The effect of two in-office and home bleaching gels on microhardness of composite resin

Background and Aim: Bleaching products as chemical materials can exert side effects on soft and hard tissues and existing restorative materials with oxidizing mechanism. The aim of this study was to evaluate the effect of 15% and 35% carbamide peroxide gels as home and in-office bleaching agents respectively, on microhardness and surface topography of composite resin.Materials and Methods: In this in vitro study, a total of 75 disc shaped specimens were prepared from Z100  composite resin (3M) and randomly divided into three groups with following treatment designs: group 1, 370C distilled water, group 2, 15% carbamide peroxide, 6 hours/day for 3 weeks, group 3, 35% carbamide peroxide 30 minutes/week for 3 weeks. The microhardness (Vickers hardness) of samples was measured using Shimadzu set on three different points of each sample. 8 samples of each group were selected randomly to be assessed by scanning electron microscopy (SEM) for probable changes in surface topography. Data were analyzed using one way ANOVA and Duncan tests with p<0.05 as the level of significance. Results: 15% carbamide peroxide group had the maximum amount of microhardness (84.59±1.87) and 35% carbamide peroxide group had the minimum (76. 14±1.77). Only the difference between home bleaching and control group was not statistically significant (P=0.24). The SEM assessing revealed no changes in surface topography.Conclusion: Based on the results of this study, in-office bleaching may decrease the microhardness of composite resin

Microtensile Bond Strength of Single Bond and Adper Prompt-L-Pop Adhesives to Dentin

Objective: The aim of this study was to evaluate the microtensile bond strength to sound and caries-affected dentin using Single Bond and Adper Prompt-L-Pop adhesives.Materials and Methods: Sixteen extracted human molars with carious lesions extended halfway through dentin were ground to expose the caries affected and the surrounding normal dentin. The samples were divided into two groups of eight samples each, including Single Bond (two-step etch and rinse) and Adper Prompt-L-Pop (one step self-etch). Z-100 (3M) was used for composite build-ups. The teeth were then sectioned and prepared for micro tensile bond strength test, at cross head speed of 1.5 mm/min. Data were ana-lyzed by 1- and 2-way ANOVA.Results: Bond strengths of Single Bond and Adper Prompt-L-Pop adhesives to sound den-tin were significantly higher than to the caries-affected one (P<0.001), besides, bond strength of Single Bond to dentin was generally found to be higher than Adper Prompt-L-Pop adhesive (P<0.001).The interaction effect was not significant (P=0.116)Conclusion: Bond strength to caries-affected dentin was compromised when one and two step adhesives were used