Biomechanical analysis of micro-implant anchorage in the infrazygomatic crest for the distal displacement of the upper dentition at different heights / 中国组织工程研究

ABSTRACT

BACKGROUND: In orthodontics, micro-implant anchorage in the infrazygomatic crest that cannot damage the tooth root can achieve an unobstructed overall movement of the upper dentition. However, little is reported on the stress and strain of the tooth and alveolar bone during the distal movement of the upper dentition. OBJECTIVE: To set up a three-dimensional finite element model to perform a biomechanical analysis of micro-implant anchorage in the infrazygomatic crest for the distal displacement of the upper dentition at different heights. METHODS: Cone-beam CT data from a female patient admitted for orthodontic treatment was saved in Dicom format, and imported into Mimics 16.01 software. Then, a three-dimensional model of the right maxilla and tooth dentition was made by automatically and manually selecting boundaries. The model was imported into Geomagic8.0 for removal of noise dots and smooth processing, and then it was imported into the Mimics16.01 software and meshed for the surface/body through 3 Matics software. Afterwards, three-dimensional models maxillary denture, archwires and traction hooks and implants were established by ProE5.0, and all the models were imported into ANSYS13.0 and assembled and analyzed for stress and strain analysis. RESULTS AND CONCLUSION: We successfully established the three-dimensional finite element model for biomechanical analysis of micro-implant anchorage in the infrazygomatic crest for the distal displacement of the upper dentition at different heights, and this model conformed to the anatomic features. With the increase of the height of traction hooks (1, 4, 7, 10 mm), the vertical stress of the maxillary teeth increased gradually, and had no correlation with the change of the horizontal stress. With the increase of the height of traction hooks, at the sagittal axis, the strain at midpoints of middle incisors, canine teeth, and first molars decreased gradually and the strain at the root of middle incisors and canine teeth also decreased gradually, but there was no change in the strain at the root of first molars. With the increase of the height of traction hooks, at the vertical axis, the strain at the midpoints and tooth root of middle incisors increased, while the strain of canine crown increased gradually and that of the canine root decreased; the strain at the midpoint of first molars changed a little, and the strain of the tooth root decreased gradually. The dentition rotated from clockwise to counterclockwise. To conclude, the three-dimensional finite element model made in the study is consistent with the anatomic structure, which provides a basis for biomechanical analysis of micro-implant anchorage in the infrazygomatic crest for the distal displacement of the upper dentition. The upper dentition impedance center located in the position of 4 to 7 mm of the arch wire can be used as the microimplant support site in the infrazygomatic crest.