Effect of thermo-cycling on micro-tensile bond strength of bulkfill resin composite using recent universal adhesive

Statement of the problem: bonding performance of newly launched universal adhesive recommended by the manufacturer to be used with sonically activated bulkfill resin composite need further investigation.
Materials and Methods: A total of 40 non carious human molar teeth were extracted and collected from diabetic patients for this study. The selected teeth were divided into two main groups, 20 teeth each, according to adhesive used (A). In group (A1), the adhesive system was universal one step self- etch adhesive (OptiBond Universal), while in group (A2), two steps universal self etch primer adhesive (OptiBond XTR) was applied. Each group was subdivided into two subgroups, 10 teeth each, according to whether thermocycling was carried out or not (T). Where (T0) class denotes the teeth that were not subjected to thermocycling and (T1) class denotes the teeth that were subjected to thermocycling. (SonicFill 2 bulkfill resin composite) restorative material was used with both adhesives. The teeth stored in distilled water for 24 hours before the rod specimens were prepared for the microtensile bond strength test. Two rods from each tooth were obtained. Half of the specimens of each group were subjected to theromcycling testing at 5oC± 2oC to 55oC± 2oC for 500 cycles. Microtensile bond strength test was carried out using a universal testing machine.
Results: showed that the mean microtensile bond strength of one step universal self-etch adhesive (OptiBond Universal) had statistically significantly higher value than the self-etch primer (OptiBond XTR) either with thermocycling or without thermocycling at (P <0.001). The mean microtensile bond strength of one step universal self etch adhesive had statistically significantly higher value without thermocycling than with thermocycling at (P <0.001). The microtensile bond strength test with the two steps universal self-etch primer (OptiBond XTR) adhesive showed that there was no statistically significant difference between mean microtensile bond strength either with or without thermocycling (P = 0.067).
Conclusion: The (SonicFill2) resin composite one of the recently used bulkfill resin composite restorative material performed higher bond strength with one step universal self etch adhesive more than with two steps universal self-etch primer adhesive when applied to the dentin substrate. However concerning bond stability, the SonicFill2 resin composite restorative material showed higher bond stability after thermocycling with two steps universal self etch primer more than with one step universal self etch adhesive.