A; Cohenour, R; Wilson, M; Solyom, D

    2004-12-20

    The silicone elastomer Dow Corning DC 745U is used in two major components in the W80. We have investigated a number of issues concerning this material. Our studies have accomplished a baseline study of the chemical composition of DC745 and LLNL now has a good understanding of the chemical composition of this material. DC745 crystallizes within the system STS. Two potential means identified to mitigate the risk associated with this phenomenon are to (1) change material formulation and (2) predose the parts to {approx} 25 MRad {gamma}-radiation. A candidate material identified by Gordon Spellman has been studied for composition and the lack of crystallization within the STS has been verified. A sensitivity study of the effects of relevant aging mechanisms also has been performed. The extent of aging due to radiation exposure or elevated temperatures is minimal over the expected course of the LEP. In addition, since the DC745 parts are expected to be replaced at rebuild, the aging clock is essentially being reset. No significant aging issues seem likely to develop for these parts. DC745 parts are also subject to permanent deformation in service. Our studies have shown that the deformation is likely due to incomplete mixing of the raw gum stock and the curing agent at production. This results in areas of low crosslink density that are subject to a higher degree of compression set in service. We have identified two production diagnostic tools based on Nuclear Magnetic Resonance spectroscopy to prescreen the parts at production at KCP. These studies are concluded with specific recommendation for changes to core surveillance for this part based on the chemical knowledge we have gained from this study.

  19. A study of the antimicrobial properties of impression tray adhesives.

    PubMed

    Herman, D A

    1993-01-01

    Three impression tray adhesives were tested for their antimicrobial actions on three bacteria strains used for disinfectant studies. The colony forming unit (CFU) counts from plating the adhesive-exposed bacteria showed a significant reduction in number compared with the CFU of the controls. Statistical analyses confirmed the significant reduction (p < 0.05) for all but one test case. Proper infection control procedures should always be followed, but the added benefits of disinfection by impression tray adhesives can help prevent cross contamination.

  20. Comparison of two impression techniques for auricular prosthesis: pilot study.

    PubMed

    Mohamed, Kasim; Mani, U M; Seenivasan, M K; Vaidhyanathan, A K; Veeravalli, P T

    2013-01-01

    The purpose of this article was to compare the accuracy of a new impression technique, the triple-layer impression technique (TLIT), with the conventional impression technique (CIT) to fabricate an auricular prosthesis. Fifteen male subjects (aged 22-45 yr) were selected. Ten markings were made on the subject's ear (super aurale [sa], sub aurale [sba], pre aurale [pra], post aurale [poa], A, A1, B, B1, C, and C1) and five measurements (sa-sba, pra-poa, A-A1, B-B1, and C-C1) were made. Custom-made trays were used to record impression in CIT and TLIT. Impressions were made using alginate, and models were cast with type IV gypsum product. Markings were transferred on the cast. Measurements were rechecked on the models. Distribution analysis of difference in measurements between the two impression techniques and the subject's actual values was evaluated. Sign test was used to analyze the statistical significance. Statistically significant differences were found in measurements A-A1, B-B1, and C-C1 between the two techniques when compared with the subject's actual dimensions (p < 0.01). TLIT was found to produce accurate models when compared with CIT. The TLIT used in the study was cost effective, less technique sensitive, and tailor made to reduce chairside orientation time during wax try-in appointments for rehabilitating patients, especially those with unilateral auricular defects.

  1. Auditory and visual spatial impression: Recent studies of three auditoria

    NASA Astrophysics Data System (ADS)

    Nguyen, Andy; Cabrera, Densil

    2004-10-01

    Auditory spatial impression is widely studied for its contribution to auditorium acoustical quality. By contrast, visual spatial impression in auditoria has received relatively little attention in formal studies. This paper reports results from a series of experiments investigating the auditory and visual spatial impression of concert auditoria. For auditory stimuli, a fragment of an anechoic recording of orchestral music was convolved with calibrated binaural impulse responses, which had been made with the dummy head microphone at a wide range of positions in three auditoria and the sound source on the stage. For visual stimuli, greyscale photographs were used, taken at the same positions in the three auditoria, with a visual target on the stage. Subjective experiments were conducted with auditory stimuli alone, visual stimuli alone, and visual and auditory stimuli combined. In these experiments, subjects rated apparent source width, listener envelopment, intimacy and source distance (auditory stimuli), and spaciousness, envelopment, stage dominance, intimacy and target distance (visual stimuli). Results show target distance to be of primary importance in auditory and visual spatial impression-thereby providing a basis for covariance between some attributes of auditory and visual spatial impression. Nevertheless, some attributes of spatial impression diverge between the senses.

