Comparison of torque expression in esthetic brackets

BACKGROUND: The objective of this work is to test the null hypothesis that there is no difference in the torque expression among different esthetic brackets. MATERIAL AND METHODS: Five ceramic self-ligating brackets (In-Ovation C – GAC, Damon Clear–Ormco, QuicKlear-Forestadent, Click-It -TP Orthodontics, Clarity SL-3M Unitek) and 4 ceramic conventional brackets (Inspire Ice–Ormco, InVu Ceramic-TP Orthodontics, Ceramic Roth–Morelli, Clarity Metal-Reinforced Ceramic Bracket-3M Unitek) were selected. Metallic Damon MX self-ligating bracket (Ormco) was used as control. Third-order moments were measured at 12º, 24º and 36º using an archwire torsion device associated with a Universal Testing Machine (EMIC DL2000), with 0.019x0.025-inch stainless steel wire. Anova followed by Tukey tests were used for intergroup comparisons. RESULTS: In all tested angulations the Damon Clear bracket presented the highest torque expression, followed by Clarity, Clarity SL and Damon Mx brackets, with the worst torque expression shown by the InVu Ceramic bracket. The InVu Ceramic demonstrated the largest while the Damon Clear brackets demonstrated the smallest slot height and clearance. CONCLUSIONS: The null hypothesis was rejected since torque expression was different among the esthetic brackets evaluated. It was also concluded that the slot height is directly related to torque expression. Key words:Torque, orthodontic brackets, orthodontic appliances, incisor, ceramics.