ORIGINAL ARTICLES Evaluation of fluoride release from an orthodontic bonding system Samir E. Bishara, DDS, BDS, D. Orth., MS,* Edward J. Swift, Jr., DMD, MS,** and Daniel C. N. Chan, DDS, MS*** Iowa City, Iowa, and San Antonio, Texas Decalcification around brackets is sometimes observed after orthodontic treatment. Fluoride-releasing orthodontic adhesives have been developed in an attempt to reduce the frequency and severity of decalcification. This study evaluated, in vitro, a light-activated, fluoride-releasing composite resin adhesive, FluorEver OBA. The findings indicate that FluorEver OBA released small concentrations of fluoride ions over time. A mean of 2.6 ppm was released on day 1, decreasing to a mean of 0.42 ppm by day 2 and to 0.04 ppm by day 43. The clinical implications of these findings are discussed. (AM J ORTHOD DENTOFAC ORTHOP1991;100:106-9.) In their attempt to minimize the incidence of decalcification around orthodontic appliances, ortho- dontists have always emphasized the need for good oral hygiene. The role of fluoride in preventing caries has been well documented, t'2 As a result, the application of fluoride solutions topically to the etched tooth during bonding and the use of fluoride rinses during treatment have been suggested as means of reducing enamel de- calcification.3 Since decalcification around orthodontic brackets and bands is a particularly frustrating and all-too- common problem, 4 several fluoride-releasing cements have been developed and used clinically to reduce de- calcification.5-7 In discussing fluoride-releasing materials, Gwinnett and Ceen 8 recommended that fluoride availability should be independent of patient cooperation and that the fluoride ion should diffuse or dissolve over a pro- longed period. In addition, it would be beneficial if the fluoride ion release were site specific to those areas most susceptible to demineralization, namely, adjacent to bonded orthodontic brackets. Fluoride-releasing resins have been studied for more than 30 years. 9t3 Underwood et al. t4 examined in vivo, the durability and caries-inhibition properties of a fluoride-exchanging resin for 60 days after bonding. They concluded that the fluoride-exchanging resin has *Professor, Department of Orthodontics, College of Dentistry, The University of Iowa. **Assistant professor, Department of Operative Dentistry, College of Dentistry, The University of Iowa. ***Assistant professor, Division of Operative Dentistry, Department of Re- storative Dentistry, The University of Texas Heahh Science Center. 811123996 106 a caries-preventive potential and reduces the incidence of very early demineralization of enamel surrounding orthodontic appliances. Commercial products, including composite resin orthodontic adhesives, have beerl introduced for clinical use. A fluoride-containing orthodontic bonding system, was recently removed from the market because of an increased incidence of bond failures. The resin initially released fluoride in very small amounts, with no mea- surable fluoride release detected after 3 days. t6 Another composite resin, FluorEver OBA (Macro- Chem Corporation, Billerica, Mass.), has recently be- come available. Accm'ding io the manufacturer, fluo- ride ions encapsulated in the resin are released by a diffusion or dissolution mechanism. In a studyby Sonis and Snell, 15a decrease in the amount of decalcification around orthodontic brackets bonded with FluorEver OBA was reported. They also reported that the fluoride- releasing resin provided bracket retention rates similar to those of conventional orthodontic bonding systems over a 2-year period. Since FluorEver orthodontic adhesive is light acti- vated, metal brackets may not allow sufficient light penetration for'adequate conversion of composite. A recent comprehensive study by Chan et al.'7 evaluated various properties of FluorEver OBA, including fluo- ride release, tensile bond strength, and polymerization through metal brackets. They concluded that the tensile bond strength of the fluoride-releasing resin was sig- nificantly less than the conventional resin at 2 and 42 days after bonding. In addition, Chan et al.t7 found that the composite resins were harder in areas outside the brackets, regardless of the exposure time. There is presently little information on the concen-