| Objective: To analyze the effects of different anchorage methods on the anterior teeth area when maxillary molars moved far away.It provides reference for the selection and design of anchorage when maxillary molars distalization in clinical invisible correction.Methods: One normal female volunteer was selected.The maxillary wisdom teeth had been removed and the bone tissues in maxillary nodules were complete.The maxillofacial region was scanned by CBCT,and the three-dimensional models of maxilla,maxillary dentition,periodontal ligament and invisible appliance were established by Mimics,Geomagic Studio12.0 and Pro/E5.0 software.The finite element mesh was divided by Hyperrmesh12.0.ANSYS WORKBENCH is used as a finite element analysis tool,and A high quality finite element model is obtained.The simulated invisible appliance pushed the maxillary molars to move far under different anchorage conditions,and the moving distance is 0.2mm.The group 1 has the 1-6 as the anchorage,and pushed the maxillary single molar7 to distal;the group 2 has 1-5 as the anchorage,the maxillary 6 and 7 were moved together;the group III was supported by the 1-5,and the II traction was used to push the upper 6 and 7 together.Take the 1-5 as the anchorage,and at the same time,with the implant anchorage between the 5 and 6 on the same side,pushed the 6 and 7 together to distal.The stress distribution and displacement trend of the periodontal membrane in the anterior maxillary region were observed.Results: The distribution of equivalent stress in periodontal ligament showed that the Von-Mises stress in the periodontal ligament of group I and group II was mainly concentrated in the labial cervical margin,the lateral incisor was concentrated near the middle cervical margin,and the canine was concentrated in the labial cervical margin and near the middle cervical margin.The stress concentration area of group 2 was twice that of group 1.The Von-Mises stress in the periodontal membrane of group 3 and group 4 was mainly concentrated in the labial cervical margin and lingual cervical margin,the lateral incisor was concentrated near the middle cervical margin and lingual cervical margin,and the canine was concentrated in the labial cervical margin,lingual cervical margin and near middle cervical margin.The stress area of periodontal ligament in group 3 and group 4 were smaller than group 2.The stress concentration of anterior labial periodontal ligament in the four groups was group 2 > group 3 > group 4 > group 1.As can be seen from the displacement trend diagram of maxillary anterior teeth,the labial displacement of anterior teeth in group 1 was the smallest and the loss of anchorage was the least,the labial displacement in group 2 was the largest,which was about twice that of group 1,and the labial displacement of anterior teeth in group 3 and 4 was significantly smaller than that in group 2.The labial displacement of maxillary anterior teeth in group 2 > group 3 > group 4 > group 1.Conclusion: During the distal movement of the molars,the four anchorage methods were accompanied by different degrees of labial inclination and anchorage consumption of the anterior teeth.The movement trend of teeth was labial-lingual movement > mesial-distal movement > vertical movement,and the movement of the central incisor was the largest and the lip vector of the lateral incisor was the smallest.The labial displacement of a single molar is the smallest,and the loss of anchorage is the least The stress concentration area of the periodontal ligament on the labial side of the anterior tooth was basically equal to that of a single molar when the whole distal molar was combined with the anchorage of the implant 2N.Compared with the II traction,the suppressive effect of the upper anterior teeth was more obvious when the molar was removed together by the microscrew anchorage. |
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