Stresses Along the Root Surfaces of Maxillary Anterior Dentition During Retraction in Labial and Lingual Mechanics with Varying Level of Bone Support: A Finite Element Study

Objective The aim of this study was to evaluate and compare the stress along the root surfaces of anterior maxillary dentition during retraction in labial and lingual mechanics with varying level of bone support. Materials and methods Eight 3D finite element models (FEM) having 340,215 nodes and 211,543 elements were created with normal periodontium and different levels of alveolar bone loss; four with labial brackets and four with lingual brackets. Sliding mechanics were simulated as en masse retraction of the anterior dentition. The equivalent stresses along the roots of six anterior maxillary teeth were measured in all the models. Results Equivalent stresses in pascals (Pa) generated at the root surfaces of central incisors are always higher in labial technique (right: 4.6013 × 10 -2 ; left: 7.1158 × 10 -2 ) and of canines (right: 10.003 × 10 -2 ; left: 16.789 × 10 -2 ) are always higher in lingual technique. Conclusion In labial technique, central incisor roots are experiencing maximum stress, which might be the explanation of commonly seen higher incidence of root resorption in them during en masse retraction. In lingual technique, canine roots are experiencing higher stresses as compared to other anterior teeth during en masse retraction. Equivalent stresses generated at the root surfaces of canines are more irrespective of the alveolar bone loss in lingual technique.