Characteristic CT findings of synovial chondromatosis in temporomandibular joint

264 Abstracts

Objective. We are developing a dentomaxillofacial x-ray conebeam CT, the CB MercuRay™. The purpose of this paper is to present its physical properties and assess its clinical applicability.. Methods and materials. The system is specifically designed for dentomaxillofacial imaging. It consists of an image intensifier and a cone-beam x-ray source. There are 2 types of this system, each with a different size of image intensifier, 9-inch or 12-inch. Each system has 3 field-of-view (FOV) modes. The 12-inch system has facial (F), panoramic (P), and implant (I) FOV modes. The 9-inch system has P, I, and dental (D) FOV modes. Images produced by these systems consist of 512 ⫻ 512 ⫻ 512 isotropic voxels. Sizes of the FOV and voxels for each mode are 192.5 mm and 0.376 mm in F-mode, 150 mm and 0.293 mm in P-mode, 102 mm and 0.200 mm in I-mode, and 51.2 mm and 0.100 mm in D-mode. Physical properties such as resolution, noise, and distortion of image were evaluated for each system. Modulation transfer function (MTF) was measured using Boone’s method. In addition, resolution of the systems was subjectively evaluated using a bar pattern phantom. A water phantom was used to evaluate the noise properties of the systems. The standard deviation of CT value in water was measured as an image noise. Circularity of the axial images yielded by the systems was measured using an 8-mm-diameter acrylic pipe. Clinical study. One hundred eighty subjects with the following suspected disorders were examined using the systems: periodontitis, impacted tooth, cleft palate, jaw deformity, dental implant, jaw cyst, TMJ disorder, and others. The images obtained were analyzed to see whether the image quality met the diagnostic purposes. Results. The resolving power at an MTF of 0.1 in D-mode was over 2.0 lp/mm, and subjective assessment of resolution was the same as MTF results. These results suggest that this system yields images of high resolution. The standard deviation of the CT value in water was 70 in P-mode. This is thought to be greater than that of conventional CT. The circularity of images obtained of the pipe was 99% of the ideal value. In clinical examination, the pattern of alveolar bone resorption, relationship between impacted teeth and the mandibular canal, 3-dimensional contours of the jaws, TMJ, and jaw lesions were clearly visible. Conclusions. This study shows that the newly developed CB MercuRay™ cone beam x-ray CT is useful for examination of dentomaxillofacial disorders.

CHARACTERISTIC CT FINDINGS OF SYNOVIAL CHONDROMATOSIS IN TEMPOROMANDIBULAR JOINT. Qiang Yu, Ninth People’s Hospital, Shanghai Second Medical University, Shanghai, China, and Temple University School of Dentistry, Philadelphia, Pa Jie Yang, Pingzhong Wang, Huimin Shi, and Jicheng Luo Background. Synovial chondromatosis of the temporomandibular joint (TMJ) is a rare, benign, monoarticular arthropathy that is characterized by cartilaginous bodies formed in the synovial membrane.1 Inasmuch as this disease process can potentially destroy the floor of the middle cranial fossa and invade the intracranial structures,2 early detection and diagnosis of this disease become extremely important for selection of an appropriate treatment procedure as well as for better prognosis. Objective. The purpose of this study was to report 8 new cases over the past 8 years and classify the characteristic computed tomography (CT) findings of synovial chondromatosis of the TMJ. Methods and materials. Eight subjects (7 Asian and 1 Caucasian) with a chief complaint of soft tissue swelling in the region of the TMJ were examined with axial and coronal CT scans. All lesions were histopathologically confirmed to be synovial chondromatosis. The CT findings of this pathological condition were classified into the following 5 categories: (1) soft tissue swelling, (2) loose calcified

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY February 2004 bodies in the soft tissue of the joint, (3) widening of the joint spaces, (4) destruction of the mandibular condyle, and (5) destruction of the central skull base. Results. Among the 8 subjects, 7 (87.5%) demonstrated soft tissue swelling, 7 (87.5%) showed loose calcified bodies, and 6 (75%) had erosion of the articular surfaces, indicating destruction of the central skull base. Widening of the joint spaces and destruction of the mandibular condyle were found in 4 (50%) and 3 subjects (37.5%) respectively. Most importantly, 1 subject, who had resorption of the articular surface, was found with extension of the synovial tissues to the dura of the temporal lobe of the cerebrum. Conclusions. Based on the CT findings and histopathological confirmation, synovial chondromatosis of the TMJ is characteristic of soft tissue swelling, loose calcified bodies, and destruction of the central skull base.

REFERENCES 1. Noyek AM, Holgate RC, Fireman SM, Rosen P, Pritzker KP. The radiologic finding in synovial chondromatosis (chondrometaplasia) of the temporomandibular joint. J Otolaryngol Suppl 1977;3: 45-8. 2. Karlis V, Glickman RS, Zaslow M. Synovial chondromatosis of the temporomandibular joint with intracranial extension. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;86:664-6.

TRICHODENTO-OSSEOUS DYSPLASIA: REPORT OF 2 CASES. Mohammad Islam, and Alan G. Lurie, University of Connecticut Health Center, Farmington, Conn Background. Trichodento-osseous dysplasia (TDO) is a rare autosomal dominant type syndrome that has characteristic manifestations in the dento-facial complex. Genotype of the disorder has been revealed. Two different phenotypes of the disease have been reported in the literature. Its association with amelogenesis imperfecta has been described. The 2 conditions, however, have distinct genetic profiles. We present 2 cases from 1 family. Some clinical features described as typical for the disease were not evident in these cases. Case report. A 13-year-old Caucasian female came to the dental clinic for orthodontic treatment. Initial examination revealed yellowish-brown teeth, retained lower right canine, and developing second and third molars. Radiographically her dentition was remarkable for larger pulp chambers and reduction of enamel thickness or absence of enamel where imaged. All second and third molars were seen to be developing without any abnormality. However the second molars did not have root furcations, and they had a somewhat taurodont appearance due to increase in height of pulp chambers. The lateral skull radiograph showed increased thickness and density of the bones in skull base. There was absence of frontal and mastoid sinuses; the sphenoid sinus was not pneumatized. Initial differential diagnosis was osteopetrosis, amelogenesis imperfecta (AI), and TDO. Radiographs from the mother showed partially dentate jaws with heavily restored and endodontically treated remaining teeth. Increased thickness and density of the skull bones were noted. The mastoid air cells were sclerosed, and the maxillary and frontal sinuses were hypoplastic. Hand-wrist images of both patients showed sclerosis of the distal ulnas and radii. Both patients had robust mandibles in Class III skeletal positions. Few features other than bony changes and AI were consistent with the TDO syndrome. Genetic linkage analysis confirmed mutation of DLX3 gene which resulted in TDO in both the mother and the daughter. Discussion. Clinical features of these 2 cases did not confirm definite presence of taurodontism or obtuse mandibular angle, which have been considered key features of TDO. This is possibly due to variable expression of the mutated gene. Cases previously reported in the literature also showed heterogeneity of the condition, which is