Curvature analysis of the mandibular condyle.

OBJECTIVE: To determine whether curvature analysis on high resolution CT images can be used as a tool for evaluation of mandibular condyle morphology. METHODS: Curvature analysis was performed on reconstructed oblique coronal CT images of 634 normal condyles from 317 patients (144 men and 173 women; age range 4-89 years) with inner or middle ear disease. The condyles were scanned with 1 mm collimation using helical CT. The CT images were analysed manually on a personal computer. RESULTS: The condyle CT images could be categorized into five curvature profile patterns: (1) bi-peak; (2) no peak; (3) tri-peak; (4) bi-peak with an intervening bottom above the base line (bi-peak with a col); and (5) bi-peak with an intervening negative phase. A separate evaluation using computer graphic condyle models indicated that these curvature patterns corresponded to flat (bi-peak), round (no peak), convex (bi-peak with a col), concave (bi-peak with a negative phase) and angled (tri-peak) contours of the condyle's superior surface. The curvature profiles were identical between bilateral condyles in 40% (126/317) of the patients. Gender-related differences in the incidence of the curvature profiles were also found, the bi-peak with a col profile being more frequently observed in women and the bi-peak with a negative phase profile being observed more frequently in men. CONCLUSION: Curvature analysis on CT images depicts condyle morphology effectively and may be an adjunctive tool for condyle morphometry.

Standardization of 3-D CT measurements for length and angles by matrix transformation in the 3-D coordinate system.

OBJECTIVE: We attempted to establish a new 3-D cephalometry with helical computed tomography (CT) by introducing the matrix transformation of the 3-D coordinate system. SUBJECTS AND METHODS: Three-dimensional cephalometric landmarks on the craniofacial bones were expressed as 3-D vectors originating from the center of the sella. These vectors were standardized by the matrix transformation so that the midsagittal plane and cranial base line coincided with the XZ plane and X axis of the 3-D coordinate system, respectively. We also applied this new method to trace the normal growth of the craniofacial bones in 44 patients with head and neck cancer (age range, 5 to 26 years; 19 women and 25 men). RESULTS: The accuracy for length measurements was less than 3% of standard error of means with a slice thickness of 1 or 3 mm for 28 out of the 29 length measurements recorded. The precision errors by repeated measurements were 0.8% to 1.0% coefficients of variation for intra- and interobserver variability. Standardization of 3-D vectors representing the cephalometric landmarks allowed us to assess successfully the age-related transition of these landmarks of the patients' craniofacial bones. CONCLUSION: A new assessment method for 3-D CT cephalometry has been developed by standardizing cephalometric landmarks using a matrix transformation of the 3-D coordinate system. This new assessment method may offer potential in planning plastic and reconstructive surgery.

Tomographic evaluation of TMJ loading affected by occlusal pivots.

PURPOSE: The purpose of this study was to clarify the direction and magnitude of condyle displacement during clenching with occlusal pivots. Temporomandibular joint (TMJ) loading and flexibility and the clinical significance of orthopedic appliance therapy are also discussed. MATERIALS AND METHODS: Participants were 16 volunteers with a mean age of 25.8 years. Maxillary and mandibular flat occlusal devices were fabricated. TMJ tomogram series were taken first with tripod support and then with maxillary clenched anterior pivot support and/or unilateral posterior pivot support. Condyle positions on the TMJ tomograms were analyzed using the digital subtraction technique. RESULTS: When clenching with the anterior pivot, the anterior reference point (A) on the mandibular condyle was translated 0.1 mm posteriorly (P > 0.05) and 0.2 mm superiorly (P < 0.01) from the tripod-support reference point. In the case of the ipsilateral posterior pivot, point A was rotated 1.2 degrees (P < 0.01) and was translated 0.4 mm (P < 0.01) posteriorly and 0.18 mm superiorly (P > 0.05). CONCLUSION: Condyle displacement during clenching with the anterior and posterior unilateral pivot was found, which supports previous findings. However, the direction and magnitude of the displacement differed from those of previous studies using jaw-tracking devices, and individual values differed greatly among subjects.

A method for quantifying positional change of the condyle on lateral tomograms by means of digital subtraction.

A method is described for quantifying the positional change of the condyle on lateral tomograms of the temporomandibular joint (TMJ) by use of digital subtraction. This method permits rotational and translational changes of condylar reference points for easy measurement. Accuracy was evaluated in vitro using both TMJs of two dry human skulls and in vivo with seven volunteers. The average absolute error of the angle of rotation in vitro was 0.67 degrees. For the anterior-posterior element of translation the average absolute error was 0.07 mm, and for the superior-inferior element of translation it was 0.06 mm. From these results, we could conclude that the method provides clinically acceptable measurement accuracy. To verify the usefulness of the method, a clinical application is presented.

Simple X-ray film holder for lateral view of the anterior jaws using dental X-ray apparatus.

A new X-ray apparatus, the occlusal X-ray film holder, was devised so that the lateral view of the jaw could be studied. This apparatus could easily be adjusted to a dental X-ray cone. In 21 cases of impacted teeth, cysts or foreign body in the maxilla and mandible and 6 cases that necessitated examination before or after implantation, the efficacy of this apparatus was confirmed. Its advantages are: it is applicable to dental X-ray equipment; it is cheap; there is no need for image intensifying to get a clear image; and follow-up examination is possible. We believe that this film holder would be useful for the diagnosis of lesions in the anterior maxilla and mandible as well as in the general dental clinic.

The clinical significance of the horizontal condylar angle in patients with temporomandibular disorders.

