Microshear bond strength of resin luting agents to monolithic zirconia

The objective of this study was to evaluate the effects of different surface treatments on the microshear bond strength (μSBS) of resin cements to zirconia. Twenty-four zirconia wafers measuring 2.0 × 9.0 × 15.0 mm were sintered and randomly distributed into 3 groups based on the resin cement (n = 8): Panavia F 2.0, NX3, and RelyX Ultimate. The resin cement groups were divided into 4 subgroups based on the surface treatment: a control subgroup (air abrasion with 50-μm alumina particles) and 3 experimental surface treatments (Alloy Primer, Ea-Z-y Primer, and tribochemical silicoating using CoJet Sand). Each surface treatment was applied to the zirconia wafers according to its manufacturer's instructions. The resin cements were mixed and placed in thermoplastic tubes, producing cylinders measuring 0.8 mm in diameter × 2.0 mm in height. Five tubes containing the resin cements were placed on each of the pretreated zirconia wafers, resulting in a sample size of 10 specimens per treatment per resin cement. The luting agents were allowed to cure chemically for 4 minutes and then light cured for 30 seconds. The thermoplastic tubes were removed after 24 hours, and specimens were stored in deionized water (37°C) for 24 hours. A shear force was applied using a wire loop attached to a universal testing machine with a crosshead speed of 0.5 mm/min, and the microshear forces required for failure were recorded. The parametric data were analyzed with a 2-way analysis of variance with post hoc Tukey and Dunnett tests (P < 0.05). The mean (SD) μSBS values ranged from 3.6 (0.9) to 9.3 (2.4) MPa. Surface treatment with Alloy Primer and Ea-Z-y Primer increased the μSBS of the 3 cements compared to their controls, but the difference was not always statistically significant. CoJet Sand only increased the μSBS of Panavia F 2.0. The results suggest that the effects of different surface treatments may be specific for each cement.