Does the bonded cross-sectional surface area affect the microtensile bond strength of resin cement to glass-ceramic?

AIM: The aim of this study was to evaluate the effect of the bonded cross-sectional area on the bond strength of a resin cement to a glass ceramic. The hypothesis tested was that the decreased bonded surface area results in increased bond strength. METHODS: Twelve glass-ceramic blocks (6x6 x4 mm) (Vita VM7) were conditioned with 10% hydrofluoric acid for 1 min, washed and rinsed thoroughly and silanized. The resin cement was applied on the treated-surface and the cement-ceramic sets were sectioned to produce specimens with the bonded areas of about 0.7x0.7 mm (0.5 mm(2)-Gr1), 1x1 mm (1 mm(2)-Gr2), 1.4x1.4 mm (2 mm(2)-Gr3), which were submitted to the microtensile test. RESULTS: The results were affected significantly by bonded surface area (P<0.0001) with the highest mean value (MPa) obtained from Gr1 (26.3+/-8.2a), followed by Gr2 (20.8+/-6.5b) and Gr3 (16.1+/-5.7c) (ANOVA and Tukey's test, alpha=0.05). A negative correlation was found between the bonded surface area and the bond strength results (r=-0.5234; P<0.0001) (Pearson correlation test). Pre-test failures were more common when the bonded surface area was 0.5 mm(2). CONCLUSIONS: With the increased bonded surface area, the mean microtensile bond strength of the resin cement to the feldspathic ceramic decreased.