Surface Quality and Long‐term Dimensional Stability of Current Elastomeric Impression Materials after Disinfection

Purpose: The objectives of this investigation were to evaluate the effect of disinfection on surface quality and dimensional stability of more recent, reformulated vinylpolysiloxane (VPS) and polyether (PE) materials. Methods: Using ANSI/American Dental Association (ADA) specification 19 protocols, 50 impressions of stainless steel dies were made with each material. Ten impressions of each material were randomly assigned to a treatment group: (1) no disinfectant; (2) 10-minute dual phenol immersion; (3) 1-hour dual phenol; (4) 10-minute sodium hypochlorite (NaOCl); and (5) 1-hour NaOCl. Impression surface quality immediately after disinfection was categorized as smooth/shiny, matte, or wrinkled/sticky. Dimensional stability was evaluated by measuring dimensional accuracy according to specification 19 after 24-hour, 1-week, and 2-week storage at ambient laboratory conditions. Results: The PE material surface quality was significantly affected (Pearson Chi-square, p≤ 0.05) by NaOCl with a mottled surface on 30% of the impressions after 10-minute immersion and a matte/sticky surface on 100% of the PE impressions after 1-hour immersion. Separate 2-factor analyses of variance (ANOVA) and Bonferroni post hoc tests of dimensional accuracy within each material indicated a significant difference (p≤ 0.05) between non-disinfected and disinfected PE impressions, which exhibited expansion. There were also significant differences (p≤ 0.05) in both VPS and PE dimensional accuracy as a function of measurement time related to increasing shrinkage over time in non-disinfected and disinfected impressions. Conclusions: Despite PE expansion following disinfection and continued shrinkage of both the non-disinfected and disinfected VPS and PE impressions over a 2-week period, all dimensional accuracy measurements met the ADA standard, ≤0.5% dimensional change. Based on this evidence, neither NaOCl nor dual phenol disinfectants used for varying time periods adversely affected the dimensional stability of the more recent formulations of VPS and PE; however, Impregum PentaSoft PE surface quality appeared to be adversely affected by increasing exposure to NaOCl.