  2. Modelling the self-assembly of elastomeric proteins provides insights into the evolution of their domain architectures.

    PubMed

    Song, Hongyan; Parkinson, John

    2012-01-01

    Elastomeric proteins have evolved independently multiple times through evolution. Produced as monomers, they self-assemble into polymeric structures that impart properties of stretch and recoil. They are composed of an alternating domain architecture of elastomeric domains interspersed with cross-linking elements. While the former provide the elasticity as well as help drive the assembly process, the latter serve to stabilise the polymer. Changes in the number and arrangement of the elastomeric and cross-linking regions have been shown to significantly impact their assembly and mechanical properties. However, to date, such studies are relatively limited. Here we present a theoretical study that examines the impact of domain architecture on polymer assembly and integrity. At the core of this study is a novel simulation environment that uses a model of diffusion limited aggregation to simulate the self-assembly of rod-like particles with alternating domain architectures. Applying the model to different domain architectures, we generate a variety of aggregates which are subsequently analysed by graph-theoretic metrics to predict their structural integrity. Our results show that the relative length and number of elastomeric and cross-linking domains can significantly impact the morphology and structural integrity of the resultant polymeric structure. For example, the most highly connected polymers were those constructed from asymmetric rods consisting of relatively large cross-linking elements interspersed with smaller elastomeric domains. In addition to providing insights into the evolution of elastomeric proteins, simulations such as those presented here may prove valuable for the tuneable design of new molecules that may be exploited as useful biomaterials. PMID:22396636

  3. Modelling the Self-Assembly of Elastomeric Proteins Provides Insights into the Evolution of Their Domain Architectures

    PubMed Central

    Song, Hongyan; Parkinson, John

    2012-01-01

    Elastomeric proteins have evolved independently multiple times through evolution. Produced as monomers, they self-assemble into polymeric structures that impart properties of stretch and recoil. They are composed of an alternating domain architecture of elastomeric domains interspersed with cross-linking elements. While the former provide the elasticity as well as help drive the assembly process, the latter serve to stabilise the polymer. Changes in the number and arrangement of the elastomeric and cross-linking regions have been shown to significantly impact their assembly and mechanical properties. However, to date, such studies are relatively limited. Here we present a theoretical study that examines the impact of domain architecture on polymer assembly and integrity. At the core of this study is a novel simulation environment that uses a model of diffusion limited aggregation to simulate the self-assembly of rod-like particles with alternating domain architectures. Applying the model to different domain architectures, we generate a variety of aggregates which are subsequently analysed by graph-theoretic metrics to predict their structural integrity. Our results show that the relative length and number of elastomeric and cross-linking domains can significantly impact the morphology and structural integrity of the resultant polymeric structure. For example, the most highly connected polymers were those constructed from asymmetric rods consisting of relatively large cross-linking elements interspersed with smaller elastomeric domains. In addition to providing insights into the evolution of elastomeric proteins, simulations such as those presented here may prove valuable for the tuneable design of new molecules that may be exploited as useful biomaterials. PMID:22396636

  4. On the source of entropic elastomeric force in polypeptides and proteins: Backbone configurational vs. side-chain solvational entropy

    SciTech Connect

    Luan, Chihao; Jaggard, J.; Harris, R.D.; Urry, D.W. )

    1989-01-01

    At physiological temperature in water, the relaxed state of the protein, elastin, and model elastomeric sequential polypeptides derived from this biological elastomer is the result of an inverse temperature transition. At lower temperatures, say at 20{degree}C, the hydrophobic side chains of the elastomers are hydrated with a low-entropy net of water. Following Flory and colleagues, thermoelasticity studies suggests that these polypeptide elastomers are dominantly entropic elastomers above the temperature of the inverse temperature transition. A central question becomes the source of the entropic elastomeric force. On stretching, hydrophobic side chains become exposed to water, resulting in an exothermic reaction of hydrophobic hydration. The issue addressed by the present report is whether this decrease in solvent entropy on stretching might make a major contribution to the entropic elastomeric restoring force. It has previously been argued that the free energy of solvation can be made very small by a 30% ethylene glycol (EG):70% water solvent mixture. This is demonstrated here using the repeating pentapeptide sequence of elastin (Val{sup 1}-Pro{sup 2}-Gly{sup 3} -Val{sup 4}-Gly{sup 5}){sub n} or poly(VPGVG) and its {gamma}-irradiation cross-linked elastomeric matrix. Differential scanning calorimetry of the inverse temperature transition of poly(VPGVG) shows the endothermic heat of the transition to become very small in EG/H{sub 2}O when compared with H{sub 2}O alone, which also indicates a very small entropy change for the transition on exposure of the hydrophobic side chains to the EG/H{sub 2}O solvent mixture. A similar result is found for the crosslinked elastomeric matrix. Significantly, however, in spite of the lower heats for hydrophobic solvation, the elastic modulus and the entropic elastomeric forces generated are greater in EG/H{sub 2}O.

