The Characteristic Of The TMJ For Adults With Severe Deep Overbite By Using Cone-Beam Computed Tomography

Objective:This study aims to provide references and accordance for clinical diagnosis and treatment through researching the morphology of condylar and joint spaces in patients with severe deep overbite, and comparing the differences between patients with these features and people with normal malocclusions and healthy temporomandibular joint by using CBCT.Methods:Test subjects consist of 20 patients who suffer from III degree of deep overbite, in which half is male and half is male, aged from 20 to 27 with average age 23.6. In the control, subjects age from 20 to 30, with average 24.8, and in which males and females account for the same proportion. All subjects are concerned with the experiment. Using the scanning and imaging examining system of CBCT to scan all the studying objects, then storage the image data into Dicom3.0 medical digital communication image. Used Invivo 5 software to read the stored image data, then reconstruct 3D of CBCT images. Applicate the software to adjust head positions, the reconstruction image is set on the direction of 3D coordinate axis, from the three dimensional direction of 3D image positioning. Using the software to choose research areas. On shaft position choose condylar maximum area layer as the reconstruction base layer, this surface as a basic layer, to rebuild the image of center of coronary position and center of sagittal position. using Invivo 5 software to reconstruct and measure all data of temporomandibular joint.Including condylar maximum axial plane, center of coronary position and center of sagittal position are measured in this test. For detail, we check anteroposterior diameter, medialateral diameter, Maximum area, medialateral diameter-sagittal plane angle, the center of condylar-mid sagittal plane distance on condylar maximum axial plane. Height of the top of condylar on center coronary position. Length of condyle, anterior joint space, superior joint space, posterior joint space, height of fossa glenoid, width of fossa glenoid on center of sagittal position.Using SPSS13.0 statistical analysis software to analysis all measurement data. All the datum received the test of normality first. If the data was normal and homogeneity, descriped it with the mean value(`x) and the standard deviation(s). Ipsilateral TMJ data between the deep overbite group and the normal group adopted independent sample T test to analysis the existence of gender differences. The difference between the both sides of the two groups were analysis by paired T-test. Independent sample t-test is chosen to analysis the difference of deep overbite group and the normal group. If the data does not follow normal distribution, then we descriped them with median(M) and quartile range(Q). Data is tested with Wilcoxon rank-sum test. For standard, we define α=0.05, and P<0.05 is statistically significant.Results:1 In the comparison of both sides in normal group, all the subjects detected by the instrument showed that there is no statistically significant difference between both sides of TMJ in the normal group, with all the P more than 0.05.2 In the comparison of both sides in deep overbite group, all the subjects detected by the instrument showed that there is no statistically significant difference between both sides of TMJ in the deep overbite group, with all the P more than 0.05.3 In the comparison of the difference between the normal group and severe deep overbite group, the measurements those P<0.05 were medialateral diameter-sagittal plane angle, height of the top of condylar, anterior joint space, superior joint space, posterior joint space, height of fossa glenoid. The measurements of severe deep overbite group less than the normal group`s were medialateral diameter-sagittal plane angle 69.91°±4.58° and 73.48°±4.96°, height of the top of condylar 6.09±0.51 mm and 7.08±0.77 mm, anterior joint space 2.21±0.09 mm and 2.46±0.13 mm, superior joint space 2.42±0.23 mm and 2.68±0.38 mm, posterior joint space 1.83±0.13 mm and 2.19±0.07 mm.The measurements of severe deep overbite group bigger than the normal group’s was height of fossa glenoid 10.34±0.52 mm and 9.19±0.42 mm.Conclusions:1 Application of CBCT measuring TMJ condylar and joint space is feasible and accurate.2 Position of condylar on severe deep overbite group tends to be superior, posterior, and inner.3 Height of fossa glenoid on severe deep overbite group increases.