Shear-Bond Strength of Resin-Inlays Bonded to Mid-Coronal and Cervical Enamel

Objectives: The purpose of this study was to evaluate the micro-shear bond strength (µ-SBS) of resin inlays bonded with a MMA-based resin cement to mid-coronal and cervical regions of human enamel. Methods: Commercially available MMA-based resin cement (M-Bond, Tokuyama Dental Corp.) with a self-etching primer system was investigated. Two regions of enamel, mid-coronal and cervical, were chosen from the buccal surface of extracted molars. Wet # 600-grit SiC paper was used to create flat surfaces with a uniform smear layer thickness. Hybrid composite inlays (Estenia, Kuraray Medical Inc.) were fabricated indirectly and cemented with the M-Bond according to the manufacturer's instructions. After 24-hours or one-week's storage in 37 degrees C water, the bonded inlays were subjected to a micro-shear bond test, whereby a shear force was applied to the inlays at a crosshead speed of 1 mm/minute until failure occurred. Number of the specimens was 10 for each group. The data were statistically analyzed using two-way ANOVA and T-test, with significance defined as p<0.05. Results: Regional µ-SBSs to enamel are given below (Mean ± SD in MPa).

Two-way ANOVA revealed that the µ-SBS values were influenced by enamel region groups (p<0.05), however they were not influenced by the one-day and one-week storage periods (p>0.05) of the specimens. Conclusions: Difference of one-week curing periods did not affect on the µ-SBS but difference of the enamel regions affected on the µ-SBS of M-Bond. The cervical enamel showed significantly lower bonding than mid-coronal enamel (p<0.05) in each time period. The bond strength of indirect restorations to cervical enamel was lower than mid-coronal enamel.