Evaluation of the shear bond strength of zirconia to a self-adhesive resin cement after different surface treatment

Background. Bond stability between zirconia and a self-adhesive resin cement is a major concern, and only limited evidence about its longevity is currently available. Moreover, no study has yet comprehensively evaluated the influence of different power levels of the neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser irradiation on the shear bond strength (SBS) of zirconia to a self-adhesive resin cement. Objectives. The aim of this study was to evaluate the SBS of pre-sintered and sintered zirconia to a selfadhesive resin cement after various treatment (air abrasion and the Nd:YAG laser irradiation at varying power levels -1 W, 2 W and 3 W). Material and methods. Ninety-nine zirconia specimens were prepared and divided into 3 groups: control (with no surface treatment); and pre-sintered and sintered groups with surface treatment. Surface treatment was applied before sintering in the pre-sintered group and after sintering in the sintered group. After following all protocols, a resin cement was layered on the zirconia surface. Shear bond strength was measured using a universal testing machine. The results were subjected to the statistical analysis. The surface topography and phase transformation of zirconia were evaluated using the atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses after surface treatment. Results. The laser irradiation (3 W, 1 W and 2 W) of the pre-sintered zirconia surface resulted in the highest SBS values (p < 0.001), while the lowest SBS values were obtained with airborne particle abrasion of the pre-sintered and sintered zirconia surfaces. Conclusions. Laser irradiation increased the SBS of pre-sintered zirconia to a resin cement. Surface treatment with air abrasion had a lesser effect on the SBS values.