Effect of dentin surface roughness on the shear bond strength of resin bonded restorations

PURPOSE: This study aimed to investigate whether dentin surface preparation with diamond rotary instruments of different grit sizes affects the shear bond strength of resin-bonded restorations. MATERIALS AND METHODS: The buccal enamel of 60 maxillary central incisors was removed with a low speed diamond saw and wet ground with silicon carbide papers. The polished surfaces of the teeth were prepared with four groups of rotary diamond burs with super-coarse (SC), coarse (C), medium (M), and fine (F) grit sizes. Following surface preparation, 60 restorations were casted with nickel-chromium alloy and bonded with Panavia cement. To assess the shear bond strength, the samples were mounted on a universal testing machine and an axial load was applied along the cement-restoration interface at the crosshead speed of 0.5 mm/min. The acquired data was analyzed with one way ANOVA and Tukey post hoc test (α=.05). RESULTS: The mean ± SD shear bond strengths (in MPa) of the study groups were 17.75 ± 1.41 for SC, 13.82 ± 1.13 for C, 10.40 ± 1.45 for M, and 7.13 ± 1.18 for F. Statistical analysis revealed the significant difference among the study groups such that the value for group SC was significantly higher than that for group F (P<.001). CONCLUSION: Dentin surface roughness created by diamond burs of different grit sizes considerably influences the shear bond strength of resin bonded restorations.