Evaluation of sandblasting with acid etching versus acid etching alone in the preparation of enamel for rebonding orthodontic brackets: An in vitro study and a randomized controlled trial.

BACKGROUND: No clinical studies have evaluated shear bond strength and the clinical failure rates of the rebonded metallic brackets following different enamel-reconditioning methods. The objective of the study was to compare the in vivo clinical failure rate and the in vitro rebond strength of bonded brackets following two enamel surface preparation methods. METHODS: For the in vitro study, 45 extracted human premolars were etched; brackets were bonded using light-cured composite resin. Forty-five premolars were divided into three groups (15 in each group): the initial bonding group (IB group), the rebonding group in which enamel was reconditioned using sandblasting before acid etching (SBE group), and the rebonding group in which enamel was reconditioned using acid etching only (E group). For the in vivo study, 80 premolars in 20 patients (13-18 years old) were rebonded using the same procedures in the SBE group and E group. The two methods were used in all patients using a split-mouth design. The number of failing brackets was quantified over 6 months. Differences were statistically analyzed by one-way analysis of variance, followed by post hoc tests. RESULTS: The mean shear bond strength for the IB, SBE, and E groups was 19.38, 22.37, and 17.31 MPa, respectively. A significant difference was observed in the bond strength of the three evaluated groups (P < 0.001). The differences in the bond strength were significant between the IB group and the SBE group, as well as between the SBE group and the E group. The clinical failure rate for bonded brackets was 10% in the SBE group, and 25% in the E group and this difference was statistically significant (P < 0.001). CONCLUSIONS: Reconditioning of enamel surfaces using both intraoral air abrasion and etching in the rebonding process led to higher rebond strength than using acid etching alone and even higher than the initial brackets bonding. This trial was retrospectively registered at ClinicalTrials.gov (ID: NCT04606043).