Clinical Study Of Maxillary Expansion With Clear Aaligner

Objective(s):In this study,Dolphin software was used to measure the change of maxillary arch width before and after treatment with clear alighner with lateral cephalometric radiograph and CBCT,and to study the effect of Invisalign appliance on maxillary expansion.It provides a reference of treatment planning.Methods:30 patients were randomly selected from September 2015 to September 2017,who were underwent orthodontic treatment with clear aligner at the Department of Orthodontics,Affiliated Stomatology Hospital of Kunming Medical University.Among them there were 13 males and 17 females,aged 18-40 years with an average of 29.43±.7.12 years old.The maxillary arch were expanded by Invisalign appliance.The lateral cephalometric radiograph and CBCT were taken before and after the arch expansion.The data were imported into the Dolphin software,and grouped according to different tooth position.1 Measure the width change of crown and apex of the maxillary canine,first premolar,second premolar and first molar before and after treatment;2 Compare the width change of crown and apex of the maxillary canine,first premolar,second premolar and first molar with the ClinCheck predisposed expansion amount,to investigate the efficiency of the expansion in each tooth position;3 To compare the width change at the apex of tooth with the change of the crown,to study the way of tooth movement;4 Compare with the lateral cephalometric radiograph in the the change of MP-FH,MP-SN,MP-PP the angle of SNB and the distance between U6-PP and ANS-Me,to compare the vertical change of mandible before and after the maxillary expansion.Data was analyzed using SPSS 25.0 software.Results:1 Compared with data taken before treatment,the width of crown and apex of each tooth position after treatment was increased(P<0.05);the increase of width between canine,first and second premolar crown and apex were larger than that of the first molar.The change in the apex width of first molar are not significant.2 The actual arch expansion amount in each tooth were less than the predisposed expansion arch,the difference was statistically significant(P<0.05).The efficiency of the arch expansion decreases from front to back,with the canine and the first premolar>the second premolar>the first molar.3 The bodily movement efficiency from front to back is:canie>first and second premolar>first molar.The largest bodily movement efficiency was found in canine,with 49±9%,and the smallest found in the first molar,with-7±13%.It shows that the movement of tooth with maxillary expansion mainly tilting movement.4 Before and after treatment,although FMA,MP-SN,SNB showed a decreasing trend,there was no statisticall significant difference.Conclusion(s):1.Clear aligner used to treat adult moderate to moderate crowding with maxillary expansion is effective.2.The tooth movement after maxillary expansion with clear aligner is maily tilting movement,and the efficiency of expansion decrease in more posterior teeth.3.The vertical change is not obvious following the maxillary expansion with clear aligner.