ESTUDO COMPARATIVO DA EXPRESSÃO DO TORQUE ENTRE OS BRÁQUETES AUTOLIGÁVEIS

Abstract

The aim of this study was to compare the torque expression in self-ligating brackets (active and passive) and conventional, generated in different twist angles. Five types of stainless steel self-ligating brackets and a brand of conventional stainless steel bracket were tested: Damon 3 MX (Ormco) and Portia (Abzil 3M), regarded as passive, and In-Ovatin R (GAC), Bioquick (Forestadent) and Roth SLI (Morelli) considered as active; the conventional one that was tested was Roth Max (Morelli). 300 segments of stainless steel wire 0.019 "x 0.025" were used. The moments when we found torsional stregth were measured at angles of 12 º, 24 º, 36 º and 48 º, using a wire twisting device associated with a Universal Testing Machine (EMIC DL2000). After the tests, the heights of the six slots of brackets brands tested were measured using as instrument a Profile Projector (Starret VB 300). Moments of torque obtained in the tests were compared by analysis of variance with a criterion (ANOVA) followed by multiple comparison tests for post hoc of Tukey. The regression was performed to generate the mathematical equation of the great curve of every brand bracket separately. Through the equations, the early record of the torsional angles and the torsion angles range considered clinically effective were calculated. Based on the dimensions found of the slots heights, the clearance between the wire and slot of the brackets tested was calculated. The results showed significant differences among all the brands of brackets when compared separately for all angles tested (P <0.05). By analyzing the brands together, it was found that the Bioquick presented the lowest meaningful torque at all the angles tested, however, the Damon 3MX bracket was the one with the most expressed torque until the angle of 36 º; at 48 º the In-Ovation R, Portia and Damon 3MX brackets had similar torque results. When observed the torsion range considered clinically effective, it was found that began at angles of twists smaller corresponding to the brackets which had the lowest height of the slot, as well as in those with the smallest clearance between the wire and the slot; among them, the bracket Damon 3MX was the one that had the lowest height slot and first manifested a clinically effective torque, as well as had the lowest torque play; in contrast, Bioquick received the greatest height slot and higher torque play, as well as expressed later a clinically effective torque. After evaluation of the data obtained, it was found that the system connecting wire / bracket (self-ligating active, passive or conventional ligation) seems not to interfere in the final torque expression, being dependent on the size of the slot, as well as the interaction between the wire and bracket chosen to be used in orthodontic mechanics.