RESUMO
OBJECTIVE: To evaluate the bond efficacy and failure rates of rebonded metallic brackets after enamel reconditioning with chemical 37% phosphoric acid (PA) and natural and synthetic photosensitizers activated by PDT. MATERIALS AND METHODS: A total of 50 non-cavitated, and cautiously extracted human premolars were congregated after sample size calculation. The enamel exterior was etched, washed, dried for adhesive application, and cured. Metallic brackets were then oriented and adapted to enamel surface using composite. Later, brackets were debonded from the surface via a Weingart plier. Enamel was finished for ensuing surface reconditioning. Ultimately, specimens were randomly distributed into five groups (n=10). Enamel surface before rebonding was reconditioned with curcumin photosensitizer (CP), riboflavin photosensitizer (RP), rose bengal photosensitizer (RBP), methylene blue photosensitizer (MBP), and 37% PA (control) respectively. After following reconditioning protocol, brackets were rebonded to the enamel exterior employing a composite adhesive system. Then, specimens were subjected to the universal testing machine for analyzing shear bond strength (SBS), and bond failures were predicted using an ARI index. One-way ANOVA and Tukey multiple comparison tests were used for statistical analysis at a variance value of p < 0.05. RESULTS: Enamel reconditioned with 37% PA demonstrated the highest SBS for bracket rebonding, and the lowest SBS was presented by CP actuated by PDT. Enamel reconditioned with RP and RBP corroborated the analogous SBS outcome to 37% PA. Likewise, enamel surface treatment with MBP revealed a statistically significant result to CP for metallic bracket rebonding. The most prevalent failure scores anticipated among groups were 0 and 1 indicating an adhesive failure with the exemption of group 5 (control) that encountered more score 2 cohesive failure on debonding metallic brackets from enamel exterior. CONCLUSIONS: Rose bengal and riboflavin photosensitizers activated by photodynamic therapy with low ARI scores have the potential to be used as viable enamel reconditioning alternatives to 37% phosphoric acid for rebonding metallic brackets.