Effect of tooth layers' segmentation on pattern of stress distribution in bracket- adhesive- tooth system

Orthodontic braces are used to modify, malocclusions of teeth and jaws. Most of problems in dentistry can be investigated from a biomechanical point of view. Stress distribution in bracket, adhesive and tooth has been used as a criterion to determine bond strength of bracket- adhesive- tooth system. Tooth is consisted of three layers including enamel, dentin and pulp with three different mechanical properties, although most of previous studies have not paid attention to this and have considered the tooth as one layer material with unique mechanical property. In this study, Micro CT images of a tooth and a bracket were imported in Mimics 10 and different layers of the tooth were segmented. The bracket, the whole tooth and each layers of tooth were exported as STL files, separately. STL files of two bracket- adhesive- tooth systems including the system that have considered the whole tooth as a unique material and the system with segmented tooth layers were imported in Hypermesh software to create high quality 3D finite element meshes. The space between enamel and bracket has been filled with orthodontic adhesive substance that sets to 0.2 mm at thickest parts. For each system, property of each layer was assigned and appropriate boundary conditions were applied. Finally, pattern of stress distribution of two systems were compared with each other. The findings of this study show that both of the systems had similar pattern of stress distribution and stresses generated on the dentin and pulp of the system with segmented tooth layers were of lower magnitude in comparison with other layers. In the other words, anatomical details of dentin and pulp do not affect the results of study, significantly.