Comparison of stress distribution in bone and miniscrew and displacement pattern of maxillary anterior teeth by two methods of en-masse retraction: A 3-D finite element analysis

Abstract

Introduction: To move the teeth in a desired pattern, the appropriate direction of the force must be selected. An inappropriate force delivers unfavourable stresses in the supporting tissues resulting in poor prognosis. It is very difficult to measure stresses accurately in vivo. Finite element analysis provides a definitive solution. Aim: To compare the stress distribution in bone and miniscrew and displacement pattern of maxillary anterior teeth with two methods of en-masse retraction i.e. NiTi coil spring and elastomeric chain, with miniscrews placed at various heights using finite element analysis. Materials and Methods: Total of four models were created i.e. two models with retraction by elastomeric chain and two models with retraction by NiTi coil spring with the help of implant placed at 3 mm and 5 mm height from alveolar crest. Results were represented in the form of stress diagrams. Results and Conclusions: Retraction with elastomeric chain produces lesser amount of von Mises stress on the bone as well as mini-implant as compared to that with NiTi coil spring. Retraction with elastomeric chain produced more sagittal and vertical displacement of canines as compared to its effect on incisors. The overall displacement of anterior teeth in both vertical as well as in sagittal direction was found to be more with elastomeric chain as compared with NiTi coil spring. Both the methods for retraction resulted in same amount of palatal root movement irrespective of the force vector. Keywords: Miniscrew; Stress; En-masse retraction; Finite Element Method