Evaluation of the Influence of Vestibular Surface Morphology Variability of Maxillary Incisors on Torque: Examination Using 3D Intraoral Scans

Proper torque is an important element of orthodontic treatment. There are many factors affecting effective torque expression, e.g., the interplay between an archwire and a bracket, the precision during bracket positioning, and the morphology of the crown vestibular surface (CrVS) of the tooth. Our study focused on the impact of the maxillary incisor CrVS morphology on the torque exerted by the archwire–bracket interplay. Three-dimensional models of 50 patients acquired through the use of an intraoral scanner were used to examine the four maxillary incisors. A total of 200 teeth were examined. The influence of the tooth crown shape on the bracket position and the related torque change was analyzed with Ortho Analyzer software 2015 (3Shape, Copenhagen, Denmark). All calculations were made for full size archwires. Central incisors showed less variability in their vestibular surfaces than lateral incisors. For the central incisors, the mean values of the additional palatal root torque ranged from 0.6° to 1.6°. For the laterals, the mean values ranged from 1.4° of additional vestibular root torque to 3.5° of additional palatal root torque. The results showed essential morphological differentiation of the CrVS of the maxillary incisors. Therefore, when the bracket is positioned, the individual variation in the tooth surface should be considered and evaluated.