Finite Element Analysis Of Upper Dentition Intrusion With Miniscrews Anchorage

It has been reported that patients with high Angle and gingival smile have been treated with miniscrews intruding the upper dentition in both anterior and posterior segments of the upper dentition.However,existing studies have not yet determined the specific implant site and optimal orthodontic force of miniscrews.According to the different tooth arrangement of patients,this study used reverse modeling technology to construct the finite element model of the orthodontic system under three conditions: maxillary complete dentition,extraction of the first premolar without closing the extraction spaces,and extraction of the first premolar with closing the extraction spaces.By calculating the stress of the periodontal membrane and the displacement of the upper dentition,the effect difference of different treatment schemes was compared.The results showed that:(1)For non-extraction orthodontic treatment,when the micro-implant anchorage was implanted between the first molar and the second molar,the optimal loading mode was 0.7N-0.8N in anterior and 1.2N-1.3N in posterior.When the microimplant anchorage was implanted between the second premolar and the first molar,the optimal loading mode was 0.6N-0.7N in the anterior and1.3N-1.4N in the posterior,and the transverse palatal arch was used to connect the contralateral second premolar.Compared with the two methods,when the micro-implant anchorage was adjusted from the first molar and the second molar to the second premolar and the first molar,the periodontal membrane was more evenly stressed and the risk of root resorption was lower.(2)For the case of extraction and correction,no matter whether the extraction space was closed or not,the ideal loading mode should be: 0.7N-0.8N labial load of the anterior teeth;1.2N-1.3N buccal load of posterior teeth.When the extraction space was closed,the upper dentition was more efficient and the risk of root resorption was lower.Compared with the intrusion with six miniscrews,when the extraction space was not closed,VHA could be used to replace two palatal miniscrews,which could not only obtain similar appropriate stress area of the periodontal membrane,but also no high stress area.For the case of closing the extraction space,it was recommended to use six micro-implants to support the molar to achieve better pressing effect.Meanwhile,close attention should be paid to the force on the root of the second molar to prevent root absorption.In summary,this study analyzed the stress distribution of periodontal membrane and the tooth displacement trend when miniscrews were pressed into maxillary complete dentition under different positions,different tooth arrangement modes,different palatal anchorage devices,and different traction forces in a comparative manner,so as to provide reference for orthodontic clinic.