Clinical Indicators And CBCT Evaluation Of Anterior Disc Displacement With Reduction Of Temporomandibular Joint In Skeletal Class Ⅱ Malocclusion With High-angel Adults

Objective:The objective of the study was to evaluate anterior disc displacement with reduction(ADDWR)of temporomandibular joint(TMJ)by checking records of the symptoms and signs of skeletal class Ⅱ malocclusion with high-angel group with ADDWR and measuring the structure of TMJ and mandibular by cone-beam computer tomography(CBCT),and compared with normal TMJ group,then to provide reference for clinical diagnosis and orthodontic treatment.Methods:This study selected the patients with CBCT images from Tianjin Medical University Stomatology Hospital Orthodontics Department and TMJ Department from September 2016 to September 2019,the experimental group is 30 cases of skeletal class Ⅱ malocclusion with high-angel adults with bilateral ADDWR diagnosed by Magnetic resonance imaging(MRI),and the control group is 30 cases of skeletal class Ⅰ malocclusion with equal-angel adults with normal TMJ.And measured the values of each structure by using Invivo5 software to rebuild the image of TMJ and mandibular,then the results were analyzed by using SPSS 22.0.Therefore,evaluating ADDWR combined with clinical examination.Results:1.There was no significant difference in the morphology and position of TMJ between the experimental group and the control group(P>0.05),but it was not symmetry completely.2.Compared with the control group,on the sagittal position,condylar head height was decreased in the experimental group(P<0.05),and there were significant decrease in the superior joint space,the posterior joint space and condylar head length(P<0.01);whereas the anterior joint space was increased significantly(P<0.01),and the condylar position was more posterior(P<0.01).In the coronal position,the intra-condylar space was increased and the lateral-condylar space was decreased(P<0.05).In the axial position,the diameter of condyle was decreased and the angle of condyle was increased significantly(P<0.01).3.Compared with the control group,mandibular ramus length was decreased and mandibular Angle was increased in the experimental group(P<0.05).And there were decreased in SNB,posterior height and face-height ratio significantly(P<0.01),while anterior height was increased significantly(P<0.01).4.In the experimental group,the open and closed mouth sounded,and the lateral movement sounded,and the open mouth shape was abnormal,and the forward extension test results were positive(P<0.05).Conclusions:1.The condyles of ADDWR of the skeletal class Ⅱ malocclusion with high-angel group were higher and posterior on the sagittal position.The condyles had the lateral displacement in the coronal position and rotation in condylar articular fossa in the axial position.The condyle of such patients was fine and short,which may be associated with occlusion pressure.2.The mandible of ADDWR of the skeletal class Ⅱ malocclusion with high-angel group was further back,and mandibular ramus length decreased,and mandibular Angle increased,and anterior face height increased,and posterior face height decreased.It’s was a vertical growth type.3.The ADDWR of the skeletal class Ⅱ malocclusion with high-angel group had a clicking noise,and the click occurred on both vertical opening and closing and during lateral excursions with abnormal opening pattern.And the forward extension test results were positive.4.We can diagnose the ADDWR of the skeletal class Ⅱ malocclusion with high-angel group by the combination of the typical clinical signs and CBCT images firstly.