A CBCT Study On Temporomandibular Joint Changes In Skeletal Class Ⅲ Patients After Orthodontic-orthognathic Treatment

Objective: The aim of this study is to investigate the effect of orthodontic-orthognathic treatment on the symptoms and bony structure of temporomandibular joint in patients with skeletal class Ⅲ malocclusion.Methods:Twenty-four patients with adult skeletal class Ⅲ malocclusion,accepted orthodontic-orthognathic treatment,were included in the study.Each patient was taken CBCT scan as well as their TMJ symptom was checked and recorded at the following stages:T:before the orthodontic-orthognathic treatment;T0:before the BSSRO;T1: witnin 1 week after BSSRO;T2:1 month after surgery;T3:6 months after the treatmentT4:1 year after the treatment.And the morphological and positional indexes of TMJ bone structure were measured at the horizontal position,the oblique direction perpendicular to the long axis of the condylar and the oblique direction parallel to the long axis of the condylar after every stage.The changes of TMJ symptoms and bone structure were analyzed at different time.And 30 normal adults(A)were selected as controls.SPSS19.0 software was used to analyze the datas,and the test level was set as α = 0.05.Results:(1)There was no significant change in TMJ symptoms before and after surgery(P> 0.05).(2)There was no significant difference in the condylar morphology between the normal adult and patients with skeletal class Ⅲ malocclusion(P> 0.05).The spatial position of the condylar in the joint fossa was different from that of the normal adult(P <0.05),the condylar is in front of the joint fossa and above the fossa.(3)Preoperative orthodontic treatment had no significant effect on TMJ structure in patients with skeletal class Ⅲ malocclusion(P> 0.05).(4)The condylar occurred significantly displacement to the rear、below、lateral direction of the joint fossa and the lateral rotation immediately after surgery(P <0.05).There was no significant change in TMJ structure between 1 month after operation and immediately after surgery(P> 0.05).After six months and one year after surgery,except the condylar level angle α was significantly increased(P <0.05),for the other indicators of TMJ bone structure,there was no significant difference from the preoperative(P> 0.05),gradually tend to return to preoperative level.Conclusion:(1)Orthodontic-orthognathic treatment make no difference to TMJ symptoms in patients with skeletal class Ⅲ malocclusion.(2)Compared with the normal adults,the condyle prefers to be in front of the joint fossa and above the fossa in patients with skeletal class Ⅲ malocclusion.(3)Preoperative orthodontic treatment had no significant effect on TMJ in patients with skeletal class Ⅲ malocclusion.(4)The condylar occurred significantly displacement to the rear、below、lateral direction and lateral rotation in a short-term after the BSSRO(within a month at least),but the condylar position gradually return to preoperative position in 6 to 12 months after surgery.