  5. Optical Manipulation of Shape-Morphing Elastomeric Liquid Crystal Microparticles Doped with Gold Nanocrystals

    SciTech Connect

    Sun, Y. R.; Evans, J. S.; Lee, T.; Senyuk, B.; Keller, P.; He, S. L.; Smalyukh, I. I.

    2012-06-11

    We demonstrate facile optical manipulation of shape of birefringent colloidal microparticles made from liquid crystal elastomers. Using soft lithography and polymerization, we fabricate elastomeric microcylinders with weakly undulating director oriented on average along their long axes. These particles are infiltrated with gold nanospheres acting as heat transducers that allow for an efficient localized transfer of heat from a focused infrared laser beam to a submicrometer region within a microparticle. Photothermal control of ordering in the liquid crystal elastomer using scanned beams allows for a robust control of colloidal particles, enabling both reversible and irreversible changes of shape. Possible applications include optomechanics, microfluidics, and reconfigurable colloidal composites with shape-dependent self-assembly.

  6. Microfluidic Automation using elastomeric valves and droplets: reducing reliance on external controllers

    PubMed Central

    Kim, Sung-Jin; Lai, David; Park, Joong Yull; Yokokawa, Ryuji

    2012-01-01

    This paper gives an overview of elastomeric valve- and droplet-based microfluidic systems designed to minimize the need of external pressure to control fluid flow. This concept article introduces the working principle of representative components in these devices along with relevant biochemical applications. This is followed by providing a perspective on the roles of different microfluidic valves and systems through comparison of their similarities and differences with transistors (valves) and systems in microelectronics. Despite some physical limitation of drawing analogies from electronic circuits, automated microfluidic circuit design can gain insights from electronic circuits to minimize external control units, while implementing high complexity and throughput analysis. PMID:22761019

  7. Fouling-release and chemical activity effects of a siloxane-based material on tunicates.

    PubMed

    Filip, Natalia; Pustam, Amanda; Ells, Veronica; Grosicki, Kathleen M T; Yang, Jin; Oguejiofor, Ikenna; Bishop, Cory D; DeMont, M Edwin; Smith-Palmer, Truis; Wyeth, Russell C

    2016-05-01

    The antifouling performance of a siloxane-based elastomeric impression material (EIM) was compared to that of two silicone fouling-release coatings, Intersleek 757 and RTV-11. In field immersion trials, the EIM caused the greatest reduction in fouling by the solitary tunicate Ciona intestinalis and caused the longest delay in the progression of fouling by two species of colonial tunicate. However, in pseudobarnacle adhesion tests, the EIM had higher attachment strengths. Further laboratory analyses showed that the EIM leached alkylphenol ethoxylates (APEs) that were toxic to C. intestinalis larvae. The EIM thus showed the longest duration of chemical activity measured to date for a siloxane-based coating (4 months), supporting investigations of fouling-release coatings that release targeted biocides. However, due to potential widespread effects of APEs, the current EIM formulation should not be considered as an environmentally-safe antifoulant. Thus, the data also emphasize consideration of both immediate and long-term effects of potentially toxic constituents released from fouling-release coatings. PMID:26986763

  8. A novel approach to the distortion assessment of denture impression trays.

    PubMed

    Hitge, M L; Torfs, P J; Bicanic, D D

    1991-01-01

    A novel method to treat and interpret distortion of denture impression trays has been proposed. When compared with the conventional method this approach, based on the general least squares principle, offers a significant advantage since the displacement for each individual point can be traced providing more profound insight into the character of the overall deformation itself. The method was applied to study dental impression trays manufactured of self-curing acrylic. The results indicate the existence of a large degree of individuality and non-uniform behaviour of a specific tray material. The method developed here can be applied to specimens of any arbitrary size and shape and it is not limited by the number of the reference points.

