Effect of thermal cycling on microtensile bond strengths of various adhesives to dentin

Abstract

Objectives: The objective of this study was to evaluate the effect of thermal cycling on microtensile bond strengths (MTBS) of various adhesives to dentin. Methods: Three adhesive systems including a 1-step self-etch adhesive system (G-Bond), a 2-step self-etch adhesive system (AdheSE), and an etch&rinse adhesive system (Prime & Bond NT) were evaluated. Twenty-four extracted molars were used. After grinding the coronal enamel surface, the teeth were randomly divided into 6 groups (n=4) (G-Bond, G-Bond+thermal cycling, AdheSE, AdheSE+thermal cycling, Prime & Bond NT, and Prime & Bond NT+thermal cycling). Adhesives were applied according to each manufacturer's instructions followed by resin composite polymerization. Groups without thermal cycling were stored in distilled water at 37 °C for 24 hours and used for immediate testing of the MTBS. Groups with thermal cycling were subjected to thermocycling (10.000 cycles between 5 °C and 55 °C, for a dwell time of 30 seconds). For MTBS test, teeth were sectioned occluso-gingivally into a serial slabs and further sectioned into composite-dentin sticks. Testing was performed on a universal testing machine at a crosshead speed of 1.0 mm/min. One-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (A=0.05) were performed on all data. Results: The results of the MTBS test showed that the highest bond strengths were observed in etch&rinse adhesive groups (3 and 3T). A statistically significant difference in MTBS was found between group 1 and group 1T (p<0.05). Moreover, there was no statistical difference in MTBS between group 1 and group 2 (p=1.000). Conclusions: Contrary to result with 1-step self-etch adhesive, thermal cycling was found ineffective on the MTBS of the 2-step self-etch and etch&rinse adhesive systems.