Ninety-one patients with unilateral temporomandibular disorders (TMD) were examined using submento-vertex projection radiography and lateral and frontal temporomandibular joint (TMJ) tomography. A comparison between clinical and radiographic findings was made to verify whether patients with TMJ osteoarthritis/osteoarthrosis (OA) tend to have high horizontal condylar angles and to determine the clinical significance of the horizontal condylar angle in the diagnosis of TMD. Our survey results did not confirm higher horizontal condylar angles in condyles with radiographic abnormal findings than in those with normal. However, significantly higher angles were observed in symptomatic TMJs with pain on movement/palpation than in those without (P < 0.05). A tendency toward higher angles was also observed in patients with other clinical findings such as TMJ sound on the symptomatic side and limitation of mouth opening, but there were no significant differences. Thus, the clinical significance of measuring the horizontal condylar angle was demonstrated. Careful diagnosis and treatment is therefore recommended with patients for whom the horizontal condylar angle is high.

Anterior mandibular repositioning in a patient with temporomandibular disorders: a clinical and tomographic follow-up case report.

A 42 year old female with temporomandibular disorders (TMD) was treated by anterior mandibular repositioning which was followed-up clinically and tomographically. The authors tomographically reconfirmed the mandibular repositioning and discovered a type of condyle remodeling which they had not seen previously. Although clinical signs and symptoms of TMD were removed and the condyle was centered tomographically by the anterior repositioning, the MRI image indicated the disk was displaced anteriorly and laterally. The results suggest that image analysis of temporomandibular joint (TMJ) is beneficial and careful application of the treatment for anterior repositioning is recommended.

Temporomandibular joint osteoarthritis: a comparative clinical and tomographic study pre- and post-treatment.

Nineteen patients with definite and suspected temporomandibular joint (TMJ) osteoarthritis participated in this study. All patients were treated by dental care including bite plane therapy. By comparing the pre-treatment clinical symptoms and TMJ tomograms with those post-treatment, efficacy of the dental treatment applied for these patients has been assessed. Since TMJ pain and limitation of mouth opening were considerably improved in almost all patients post-treatment, this suggests that the clinical prognosis of TMJ osteoarthritis can be favourable. On the other hand, radiographic changes post-treatment were variable. The longitudinal changes found in the TMJ tomograms were classified into four types. The frequency of Type 2 and Type 3, which indicate the occurrence of TMJ remodelling during the observation period, was fairy high (20 TMJs and 14 patients).

Evaluation of spinal bone changes in patients with chronic renal failure by CT and MR imaging with pathologic correlation.

To investigate bone changes in patients with chronic renal failure (CRF), bone mineral density (BMD) and T1 relaxation times were measured with CT and MR imaging and the results were correlated to histology. Excised lumbar vertebrae from 25 autopsy cases of CRF (18 males and 7 females), including 12 cases in which the patients had been receiving hemodialysis were examined. BMD and T1 relaxation time values were associated with specific histologic findings for cellularity, trabeculae, and peritrabecular fibrosis. Three vertebrae with low BMD showed increased hematopoietic marrow content, a finding not observed in primary osteoporosis. The vertebrae with osteosclerosis showed prolonged T1 relaxation time, which was due to increased amount of hematopoietic marrow, and the presence of thickened or many small irregular trabeculae or peritrabecular fibrosis. These findings may be useful in the evaluation of bone changes in patients with CRF.

Bone mineral and other bone components in vertebrae evaluated by QCT and MRI.

To evaluate the usefulness of assessing bone components using magnetic resonance imaging (MRI), the contributions of bone components, including mineral, fat and collagen, to bone mineral density (BMD) and T1 relaxation time (T1) were studied using phantoms. Excised human vertebrae were also evaluated by quantitative computed tomography (QCT) and MRI. T1 was shortened with increasing quantities of fat and collagen. In water, T1 was significantly affected by bone density, while in oil, T1 became slightly longer as bone density increased. The presence of fat and collagen caused under- and overestimations of BMD, respectively. There was good correlation between T1 and BMD in osteoporotic vertebrae and the vertebrae with long T1 showed an increased content of hematopoietic marrow and/or abnormally increased bone mineral. It was concluded that the experimental data showed that MRI can contribute to the assessment of bone quality.

The contribution of frontal tomography to the diagnosis of temporomandibular joint osteoarthritis.

The contribution of frontal tomography to the diagnosis of temporomandibular joint (TMJ) osteoarthritis has been investigated. Ninety-one patients with clinically defined TMJ disorders were examined by simultaneous lateral and frontal TMJ tomograms taken in the intercuspal position. Abnormal findings were observed on frontal tomograms in 31 joints and suspicious findings in 22 joints. On the other hand, there were 41 joints with abnormal findings and 22 joints with suspicious findings on the lateral tomograms. Suspicious or abnormal findings were found on frontal tomograms alone in 14 joints (7.7%) of 14 patients (15.4%). It is concluded that simultaneous lateral and frontal tomography produces a more accurate radiographic diagnosis of TMJ osteoarthritis.

Standardized lateral oblique projection of the mandible for digital subtraction radiography.

A special apparatus was developed for standardization of the lateral oblique projection of the mandible (LOPM) in order to apply the digital subtraction method. Geometric reproducibility was examined over an 8-week period using a dry skull. Angulation errors were determined by the relation to image noise in the subtraction image. It was found that the relation between image noise and angulation error was approximated by a second-order polynomial. Geometric reproducibility was within 1 degree over the experimental period. These results suggest that this standardized LOPM is satisfactory for clinical application of digital subtraction. Two cases are presented where this technique was used to demonstrate longitudinal changes in bone density.