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The use of gradually increasing orthodontic force induces increased activity of osteoblasts during the initial stage of orthodontic tooth movement compared to that induced by a relatively constant orthodontic force.

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AIM: The aim of this study was to evaluate the shear bond strength (SBS) of ceramic brackets to glazed monolithic zirconia using three different bonding protocols. MATERIALS AND METHODS: Forty-five monolithic glazed zirconia embedded into acrylic resin were randomly assigned to 3 groups (n = 15) following air abrasion by 50 μm aluminum oxide particles, the groups were treated with: (A) Assure Plus, (B) Silane + Assure Plus (C) Hydrofluoric acid + Silane + Transbond XT primer. Ceramic brackets were bonded to the zirconia discs using Transbond XT. Following thermocycling (500 cycles, 5° -55° C), SBS, failure mode and Adhesive Remnant Index were assessed. RESULTS:Group C showed the highest SBS followed by Group B with no statistically significant difference. Most of the specimens in Group C showed an adhesive failure between the bracket base and the adhesive, whereas Group B presented mainly a mixed cohesive adhesive failure. SBS in Group A was significantly lower than either groups showing an adhesive failure at the zirconia-adhesive interface. CONCLUSIONS: Both Assure Plus + Silane and the classical ceramic bonding protocol achieved clinically acceptable SBS of ceramic brackets bonded to glazed zirconia. However, Assure Plus + Silane achieved better debonding characteristics.