Objectives: this study aimed to evaluate the thermocycling effect on shear bond strength of two different adhesive systems.
Materials and Methods: The study was performed on 60 extracted human molar teeth, randomly divided into two equal groups. In Group I, conventional light cure adhesive system was used for bonding molar tube. While, Group II was bonded with single component adhesive system. Specimens from each group were thermocycled between 5 and 55oC for 1000 cycles. Teeth in all groups were deboned using a universal testing machine. Student's t- test was used to compare the shear bond strength between the groups. Scanning electron microscope was used to evaluate the depth of resin tag penetration.
Results: The mean shear bond strength of group I was (15.9 +/- 3.4 Mpa) and that for group II was (13.1 +/- 3.9 Mpa).There was a statistically significant difference between the two groups (p= 0.04).The result of student's t- test comparisons of shear bond strength of group I and II following thermocycling indicated that there was a statistically significant difference where (p= 0.02), (p= 0.01) respectively. The comparison of resin tag penetration showed that there was a statistically significant difference between the two groups (p= 0.0003).
Conclusion: Conventional adhesive group had a significantly higher mean shear bond strength than single component adhesive group. The mean shear bond strength value was significantly decreased following thermocycling at both adhesives. The depth of resin tag penetration at conventional adhesive group was higher than the single component adhesive group.