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Comparison of stress distribution on bone and mini-implants during en-masse retraction of maxillary anterior teeth in labial and lingual orthodontics: A three-dimensional finite element analysis

INTRODUCTION: In fixed orthodontic treatment, space closure is one of the most challenging aspects. The common method of en-masse retraction in sliding mechanics is the use of the elastomeric chain and power arm. Recently, titanium mini-implants are used as absolute sources of orthodontic anchorage. Lingual and labial bracket placement influences the pattern of tooth movement, but the stress that occurs around the teeth, the mini-implants, and the surrounding bone can be accurately mapped using a three-dimensional (3D) finite element method. AIM: The aim of this study was to evaluate the stress distribution on bone and mini-implants during en-masse retraction of maxillary anterior teeth in labial and lingual orthodontics with the help of finite element analysis. MATERIALS AND METHODS: Following the standard protocol for 3D finite element models, two models were created for en-masse retraction of the six anterior teeth: one model using the labial technique with the mini-implant placed at a height of 5 mm from the alveolar crest bucally and the second model using the lingual technique with the mini-implant placed at a height of 5 mm from the gingival margin palatally, and 200 g of retraction forces was given using a elastomeric chain. RESULTS AND CONCLUSIONS: The Von Mises stresses in the bone and mini-implant were significantly higher in the lingual technique as compared to the labial technique. The variations in stress patterns in the bone and the mini-implant in the labial and lingual technique could be the result of difference in the inter-bracket distance, point of force application, and its location to the center of resistance of the dentition.