  9. Roofing: Workbook and Tests. Common Roofing and Waterproofing Materials and Equipment.

    ERIC Educational Resources Information Center

    California State Dept. of Education, Sacramento. Bureau of Publications.

    This workbook on materials and equipment is one of a series of nine individual units of instruction for roofing apprenticeship classes in California. The workbook covers eight topics: production of bitumens and asphaltic roofing materials; built-up roofing materials and adhesives; asphaltic products and rigid roofing materials; elastomeric and…

  10. Interactions between sealing materials and lubricating oil additives

    SciTech Connect

    Winkenbach, R.; Von Arndt, E.M.; Mindermann, H.

    1987-01-01

    Due to the increasingly higher application demands, engine and transmission manufactures are today using lubrication oils with more and more additives. The result is that seal materials are being damaged when exposed to such conditions and such additives. This paper shows the effects of basic oils with, and without, additives on elastomeric materials such as NBR, ACM, MVQ and FPM.

  11. In vivo performance of a phospholipid-coated bioerodable elastomeric graft for small-diameter vascular applications

    PubMed Central

    Soletti, Lorenzo; Nieponice, Alejandro; Hong, Yi; Ye, Sang-Ho; Stankus, John J.; Wagner, William R.; Vorp, David A.

    2011-01-01

    There remains a great need for vascular substitutes for small-diameter applications. The use of an elastomeric biodegradable material, enabling acute antithrombogenicity and long-term in vivo remodeling, could be beneficial for this purpose. Conduits (1.3 mm internal diameter) were obtained by electrospinning biodegradable poly(ester urethane)urea (PEUU), and by luminally immobilizing a non-thrombogenic, 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer. Platelet adhesion was characterized in vitro after contact with ovine blood. The conduits were implanted as aortic interposition grafts in the rat for 4, 8, 12, and 24 weeks. Surface treatment resulted in a 10-fold decrease in platelet adhesion compared to untreated material. Patency at 8 weeks was 92% for the coated grafts compared to 40% for the non-coated grafts. Histology at 8 and 12 weeks demonstrated formation of cellularized neotissue consisting of aligned collagen and elastin. The lumen of the grafts was confluent with cells qualitatively aligned in the direction of blood flow. Immunohistochemistry suggested the presence of smooth muscle cells in the medial layer of the neotissue and endothelial cells lining the lumen. Mechanically, the grafts were less compliant than rat aortas prior to implantation (4.5 ± 2.0 × 10–4 mmHg–1 vs. 14.2 ± 1.1 × 10–4 mmHg–1, respectively), then after 4 weeks in vivo they approximated native values, but subsequently became stiffer again at later time points. The novel coated grafts exhibited promising antithrombogenic and mechanical properties for small-diameter arterial revascularization. Further evaluation in vivo will be required to demonstrate complete remodeling of the graft into a native-like artery. PMID:21171163

  12. Towards development of lignin reinforced elastomeric compounds with reduced energy dissipation

    NASA Astrophysics Data System (ADS)

    Bahl, Kushal

    This research deals with development of lignin as reinforcing filler for elastomeric compounds. Lignins are naturally abundant and cost competitive wood derivatives possessing strong mechanical properties and offering reactive functional groups on their surfaces. The presence of the functional groups imparts polarity to the lignin molecules and makes them incompatible with non-polar elastomers. Also, the large particle size of lignin does not produce desired mechanical reinforcement. The present study deals with solving the outstanding issues associated with the use of lignin as fillers for polymeric compounds. In addition, the work specifically focuses on producing rubber compounds with reduced energy dissipation via partial replacement of carbon black with lignin. The first part of this study is devoted to suppression of the polarity of lignin and achievement of compatibility with rubber matrix via modification of lignosulfonates (LS) with cyclohexylamine (CA). CA reduces the polarity of lignin via interactions originating from proton transfer and hydrogen bonding. X-ray Photoelectron Spectroscopy (XPS) confirms the attachment of CA on the surfaces of lignin. The mechanical properties of rubber compounds increase substantially along with improvement in cure properties and increase in crosslink density in the presence of LS particles modified with CA. The tensile strength and storage modulus show an increase by 45% and 41% respectively. The values of the 100% modulus and elongation at break also improve by 35% and 60% respectively. The second part of this study exploits the non-covalent interactions between lignin and carbon black (CB) for the design of novel hybrid filler particles exhibiting lower energy loss in rubber compounds. The hybrid fillers offer unique morphology consisting of coating layers of lignin on carbon black particle aggregates. It is found that such coating layers are formed due to pi-pi interactions between lignin and carbon black. Raman

  13. Encoding Gaussian curvature in glassy and elastomeric liquid crystal solids

    PubMed Central

    Mostajeran, Cyrus; Ware, Taylor H.; White, Timothy J.

