Methods: Healthy human third molars were sectioned into 1.5 mm slices. Clearfil Tri-S Bond (kuraray-japan) was applied on the prepared dentin surfaces according to the manufacturer,s instruction. Clearfil AP-X (kuraray-japan) composite resin inserted in 0.75 mm x 1 mm tubes was placed and light cured on the prepared dentin. The samples were randomly divided into three subgroups and subjected to 0, 3000 and 5000 thermal cycles (5 ± 2 ºC and 55 ± 2 ºC). Micro shear bond strength of samples was measured by microtensile tester (Bisco-USA). The results were compared by one-way ANOVA and multiple comparison of Tukey with confidence interval of 0.95 %.
Results: Mean micro shear bond strength of Tri-S Bonding agent was 19.27 ± 4.56 (in 0 cycles), 17.00 ± 6.52 (in 3000 cycles) and 11.58 ± 4.64 (in 5000 cycles). The data analysis with ANOVA test indicated that decrease in strength between 0, 3000, is not statistically significant. However, there are significant decrease in strength between 3000 and 5000 or 0 and 5000 cycles (p< 0.002 and p< 0.03).
Conclusions: In the condition of this study thermal cycles more than 3000, reduces Tri-S bonding micro shear bond strength.