Maxillary Molar Distalization Efficiency Using Invisible Orthodontic Technique In Skeletal Class Ⅱ Patients

Purpose:The purpose of this study is to investigate the effect of temporary anchorage devices and resin attachment on the distalization rate of maxillary molars and premolars in patients with skeletal Class II malocclusion,in order to provide basis and reference for clinical application of invisible orthodontic technique treatment.Methods:a total of 29 patients with skeletal Class II malocclusion were selected from the Department of Orthodontics,Dalian Stomatological Hospital Affiliated to Dalian Medical University.The sample includes 4 males and 25 females with mean age of（24.4±6.9）years.All patients were treated as non-extraction treatment by maxillary molars distalization using invisible orthodontic appliance.The sample was divided into 2 groups:In group A（16 cases）,the maxillary molars were distalized only by invisible orthodontic devices;Group B（13 cases）,maxillary molars and premolars were distalized using invisible orthodontic appliance and temporary anchorage devices inserted bilaterally in the maxillary molar area.The three-dimensional digital models were reconstructed and collected by digital oral scanning at 3 points of time:before treatment（T0）,at the end of distalization of maxillary 1^stand 2^nd molars（T1）,at the end of distalization of maxillary 1^st and 2^nd premolars.Digital models were then imported into Geomagic Control X software and superimposed to analyze the distalization efficiency of maxillary molars and premolars,and to analyze the change of position of maxillary molars between group A and B at T1 and T2.IBM SPSS 26.0 software was used for statistical analysis.Levene’s homogeneity of variance test and independent t test were used to compare groups A and B for distalization efficiency of maxillary molar at T1,the distalization efficiency of maxillary premolar at T2,and the effect of using temporary anchorage devices and resin attachment on the efficiency of maxillary molar distalization.paired t-test was used to assess the change of maxillary molar position at T1 and T2 for groups A and B.Results:（1）At T1,the mean distalization efficiency of maxillary molars for group A and group B were 74.56%and 87.15%respectively;at T2,the mean distalization efficiency of maxillary premolars of group A and group B was 70.29%and 86.06%respectively;distalization efficiency of maxillary molars and premolars in group A were significantly lower than those in group B（P<.01）;（2）at T2 after the2^nd premolars finished distalization,maxillary 1^st and 2^nd molars of group A moved mesially 0.04mm,0.09 mm respectively,and maxillary 1^st and 2^nd molars of group B moved mesially 0.01,with no significant difference（P>.05）;（3）there was no significant difference in maxillary 1^st and 2^nd molars distalization efficiency with or without using attachments（P>.05）.Conclusions:（1）In skeletal class II patients treated with invisible orthodontics only of group A,maxillary molars and premolars distalization mean efficiency were74.56%,70.29%respectively,while using TADs in group B,the mean distalization efficiency of maxillary molars and premolars were 87.15%,86.06%respectively;（2）in group（A）whish were treated by invisible orthodontics only and in group（B）which were treated by invisible orthodontics with TADs,At T2,both maxillary 1^st and 2^ndmolars moved mesially,although there was no significant difference,the results indicate that TADs provided better stability;（3）in groups A and B,there was no significant difference in maxillary molars distalization efficiency distalized with or without using resin attachments.