| Objective:This study was to investigate the efficiency and movement pattern of upper molar distalization in Invisalign system as well as determine the change of anteriors,mandibular position and profile.The influence of therapy time and molar tip to efficiency of distalization were also evaluated.Methods:In this study,15 adult volunteers were selected and treated by Invisalign system(Align Technology)in Stomatology Hospital of Shandong University according to the strict criteria.The treatment plan which contained upper molar distalization was designed in ClinCheck Pro(Align Technology).In initial(TO stage)and progress(T1 stage),CBCT,lateral cephalogram and 3D digital models were taken.The patients were divided randomly into A/B group according to different wearing time.They were also divided into C/D/E group based on their initial molar tip.The data was measured and superimposed by using Dolphin and Geomagic Studio.A paired t-test,an independent-samples t test,a one-way anova and a Pearson anaylsis were taken(P<0.05).Results:1.The efficiency and movement pattern of upper molar distalizationThe average efficiency of molar crown was 83.28±9.52%and root efficiency was 48.35±24.59%.The average efficiency of totally distalization was 55.02±14.63%.The movement pattern of molars was mainly tipping movement.The change of molar crown,root,vertical dimension,tip and torque had a significant differences(P<0.05).The molars tended to have a 0.28±0.51mm buccal movement,a 0.95±1.04mm intrusion in buccal cusp,a 0.65±0.33mm intrusion in palatine cusp with a 9.29±5.43°decrease in tip and a 5.87±4.80°increase in buccal crown torque.2.The differences between TO and T1 in anteriors,mandibular position and profileThe anteriors had a significant retrusion(0.38±0.36mm),extraction(0.44±0.45mm)and linguoclination(3.07±3.62°).The lower facial height(ANS-Me)had a significant increase of 1.04±0.69mm(P<0.05).There were some improvements in nasolabial angle and protrusion of upper lip,lower lip and pogonion.3.The differences between group A and B in average totally distalization efficiencyThere was a significant increase in average bodily distalization efficiency in group B(P<0.05).The efficiency in group A was 49.70%±9.95%,while in group B was 61.20±13.00%.4.The differences between group C,D,and E in average totally distalization efficiencyThere was a significant differences between group C and E,D and E,while no significant differences between group C and D(P<0.05).The group C had a lowest efficiency of 27.00±31.25%,and group D had a higher efficiency of 46.20±7.89%,and group E had a highest efficiency of 69.80±6.38%.5.The initial tip of second molars had a significant positive correlation with efficiency of bodily distalizaion(P<0.05):Conclusions:1.The Invisalign system has a good efficiency in the treatment of upper molar distalization.To accomplish totally movement completely,it depends on wearing time and molar mesial-distal tip.It is necessary to increase overcorrection in posteriors.2.During the treatment of molar distalization,there is a little anchorage loss in anteriors and tend to extract and inlcine lingually.And there is an intrusion in posteriors which contribute to a little bit counterclockwise rotation of mandible.It is necessary to increase anchorage preparation in anteriors. |
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