ORIGINAL ARTICLE Porcelain surface treatment by laser for bracket-porcelain bonding Tolga Akova, a Oguz Yoldas, b M. Serdar Toroglu, c and Hakan Uysal d Balcali, Adana, Turkey Introduction: The purposes of this study were to investigate the effect of laser irradiation on the adhesion of brackets bonded to feldspathic porcelain and to compare it with brackets bonded with conventional techniques. Methods: One hundred porcelain-fused-to-metal specimens were divided into 10 groups of 10. The treatment groups were sandblasted (SB), sandblasted with silane (SB+S), orthophosphoric acid (OFA), orthophosphoric acid with silane (OFA+S), hydrofluoric acid (HFA), hydrofluoric acid with silane (HFA+S), laser etched (L), laser etched with silane (L+S), glazed (Control 1/C1), and deglazed (Control 2/C2). Five other specimens were irradiated by 2-, 3-, 5-, 10-, and 15-watt superpulse carbon dioxide (CO 2) laser for 20 seconds and examined by scanning electron microscopy. Metal brackets were bonded with a self-cure composite material and the specimens were stored in water at 37°C for 24 hours and then thermocycled in water baths between 5°C and 55°C 500 times. Bond strength was determined in megapascals (MPa) by shear test at 1 mm/minute crosshead speed. Bond failure modes were observed under stereomicroscope. For the statistical analysis, 1-way ANOVA and Tamhane post hoc test were used. Results: Statistical analysis showed significant differences between the groups at the .05 level. The HFA+S group yielded the highest mean strength (15.07  1.44). This was followed by SB+S (13.81  2.00), HFA (10.78  0.62), OFA+S (10.73  1.12), L+S (8.25  0.90), L (6.26  0.58), C2 (2.45  0.54), OFA (2.36  0.41), SB (2.04  0.41), and C1 (1.64  0.33). The bond failure modes of HFA and silane groups, except L+S, were cohesive in porcelain. Control groups and other test groups showed adhesive failure. Only irradiation by 2 watts for 20 seconds provided a porous surface texture without cracks. Conclusions: Two-watt/20second superpulse CO 2 laser irradiation might be an alternative conditioning method for pretreating ceramic surfaces. Increased bond strength can be achieved by silanation after CO 2 laser irradiation. (Am J Orthod Dentofacial Orthop 2005;128: 630-7) T he demand for adult orthodontic treatment has been gradually increasing. Because many adult patients have porcelain crowns or bridges, ortho- dontists are faced with the problem of bonding brackets onto porcelain surfaces. Optimal bracket adhesion to a porcelain surface requires that orthodontic forces be applied without bond failure during treatment and that the porcelain integrity not be jeopardized during the debonding procedure. Porcelain is not appropriate for orthodontic bonding because of the physical properties of glazed surfaces and the chemical properties of bonding resins. Various techniques have been suggested for surface treatment of porcelain before bonding attachments, including de- glazing the porcelain by roughening the surface with a diamond bur or microetching with aluminum oxide particles and then bonding the brackets with or without a coupling agent, 1 and chemical preparation of the previously deglazed porcelain surface by etching with orthophosphoric (OFA) or hydrofluoric acid (HFA) and then bonding the brackets with or without a coupling agent. 2 However, previous studies have indicated that sandblasting and acid-etching with OFA produces in- sufficient bond strength for clinical requirements. 2-6 Bond strength with hydrofluoric acid etching has been shown to have clinically acceptable values, but the danger of acid burns must be considered. 2,7 Studies on the use of a silane coupling agent have presented evidence of increased bond strength of brackets to porcelain 8,9 but have also shown the risk of cohesive failure during debonding. 3,10 These laboratory findings are not meant to be clinical recommendations because many environ- mental factors can influence the bond strength of brackets to ceramic in vivo. Laboratory findings, however, can be used to indicate which products and From Cukurova University, Turkey. a Research assistant, Department of Prosthodontics. b Assistant professor, Department of Endodontics and Operative Dentistry. c Assistant professor, Department of Orthodontics. d Associate professor, Department of Prosthodontics. Reprint requests to: Dr Tolga Akova, Cukurova Universitesi, Dishekimligi Fakültesi Protetik Dis Tedavisi Ab.D., Adana, Turkey; e-mail: akovat@cu.edu.tr. Submitted, November 2003; revised and accepted, February 2004. 0889-5406/$30.00 Copyright © 2005 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2004.02.021 630