Comparison of the Effect of Transpalatal Arch on Periodontal Stress and Displacement of Molars When Subjected to Orthodontic Forces. A Finite Element Analysis.

Introduction: The transpalatal arch has been used successfully for decades during routine orthodontic treatment for various purposes, including reinforcing anchorage. In the light of current scientific advancements with more precise knowledge of biology of tooth movement, it is prudent to study whether transpalatal arch is effective in preserving anchorage. Objectives: The aim of this finite element study was to evaluate and compare the effects of the transpalatal arch on periodontal stresses of molars and displacements when subjected to orthodontic forces. Methods: Stress patterns and displacements between models with and without a transpalatal arch were investigated by means of 3-dimensional finite element analysis. A finite element model of the maxillary first molars, periodontal ligament, alveolar bone, and transpalatal arch was created, that consisted of 1, 69,036 elements and 29,518 nodes. A simulated orthodontic retraction force of 2N was applied to the maxillary first molar in a mesial direction. Resultant von mises stresses were evaluated and compared in models with and without transpalatal arch, as well as displacement in models with and without transpalatal arch. Results: Results suggested that the presence of a transpalatal arch has no effect on molar tipping, decreases molar rotations, and reduces periodontal von mises stress magnitudes by less than 1%. Conclusions: The presence of the transpalatal arch induces only minor changes in the dental and periodontal stress distribution. Alternative methods can be used where absolute anchorage is required however transpalatal arch should not be considered an unnecessary tool in the treatment of orthodontic patients because of its various functions.