406 S ince Newman 1 published the ﬁrst clinical report concerning successfully using epoxy adhesive in directly bonding orthodontic brackets to teeth, bonding has routinely replaced the former system of cementing bands. Composite resins have become the material of choice for bonding brackets. However, composite resins require a completely dry environ- ment 2-8 and enamel etching with 35% to 40% phos- phoric acid to dissolve the superﬁcial layer of the enamel (8-15 µ m). 8 Enamel loss occurs not only during etching but also during debonding procedures. Brown and Way 9 and Thompson and Way 10 have estimated the total loss at 30 to 60 µ m. Diedrich 11 estimated that 150 to 160 µ m of enamel loss can occur after debonding. Recently, interest has developed in the use of glass ionomer cements (GICs) as orthodontic bonding agents. Their use for directly bonding orthodontic brackets was described by White 12 in 1986, and since then GICs have been assessed by a number of other authors. 13-16 GICs have excellent physico-chemical interactions with enamel surfaces without acid etching 17 and a low sensitivity to a moist environment. They both release ﬂuoride and absorb it from ﬂuoridated toothpaste; this could reduce the risk of decalciﬁcation at the periphery of the brackets. 18-20 Some in vivo studies have reported that plaque samples taken from around glass ionomer restorations 21,22 or around brackets cemented with a Assistant Professor, Department of Biomaterials, Faculty of Dental Surgery, University of Paris V, Montrouge, France. b Specialist Orthodontist in private practice, Paris, France. c Senior Lecturer, Department of Biomaterials, Faculty of Dental Surgery, Uni- versity of Paris V, Montrouge, France. Reprint requests to: Dr. Laïla Hitmi, Department of Biomaterials, Faculté de Chirurgie Dentaire, Université Paris V, 1 Rue Maurice Arnoux, F-92120, Mon- trouge, France; e-mail, hitmi@odontologie.univ-paris5.fr. Submitted, July 2000; revised and accepted, December 2000. Copyright © 2001 by the American Association of Orthodontists. 0889-5406/2001/$35.00 + 0 8/1/115931 doi:10.1067/mod.2001.115931 ORIGINAL ARTICLE An 18-month clinical study of bond failures with resin-modiﬁed glass ionomer cement in orthodontic practice Laïla Hitmi, DDS, a Christine Muller, DDS, DipOrtho, b Magali Mujajic, DDS, DipOrtho, b and Jean-Pierre Attal, DDS, PhD c Montrouge and Paris, France The purpose of this study was to evaluate, over an 18-month period, the clinical performances of a resin- modiﬁed glass ionomer cement for bonding orthodontic brackets and to analyze various factors that inﬂuenced their survival and failure rates. Two orthodontists using the edgewise technique participated in this study; 6113 brackets, including 20 molar tubes, were bonded with Fuji Ortho LC (GC, Europe, N.V. Leuven, Belgium) in 135 patients. Ceramic, metal, and resin brackets were tested, and both operators used the same bonding method for the brackets. The survival rate and the failure rate of the brackets were evaluated. The rates were determined by operator, bracket type, tooth position in the dental arch, and age and sex of the patients. Bracket survival rates were estimated using the Kaplan-Meier test. The Cox-Mantel statistical test with a level of signiﬁcance set at 0.05 was used to compare survival curves. The chi-square test was used at a level of P < .05 to compare failure rates. The overall failure rate for the sample was 7%, and the overall survival rate was equal to 0.918. Age had no signiﬁcant inﬂuence on the failure rate (P = .07); however, it had a signiﬁcant inﬂuence on the survival rate (P < .01). The best survival rates were obtained in the groups aged 16 to 20 years (S[t] = 0.943) and older than 20 years (S[t] = 0.929). The diﬀerence between males and females was not statistically signiﬁcant in terms of failure rate ( P = .17). However, the Cox-Mantel test showed a higher bracket survival rate for the males (S[t] = 0.924) than for the females (S[t] = 0.839) (P < .00001). The inﬂuence of the operator was not statistically signiﬁcant on the failure rate (P = .08); however, it was signiﬁcant on the survival rate ( P < .0002). Location in the arch had a signiﬁcant inﬂuence on the failure and survival rates. The worst results were obtained in the upper incisors and the canines, and the best results in the lower premolars. Fifteen percent of the molar tubes failed; their survival rate was equal to 0.833. The failure rate was signiﬁcantly greater for resin brackets than for metal or ceramic brackets (P = .007). The highest survival rate was obtained with ceramic brackets (P = .0001). This in vivo study showed that bonding brackets and molar tubes with Fuji Ortho LC is compatible with clinical orthodontic practice. (Am J Orthod Dentofacial Orthop 2001;120:406-15) C E