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 curin g lights, are being investigated for use in bonding orthodontic brackets. T hey are also being investigated for their ability to confer demineralizatio n resistance on enamel. The purpose of this study was to evaluate the effec ts of argon laser irradiation on bond strength at 3 different laser energie s (200, 230, and 300 mW) and at 3 unique time points of laser application ( before, during, or after bracket placement). One hundred-fifty human poster ior teeth were divided into 9 study groups and 1 control group. After debon ding, the adhesive remnant index was scored for each tooth. There was no ev idence of an effect of energy level on bond strength, P=.903, or of an inte raction between timing of bracket placement and energy level, P=.858. When combining data across energy levels, the mean bond strength was significant ly different between all 3 bracket placement groups, P <.001. In addition, the mean bond strength of teeth lased after bonding was significantly highe r than the control group, P <.05. There were no statistically significant d ifferences between adhesive remnant index scores among the 10 groups. Lasin g the enamel before or after bonding does not adversely affect bond strengt h. 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.