Objectives: To determine the optimal curing time, laser curing tip diameter and bond strength of orthodontic adhesives polymerized by argon laser. Methods: Metal brackets were bonded to 60 extracted human premolars, divided into 5 treatment groups(n=12): Light-cured 40 sec; 1mm laser-tip 10 sec; 1mm laser-tip 20 sec; 10mm laser-tip 10 sec and 10mm laser-tip 20 sec. All bonded specimens were debonded within 30 min. Bracket shear bond strengths (MPa) were determined using an Instron testing machine at a crosshead speed of 1 mm/min. Bracket failure interface was determined using the modified Adhesive Remnant Index (ARI). Data were analyzed using ANOVA and Student's t-test. Results: ANOVA found significant differences among the 5 test groups (p<.0001). Light-cured 10.2 ± 0.7 MPa; Laser 1mm, 10sec 7.9 ± 0.6 MPa; Laser 1mm, 20sec 10.8 ± 0.7 MPa; Laser 10mm, 10sec 6.8 ± 0.7 MPa; Laser 10mm,20sec 10.4 ± 0.8 MPa. Significantly lower bond strength (p<.05) was found between the 10 sec laser groups as compared to the light-cured group. Significantly higher bond strength were found between the 20 sec as compared to the 10 sec laser groups. No differences were found between the 1mm and 10mm laser curing tips. Most of the bracket failure occurred between the adhesive/enamel interfaces in the 20 sec laser groups (mean ARI score 4.5) as compared to the light-cured group (mean ARI score of 3.2) Conclusions: A 20 sec cure using a 1 mm or 10 mm laser-tip produced similar bond strength to those obtained after 40 sec cure with conventional light. Supported by WVU Health Associates.

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