Abstract
This study evaluated the degree of buccolingual inclination of mandibular tooth crowns relative to torque. For such purpose, mandibular and maxillary stone casts from 31 Caucasian Brazilian adults with normal occlusion, pleasant facial aspect and no history of previous orthodontic treatment were examined. A custom device was developed for measuring the degree of inclination (torque) of bracket slots of orthodontic appliances relative to the occlusion plane, at three bonding height: standard (center of clinical crown), occlusal (0.5 mm occlusally from standard) and cervical (0.5 mm cervically from standard). Except for the mandibular incisors, which presented a small difference in torque from one another (lingual root torque for central incisors and buccal root torque for lateral incisors), the remaining average values are close to those found in the literature. Due to the convexity of the buccal surface, the 1-mm vertical shift of the brackets from occlusal to cervical affected the values corresponding to the normal torque, in approximately 2 degrees in central and lateral incisors, 3 degrees in canines and 8 degrees in premolars and molars.
Highlights
Despite several innovations incorporated to the original “edgewise” system, its principles and applications remain essentially the same of those introduced by Angle [1] in 1928, when a rectangular wire was associated to a bracket with a rectangular slot, enabling three-dimensional movements.The force of the torque is probably the most important and powerful force produced by this mechanism [2]
The clinical parameter for assessing the buccolingual inclination of each tooth is the angle formed by its buccal surface in relation to the occlusal plane [3,4,5]
Whenever conventional brackets are positioned on the buccal surface of the teeth of patients with normal occlusion, in predetermined heights, the inclination of the bracket slot in relation to the occlusal plane indicates the amount of torque necessary to reach the ideal torque for the case
Summary
Despite several innovations incorporated to the original “edgewise” system, its principles and applications remain essentially the same of those introduced by Angle [1] in 1928, when a rectangular wire was associated to a bracket with a rectangular slot, enabling three-dimensional movements.The force of the torque is probably the most important and powerful force produced by this mechanism [2]. Its introduction in Orthodontics has enabled the control of dental movements in the buccolingual direction, which has greatly widened the possibilities of orthodontic treatment. The clinical parameter for assessing the buccolingual inclination of each tooth is the angle formed by its buccal surface in relation to the occlusal plane [3,4,5]. Because the orthodontist works mainly with dental crowns, they should be the basis of the communication or reference, in the same manner as they are used as a clinical parameter for assessing the treatment prognosis [6]. Whenever conventional brackets are positioned on the buccal surface of the teeth of patients with normal occlusion, in predetermined heights, the inclination of the bracket slot in relation to the occlusal plane indicates the amount of torque necessary to reach the ideal torque for the case
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