    2016-01-01

    We describe shape transitions of thin, solid nematic sheets with smooth, preprogrammed, in-plane director fields patterned across the surface causing spatially inhomogeneous local deformations. A metric description of the local deformations is used to study the intrinsic geometry of the resulting surfaces upon exposure to stimuli such as light and heat. We highlight specific patterns that encode constant Gaussian curvature of prescribed sign and magnitude. We present the first experimental results for such programmed solids, and they qualitatively support theory for both positive and negative Gaussian curvature morphing from flat sheets on stimulation by light or heat. We review logarithmic spiral patterns that generate cone/anti-cone surfaces, and introduce spiral director fields that encode non-localized positive and negative Gaussian curvature on punctured discs, including spherical caps and spherical spindles. Conditions are derived where these cap-like, photomechanically responsive regions can be anchored in inert substrates by designing solutions that ensure compatibility with the geometric constraints imposed by the surrounding media. This integration of such materials is a precondition for their exploitation in new devices. Finally, we consider the radial extension of such director fields to larger sheets using nematic textures defined on annular domains. PMID:27279777

  14. Transient Dynamic Mechanical Analysis of Resilin-based Elastomeric Hydrogels

    NASA Astrophysics Data System (ADS)

    Li, Linqing; Kiick, Kristi

    2014-04-01

    The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young’s modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (< 15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels.

  15. Buckling of Dielectric Elastomeric Plates for Electrically Active Microfludic Pumps

    NASA Astrophysics Data System (ADS)

    Holmes, Douglas; Tavakol, Behrouz; Bozlar, Michael; Froehlicher, Guillaume; Stone, Howard; Aksay, Ilhan

    2013-11-01

    Fluid flow can be directed and controlled by a variety of mechanisms within industrial and biological environments. Advances in microfluidic technology have required innovative ways to control fluid flow on a small scale, and the ability to actively control fluid flow within microfluidic devices is crucial for advancements in nanofluidics, biomedical fluidic devices, and digital microfluidics. In this work, we present a means for microfluidic control via the electrical actuation of thin, flexible valves within microfluidic channels. These structures consist of a dielectric elastomer confined between two compliant electrodes that can be actively and reversibly buckle out of plane to pump fluids from an applied voltage. The out-of-plane deformation can be quantified using two parameters: net change in surface area and the shape of deformation. Change in surface area depends on the voltage, while the deformation shape, which significantly affects the flow rate, is a function of voltage, and the pressure and volume of the chambers on each side of the thin plate. The use of solid electrodes enables a robust and reversible pumping mechanism that will have will enable advancements in rapid microfluidic diagnostics, adaptive materials, and artificial muscles.

  16. Transient dynamic mechanical properties of resilin-based elastomeric hydrogels

    PubMed Central

    Li, Linqing; Kiick, Kristi L.

    2014-01-01

    The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young's modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (<15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels. PMID:24809044

  17. Encoding Gaussian curvature in glassy and elastomeric liquid crystal solids

    NASA Astrophysics Data System (ADS)

    Mostajeran, Cyrus; Warner, Mark; Ware, Taylor H.; White, Timothy J.

    2016-05-01

    We describe shape transitions of thin, solid nematic sheets with smooth, preprogrammed, in-plane director fields patterned across the surface causing spatially inhomogeneous local deformations. A metric description of the local deformations is used to study the intrinsic geometry of the resulting surfaces upon exposure to stimuli such as light and heat. We highlight specific patterns that encode constant Gaussian curvature of prescribed sign and magnitude. We present the first experimental results for such programmed solids, and they qualitatively support theory for both positive and negative Gaussian curvature morphing from flat sheets on stimulation by light or heat. We review logarithmic spiral patterns that generate cone/anti-cone surfaces, and introduce spiral director fields that encode non-localized positive and negative Gaussian curvature on punctured discs, including spherical caps and spherical spindles. Conditions are derived where these cap-like, photomechanically responsive regions can be anchored in inert substrates by designing solutions that ensure compatibility with the geometric constraints imposed by the surrounding media. This integration of such materials is a precondition for their exploitation in new devices. Finally, we consider the radial extension of such director fields to larger sheets using nematic textures defined on annular domains.

