Ceramic bracket bonding: a comparison of shear, tensile, and torsional bond strengths of ceramic brackets.

The purpose of this study was to evaluate whether shear, tensile, or torsional forces were best suited for debonding ceramic brackets. Four commercially available ceramic brackets were evaluated. The brackets included both polycrystalline and monocrystalline types with either chemical or mechanical retention in the bracket bases. The ceramic brackets were bonded to one hundred and twenty bovine teeth, using Concise. The brackets were stressed until bond or bracket failure occurred with either shear, tensile, or torsional forces on the Instron machine. The maximum bond strength and the site of bond failure was recorded. Starfire TMB brackets fractured 30% of the time during shear debonding, whereas, Quasar 1000, Lumina, and Transcend 2000 brackets exhibited no bracket fractures. The shear bond strengths of Quasar 1000 brackets were significantly higher than Starfire TMB brackets. Starfire TMB was the only bracket type that exhibited no bracket fractures with tensile force. Tensile bond strengths were not significantly different between the four bracket types. In torsion, Lumina was the only bracket type that did not exhibit any bracket failures. Shear and tensile bond strengths of chemically retained brackets were not significantly different than mechanically retained brackets. Torsional bond strength of chemically retained brackets was significantly higher than mechanically retained brackets. The results suggest Quasar 1000, Lumina, and Transcend 2000 are best removed with shear or tensile forces. Starfire TMB is best removed with tensile forces.