STRESS AND STRAIN DISTRIBUTION IN TEMPOROMANDIBULAR JOINT AFTER MANDIBULAR GROWTH RETARDATION: A THREE DIMENSIONAL FINITE ELEMENT STUDY

Abstract

Introduction: Angle’s Class III malocclusion occurs when lower teeth occlude mesial to their normal relationship or ahead by one premolar width or even more in extreme cases. Etiology of Skeletal Class III malocclusion is considered as multifactorial because of an interaction of both hereditary (genotype) and environmental factors (phenotype). Orthopedic chin cup used in treatment of Class III malocclusion apply force on temporomandibular joint to inhibit or redirect condylar growth. The effects of an orthopedic appliance essentially depend on magnitude and direction of force. Hence, the purpose of study was to analyze and compare the stress and strain distribution in temporomandibular joint after growth retardation of the mandible by orthopedic procedure.Material and Methodology. Construction of the geometric model. b. Conversion of geometric model to finite element model. c. Material Property Data Representation. d. Defining the boundary condition. e. Application of forces. f. Evaluation of stress and strain distribution.Results & FEM study reveals changes in stress and strain generation at different anatomical locations after applying force at symphysis region. The pogonion condyle axis is key for direction of forces to induce orthopaedic effects generated by chin cup. However, in clinical situation, study can be utilized for direction planning of chin cup force with anticipated results but magnitude has to be calculated by operator withstanding in physiologic limits of patient. The orthopaedic force can be started with 300 g per side and incrementally increased according to clinical demand, physiologic limits and skeletal age of patient to avoid untoward results of orthopaedic force appliedKey words: finite element analysis, chin cup, class III, stress & strain on TMJ