Effect of argon laser irradiation on shear bond strength of orthodontic brackets: an in vitro study

Argon lasers, due to their significant time savings over conventional curing lights, are being investigated for use in bonding orthodontic brackets. They are also being investigated for their ability to confer demineralization resistance on enamel. The purpose of this study was to evaluate the effects of argon laser irradiation on bond strength at 3 different laser energies (200, 230, and 300 mW) and at 3 unique time points of laser application (before, during, or after bracket placement). One hundred-fifty human posterior teeth were divided into 9 study groups and 1 control group. After debonding, the adhesive remnant index was scored for each tooth. There was no evidence of an effect of energy level on bond strength, P =.903, or of an interaction between timing of bracket placement and energy level, P =.858. When combining data across energy levels, the mean bond strength was significantly different between all 3 bracket placement groups, P <.001. In addition, the mean bond strength of teeth lased after bonding was significantly higher than the control group, P <.05. There were no statistically significant differences between adhesive remnant index scores among the 10 groups. Lasing the enamel before or after bonding does not adversely affect bond strength. Use of the argon laser to bond orthodontic brackets can yield excellent bond strengths in significantly less time than conventional curing lights, while possibly making the enamel more resistant to demineralization.