Clinical Study On Stability Of Maxillary Molar Distalization With Clear Aligner

Objective:To analysis the changes of maxillary molar teeth in three dimensions after distalization with clear aligner by the measurement of three-dimension digital model and X-ray cephalometric analysis both after treatment and 4 months later,in order to provide references for the stability of molar distalization in slight or moderate crowding patients with clear aligner.Methods: 10 cases of patients were selected in orthodontic Department of Shenyang stomatological hospital during November 2015-February 2018.The inclusion criteria were:(1)at the age of 16-30(2)low to moderate crowding,less than 8mm(3)no orthodontic treatment history(4)non extraction treatment(interproximal reduction allowed)(5)obtain space by molar distalization to relieve dental crowding(6)with good compliance,wearing appliance more than 20 h per day(7)maxillary third molar missing or extraction(8)all wear traction of II(9)all the first,second molars were not designed accessories in the Clincheck design.The orthodontic treatment of patients who met the criteria was divided into three stages: T0 stage: before molar distalization(starting orthodontic period);T1 stage: after molar distalization;T2 stage: 4 months later after molar distalization.Plaster models and lateral cephalometric radiographs were taken at the stage of T0,T1 and T2.Measurement and data analysis were performed on each patient’s lateral cephalometric radiograph.All the models obtained were scanned and 3D reconstructed using Danish 3Shape R700 3D laser scanner.And then analysis 3D digital models of all three stages(T0,T1,T2)by 3 Shape OrthoAnalyze analysis software.Import all the data into Microsoft Excel software.For the statistical analysis independent samples t-test was used to compare the difference intergroup and paired samples t-tests were performed comparing the difference between groups bySPSS19.0 software,data was considered significant at p < 0.05,data was considered no significant at p > 0.05.Results: In maxillary molar distalization with clear aligner,data was considered significan in the sagittal direction of the molar mobile(P < 0.05);in the arch width,data was considered significan in arch width increased of distalize molar(P < 0.05);in the vertical,data was considered significan in intrusionon of distalize molar(P < 0.05),but lower anterior teeth phenomenon,the difference was not significant(P > 0.05);in the rotation of tooth axial,data was considered significan in distal palatal rotation of distalize molar(P < 0.05).4 months later after molar distalization,in the sagittal,width,vertical and axial rotation direction,molar distalization have been changed,but data was considered no significant(P > 0.05).Conclusion: 1.In the sagittal direction,maxillary molar distalization with clear aligner of have remarkable effect,the anterior teeth has slight anchorage loss,distal molar has inclined to move far away.2.In the arch width,maxillary molar distalization with clear aligner,distalize molar have a certain extent buccal movement.3.In the vertical,maxillary molar distalization with clear aligner,distalize molar exists a phenomenon of down.4.In the rotation of tooth axial,maxillary molar distalization with clear aligner,distalize molar occurred distal palatal rotation.5.4 months later after molar distalization,the three-dimensional direction of the molars is more stable.According to the size of the mobile efficiency,the stability is in the axial direction > buccal and tongue direction > sagittal direction > vertical direction.