Abstract:

To analyze displacement and stress distribution of the periodontal ligament of the first molars and premolars during different extraction healing stages by using the finite element method. MethodsAdvanced CT scanning and MIMICS, IDEAS software were used to establish three finite element models: simulated existence of the second molar, simulated one week after the second molar was extracted (clinical healing stage), simulated three months after the second molar was extracted (bone healing period). The three groups of models  were carried out under the same power load and calculation. ResultsThe stress concentration area of the first molar′s periodontal ligament was similar in the three models, pressure stress concentration area was mainly located at the near level of the palatal root, the distal  level of the near buccal root and near furcation department, and the distal cervical level of the far buccal root. In the three model groups, the near initial displacement of the first premolars: model Ⅰ＞ model Ⅲ＞ model Ⅱ, and the distal initial displacement of the first molars: model Ⅱ＞ model Ⅲ＞ model Ⅰ. ConclusionExtraction of the second molars is of help to early shift the first molars to a distal level.

Key words: Orthodontics, corrective； Tooth extraction； Molars；   Anchorage； Finite element analysis