Effect of Thermocycling on Microleakage of Class V Resin Composite Restorations Bonded by Self and Total Etch Bondings

Thermocycling is used in most invitro studies to produce conditions similar to clinical studies, but results about the effect and number of thermocycling cycles have been different in different studies. The purpose of this study was to evaluate the effect of thermocycling on microleakage of self and total etch bondings in class V resin composite restorations. A total of 80 anterior bovine teeth were collected and class V cavities were prepared with incisal and gingival margins in enamel and dentin. The teeth were randomly divided into two groups. In the first group, prompt L-pop(PLP) and in second group, singlebond(SB) was applied and restored with Z250 resin composite. Each group was divided to four subgroups with zero, 500, 1000, 2500 cycles of thermocycling at 5-55° c. Then the teeth were sealed and immersed in 50% silver nitrate followed by a developer solution for 16 hours. Microleakage rate was evaluated by stereomicroscope with 25x magnification. Data was analyzed by Mann-Whitney and Wilcoxon tests. Both SB and PLP groups showed microleakage. Statistical analysis showed significant difference between enamel and dentin margins of PLP group with 1000 cycles(p=0.02), 2500(p=0.014) and in SB with 2500 cycles P=0.046). Statistical analysis showed significant difference in incisal and cervical margins of SB and PLP groups (p=0.013) (p=0.001). Microleakage was seen in self etch and total etch bondings with minimum 1000 and 2500 cycles.