Isfahan University of Medical SciencesDental Research Journal1735-33279320120821Evaluation of shear bond strength of orthodontic brackets bonded with Er-YAG laser etching10861086ENS. HamidRajiRezaBirangFatemeMajdzadeDepartments of Orthodontics,, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran. fmajdzade@yahoo.comRezaGhorbanipour20120821Background: Based on contradictory findings concerning the use of lasers for enamel etching,the purpose of this study was to investigate the shear bond strength of teeth prepared for bondingwith Er-YAG laser etching and compare them with phosphoric acid etching.Materials and Methods: In this in vitro study forty – eight premolars, extracted for orthodonticpurposes were randomly divided in to three groups. Thirty-two teeth were exposed to laser energyfor 25 s: 16 teeth at 100 mj setting and 16 teeth at 150 mj setting. Sixteen teeth were etched with37% phosphoric acid. The shear bond strength of bonded brackets with the Transbond XT adhesivesystem was measured with the Zwick testing machine. Descriptive statistics, Kolmogorov–Smirnovtest, of homogeneity of variances, one- way analysis of variances and Tukey’s test and Kruskal Walliswere used to analyze the data.Results: The mean shear bond strength of the teeth lased with 150 mj was 12.26 ± 4.76 MPa, whichwas not significantly different from the group with acid etching (15.26 ± 4.16 MPa). Irradiation with100 mj resulted in mean bond strengths of 9.05 ± 3.16 MPa, which was significantly different fromthat of acid etching (P < 0.001).Conclusions: laser etching at 150 and 100 mj was adequate for bond strength but the failurepattern of brackets bonded with laser etching is dominantly at adhesive – enamel interface and isnot safe for enamel during debonding.Key Words: Acid etching, bond strength, Er-YAG laser, orthodontic brackets