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Original Article

Anterior tooth morphology and its effect on torque

2007, Volumen 37, Número 2
M. van Loenen, J. Degrieck, Guy A.M. de Pauw, Luc René Dermaut
Departamento de Ortodoncia. Facultad de Odontología. Universidad de Gante. Gante, Bélgica

This study was undertaken to determine the variation in crown-root angle (CRA) of the upper incisors and canines as well as the variation in their labial contour. In addition, the influence of the variability of the labial contour and of different bracket heights on torque was evaluated. Proximal radiographs were taken of 160 extracted maxillary teeth (81 incisors and 79 canines). They were digitized and analyzed with Jasc® Paint Shop Pro 7 TM (Eden Prairie, United States of America) and Mathcad 2001 Professional® (Cambridge, United Kingdom). The CRA has a great variability ranging from 167 to 195 degrees for the canines (mean value 183 degrees) and from 171 to 195 degrees for the incisors (average 184 degrees). The mean inclinations of the labial surfaces for the incisors varied greatly. Between 4 and 4.5 mm from the incisal edge the standard deviations (SD) were the smallest and between 2 and 4.5 mm from the incisal edge the labial surface angle differed approximately 10 degrees. For the canines the mean inclinations of the buccal surface also varied. This angle differed around 10 degrees between 2 and 4.5 mm from the incisal edge, but the SD were much larger than for the incisors. It can be concluded that placement of a bracket on a tooth at varying heights, still within a clinically acceptable range, results in an important difference in the amount of root torque.  (Rev Esp Ortod. 2007;37(2):071-078)

Key words:
Torque. Crown-root angle.
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