Changs Of TMJ In Patients With Skeletal Class Ⅲ Malocclusion In Different Stages Of Combined Orthodontic And Surgical Treatment

Objective: Our study was to measure the position and shape of temporomandibular joint(TMJ)condyle in patients with skeletal Class III malocclusion before and after combined orthodontic-orthognathic surgery treatment and to evaluate its effect on TMJ,which could provide a valuable reference for comprehensive preoperative evaluation of the treatment.Methods: Twenty adult patients with severe skeletal Class III malocclusion treated at the Affiliated Stomatological Hospital of Nanjing Medical University from 2014to 2018 were enrolled in the study.CBCT images of these patients before orthodontic treatment,after preoperative orthodontic treatment and after combined orthodontic-orthognathic surgery treatment were introduced into Dolphin software to obtain accurate corrected horizontal plane,coronal plane and sagittal plane.The diameter,clearance and angle of temporomandibular condyle-glenoid fossa,a total of 13 measurement items,were precisely measured,including internal and external diameter of condyle(d1),anterior and posterior diameter of condyle(d2),internal and external diameter extreme value of condyle(d3),bilateral condylar distance(D),condylar upper height(h),anterior condylar space(DA),posterior condylar space(DP),supra condylar space(DU),the depth of articular fossa depth(FD),the width of the articular fossa(FW),the horizontal angle of the condyle(α),the vertical angle of the condyle(β),and the oblique angle of the articular tubercle(γ).To compare the changes of bone structure of temporomandibular joint(TMJ)before and after treatment,Paired t-test was performed in different stages of the treatment,and P<0.05 illustrated significant difference.Results:(1)There was no significant difference in the measurement items of TMJ between the left and right sides before and after treatment(P>0.05).(2)The horizontal angle of the left condyle before and after preoperative orthodontic treatment changed significantly(P<0.05)while there was no significant difference in the other three-dimensional measurement items of TMJ(P>0.05).(3)The horizontal angle of the left and right condyles,the supra condylar space and anterior condylar space increased significantly before and after orthodontic-orthognathic surgery treatment(P<0.05).Conclusion:(1)The bilateral temporomandibular joints were symmetrical before and after orthodontic-orthognathic surgery in patients with skeletal Class III.(2)There was no significant effect on the temporomandibular joint after preoperative orthodontic treatment.(3)The inner and outer poles of the condyle rotate clockwise in the horizontal plane,the condyle position changed backward and downward after orthodontic-orthognathic surgery treatment.