Are torque values of preadjusted brackets precise?

Objective: The aim of the present study was to verify the torque precision of metallic brackets with MBT prescription using the canine brackets as the representative sample of six commercial brands. Material and Methods: Twenty maxillary and 20 mandibular canine brackets of one of the following commercial brands were selected: 3M Unitek, Abzil, American Orthodontics, TP Orthodontics, Morelli and Ortho Organizers. The torque angle, established by reference points and lines, was measured by an operator using an optical microscope coupled to a computer. The values were compared to those established by the MBT prescription. Results: The results showed that for the maxillary canine brackets, only the Morelli torque (-3.33 degrees) presented statistically significant difference from the proposed values (-7 degrees). For the mandibular canines, American Orthodontics (-6.34 degrees) and Ortho Organizers (-6.25 degrees) presented statistically significant differences from the standards (-6 degrees). Comparing the brands, Morelli presented statistically significant differences in comparison with all the other brands for maxillary canine brackets. For the mandibular canine brackets, there was no statistically significant difference between the brands. Conclusions: There are significant variations in torque values of some of the brackets assessed, which would clinically compromise the buccolingual positioning of the tooth at the end of orthodontic treatment.