Effect of surface treatments on the tensile bond strength of heat cure silicone soft liner to an acrylic resin denture base in a simulated oral environment - A comparative SEM study

Aim: To assess and compare the effect of surface treatments in a simulated oral environment through thermocycling on tensile bond strength of silicone soft liner with acrylic resin base. Settings and Design: In Vitro Comparative and SEM analytical study. Materials and Methodology: 120 samples of heat cured acrylic resin (DPI) and silicone soft liner (Molloplast B) with desired dimensions were fabricated using customized brass flask. 120 samples were divided into 1 control group (untreated) and 3 test groups (treated) consisting of 30 samples each. 3 test groups were divided based on surface treatments of resin samples to adhere to silicone soft liner to them via acid etching (36% phosphoric acid), air abrasion (50 μm Al2O3) and laser treatment (Er-YAG). All the 4 groups (1 control and 3 test groups) were subdivided into two subgroups based on their subjection to thermocycling i.e., 15 samples of each group were not subjected to thermocycling (before) and remaining 15 samples of each group were subjected to thermocycling (after). Statistical Analysis Used: All the samples were evaluated for tensile bond strength using universal testing machine. Obtained values were statistically analyzed with student paired T test, one way ANOVA and post HOC Tukey B test to compare, identify significant differences and also to arrive at order of groups. The effects of surface treatments and silicone liner on the surface of denture base resin were examined with scanning electron microscopy. Results: The tensile bond strength was significantly different between control and test groups and also among test groups before and after thermocycling (P < 0.05). The specimens of acid group had higher bond strength values followed by laser treated and abraded groups. Thermocycling had decreased bond strength values. SEM observations also revealed that, surface treatments modified the surface of the denture base resin with variability. Conclusions: Surface treatments increased the bond strength values while thermocycling had decreased them. Among all the groups tested, acid etching group of samples exhibited higher bond strength values of all test groups before and after thermocycling followed by laser, abrasion and control groups. Bond strength values of all test groups before and after thermocycling were still higher than 0.45 MPa, which is clinically acceptable bond strength level.