Optimum conditions for parallel translation of maxillary anterior teeth under retraction force determined with the finite element method

Introduction: In this study, we used the finite element method to examine the optimum conditions for parallel translation of the anterior teeth under a retraction force. Methods: Finite element models of the 6 maxillary anterior teeth and the supporting structures ( periodontal ligament and alveolar bone) were generated as a standard model based on a dental model (Nissin Dental Products, Kyoto, Japan). After designating the position and length of the power arm as variables, the initial displacement of each tooth was measured with finite element simulation, and the rotation angle of each tooth was calculated. Results: The relationship between the position and length of the power arm was analyzed, and model equations for this relationship were proposed. As a result, the length of the power arm was either 4.987 or 8.218 mm when it was located either between the lateral incisor and the canine or between the canine and the first premolar, respectively. Conclusions: The length of the power arm increased as its position was moved from the lateral incisor to the premolar. This was because the length of the power arm must be increased to be in equilibrium mechanically. Overall, it is expected that the efficient positions and lengths of the new dental models can be calculated if these total procedures are established as a methodology and applied to new dental models. Moreover, the parallel translation of the maxillary anterior teeth can be generated more effectively. (Am J Orthod Dentofacial Orthop 2010;137:639-47)