Surface reproducibility of impression materials

by M.S. Shah, Amit

Abstract (Summary)
The inability to absorb or release moisture limits the ANSI/ADA specification 19 stainless steel mold from accurately mimicking tooth structure and oral conditions while evaluating in vitro detail reproduction of elastomeric impression materials. Moreover, studies utilizing this mold have been graduated at room temperature, not normal mouth temperature. Bovine teeth, being similar to human teeth in microstructure and composition, are the closest substitutes that can be used to evaluate surface detail reproducibility of impression materials. The objectives of this study were (1) to develop a new bovine in vitro test model at controlled temperature and humidity in order to simulate in vivo detail reproduction of enamel and dentin; (2) to examine and compare the detail reproduction of three medium bodied elastomeric impression materials using the standard ADA model and bovine models on a dry and contaminated surface. Impressions, employing a poly-vinyl siloxane, a polyether and a polysiloxanepolyether hybrid, were made of the bovine and stainless steel models scored with horizontal lines of varying dimensions as specified by ADA Specification 19. Both the models and their impressions were scanned on a non-contact profilometer for line widths, volumes and mean heights. Superimposition of impression scans over model scans was done to evaluate volume and mean height differences. Statistically significant differences were found among all models (p < 0.0001) & conditions (p < 0.0001) for outcome variables width and mean height across all horizontal ii lines. Wet bovine impressions showed significant differences to their dry counterparts, thus indicating that they are better predictors of surface detail parameters like moisture, considering the limitations of stainless steel. Impregum reproduced detail better than the other impression materials in dry environment whereas Aquasil reproduced on par with Impregum in the wet conditions with Senn faring significantly worse. Overall, all impression material types reproduced equally well in dry conditions, whereas surface detail on impressions deteriorated when the mold was wet. Even though manufacturers claim that their impression materials are hydrophilic and can displace moisture, none of the materials tested showed enough promise to reproduce surface details in the wet conditions as accurately as in dry conditions. iii
Bibliographical Information:


School:University of Alabama at Birmingham

School Location:USA - Alabama

Source Type:Master's Thesis

Keywords:analysis of variance dental impression materials dentin elastomers surface properties


Date of Publication:

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