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.

Orthodontic tooth movement and bioelectricity.

Research in the field of orthodontics is now focused on the biology of tooth movement. Advanced molecular biology techniques has showed the researchers new avenue towards finding answers to the questions asked for the last few decades. Now it is possible for the researches to explore the lacunae in the field. One such field is, pharmaco-therapeutically or electrophysiologically enhancing the rate of tooth movement, improving the stability of the results, augmenting the anchorage. The voltage gated channels of cell membrane of connective tissue cells of the periodontal ligament can be modulated by electrophysiological ways. The application of an electric current may alter the electrolytic environment allowing changes in the type and rate of ions that move across the cell membranes. Changes of the flux of K+, Ca++, Na+, Mg+, and Cl. can act as a mediator for cellular changes. Micro-pulsed electrical stimulation could reach bone osteoblasts non-invasively and this current can result in an increase in the cAMP and cGMP. These cyclic nucleotides are a type of second messenger, which play a role in the efficient remodeling of alveolar bone and in including more tooth movement. This article discusses the role of electrical potential in orthodontic tooth movement, methodology of studying the electrophysiology of cell membrane and the recent advances in the field and its possible clinical application.