Shear bond strength of rebonded metal brackets using four light-curing resins: an in vitro study

Background: Rebonding of orthodontic brackets requires effective surface conditioning to restore adequate adhesive retention. Objective: To compare the shear bond strength (SBS) of rebonded metal brackets using four light-curing resins. Material and methods: = 10 per subgroup): Orthocem (FGM), Bracespace (3M), Transbond XT (3M), and Z250 (3M). Brackets were bonded, debonded, reconditioned, and rebonded. SBS was tested using a universal testing machine (0.5 mm/min). Data were analyzed using Kruskal-Wallis and Dunn's post-hoc tests (α = 0.05). Results: = 0.044). Dunn's post-hoc test identified higher SBS for Bracespace (3M) and Transbond XT (3M) compared with Orthocem (FGM) and Z250 (3M). When comparing conditioning methods within each resin, sandblasting of the bracket bases resulted in significantly higher SBS only for Bracespace and Transbond XT, whereas Orthocem and Z250 showed no significant change. Conclusions: Rebonding of metal brackets showed comparable SBS among resins after acid etching. However, when the bracket bases were sandblasted, Bracespace and Transbond exhibited significantly higher bond strengths. Surface preparation of the bracket base is therefore a key factor influencing SBS in rebonding procedures.