Pattern of stress distribution in different bracket-adhesive-tooth systems due to debonding load application

Abstract

Purpose: Orthodontic bracket debonding during treatment period is an unbecoming occurrence for both orthodontists and patients. Various clinical and numerical studies have been done to specify different parameters which affect the bond strength of bracket-adhesive-tooth system. Pattern of stress distribution seems to be an appropriate factor to estimate bond strength of different systems. Since it is not possible to experimentally define stress distribution in bracket-adhesive-tooth systems, three dimensional finite element method is used. The purpose of this study is to obtain and compare stress distribution of five bracket-adhesive-tooth systems with various enamel surface morphologies as an indicator parameter of these systems' bond strength. Materials and methods: In order to specify and compare stress in five different teeth, including maxillary central incisor, mandibular central incisor, maxillary canine, and maxillary and mandibular premolar, 3D STL files of teeth and brackets were reconstructed in MIMICS10 and were imported to HYPERMESH for each tooth, separately. Space between enamel and bracket was filled with orthodontic adhesive, mechanical property of each layer was assigned and appropriate boundary conditions were applied. Results: It was observed that stress distribution in bracket, adhesive and tooth due to shear load application had irregular pattern. For all of systems stress concentration was observed either on the borders or incisal and gingival regions of enamel-adhesive bonding region and adhesive layer. Conclusion: Despite the overall similarity in stress distribution pattern of different bracket-adhesive-tooth systems, some differences on pattern of stress distribution and magnitude of stress were also observed. This may bring about more susceptibility of curved enamel surface teeth to lower bond strength, damage and fracture than flat enamel surface teeth. © 2013 Elsevier Ltd and the Japanese Orthodontic Society.