Effect of thermal treatments on optical properties of bis-acryl resins

Tese de mestrado, Medicina Dentária, Universidade de Lisboa, Faculdade de Medicina Dentária, 2018Aim: The purpose of this study was to evaluate the effect of various thermal treatments on the chromatic stability of two bis-acrylic resins, after 24h and 7d. Materials and Methods: Ten experimental groups (n=10) were set according to the several possible combinations between the bis-acrylic resin (Protemp 4, P4; Structur 3, S3) and post-polymerization thermal treatment (without any post-polymerization treatment, nt; post-polymerization in a water bath at 60°C for 5 minutes, wb5; microwave at 750W for 1 minute, mw1; water bath at 60°C for 1 minute, wb1; conventional hairdryer for 1 minute, hd1). Thirty minutes after the polymerization, the baseline color values were measured, and all the specimens were immersed in the staining solution (coffee). After 24h and 7d new measurements were taken and ΔE calculated. A ΔE higher than 3.7 was considered clinically unacceptable. After confirming the normality and homogeneity of the data with Shapiro-Wilk and Levene’s testes (p>0.05), the ΔE data were submitted to a 2-way ANOVA, followed by 1-way ANOVA and Tukey post-hoc tests for each material (α=0.05). Results: The ΔE ranged between 5.9 and 13.0, at 24h, and between 9.1 and 24.7, after 7d. The ΔE was statistically (p0.05) ΔE than nt group. At 7d, no differences were found between S3 groups. In the P4 specimens, the wb5 showed a lower ΔE than nt, and only the wb1 and the hd1 obtained a ΔE higher than nt. Conclusion: Both, bis-acrylic resin and post-polymerization treatments, influence the ΔE, at 24h and 7d