effect of co2 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.