A Nonlinear Finite Element Analysis Of Closing Central Incisors Gap With Invisible Appliance

Part 1 Set up A three-dimensional finite element model composed of maxillary dentition, alveolar bone, periodontal membrane and invisible applianceObjective:To set up a three-dimensional finite element model composed of maxillary dentition, alveolar bone, periodontal ligament and invisible appliance,the nonlinear contact analysis was used to calculate the stress distribution in periodontal ligament and alveolar bone when the invisible appliance was inserted to the dentition. This will provide a model for the study of the mechanism of invisible appliance.Methods:We set up a 3D geometric model based on the digital files of the maxillary dentition and alveolar bone images scanned by spinal CT and dental crowns images aquired by chromatographic analysis.Then we use Abaqus finite element software to build a whole three-dimensional finite element model composed of maxillary dentition, alveolar bone, periodontal membrane and no-bracket invisible appliance.The relationships between teeth and teeth, teeth and invisible appliance were defined as contact and the nonlinear contact analysis was used in calculation.Results:A three-dimensional finite element model composed of the invisible appliance, maxillary dentition, alveolar bone and periodontal ligament was set up, and the nonlinear analysis was successful.Conclusion:The method to set up the geometry model by Spiral CT scanning and chromatography techniques was convenient and effective.We first set up a whole three-dimensional finite element model composed of the invisible appliance, maxillary dentition, alveolar bone and periodontal ligament by Abaqus software.The contact nonlinear calculation simulated process that a invisible appliance were inserted to the dentition. The model provides a good platform for further analyzing the mechanism of invisible appliance.Part 2 Three-dimensional nonlinear finite element analysis of maxillary central incisors moved to the mesial by invisible applianceObjective:To reveal the mechanism of invisible appliance by analyzing the tooth movement type, stress variation and distribution of the periodontium when invisible appliance was used to close central incisors gap.Methods: When the central incisors was designed to move to the mesial 0.3 mm the teeth movement type, the instantaneous center of rotation, the displacement of anchor teeth and the stress distribution of the whole treatment system were analized by finite element model built in part 1.Results:The displacement on the central incisors crown was greater than that on the apical.The line showed displacements were zero was at the connection of 1/3 the middle and 1/3 apical root. The high stresses area was found at the cervical periodontium of central incisor.Conclusion:When the incisor was designed to move to the mesial 0.3mm by invisible appliance,(1)The stresses on the central incisor PDL were highest at the cervical periodontium, but the stresses on the apical were not high.(2) The instantaneous rotation center of central incisors was at the point 1/3 root length away from the apical.The center of rotation was nearer the apical than the center of resistance was.(3)The type of central incisor movement was tipping.