COMPARISON OF SHEAR BOND STRENGTH OF NEW AND REBONDED SYMETRI™ CLEAR CERAMIC BRACKETS

Abstract

Objective: The purpose of this study was to compare the shear bond strength of the Symetri™ Clear brackets bonded initially to enamel versus after rebonding. An additional aim was to see how a generic debond pliers compares to the Symetri™ Debonding pliers in terms of shear bond strength and bracket morphology after debond. Methods: Sixty extracted premolars and nine extracted canines were collected and stored in 1% Chloramine T solution. The canines were used for a pilot study to test methodology. The premolars were randomly assigned to one of three Groups: Group 1 (single bond), Group 2A (debond with Symetri™ pliers) and Group 2B (debonded with generic pliers). Premolars from Group 2A & 2B were prepared for bonding using the manufacturer\u27s protocol: cleaned with prophy paste, etched using 37% phosphoric acid, rinsed with water, and air dried. Ortho Solo primer was applied to the enamel surface before the bracket was bonded using Blugloo adhesive. Teeth were then mounted and stored in distilled water at 37oC. Forty-eight hours later, brackets from Group 2A & 2B were debonded using their designated pliers, Symetri™ or generic. Adhesive was removed from the enamel surface using a dental handpiece and a 12-fluted carbide finishing bur and bracket was cleaned using 90 grit aluminum oxide air-abrasion. Brackets were then rebonded to the same teeth at the same time as bonding Group 1 using the above protocol. Premolars from Group 1 were then mounted. All teeth were stored in distilled water for forty-eight hours before using the universal testing machine to test shear bond strength. After the final debond, premolars were evaluated using a microscope to score Adhesive Remnant Index (ARI) to help identify where the bond failure occurred. Results: There were no significant differences in shear bond strength (ANOVA; P\u3e0.05) between Groups 1, 2A, and 2B. ARI scores for Group 1 were significantly lower than Group 2A and 2B (Kruskal-Wallis and Pairwise Comparisons with the Bonferroni Correction; P\u3c 0.05). Conclusions: There was no statistically significant difference in shear bond strength between the initial bonding and rebonding of Symetri™ Clear brackets, nor did the type of debonding pliers used have an impact on bond strength. Bond failure during the initial debond typically occurred within the adhesive layer, whereas subsequent failures more commonly occurred at the adhesive–bracket interface