About 4 million people in the US wear braces to help correct the alignment of their teeth. Bonding of the orthodontic brackets, the part attached to each tooth, is important for effective treatment. Bracket failure may extend treatment time and increase oral health risks, such as irreversible enamel decalcification. Light-cured adhesives for bonding the brackets to the enamel have proved to be strong. Dr. Paul W. Major from the University of Alberta in Calgary, Canada, and his colleagues compared the bracket-bonding strength of an argon laser with that of conventional curing light because argon lasers work about four times faster than conventional curing light. As reported in the April issue of the American Journal of Orthodontics and Dentofacial Orthopedics, the scientists conducted both an in vivo study of 23 patients who each needed four premolar extractions and an in vitro study of 25 patients who each needed four premolar extractions. In the in vivo study, the researchers randomly assigned each patient to either argon laser curing, which takes 10 seconds per bracket, or to conventional light curing, which takes 40 seconds per bracket. Both curing devices were held about 3 mm away from the tooth surface at a 45° angle. Shear bond strengths were measured after 14 days with custom-designed debonding pliers. The premolars were extracted after the study.By contrast, the tooth extractions were performed at the beginning of the in vitro study. The sets of teeth were randomly assigned to either bonding method. The brackets were bonded in the same way as in the in vivo study, but the teeth, along with their brackets, were stored in distilled water for 14 days after treatment to imitate the oral environment. The shear bond strengths were measured with the debonding pliers.The researchers found no significant differences in bond strength between the two light-curing methods. They therefore believe that argon laser curing is comparable to conventional light curing and can be used in clinical applications.