A Study of the developmental mechanisms of mandibular torus by three-dimensional finite element analysis and immunohistochemical staining

Abstract

Background: Mandibular torus is one of exostosis which often develops lingually at mandibular molar region. It has been recognized as a product of long-continued occlusal force (mechanical stress) for years, because it is observed with clinical features such as attrition that suggests excessive local force. Few reports, however, have been published regarding the developmental mechanisms. With three-dimensional finite element analysis and immunohistochemical test, the developmental mechanisms are reviewed in this report. Methods: CT image data of patients whose mandible and maxillary teeth were thought to be in relatively normal contact, and thus whose occlusions were classified as Angle Class I malocclusion, were modeled using MECHANICAL FINDER version 5.0 (Research Center of Computational Mechanics, Inc., Tokyo) to evaluate mechanical behaviors of the mandibular body from stress distribution of a condition which represented centric occlusion (Case 1) and a condition which represented lateral movement with eccentric load (Case 2) selected from conditions that mimicked movements of masseter muscle. Also, tissues harvested from mandibular tori were immunohistochemically evaluated to examine the relationship between mechanical stress and bony growth. Results: The areas of stress concentration and mandibular tori formation were found to match by finite element analysis. Also, findings of immunostaining suggested involvement of mechanical stress with development of mandibular torus.