Objective. We are developing a dentomaxillofacial x-ray cone-beam CT, the CB MercuRay™. The purpose of this paper is topresent its physical properties and assess its clinical applicability..

Methods and materials. The system is specifically designed fordentomaxillofacial imaging. It consists of an image intensifier and acone-beam x-ray source. There are 2 types of this system, each witha different size of image intensifier, 9-inch or 12-inch. Each systemhas 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 systemsconsist of 512 � 512 � 512 isotropic voxels. Sizes of the FOV andvoxels for each mode are 192.5 mm and 0.376 mm in F-mode, 150mm and 0.293 mm in P-mode, 102 mm and 0.200 mm in I-mode, and51.2 mm and 0.100 mm in D-mode. Physical properties such asresolution, noise, and distortion of image were evaluated for eachsystem. Modulation transfer function (MTF) was measured usingBoone’s method. In addition, resolution of the systems was subjec-tively evaluated using a bar pattern phantom. A water phantom wasused to evaluate the noise properties of the systems. The standarddeviation of CT value in water was measured as an image noise.Circularity of the axial images yielded by the systems was measuredusing an 8-mm-diameter acrylic pipe.

Clinical study. One hundred eighty subjects with the followingsuspected 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 seewhether the image quality met the diagnostic purposes.

Results. The resolving power at an MTF of 0.1 in D-mode wasover 2.0 lp/mm, and subjective assessment of resolution was the sameas MTF results. These results suggest that this system yields imagesof high resolution. The standard deviation of the CT value in waterwas 70 in P-mode. This is thought to be greater than that of conven-tional CT. The circularity of images obtained of the pipe was 99% ofthe ideal value. In clinical examination, the pattern of alveolar boneresorption, relationship between impacted teeth and the mandibularcanal, 3-dimensional contours of the jaws, TMJ, and jaw lesions wereclearly visible.

Conclusions. This study shows that the newly developed CBMercuRay™ cone beam x-ray CT is useful for examination ofdentomaxillofacial disorders.

CHARACTERISTIC CT FINDINGS OF SYNOVIALCHONDROMATOSIS IN TEMPOROMANDIBULARJOINT. Qiang Yu, Ninth People’s Hospital, Shanghai Sec-ond Medical University, Shanghai, China, and Temple Uni-versity School of Dentistry, Philadelphia, Pa Jie Yang, Ping-zhong Wang, Huimin Shi, and Jicheng Luo

Background. Synovial chondromatosis of the temporomandib-ular joint (TMJ) is a rare, benign, monoarticular arthropathy that ischaracterized by cartilaginous bodies formed in the synovial mem-brane.1 Inasmuch as this disease process can potentially destroy thefloor of the middle cranial fossa and invade the intracranial struc-tures,2 early detection and diagnosis of this disease become extremelyimportant for selection of an appropriate treatment procedure as wellas for better prognosis.

Objective. The purpose of this study was to report 8 new casesover the past 8 years and classify the characteristic computed tomog-raphy (CT) findings of synovial chondromatosis of the TMJ.

Methods and materials. Eight subjects (7 Asian and 1 Cauca-sian) with a chief complaint of soft tissue swelling in the region of theTMJ were examined with axial and coronal CT scans. All lesionswere histopathologically confirmed to be synovial chondromatosis.The CT findings of this pathological condition were classified into thefollowing 5 categories: (1) soft tissue swelling, (2) loose calcified

bodies in the soft tissue of the joint, (3) widening of the joint spaces,(4) destruction of the mandibular condyle, and (5) destruction of thecentral skull base.

Results. Among the 8 subjects, 7 (87.5%) demonstrated softtissue swelling, 7 (87.5%) showed loose calcified bodies, and 6 (75%)had erosion of the articular surfaces, indicating destruction of thecentral skull base. Widening of the joint spaces and destruction of themandibular condyle were found in 4 (50%) and 3 subjects (37.5%)respectively. Most importantly, 1 subject, who had resorption of thearticular surface, was found with extension of the synovial tissues tothe dura of the temporal lobe of the cerebrum.

