Evaluation of Cavity-wall Property and Bond Strength Using Iris Method

Objectives: It was hypothesized that in the class¥°cavity reproduced by unique dentin iris method, the polymerization stress resulting from the cavity wall property during polymerization of composite resin may affect the nominal shear bond strength values. The aim of this study is to evaluate the effect of cavity wall property on the shear bond strength(SBS) using different types of iris - metal and dentin. Methods: 96 caries-free human third molars were used. Stainless-steel metal iris(M) and dentin iris(D) which have a hole of 1mm and 3mm in diameter, respectively, were used as a mold for composite resin. Eight experimental setups (n=12) were used to simulate different levels of cavity wall property representing by iris and two bonding agents (Scotchbond^TM Multi-purpose(SBMP);3M ESPE and Xeno^¢ç¬º;Dentsply). After positioning the iris on dentin surface, Z-250 composite resin (3M ESPE) was packed and light-cured. After 24 hours, SBS were measured at a crosshead speed of 1.0 mm/min. The fractured surfaces were examined under microscope and SEM. The results were analyzed by an One-way ANOVA and t-test (p < 0.05). Results: The SBSs in MPa were SBMP: 41.77(7.04)(M1), 35.84(10.33)(M3), 34.30(15.77)(D1), 15.39(7.60)(D3), Xeno^¢ç¬º: 23.03(8.86)(M1), 18.88(6.39)(M3), 22.87(8.92)(D1), 10.68(3.10)(D3). The fractured surfaces showed mostly adhesive failures and no cohesive failure in dentin. Conclusion: The D3-group showed the lowest shear bond strength in both bonding agent groups. Among the SBMP groups, there was no statistical difference between M1, M3, D1-groups(P>0.05). Among the Xeno^¢ç¬º groups, there was no statistical difference among M1, M3, D1-groups and among M1, D3-groups, respectively(P>0.05). The SBSs of Xeno^¢ç¬º groups were significantly lower than those of SBMP groups in all types of iris groups(p<0.05) except in the D3-groups ( P=0.066). There was no cohesive failure in dentin in this study. Supported by the KSEF through IBEC at SNU.