Comparison of Periodontal Stresses in Maxillary Anterior Teeth by Two Methods of En-Masse Retraction: A 3-D Finite Element Analysis

Abstract

Introduction: Periodontal ligament, tooth, and alveolar bone react as deformable entities under loads. Stresses in the PDL believed to be the starting factor in tooth movement, and various types of stresses are transmitted to bone through the PDL. Therefore, it is essential to consider these tissues as continuous unit to help in quantitative assessment of stress and strain in periodontium. FEM provides an approximate solution for response of the 3-dimensional (3D) structures to applied external loads under certain boundary conditions.

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 help of implant placed at 3 mm and 5 mm height from alveolar crest. Results were represented in the form of stress diagrams.

Results: En-masse retraction with elastomeric chain showed more periodontal stresses. Increasing the height of mini-screw implant was also associated with increase in periodontal stresses.

Conclusions: For the same height of mini-screw implant, en masse retraction with elastomeric chain demonstrated a higher amount of periodontal stresses as compared to NiTi coil springs. The highest stress throughout the PDL was always present around cervical area in both types of en-masse retraction, indicating that cervical area, apart from apex, bears the most loads and might be considered as susceptible area for potential tissue damage. Increasing height of mini-screw implant more gingivally associated with more amount of periodontal stresses in both types of en-masse retraction.