Effect of different laser surface treatment on microshear bond strength between zirconia ceramic and resin cement

Aim: The purpose of this study was to evaluate the effect of sandblasting, carbon dioxide (CO2), and erbium, chromium: yttrium-scandium-gallium-garnet (Er, Cr: YSGG) lasers on the microshear bond strength of zirconia to resin cement. Methods: Sixty-one sintered yttria stabilized tetragonal zirconia blocks (10 x 5 x 2 mm) were prepared and divided into four experimental groups (n = 15); one sample was retained as a control. The samples were treated by aluminium oxide air abrasion, CO2 4 W, Er, Cr: YSGG 3W, and Er, Cr: YSGG 2W, respectively. One sample from each group and the control sample were analyzed by scanning electron microscope. Panavia F2.0 resin microcylinders were prepared and placed on treated surfaces, light cured, and incubated for 48 h. Microshear bond strength testing was done by a microtensile tester machine, and the type of bond failures were determined by stereomicroscope. Data were analyzed by one-way ANOVA and Tukey's test at a significance level of P < 0.05. Results: Air abrasion showed the highest microshear bond strength (P < 0.05) among all groups. CO2 and Er, Cr: YSGG 3W laser showed significantly higher bond strength than Er, Cr: YSGG 2W (P < 0.05). Apparent micromechanical roughening and irregularities were seen in the air abrasion-treated samples, and the bond failure was mostly mixed type. In the laser-treated surfaces, the roughness was much less than the air abrasion-treated surfaces, and the mode of failure was almost pure adhesive. Conclusion: Air abrasion has a greater effect than CO2 and Er, Cr: YSGG lasers in the treatment of zirconia ceramic surfaces to enhance the bonding strength of resin cement to zirconia. CO2 laser at 4W and Er, Cr: YSGG laser at only 3-W output power can be regarded as surface treatment options for roughening the zirconia surface to establish better bond strength with resin cements.