Evaluation of bond strength and detachment interface distribution of different bracket base designs

Introduction: The bond failure in metal brackets bonded on enamel was found to occur either at the bonding agent-bracket base interface, within the bonding agent itself or between the bonding agent and enamel. The aim of this study was to evaluate the influence of several bracket base designs and dimensions on bond strength and detachment interface distribution of 5 types of metal brackets each one characterized by a specific base design and dimension. Materials and methods: The following base designs were tested: single mesh, (Alexander LTS, American Orthodontics, Sheboygan, WI; Damon Q, Ormco, Orange, CA; Empower, American Orthodontics, Sheboygan, WI), double mesh (Omniarch, Dentsply GAC, Bohemia, NY) and large grooves on an integral microetched base (Time 3 American Orthodontics, Sheboygan, WI). Brackets were bonded to human teeth and then debonded on custom-made testing machine, based on the Universal testing machine. A scanning electron microscope was used to examine the base design and the detachment interfaces of each bracket selected for this study. The detachment interfaces were mapped with energy-dispersive x-ray spectrometry. Results: The Omniarch bracket showed the higher bond strength corresponding to 84,1 kg/base or 6,78 MPa; no significant differences (p > 0.05) were found among the other brackets tested for the bond strength of individual bases (kg/base). Time 3 bracket showed the lower percentage of failure between the bracket and resin and the higher percentage of cohesive failure (respectively 25% and 62 %). Conclusions: The results of this study showed that brackets with a greater mesh spacing demonstrated the best bond strength results and a double layer mesh pattern (80/150 gauge double mesh) guaranteed, in this study, the best bonding performance.