Comparison of dimensional accuracy in casts yield from three types of silicone impression material with different techniques of impression and repeated pouring of models

Abstract

Dimensional accuracy of impressions is crucial to the quality of fixed prosthodontics 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 in casts yield from three types of silicone impression material with different techniques of impression and repeated pouring of models. Materials & Methods: A metallic model with 2 abutment preparations was fabricated, and impressions were made 10 times with each material-technique. Custom trays made for each impression. 2mm-thick wax-spacers were made for monophase impressions on dies of model and 6mm-thick wax-spacers were made for other impression materials. Impressions were made with condensation-silicone (1-step and 2-step impression), addition-silicone (1-step and 2-step impression) and monophasic-polyvinyl-siloxane impression materials. Impressions were poured at 1hour, 24 hours and 14 days after impression. The data were analyzed by Repeated Measure ANOVA and P-value less than 0.05 was known significant. Results: Under the conditions of this study, all of five material-technique impressions were equally dimensionally accurate of diameter and inter-die-space and the time of the pour did not affect the accuracy. Also, results show that dimension accuracy of 1-step speedex, 1-step panasil and monophasic-polyvinyl-siloxane material-techniques were approximately same and 1-step technique yielded more accurate casts in compared to 2-step technique of same impression material. No significant difference exists between the cast height of 1-step technique of speedex and panasil compared to the 2-step technique of same impression material. Conclusions: Generally, the 1-step condensation-silicone, 1-step addition-silicone and monophasic-polyvinyl-siloxane material-techniques were the most dimensionally accurate impression methods in terms of resultant casts. Also, all of five material-technique impressions were equally dimensionally accurate of diameter and inter-die-space and the time of the pour did not affect the accuracy.