Effect of Er,Cr:YSGG laser parameters on shear bond strength and microstructure of dentine

Objective: The objective of this study was to investigate the effect of different Er,Cr:YSGG laser parameters on the morphology of irradiated dentine and the shear bond strength between resin composites and irradiated dentine. Materials and Methods: Dentine specimens prepared from extracted human third molars were randomly assigned to six groups, including one receiving phosphoric acid etching, and five others with different laser parameters: 5W for 30sec, 2.5W for 30sec, 2.5W for 60sec, 1.5W for 30sec, and 1.5W for 100sec. Surface morphology was examined using a scanning electron microscope (SEM). Average roughness (Ra) was determined with a profilometer. Bonding of resin composites to the dentine specimens was tested in shear mode. Results: The dentine surfaces irradiated by the Er,Cr:YSGG laser showed a scaly and rugged appearance and open dentinal tubules without smear layer production. The 5-W-irradiated group had the highest roughness value (p<0.05). One-way ANOVA revealed that the shear bond strength of resin composites to the laser-irradiated dentine ranged from 12.35-15.61MPa, and was not significantly (p>0.05) different from the bond strength seen in the acid-etched dentine of 19.06MPa. However, the surface roughness of the laser-irradiated dentine was significantly (p<0.05) higher than that of the acid-etched dentine. Conclusions: The 5-W power setting may be suitable for dental restoration applications in terms of shear bond strength and activation area.