Comparison of brackets bonded with bulk-fill composite and conventional composite: a split-mouth randomized controlled trial

The primary objective of this study was to compare the survival rate of orthodontic brackets bonded with bulk-fill composite and conventional light-cured composite. The secondary objective was to compare plaque accumulation and gingival health between the two bonding materials using plaque index and gingival index. Single-center, prospective, split-mouth randomized controlled trial. This single-center, split-mouth randomized controlled clinical trial was conducted at Aga Khan University Hospital, Karachi, from July 2025 to February 2026. A total of 53 participants were included, contributing 212 quadrants. Bulk-fill composite was allocated to 106 quadrants and conventional light-cured composite to 106 quadrants. Bracket bond survival was assessed over four months. Plaque accumulation and gingival health were evaluated using plaque index and gingival index at baseline and monthly follow-up visits. Fisher’s exact test, Kaplan–Meier survival analysis, Cox regression, and linear mixed model analysis were applied. The study investigators, participants, and outcome assessors were not blinded because of the nature of the bonding materials and clinical procedure. In the conventional composite group, bracket bond failure occurred in 9 quadrants (8.5%), while in the bulk-fill composite group, failure occurred in 5 quadrants (4.7%). Although bulk-fill composite showed a lower percentage of bracket failure, the difference was not statistically significant ( p = 0.408). Cox regression showed that material type was not a significant predictor of bracket survival. However, hard food chewing was significantly associated with bracket failure, increasing the risk by 18.54 times ( p < 0.001). Material type had no significant effect on plaque index or gingival index, although both indices changed significantly over time. Bulk-fill composite showed comparable bracket survival, plaque accumulation, and gingival health outcomes to conventional light-cured composite. Patient compliance, particularly avoidance of hard food chewing, remains essential for reducing bracket failure. Retrospectively registered at the ClinicalTrials.gov under identifier NCT07155343 on 20 July 2025.