ORIGINAL ARTICLE Effect of argon laser curing on the shear bond strength of metal brackets bonded with light-cured glass ionomer cement Glaucio Serra, a Aldo Brugnera, b Carlos Nelson Elias, c and Ana Maria Bolognese d Rio de Janeiro and São Paulo, Brazil Introduction: The purpose of this study was to evaluate the shear bond strength and debonding characteristics of glass ionomer cement cured with an argon laser. Methods: Thirty extracted first premolars were divided into 2 groups of 15. The teeth were cleaned and mounted in resin, and metal brackets were bonded with glass ionomer cement. In the control group, the bond was cured with a halogen light for 40 seconds (20 seconds mesial and 20 seconds distal). In the test group, the specimens were cured with an argon laser for 5 seconds. Brackets were debonded in shear; bond strength was measured, and the adhesive remnant index was scored. Results: The difference in mean shear bond strength was not statistically significant between groups when compared with a t test. More adhesive remained on the enamel surface in the laser group than in the control group. Conclusions: Argon laser curing produces bond strengths equivalent to those obtained with traditional light curing in much less time, but it leaves more adhesive on the tooth surface. (Am J Orthod Dentofacial Orthop 2005;128:740-3) S ince their introduction to dentistry in the 1960s, many uses have been found for lasers, 1 including applications in orthodontics. The argon laser was introduced in the 1990s. In 1993, Hicks et al 2 reported that enamel demineralization induced with 37% phos- phoric acid could be reduced if the teeth were first exposed to the argon laser. 2 Later, the same authors combined the argon laser with fluoride treatment and concluded that applying fluoride after laser exposure significantly increased the resistance to demineraliza- tion. 3 Shanthala 4 compared bond strengths when compos- ite resin was cured with visible light and with an argon laser and concluded that the argon laser produced higher shear bond strengths. 4 Lalani et al 5 evaluated the bonding of metal brack- ets cured with the argon laser or halogen light and found that curing time was shortened by 87.5% with the argon laser and there were no statistical differences in shear bond strength or adhesive remnant index scores. 5 Talbot et al 6 varied the laser intensity and found that argon laser bonding could reduce curing time by 75%. They reported that laser curing after regular curing resulted in greater bond strength and that a power of 200 to 300 mW should be used for efficient curing. Pulpal histology from in-vivo testing confirms that the argon laser, when used at the energy levels recom- mended for restorative dentistry applications, creates neither short-term nor long-term pulpal pathology. 7 Glass ionomer cement can be used with the argon laser for orthodontic bonding. 8-11 The physical-chemi- cal adhesion of the cement to enamel improves biocom- patibility and has anticariogenic effects because fluo- ride is released by ionic dissolution around the bond. However, the cement has a short working time and a long setting time. 11-13 The development of photo-cured glass ionomers led to greater working and curing times. 10,11 The purpose of this study was to evaluate the shear bond strength and debonding characteristics of metal brackets bonded with glass ionomer to human premo- lars and cured with an argon laser. MATERIAL AND METHODS Thirty extracted first premolars were selected. The soft tissues were removed, and the teeth were evaluated under halogen light 12 to determine their soundness. The teeth were stored in 0.1% thymol dissolved in distilled water and held at 31°C  1°C. 13,14 They were randomly divided into 2 groups of 15 teeth each: a a Private practice, Rio de Janeiro, RJ, Brazil. b Chairman of biomedical laser center, IPD-UNIVAP, São José dos Campos, São Paulo, Brazil. c Professor, University Federal Fluminense, Rio de Janeiro, Brazil. d Professor, Department of Orthodontics, University of Brazil (UFRJ), Rio de Janeiro, RJ, Brazil. Reprint requests to: Glaucio Serra, Av Nossa Senhora de Copacabana 1355, Apartment 805, Copacabana, Rio de Janeiro, RJ, Brazil; e-mail, dr.g.serra@ medcenter.com. Submitted, February 2004; revised and accepted, August 2004. 0889-5406/$30.00 Copyright © 2005 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2004.08.021 740