Effect of Laser irradiation on the shear bond strength of zirconia ceramic surface to dentin

ABSTRACT

Reliable bonding between tooth substrate and zirconia-based ceramic restorations is always of great importance. The laser might be useful for treatment of ceramic surfaces. The aim of the present study was to investigate the effect of laser irradiation on the shear bond strength of zirconia ceramic surface to dentin. In this experimental in vitro study, 40 Cercon zirconia ceramic blocks were fabricated. The surface treatment was performed using sandblasting with 50-micrometer A12O3, CO[2] laser, or NdYAG laser in each test groups. After that, the specimens were cemented to human dentin with resin cement. The shear bond strength of ceramics to dentin was determined and failure mode of each specimen was analyzed by stereo-microscope and SEM investigations. The data were statistically analyzed by one-way analysis of variance and Tukey multiple comparisons. The surface morphology of one specimen from each group was investigated under SEM. The mean shear bond strength of zirconia ceramic to dentin was 7.79 +/- 3.03, 9.85 +/- 4.69, 14.92 +/- 4.48 MPa for CO[2] irradiated, NdYAG irradiated, and sandblasted specimens, respectively. Significant differences were noted between CO[2] [P=0.001] and NdYAG laser [P=0.017] irradiated specimens with sandblasted specimens. No significant differences were observed between two laser methods [P=0.47]. The mode of bond failure was predominantly adhesive in test groups [CO[2] irradiated specimens 75%, NdYAG irradiated 66.7%, and sandblasting41.7%]. Under the limitations of the present study, surface treatment of zirconia ceramics using CO[2] and NdYAG lasers was not able to produce adequate bond strength with dentin surfaces in comparison to sandblasting technique. Therefore, the use of lasers with the mentioned parameters may not be recommended for the surface treatment of Cercon ceramics