Comparative Evaluation of the Effect of Different Surface Treatments on the Shear Bond Strength between Silicone Soft Liner and Denture Base Resin: An In Vitro study

PURPOSE OF STUDY: The present in vitro study was to comparatively evaluate the effect of two different surface treatments on the shear bond strength between silicone soft liner and heat polymerized denture base resin after thermocycling. MATERIALS AND METHODS: Thirty three heat cure acrylic blocks of 14mmx14mmx25mm were prepared and randomly divided into three groups A, B, C of eleven each blocks based on the method of surface treatment rendered. One of the 14mmx14mm surfaces of each block was designated as test surface. Group A test surfaces were left untreated (Control), Group B were sandblasted and Group C were laser irradiated. One representative surface treated test surface from each group was subjected to 3-D surface texture analysis. Silicone soft liner was bonded to the remaining test surfaces. The test samples were subjected to thermocycling and then shear bond strength testing in universal testing machine. One representative debonded sample from each group was qualitatively analysed for mode of failure using scanning electron microscopy. The results were tabulated and statistically analysed using ANOVA and post-hoc Tukey’s HSD analysis (P value < 0.05 considered significant). RESULTS: Surface texture analysis revealed well defined peaks and valleys for both sandblasted (1.40μm) and laser irradiated (1.59μm) groups compared to control (0.449μm). Laser irradiated group exhibited the maximum and significantly higher shear bond strength (0.553513Mpa) compared to sandblasted (0.495116Mpa) and control (0.320557Mpa) groups. Control group showed significantly least bond strength (0.320557Mpa). SEM analysis revealed mixed type of failure for all three groups. Group A exhibited a predominantly adhesive pattern of failure, whereas Groups B and C exhibited a predominantly cohesive pattern of failure. CONCLUSION: Surface treatment by sandblasting and laser irradiation increases the surface roughness of acrylic resin and also significantly improves the shear bond strength compared to untreated surfaces