Micro-Shear Bond-Strength of Resin-Inlays to Different Enamel Regions

Objectives: The purpose of this study was to evaluate the micro-shear bond-strength (”-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) 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) were fabricated indirectly and cemented with the M-Bond and Super-Bond C&B according to the manufacturer's instructions. After 24-hours or one-week storage in 37 șC 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, whereby a shear force was applied to the bonded interface. Number of the specimens was 10 for each group. The data of shear bond-strengths were analyzed by three-way ANOVA and T-test at 95% level of confidence. Results: Regional ”-SBSs to enamel are given below (Mean ± SD in MPa). Three-way ANOVA revealed that the ”-SBS values were influenced by enamel regions & storage periods (p<0.05), however, they were not influenced by material groups (p>0.05).

Materials		M-Bond		Super-Bond C&B
Substrate		Enamel		Enamel
Regions		Mid-coronal	Cervical	Mid-coronal	Cervical
Storage periods	1-day	31.2 ± 4.70	25.2 ± 3.56	33.0 ± 7.32	25.5 ± 5.36
	1-week	30.7 ± 7.30	24.3 ± 3.09	25.7 ± 5.75	20.9 ± 5.08

Conclusion: Difference of one-week curing periods did not affect on the ”-SBS but difference of the enamel regions affected on the ”-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.