| Objective:1.The aim of this study was to assess the efficiency and movement pattern of upper arch expansion using Invisalign system and change of upper anteriors after arch expansion,while the correlation between designed expansion amount as well as initial molar torque and efficiency of expansion movement.2.To assess the maxillary basal bone width,alveolar width and arch width,as well as the thickness and height of buccal alveolar bone for maxillary first permanent molar.3.To evaluate the change of mandibular position and profile after arch expansion.Methods:20 adult Chinese patients from Stomatology Hospital of Shandong University subjected to arch expansion with Invisalign aligners(Align Technology)according to strict criteria were considered for this study.The treatment plan containing upper arch expansion was designed in ClinCheck Pro(Align Technology).In the first N aligners just expand the upper arch while don't do any other teeth movement.Pre-treatment(TO stage)and immediately after finishing expansion phase(T1 stage)records for each of participant were collected which including digital models,lateral cephalometric radiographs and cone-beam computerized temography(CBCT).The upper first molars were divided into A,B and C groups based on different designedexpansion amount.They were also divided into D,E and F groups according to their initial molar torque.Data were measured by using Dolphin 3D(Dolphin,chatsworth,Calif.),Geomagic Studio 12.0(Research Triangle Park,NC)and Meazure software.The parameters were analyzed with SPSS 19.0.Result:1.The efficiency and movement pattern of upper arch expansionThe average expansion efficiency of upper canine crown,first premolar crown,second premolar crown and first molar crown was 79.75±15.23%,76.1±18.32%,73.27±19.91%and 68.31 ±24.41%respectively.The expansion movement pattern was mainly tipping movement.Compared to the planned value,the torque of upper first molar increased by 2.07±3.27°(P<0.05),and the average efficiency of totally expansion movement was 36.35±29.32%?2.The differences between TO and T1 in maxillary basal bone width,alveolar bone width and arch width,as well as the thickness and height of buccal alveolar bone in maxillary first permanent molarThere were no significant changes in the basal bone width and alveolar bone width in upper first molar.The buccal and palatal alveolar bone crest width of upper first molar increased by 0.87±0.63mm,0.75±0.80mm respectively(P<0.05).The buccal tip width,central fossa width and palatal tip width of upper first molar increased by 1.47±0.98,1.33±0.88,1.48±1.02mm respectively(P<0.05).The distal buccal root apex width,root furcation width and palatal root apex width increased by 0.59±0.61,0.43±0.51,0.54±0.51mm respectively(P<0.05).The CEJ10 decreased by 0.34±0.53mm(P<0.05),while no significant changes were noted in the height of buccal alveolar bone in maxillary first permanent molar.3.The differences between TO and T1 in anteriors,mandibular position and profileThe 11 had a significant extraction(0.46±0.53mm),retrusion(0.33±0.39mm),and linguoclination(1.42±1.460),while the 21 had a significant extraction(0.35±0.37mm),retrusion(0.41±0.47mm),and linguoclination(1.43±1.40°).There were significant decrease in Ls-TVL(0.49±0.56mm)and Pog'-TVL(1.05±1.22mm).4.The differences between group A,B and C in average bodily expansion efficiencyThe efficiency of group A was 56.03±19.79%,while in group B was 29.76±30.77%,in group C was 12.40±11.95%.There was significant differences in average bodily expansion efficiency between group A and B,A and C(P<0.05),while no significant differences between group B and C(P>0.05).5.The differences between group D,E and F in average bodily expansion efficiencyThe efficiency in group D was 56.37±24.68%,while in group E was 37.03±30.87%,in group F was 14.42± 18.67%.There was significant differences in average bodily expansion efficiency between group D and E,D and F,E and F(P<0.05).6.The designed expansion amount and initial maxillary first molar torque had a significant negative correlation with the efficiency of bodily expansion movement(P<0.05).Conclusion:1.The Invisalign system can achieve arch expansion effectively.The presetting expansion movement and initial torque have an effect on bodily buccal expansion,and the larger the amount of presetting expansion movement and the buccal inclination of molars crown,the lower the bodily efficiency of buccal movement.Thus,there must be more presetting buccal movement for root when expansion amount and the initial buccal inclination of molar crown is large.2.During the treatment of arch expansion using Invisalign,anteriors tend to extract and inlcine lingually.And there is a light buccal inclination in posteriors which represent buccal tip lift.It is necessary to increase anchorage preparation in anteriors and preset adequate buccal torque of posteriors root to prevent clockwise rotation of mandible.3.There is no adverse effect in posteriors buccal alveolar bone height and thickness through comprehensive diagnosis and optimum design for the patients whose periodontal condition is good. |
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