Computational Analysis of Bone Remodeling in Orthodontics

Abstract

When orthodontic force is applied to a tooth, alveolar bone remodeling occurs, resulting in tooth movement. The way in which an orthodontic force is transferred to the tooth root is of fundamental importance in orthodontics. It is believed that there is an optimal stress distribution to bring about efficient tooth movement. However, there is little information concerning the quantitative relationship between stress and alveolar bone remodeling. In this chapter, two kinds of studies concerning this relationship are described, preceded by a brief review on computational analysis of orthodontics. The resorption rate of the alveolar bone during orthodontic treatment was first investigated. The stress distributions around the canine tooth were analyzed using a three-dimensional (3-D) finite-element method (FEM) model. The amounts of alveolar bone resorption were obtained indirectly from 3-D tooth movement under various clinical treatments. From these results, the alveolar bone resorption rate from a unit stress was found to be 0.6/am/(kPa-day), ranging from 0.4 to 0.8/am/(kPa-day). The relationship between the appearance of osteoclasts and stress distribution was also investigated. Histological observations of tissue sections taken from animals subjected to experimental tooth movement were compared with the analytical findings obtained by specimen-specific FEM models. The results clearly demonstrated that there is a close correlation between the appearance of osteoclasts and the principal stress distribution in the periodontal ligament. The osteoclasts appeared at the specific sites where the compressive stress was within a relatively narrow range. The obtained stress level is discussed from the aspect of optimal stress.