The Study About The Change Of TMJ And The Skeleton-face Type In Adults Of Skeletal Class Ⅲ Malocclusion By Camouflage Therapy

Objective:Though non-extraction orthodontic treatment of adult patients with mild to moderate skeletal class Ⅲ malocclusion,the morphological position of the temporomandibular joint and the vertical and sagittal changes of the cranial and maxillofacial regions before and after treatment were studied.The influence of this type of malocclusion on the temporomandibular joint and craniofacial morphology provides a theoretical basis for the orthodontic treatment of adults with mild to moderate skeletal class Ⅲmalocclusion.Methods: Thirty patients with mild to moderate and normal-angle skeletal class Ⅲcases(including 17 males and 13 females)whose treatment are finished were selected.Cone-beam computed tomography(CBCT)was used before and after treatment.Scanning images of cranio-maxillofacial slices in each group were performed.Invivo5 software was used to generate three-dimensional reconstruction images of the lateral image of the skull and the temporomandibular joint.The common and representative cephalometric measurements and the temporomandibular joints in the three-dimensional direction were measured.The values of the bony structures were statistically analyzed using GraphPad Prism 5 to compare the differences in the relevant indicators of the study samples before and after the camouflage treatment.Results:1.There was no significant difference in the measurement indexes between the left and right sides of the temporomandibular joint before treatment(P>0.05).There was no significant difference between the left and right indexes after treatment(P>0.05).2.Morphological changes of the temporomandibular joint: After treatment,the height of the socket increased and the length of the condyle in the sagittal layer decreased,above changes were statistically significant(P<0.05).The length of inside and outside the condyle in coronal layer changed smally(P>0.05).The increase of the anteroposterior diameter of the fossa and the decrease of the anteroposterior diameter of condyle in the axillary layer were statistically significant(P<0.05).3.Changes in the position of the temporomandibular joint: After treatment,the upper joint space and the anterior joint space in the sagittal layer increased,with statisticaldifference(P<0.05),but there was no statistically significant difference in the posterior space of the joint(P>0.05).In the axial layer,the condyle angle increased and the distance from the geometric center of the condyle to the central sagittal line decreased,above two changes were statistically significant(P<0.05).4.Two indicators of the relative position of the condyle,which are ln(P/A)and(P-A)/(P+A)(P: posterior joint space,A: anterior joint space),changed without statistically significant after orthodontic treatment(P>0.05).5.Sagittal changes of the cranial and maxillofacial regions: the bone index APDI and∠NP-FH decreased,the Wits value,the Y-axis and the ∠NA-PA increased,and the dental index ∠U1-NA and U1-NA(mm)increased.∠L1-NB,L1-NB(mm)and ∠U1-L1 decreased(P<0.05),and the above changes were statistically significant(P<0.05).6.Vertical changes of the cranial and maxillofacial regions: the mandibular plane angles(∠ MP-FH and ∠ MP-SN),the height of the frontal skeleton and the low-front skeleton increased,the value of ODI and the angle between the anterior occlusal plane(A-OP)is reduced.The angle between the occlusal plane(OP)and the posterior occlusal plane(P-OP)became larger.Above changes were statistically significant(P<0.05).Conclusion:1.Before and after orthodontic treatment,the temporomandibular joints of the left and right sides of the patients with mild to moderate skeletal class Ⅲmalocclusion were basically symmetrical.2.Morphological changes of the temporomandibular joint: the length of the condyle in the sagittal position decreased and the height of the socket increased.The diameter of the anteroposterior diameter of the condyle decreased and the anteroposterior diameter of the fossa increased.There was no significant change in the inner and outer diameter of the coronal condyle.3.Changes in the position of the temporomandibular joint: the anterior and upper joint in the sagittal position increased,and the posterior joint space did not change significantly.But the location of condyle didn’t change a lot.The abduction angle inthe axial position becomes larger,and the distance between the geometric centers of the condyles on both sides decreases.4.Sagittal changes in the cranial and maxillofacial regions: The mandibular rotation in the osseous changes clockwise,and the sagittal lower jaw regressed relatively to the cranial and maxilla.The change of tooth is the compensatory lip tilt of the upper anterior teeth and the compensatory tongue tilt of the lower anterior teeth.5.Vertical change of cranio-maxillofacial surface: the mandibular plane angle convoluted clockwise,the vertical height of the anterior part and anterior lower part increased,the anterior teeth occlusal plane reversed,the occlusion of posterior teeth and the whole dentition enlarged.