  18. Inorganic particle analysis of dental impression elastomers.

    PubMed

    Carlo, Hugo Lemes; Fonseca, Rodrigo Borges; Soares, Carlos José; Correr, Américo Bortolazzo; Correr-Sobrinho, Lourenço; Sinhoreti, Mário Alexandre Coelho

    2010-01-01

    The aim of this study was to determine quantitatively and qualitatively the inorganic particle fraction of commercially available dental elastomers. The inorganic volumetric fraction of two addition silicones (Reprosil Putty/Fluid and Flexitime Easy Putty/Fluid), three condensation silicones (Clonage Putty/Fluid, Optosil Confort/Xantopren VL and Silon APS Putty/Fluid), one polyether (Impregum Soft Light Body) and one polysulfide (Permlastic Light Body) was accessed by weighing a previously determined mass of each material in water before and after burning samples at 600 ºC, during 3 h. Unsettled material samples were soaked in acetone and chloroform for removal of the organic portion. The remaining filler particles were sputter-coated with gold evaluation of their morphology and size, under scanning electron microscopy (SEM). Flexitime Easy Putty was the material with the highest results for volumetric particle fraction, while Impregum Soft had the lowest values. Silon 2 APS Fluid presented the lowest mean filler size values, while Clonage Putty had the highest values. SEM micrographs of the inorganic particles showed several morphologies - lathe-cut, spherical, spherical-like, sticks, and sticks mixed to lathe-cut powder. The results of this study revealed differences in particle characteristics among the elastometic materials that could lead to different results when testing mechanical properties.

  19. Inorganic particle analysis of dental impression elastomers.

    PubMed

    Carlo, Hugo Lemes; Fonseca, Rodrigo Borges; Soares, Carlos José; Correr, Américo Bortolazzo; Correr-Sobrinho, Lourenço; Sinhoreti, Mário Alexandre Coelho

    2010-01-01

    The aim of this study was to determine quantitatively and qualitatively the inorganic particle fraction of commercially available dental elastomers. The inorganic volumetric fraction of two addition silicones (Reprosil Putty/Fluid and Flexitime Easy Putty/Fluid), three condensation silicones (Clonage Putty/Fluid, Optosil Confort/Xantopren VL and Silon APS Putty/Fluid), one polyether (Impregum Soft Light Body) and one polysulfide (Permlastic Light Body) was accessed by weighing a previously determined mass of each material in water before and after burning samples at 600 ºC, during 3 h. Unsettled material samples were soaked in acetone and chloroform for removal of the organic portion. The remaining filler particles were sputter-coated with gold evaluation of their morphology and size, under scanning electron microscopy (SEM). Flexitime Easy Putty was the material with the highest results for volumetric particle fraction, while Impregum Soft had the lowest values. Silon 2 APS Fluid presented the lowest mean filler size values, while Clonage Putty had the highest values. SEM micrographs of the inorganic particles showed several morphologies - lathe-cut, spherical, spherical-like, sticks, and sticks mixed to lathe-cut powder. The results of this study revealed differences in particle characteristics among the elastometic materials that could lead to different results when testing mechanical properties. PMID:21271042

  20. Optical fiber sensor for pressure measurement based on elastomeric membrane and macrobending loss

    NASA Astrophysics Data System (ADS)

    Ribeiro, Livia A.; Rosolem, Joao B.; Dini, Danilo C.; Floridia, Claudio; Bezerra, Edson W.; Cezar, Fabio A.; Loichate, Marcelo D.; Durelli, Anderson S.

    2012-04-01

    We propose a fiber optic sensor array based on bend loss assessed by optical time domain reflectometry (OTDR). The sensor mechanism is based on optical fiber bending loss compressed by external pressure. An elastomeric surface is applied to the sensor in order to communicate external pressure to the fiber coil and also, this make sensor able to deal with degradation coming from aggressive environments. The sensing system proposed is able to monitor liquid or gas pressure in different environments, such as water, oil, alcohols, some diluted acids and others, depending only of elastomeric membrane choice. In order to protect the sensor stage against environmental degradation a plastic packaging was chosen. Bend loss measurements is taken concerning the number of fiber loops involved in the sensor, pump signal wavelength and temporal width. This long for the best parameters in the sensor construction. The specific case of the sensor applied to water percolation monitoring from embankment damns is detailed in this paper; for this application the sensor array have a number of at least six stages totally independent each other, in such a way that each stage can be developed to monitor a specific environment. Sensors have shown good performance in field tests, reaching work range from 0.1 to 0.6 atm with 0.05 atm of precision.