Biomechanical Characteristics Of Lingual Bracket System During Retracting Maxillary Anterior Teeth With Different Length Of Hooks

Objective To analyze the biomechanical characteristics of lingual bracket system during retracting maxillary anterior teeth with a fixed position of the maxillary micro-implants sliding method using different length of hooks.Methods A 3D FEM including the e-Brace customized lingual brackets, maxillary dentition(removal of left and right maxillary first premolar), periodontal ligament, alveolar bone, lingual arch wire, palatal micro-implants and the hooks was constructed. By using a 3D FEM model,at the fixed micro-implant loading position between the second molar and the first molar,6mm from the alveolar ridge crest, the displacement and stress distribution of the maxillary dentition were analyzed with 1.5 N palatal forces during retracting maxillary anterior teeth retraction using different length of hooks between the maxillary lateral incisor and canine,including 2mm、4mm、 6mm、8mm and 10mm, which conforming to the shape of the palate and closing to the surface of the palate.Results ① An entire 3-D FEM model including e-Brace brackets, dentition, periodontal ligament, alveolar bone, lingual arch wire, palatal micro-implants and the hooks was constructed by this method. ②when the length of hook is less than 4mm,the maxillary incisors are all lingual inclination, while the maxillary canines-mesial part are moving to lingual side during retracting maxillary anterior teeth;the maxillary incisors and canines are all moving to the labia side when the hook is longer than 6mm,and the longer of the hook is,the more labial side movement is.The periodontal stress concentrated area are mainly lateral cervix and canine cervix.Conclusion ①The originated e-Brace customized lingual 3-D FEM model has high geometrical similarity, and is hence reasonable, reliable and practical. ②In lingual appliance, the length of the hook will affect the movement of the movement of the anterior teeth when retracting them.The lingual inclination movement for the anterior teeth will ruduce when the hook become long,which may be conductive to the bodily movement of the anterior teeth.