Bond Strength of Orthodontic Brackets Using Bioactive and Traditional Adhesives

Objectives: The objective of this study was to evaluate the bond strength of orthodontic brackets with current bioactive and traditional adhesives
Methods: Forty-eight extracted maxillary premolars (N=32/gp) were mounted in resin. Buccal and lingual surfaces were scrubbed with pumice, rinsed/dried, etched with 37% phosphoric acid for ten seconds, rinsed/dried, AssurePlus primer was applied with microbrush and cured three seconds. Adhesive materials (Fuji ORTHO (FO), Light Bond (LB), or OBA with MCP (OBA)) were applied to mesh backing of 0.022 stainless steel Empower™ self-ligating brackets, according to manufacturers’ instructions. Brackets pressed onto tooth surface, and excess removed with explorer. Each bracket was cured for twenty seconds (five seconds incisal, gingival, mesial, distal). Mounted teeth were stored in D-PBS at room temperature (25°±2°) until debonding forty-seven days later. Shear testing utilized Instron testing machine with brackets aligned with the loading axis of the machine (approximately 25°offset). A statistical analysis using two-way ANOVA was performed.
Results: Results demonstrated that LB was significantly greater than OBA (P=0.043), and there was no significant difference between buccal and lingual surfaces (P=0.486). LB was not significantly greater than FO, and FO was not significantly greater than OBA or OBA without primer. Analysis of buccal surface brackets resulted in significant differences in shear stress strength with LB being significantly greater than both OBA (P=0.037) and FO (P=0.013).
Conclusions: All three materials demonstrated acceptable adhesive strengths. LB adhesive did prove to have better adhesion to the enamel surface than both FO and OBA. The experimental adhesive, OBA with and without primer, had adhesive strength in the range of FO. The bond strength of the adhesives is at its strongest within a few days of bonding, thus this experiment tested more long-term adhesive ability. Further evaluation of the bracket and teeth surfaces will provide information on type of failure encountered.