IN-VITRO EVALUATION OF MATRIX-BOUND FLUORIDE-RELEASING ORTHODONTIC BONDING ADHESIVES

Sustained fluoride-releasing composite resins have the potential to pr event decalcification of enamel that may occur during the course of or thodontic treatment. The purpose of this study was to evaluate the pot ential of matrix-bound fluoride-releasing adhesives (MBF) for orthodon tic use by comparing the shear bond strengths (in MPa) and remnant adh esive on debonding (ARI scores) of these resins with commercially avai lable orthodontic adhesives. Two types of resins were evaluated in sep arate groups: The light-cured resins (group I) consisted of two light- cured MBF, designated resins LA and LB, and five nonfluoride releasing resins, designated LC, LD, LE, LF, and LG. The self-cured resins (gro up II) consisted of one MBF, designated resin SA, and six nonfluoride releasing resins, designated resins SE, SC, SD, SE, SF, and SG. These resins were used to attach upper right central incisor metal (foil mes h based) orthodontic brackets to 210 freshly extracted bovine incisors in groups of 15 each. Student-Newman-Keuls multiple comparison tests were performed at p < 0.05 to determine significant differences among the resin types. Resin LA was significantly higher in bond strength (( x) over bar = 27.4 MPa) compared with LD and LG ((x) over bar = 18.9, 10.7 MPa, respectively). Further, LA demonstrated a higher mean bond s trength compared with LB, LC, LE, and LF ((x) over bar = 21.9, 24.1, 2 4.3, and 20.8 MPa, respectively). Resin LB had significantly lower ARI scores ((x) over bar = 0.33) compared with LF and LG ((x) over bar = 1.20 and 1.80). LA, LB, LC, LD, and LE ((x) over bar = 0.47, 0.33, 0.6 0, 0.73, and 0.73, respectively) were not significantly different in t heir ARI scores. Resin SE demonstrated significantly lower bond streng th ((x) over bar = 17.2 MPa) compared with SC, SD, SE, SF, and SG ((x) over bar = 23.9, 23.7, 23.4, 23.8, and 22.9 MPa, respectively). Resin SA ((x) over bar = 19.0 MPa) was not significantly different in bond strength from SE, SC, SD, SE, SF, and SG. Resin SA demonstrated signif icantly lower ARI scores (x = 0.73) compared with SD and SE ((x) over bar = 2.13 and 1.87). Resin SA had lower mean ARI scores compared with SE, SC, SF, and SG ((x) over bar = 1.00, 1.27, 1.13 and 0.87, respect ively). Sustained fluoride-releasing (matrix-bound) orthodontic adhesi ve systems demonstrated bond strength and ARI scores that compared fav orably with commercially available orthodontic adhesives.