Characteristics of the Tooth in the Initial Movement: The Influence of the Restraint Site to the Periodontal Ligament and the Alveolar Bone

Kyoko Shinya,Akikazu Shinya,Akiyoshi Shinya,Yuji Nakasone,Rizako Nakahara

doi:10.2174/1874210600903010085

Abstract

It is critical to clarify orthodontic load transfer mechanism from tooth to alveolar bone, and to determine the influence of applied orthodontic force on tooth behaviour. In this study, two dimensional (2-D) finite element (FE) models were constructed to simulate to mechanical behaviour observed during the initial movement of periodontal ligament (PDL) deformation, and to evaluate the effects of the presence of PDL and various restraint sites on tooth behaviour.A 2-D solid FE model of the tooth-PDL-alveolar bone system was constructed and investigated into stress distribution pattern and displacement. The first analysis was carried out with combinations of FE model with and without PDL. The second analysis was compared with three different sites restraint of alveolar bone. By incorporating PDL in FE models, excessively large stress values and deformation generated in a tooth and alveolar bone were relieved. Since restraint conditions did not affect a tooth and PDL, but had an effect on alveolar bone, orthodontic force necessary for tooth displacement was transmitted correctly. The results of this study revealed that inclusion of PDL in FE models is indispensable to transmit orthodontic force appropriately when investigating tooth behaviour for orthodontic treatment. Restrained sites affected stress distribution in alveolar bone.

Highlights

In orthodontic treatment, an esthetics are restored by moving an irregular tooth to right position by applying orthodontic forces to bracket, wire, and elastic band
The results of this study indicate that, during initial movement of periodontal ligament (PDL) deformation, the presence of PDL enabled to alleviate excessive stress concentration generated in tooth and alveolar bone, to appropriately transmit orthodontic force necessary to move tooth
2D finite element (FE) models were constructed to simulate mechanical behaviour observed during the initial movement of PDL deformation, and evaluated the effects of the presence of PDL and various restraint sites on tooth behaviour, stress distribution pattern and displacement

Summary

Introduction

An esthetics are restored by moving an irregular tooth to right position by applying orthodontic forces to bracket, wire, and elastic band. To displacement of a tooth, large orthodontic force exceeding friction force generated in a bracket and a wire must be applied [1]. Due to strict restrictions on in vivo experiments, orthodontic bone remodelling processes have been mainly analysed from a biomechanical point of view using models simulating what occurs in the oral environment. Several studies such as dial gauge method, straight gauge method, distribution method and vibration method have been reported regarding orthodontic tooth movement [5, 6]

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Discussion

Conclusion