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The aim of present study was to evaluate the infl uence of convexity of upper central incisor on expression of torque. The variation in crown root angle of maxillary central incisor and the co-relation between crown root angle and convexity of crown of maxillary central incisor was also assessed. Thirty extracted maxillary central incisors and a central incisor bracket (American Orthodontics—Roth prescription 0.018 inch slot) were used for the study. The study was carried out in three parts. In fi rst part, proximal radiographs of each sample were traced and crown to root angle was measured. In second part, labial surface each sample was scanned using cyclone scanning system (Renishaw) to obtain profi le image of each sample which were analyzed using AutoCAD 2002 software. Convexity of labial surfaces at various heights, i.e. X + 1, X + 2, X + 3, X – 1, X – 2, X – 3 was measured. Third part consisted of preparation of 3D photographic model of one randomly selected sample using Stereo Scan 3D (Breuckmann) machine and 3D composite image of central incisor bracket using Esson optical profi le projector. Torque values at X + 1, X + 2, X + 3, X – 1, X – 2, X – 3 were 2.27°, 5.08°, 8.96°, –5.01°, –8.35° and –12.33° respectively and mean value of crown to root angle of all 30 studied samples was 180.27°. It was concluded that when bracket is displaced 1, 2 or 3 mm incisally, there is increase in lingual root torque by an average value of 2.27°, 5.08° or 8.96° respectively while when bracket is displaced 1, 2 or 3 mm gingivally, there is decrease in lingual root torque or increase in labial root torque by an average value of 5.01°, 8.35° or 12.33° respectively. These fi ndings were confi rmed on analysis of 3D photographic model of one randomly selected sample.

world journal of dentistry

Influence of Morphology of Maxillary Central Incisor on Expression of Torque using 2D Surface Scanning and Confirmation with 3D Photographic Model: An in vitro Study