Repeated bonding of orthodontic brackets is a common clinical necessity, yet its impact on shear bond strength (SBS) and enamel integrity remains inadequately characterized. This study evaluated the effect of multiple bonding cycles using the same bracket on SBS and enamel surface characteristics. Twenty human premolars extracted for orthodontic purposes were randomly allocated to two groups (n=10 per group): Group A (Enlight® adhesive, Ormco) and Group B (Transbond XT® adhesive, 3M Unitek). Specimens underwent five consecutive bonding-debonding cycles using stainless steel mesh-based brackets. After each debonding, brackets were cleaned using a flaming technique (5 seconds), and enamel surfaces were polished with a tungsten carbide bur. SBS was measured using a universal testing machine (crosshead speed: 6 mm/min). Data were analyzed using repeated measures MANOVA with Bonferroni post hoc tests (α=0.05). Initial SBS values differed significantly between groups (Group B: 22.38±17.41 MPa vs. Group A: 9.92±4.36 MPa; p<0.05). Group B demonstrated a progressive decline in SBS, reaching 4.73±3.82 MPa by the fifth cycle—below the clinically acceptable threshold of 5.9 MPa. Group A maintained more stable SBS values across all cycles (range: 8.31–14.86 MPa). Statistical analysis revealed significant effects of bonding cycle (p<0.001) and adhesive type (p<0.05), with a significant interaction effect (p<0.05). Repeated bonding significantly compromises SBS, with high-filler adhesives showing greater degradation despite superior initial performance. Adhesives with simpler formulations demonstrate better stability across multiple cycles. Clinical protocols should prioritize optimal cleaning techniques and consider bracket replacement after multiple failures to ensure treatment efficacy and enamel preservation.
