[Comparative study on bilateral temporomandibular joint of patients with unilateral multiple symptoms in cone-beam computed tomography].

PURPOSE: To investigate bilateral temporomandibular joint of patients with unilateral multiple symptoms in cone-beam computed tomography (CBCT) and explore the reference planes that may be different,providing reference for the diagnosis of temporomandibular disorders and comparative study. METHODS: 50 cases with unilateral multiple symptoms（except for cases with unilateral single symptom）were examined by CBCT and the following indexes were observed and analyzed,including horizontal angles of the cross-sectional condyle after the reconstruction in the same patient, joint space, macroaxis diameter of condyle and vertical angles of condyle, which were commonly used at oblique position parallelled to the long axis of condyle, the gradient of articular tubercle and the joint space,which could be obtained at sagittal and oblique position vertical to the long axis of condyle.The data obtained was analyzed by paired t test with SPSS13.0 software package. RESULTS: There was significant difference between the bilateral measured value of joint space when the angle was 60° in sagittal plane (P<0.05).The difference was more significant when the angle was 120° in parallel plane and 90° in sagittal plane (P<0.01). The other measured parameters were not significant different. CONCLUSIONS: For patients with TMD, it is more easily to observe differences between the bilateral measured value of joint space in the sagittal or vertical plane,where the increase of the front joint space can be seen and construction was more significant.

Measurement of cortical bone thickness in adults by cone-beam computerized tomography for orthodontic miniscrews placement.

The purpose of this study was to investigate the cortical bone thickness of the inter-dental area of both jaws for orthodontic miniscrew placement. The cone-beam computerized tomography images of 32 non-orthodontic adults with normal occlusion were taken to measure the cortical bone thickness in both jaws. One-way analysis of variance (ANOVA) was used to analyze the differences in cortical bone thickness. Buccal cortical bone in the mandible was thicker than that in the maxilla. In the maxilla, cortical bone thickness was thicker in the buccal side than in the palatal side. Buccal cortical bone thickness in the mandible was thickest at the site distal to the first molar, and in the maxilla it was thickest at the site mesial to the first molar, while in the palatal side of maxilla it was thickest at the site mesial to the second premolar. The changing pattern of cortical bone thickness varies at different sites. In the buccal side of maxilla, the thinnest cortical bone thickness was found to be at 4 mm level from the alveolar crest, while the thickest was at 10 mm level (except for the site mesial to the first premolar). The buccal cortical bone thickness at the sites mesial or distal to the first molar in the mandible and palatal cortical bone thickness of maxilla tended to increase with increasing distance from the alveolar bone.

[Study of radiographic method of increasing vertical angle for identifying double root in maxillary premolar with cone-beam CT].

PURPOSE: To explore the feasibility of radiography method of increasing vertical angle for identifying double root in maxillary premolar with cone-beam computed tomography(CBCT). METHODS: Thirty-one patients with 109 maxillary premolars who needed CT scan for maxillary teeth were selected and scanned by CBCT. The interested region was chosen to reconstruct the image of maxillary premolar at axial, coronal and sagittal section. The actual diameter of root in maxillary premolar and the projection diameter at the center vertical angle of 45° and horizontal angle of 38.5° were measured with CBCT. The data was analyzed with SPSS12.0 software package for Student's t test. RESULTS: There were no significant differences between the actual diameter of double root tip which was (3.74±0.22)mm and projection diameter which was (3.69±0.16)mm of maxillary premolar at the central vertical angle of 45° and horizontal angle of 38.5° with CBCT (P>0.05); There were also no significant difference between the actual diameter of middle 1/3 section of buccal-lingual diameter (7.87±0.66)mm and projection diameter (7.95±0.52)mm of maxillary premolar at the center vertical angle of 45° and horizontal angle of 38.5° with CBCT (P>0.05). CONCLUSION: CBCT can provide an evidence for radiographic method of increasing vertical angle for identifying double root of maxillary premolar.

[Evaluation of palatal bone thickness in adults with normal occlusion for orthodontic miniscrews placement].

OBJECTIVE: To investigate the palatal bone thickness in adult with normal occlusion. METHODS: The cone beam computerized tomography records of 32 adults with normal occlusion (16 males and 16 females), mean age (30.1 ± 6.5) years, were used to measure the bone thickness at midpalatal area and the right and left palatal sides. Coronal slices at 3 mm intervals were generated. Slice 1 was the coronal slice through the posterior border to the incisive foramen, while Slice 7 was the coronal slice 18 mm away from the incisive foramen. At each coronal slice, the midpalatal sites were Site M and the sites on the exterior margin of the hard palatal were Site D. Four equally divided parts on the line linking Site M to Site D were named Site A, B, C from the interior to the exterior respectively. Palatal bone thickness were measured at these sites. RESULTS: Significant differences were noted from Slice 1 to Slice 7, the bone thickness of palate tended to decrease from the front to the back. The thickest site at hard palatal was 12.6 mm, locating at Site D of Slice 1, while the thinnest site was 2.7 mm, locating at Site B of Slice 7. The palatal bone thickness ranged from 10.5 mm (maximum) to 5.8 mm (minimum) at Slice 2 and Slice 3. No statistical significance was found between the left and right sides (P > 0.05). CONCLUSIONS: The favorable sites for miniscrew placement were the anterior region of the hard palate in adult. The length of miniscrew ranged from 5 mm to 10 mm can be placed from 6 mm posterior to the incisive foramen.

[Effect of right chewing-side preference on morphological temporomandibular joint changes].

PURPOSE: To explore the effect of right chewing-side preference on temporomandibular joint with cone-beam computed tomography (CBCT). METHODS: Fifty-two patients who were diagnosed as right chewing-side preference were selected and scanned by CBCT in the intercuspal position. The interested region was chosen to reconstruct and the images of bony structure of TMJ at axial view, coronal position, sagittal position, oblique position parallelled to the long axis of condyle and oblique position vertical to the long axis of condyle were evaluated. The data was analyzed with SPSS12.0 software package for paired t test. RESULTS: There was significant difference between the habitual and unhabitual sides of the joint space of 60° and 90° at oblique position parallelled to the long axis of condyle (P