ABSTRACT AIM: the present study determined the force systems produced by T-loop and T-loop with helices, with employment of different alloys (stainless steel and beta-titanium), different preactivation bends intensities (0º and 40º/180º) and different transverse sections (0.017" x 0.025" and 0.019" x 0.025"). METHODS: 80 loops for space closure were submitted to mechanical testing, which were centralized in a space of 21mm. The magnitudes of horizontal force, moment/force ratio and load/deflection ratio were quantified using a moment transducer connected to a digital indicator for extensometry adapted to an Instron universal testing machine (model TTDML). The specimens were distended to a total activation of 5mm, being registered the values at every 1mm of activation. The data achieved were statistically analyzed by means of variance analysis and the Tukey test for multiple comparisons at a significance level of 5%. RESULTS AND CONCLUSION: in general, the results indicated that the T-loops with helices produced lower magnitudes of horizontal force and load/deflection ratio than the T-loops. When inserted with the preactivation bends, the loops yielded high magnitudes of moment/force ratios, while when these preactivation bends were not presented, the moment/force ratios were low. The metallic alloy was the variable that presented the largest influence on the horizontal force and load/deflection ratio. The moment/force ratio was more intensely influenced by the incorporation of preactivation bends in the closure loops.
Orthodontics; Biomechanics; Orthodontic space closure
