Effect of CO(2) and Nd:YAG Lasers on Shear Bond Strength of Resin Cement to Zirconia Ceramic

OBJECTIVES: Because of poor bond between resin cement and zirconia ceramics, laser surface treatments have been suggested to improve adhesion. The present study evaluated the effect of CO(2) and Nd:YAG lasers on the shear bond strength (SBS) of resin cement to zirconia ceramic. MATERIALS AND METHODS: Ninety zirconia disks (6×2 mm) were randomly divided into six groups of 15. In the control group, no surface treatment was used. In the test groups, laser surface treatment was accomplished using CO(2) and Nd:YAG lasers, respectively (groups two and three). Composite resin disks (3×2 mm) were fabricated and cemented to zirconia disks with self-etch resin cement and stored in distilled water for 24 hours. In the test groups four-six, the samples were prepared as in groups one-three and then thermocycled and stored in distilled water for six months. The SBS tests were performed (strain rate of 0.5 mm/min). The fracture modes were observed via stereomicroscopy. Data were analyzed with one and two-way ANOVA, independent t and Tukey’s tests. RESULTS: The SBS values of Nd:YAG group (18.95±3.46MPa) was significantly higher than that of the CO(2) group (14.00±1.96MPa), but lower than that of controls (23.35±3.12MPa). After thermocycling and six months of water storage, the SBS of the untreated group (1.80±1.23 MPa) was significantly lower than that of the laser groups. In groups stored for 24 hours, 60% of the failures were adhesive; however, after thermocycling and six months of water storage, 100% of failures were adhesive. CONCLUSION: Bonding durability of resin cement to zirconia improved with CO(2) and Nd:YAG laser surface treatment of zirconia ceramic.