Conclusions. Based on the CT findings and histopathologicalconfirmation, synovial chondromatosis of the TMJ is characteristic ofsoft tissue swelling, loose calcified bodies, and destruction of thecentral skull base.

REFERENCES1. Noyek AM, Holgate RC, Fireman SM, Rosen P, Pritzker KP. The

radiologic finding in synovial chondromatosis (chondrometapla-sia) of the temporomandibular joint. J Otolaryngol Suppl 1977;3:45-8.

2. Karlis V, Glickman RS, Zaslow M. Synovial chondromatosis ofthe temporomandibular joint with intracranial extension. OralSurg Oral Med Oral Pathol Oral Radiol Endod 1998;86:664-6.

TRICHODENTO-OSSEOUS DYSPLASIA: REPORT OF 2CASES. Mohammad Islam, and Alan G. Lurie, University ofConnecticut Health Center, Farmington, Conn

Background. Trichodento-osseous dysplasia (TDO) is a rareautosomal dominant type syndrome that has characteristic manifes-tations in the dento-facial complex. Genotype of the disorder hasbeen revealed. Two different phenotypes of the disease have beenreported in the literature. Its association with amelogenesis imper-fecta has been described. The 2 conditions, however, have distinctgenetic profiles. We present 2 cases from 1 family. Some clinicalfeatures described as typical for the disease were not evident in thesecases.

Case report. A 13-year-old Caucasian female came to the dentalclinic for orthodontic treatment. Initial examination revealed yellow-ish-brown teeth, retained lower right canine, and developing secondand third molars. Radiographically her dentition was remarkable forlarger pulp chambers and reduction of enamel thickness or absence ofenamel where imaged. All second and third molars were seen to bedeveloping without any abnormality. However the second molars didnot have root furcations, and they had a somewhat taurodont appear-ance due to increase in height of pulp chambers. The lateral skullradiograph showed increased thickness and density of the bones inskull base. There was absence of frontal and mastoid sinuses; thesphenoid sinus was not pneumatized. Initial differential diagnosiswas osteopetrosis, amelogenesis imperfecta (AI), and TDO. Radio-graphs from the mother showed partially dentate jaws with heavilyrestored and endodontically treated remaining teeth. Increased thick-ness and density of the skull bones were noted. The mastoid air cellswere sclerosed, and the maxillary and frontal sinuses were hypoplas-tic. Hand-wrist images of both patients showed sclerosis of the distalulnas and radii. Both patients had robust mandibles in Class IIIskeletal positions. Few features other than bony changes and AI wereconsistent with the TDO syndrome. Genetic linkage analysis con-firmed mutation of DLX3 gene which resulted in TDO in both themother and the daughter.

Discussion. Clinical features of these 2 cases did not confirmdefinite presence of taurodontism or obtuse mandibular angle, whichhave been considered key features of TDO. This is possibly due tovariable expression of the mutated gene. Cases previously reported inthe literature also showed heterogeneity of the condition, which is

264 Abstracts ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGYFebruary 2004

explainable as well from a genetic point of view. Another syndrome,Tricho-odonto-onychial dysplasia, is manifested by severe dystrophicchanges in nails and secondary anodontia. Owing to its rarity, thegenetic background of this condition is yet to be discovered. Whetherthese 2 conditions originate from differential expression of the samemutated gene remains to be clarified.

EARLY DETECTION AND QUANTITATIVE ASSESSMENTOF APICAL ROOT RESORPTION USING CROWN-ROOT RATIO AND TUNED-APERTURE COMPUTEDTOMOGRAPHY (TACT). Andre Mol, Julie H. Mol,Onanong Chai-u-dom, and Donald A. Tyndall, University ofNorth Carolina, Chapel Hill, NC, and Chulalongkorn Uni-versity, Bangkok, Thailand

Background. Apical root resorption (ARR) is a complication oforthodontic treatment without clear causative factors. The relation-ship between causative factors and ARR may be obscured by inac-curacies in current methods of detection and quantification. Two-dimensional imaging, lack of image standardization, as well asorthodontic tooth movement and remodeling of the surrounding tis-sues all pose considerable challenges.

