| Objective:CBCT combined with Mimics and Dolphin Imaging software will be used to measure and analyze the changes of teeth,jaw and airway of children,which are diagnosed with skeletal Class Ⅱ malocclusion,before and after treatment with Invisalign MA appliance.Besides,comparing with Twin-block appliance,exploring the similarities and differences of the effects,analyzing their advantages and disadvantages,so as to provide reference for clinical scheme design and appliance selection.Methods:A sample of 30 patients(mean age of 10.5 years),including 16 males and 14 females,was selected with mandibular retrusion during January 2017 to 2019 from the Department of Orthodontics,Affiliated Stomatological Hospital of Kunming Medical University.These patients were randomly and equally allocated into group MA(treated with the Invisalign MA)and group TB(treated with Twin-block appliance).CBCT data were collected before(T0)and after(T1)orthodontic treatment.The related changes of jaw,teeth and upper airway were measured by Mimics and Dolphin imaging software and analyzed statistically with SPSS20.0 software.Results:1.Changes of mandible length:the length of mandible increased by 5.65mm in group MA and 5.21mm in group TB(P<0.05).There was no significant difference between the two groups.2.Changes of sagittal relationship of jaw:ANB decreased by 2.73° in group MA and 3.40° in group TB(P<0.05).Wits value decreased by 4.66 in group MA and 4.63 in group TB(P<0.05).There was no difference between the two groups.3.Changes of vertical relationship of jaws:in group MA,mandibular plane(SN-MP)and the lower third of face(ANS-Me/N-Me)increased by 1.87° and 1.40%respectively(P<0.05),the ratio of posterior and anterior facial height(S-Go/N-Me)reduced by 2.06%.In group TB,SN-MP and ANS-Me/N-Me increased by 2.81° and 2.93° respectively(P<0.05),and S-Go/N-Me reduced by 3.01%(P<0.05).There was significant difference between the two groups.4.Changes of anterior teeth torque:U1-SN decreased by 5.73° in group MA and 6.56° in group TB(P<0.05).L1-MP increased by 2.79° in group MA and 5.46° in group TB(P<0.05).There was significant difference between the two groups.5.Comparison of bone and tooth effects:In group MA,the bone and tooth effects of reduced overjet accounted for 64.48%and 35.52%respectively.In group TB,the bone and tooth effects of reduced overjet accounted for 50.87%and 49.13%respectively.6.Changes of airway:the total volume of airway and increased by(5238.45±4207.1)mm3 in group MA and(3852.99±1993.09)mm3 in group TB(P<0.05).The minimum cross-sectional area increased by 44.14mm2 in group MA and 44.53mm2 in group TB(P<0.05).Conclusions:1.The Invisalign MA appliance can effectively promote the development of mandible and improve the sagittal jaw’s relationship in growing patients with skeletal Class Ⅱ malocclusion.After treatment,it will lead to clockwise rotation of mandible,but the rotation is smaller than that of Twin-block appliance.2.Compared with Twin-block appliance,the Invisalign MA appliance can adjust the torque of the anterior tooth to reduce the anchorage’s loss of anterior tooth and obtain more bone effects in the improvement of overjet.3.Both the invisible appliance and Twin-block appliance can effectively increase the airway’s volume and improve the ventilation capacity of the oropharynx and the laryngopharynx. |
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