Effect of hydrofluoric acid surface treatments on micro-shear bond strength of CAD/CAM ceramics

Dental ceramics are appreciated as highly esthetic restorative materials that can simulate the appearance of natural dentition better than other materials. The aim of this study was to evaluate the effect of hydrofluoric acid concentration and etching time on micro-shear bond strength (μSBS) to IPS e.max CAD and Vita Mark II of a dual cured resin cement (Panavia F2.0).

This study was an experimental in vitro study, performed in the dental material research center of Babol University of Medical Sciences in 2016. Two hydrofluoric acid concentrations (5% and 10%) and three different etching times (20, 60 and 120 seconds) were used to etch the specimens respectively. A silane coupling agent (Clearfil porcelain activator) and priming and bonding agent (Clearfil SE bond) were used on the etched surfaces in accordance to the manufacturer's instructions of use. Then resin cement was applied on the prepared ceramic surfaces and light cured. μSBS between resin cement and the porcelains were measured with a universal testing machine. Mode of failure was observed with 40× magnification by means of a Stereo microscope. Data were analyzed with ANOVA and independent-samples t-test and Chi-square tests.

In both e.max and Vita Mark II groups, μSBS were not significantly different when different etching times (one-way ANOVA) and HF acid concentrations (Independent-samples t-test) were used (p>0.05), but the highest μSBS was shown in e.max specimens etched 60 s with 5% HF and Vita Mark II specimens etched 20 s with 10% HF. μSBS of e.max was significantly higher than Vita Mark II (p=0.00).

Best surface treatment for e.max and Vita Mark II ceramics is 20 s etch using 5 % hydrofluoric acid.