EFFECT OF DISINFECTION AND TIME ON THE DIMENSIONAL STABILITY OF VINYLSILOXANETHER, POLYETHER, AND POLYVINYLSILOXANE IMPRESSIONS – AN IN VITRO PILOT STUDY

Statement of problem: The success of an indirect restoration or prosthesis is determined by the quality of fit and retention, which in turn, depends on the dimensional stability of the impression material used to fabricate it. The disinfection of impression material before pouring the model/cast can significantly alter the dimensions and, in turn, affect the overall fit of the prosthesis. This in vitro study evaluates and compares the dimensional stability of a new elastomeric impression material, Vinylsiloxanether with its parent materials, Polyvinylsiloxane and Polyether upon immersion disinfection. Purpose: This in-vitro study aims to evaluate and compare the dimensional stability of Vinylsiloxanether (VSE) impressions with that of Polyvinylsiloxane (PVS) and Polyether impression systems (PE) at time intervals of 2hrs, 24 hrs and one week upon disinfection with 0.525% Sodium hypochlorite and 0.12% Chlorhexidine. Material and methods: Twelve impressions of replicated crown preparations on the mandibular first molars, with reference points at the position of two central incisors were made on a typhodont model for all three test impression materials. Of the twelve, four impressions were used as control with the remaining disinfected using 0.525% Sodium hypochlorite or 0.12% Chlorhexidine, in equal numbers. These impressions were then poured with Type IV gypsum at different intervals of 2hrs, 24hrs, and 7days to retrieve casts. Subsequently, measurements were recorded on all the casts poured, including anteroposterior, cross-arch, mesiodistal, buccolingual, and occlusogingival dimensions utilizing a Coordinate Measuring Machine. Statistically, Two-way ANOVA, One-way ANOVA, and Dahlberg’s formula were applied. All hypothesis testing was conducted at α = 0.05. Results: The anteroposterior and cross-arch dimensions showed significant time-dependent changes. The bucco lingual dimension also showed a statistically significant difference between casts poured after 24 hrs and one week. However, no significant differences were found between groups that were disinfected with 0.12% Chlorhexidine and 0.525% Sodium hypochlorite. Conclusions: Vinylsiloxanether monophase impression material demonstrated good dimensional stability for clinical use since the results were comparable to that of Polyether and Polyvinylsiloxane impression materials. Clinical Implications: The dimensional stability of Vinylsiloxanether is comparable to Polyvinylsiloxane, and Polyether upon disinfection, however with time, Polyvinylsiloxane is dimensionally more stable. 0.12% Chlorhexidine gluconate did not affect the dimensional stability of the elastomers studied and can be used as a viable alternative for disinfecting impression materials. Based on this evidence, it is essential to keep in mind the nature of disinfection and the time of cast fabrication to deliver superior prosthesis for better patient satisfaction.