Objective. The purpose of this study was to develop and test atuned-aperture computed tomography (TACT) application and toassess the validity of the crown-root ratio (CRR) method for thedetection and quantification of small oblique apical root resorptionlesions.

Methods and materials. A registered (R) and a nonregistered(NR) version of TACT were tested. In TACT-R, the detector movedwith the tooth through mechanical standardization. TACT-NR al-lowed the tooth to move independently of the detector. Ten basisimages with a maximum angular disparity of 20° were used. Obliqueslicing of TACT-NR follow-up stacks was required for registrationwith baseline stacks. A slice shifting algorithm was applied to preventdrifting of cross-talk shadows.

Twenty extracted maxillary incisors placed in a widened alveolusof a maxillary jaw segment served as test and control sites. Baselineimages were acquired without lesions. Follow-up images were ac-quired with and without lesions. Lesions were created by cutting anoblique buccolingual segment of the root just below the apex. Teethwere moved between baseline and follow-up (rotation and torque),and a bone-putty mixture was used to simulate remodeling of thesurrounding bone. CRR, TACT-R, and TACT-NR were tested by 6radiologists using ROC-analysis. CRR and TACT-R were also testedfor their quantitative ability.

Results. Low Az-values were obtained for CRR (0.68; SD �.09), TACT-R (0.64; SD � .09), and TACT-NR (0.60; SD � .09).Differences between modalities were not statistically significant(ANOVA: P � .05). Lesion quantification was poor for both CRR(R2 � .03) and TACT-R (R2 � .13).

Conclusions. Crown-root ratio and TACT are not valid for thedetection and quantification of small oblique apical root resorptionlesions. Imaging techniques with greater angular disparity betweenbasis images reduce cross-talk effects and are likely to improveperformance.

RADIOTHERAPY FOR TONGUE CARCINOMA IN A PA-TIENT WITH SYSTEMIC LUPUS ERYTHEMATOSUSAnitha Potluri, Robert J Dowset and Sanjay Mallya, Uni-versity of Connecticut Health Center, Farmington, Conn

Background. Systemic lupus erythematosus (SLE) is an auto-immune chronic inflammatory multisystem disease that is character-ized by musculoskeletal, dermatologic, and immunological manifes-tations. There are several reports of serious acute and late skin andother tissue reactions to therapeutic radiation in SLE patients. Areview of the literature reveals few case-control studies documentingthe incidence of acute and late radiation therapy complications inpatients with collagen vascular diseases. It was evident that patientswith scleroderma and possibly rheumatoid arthritis suffer exagger-ated sequelae from radiation therapy, but there was only a slight trendtoward increased acute reactions in the patients with SLE. In previousstudies patients with lupus showed only slight increase of acutereactions. The mechanism of interaction of radiation with skin andsubcutaneous tissues in these patients is not clearly understood.

Case Report. The present case report describes the sequelae ofradiation therapy in a 41-year-old female with history of SLE andSjogren’s syndrome. The patient was diagnosed with a stage IIsquamous cell carcinoma of the left lateral tongue and was treatedsurgically, with selective neck dissection of left neck at levels 1, 2,and 3. Four months later she developed recurrence of carcinoma inthe left lateral tongue and a right neck mass at level 2. The neck masswas treated surgically with neck dissection. The patient was referredto combined chemo- and radiation therapy and made aware of thecomplications possible because of her existing condition of SLE. Shereceived a total dose of 7400 cGy, with fractionated doses to includethe oral cavity and neck, using opposed lateral technique and brachy-therapy with interstitial Iridium-192 implants. The patient developedmoderate to severe acute reactions—extensive mucositis, pancytope-nia, radiation dermatitis, and thrush. Three months since her lastradiation treatment, she still suffered from pain, xerostomia, fatigue,reduced mobility of the tongue, pharyngeal edema, and pain in thetemporomandibular joint area with limited opening of the mouth.

Discussion. The present case describes reactions to radiationtherapy in a patient with SLE. The patient’s early reactions toradiation cannot be wholly attributed to her preexisting condition ofSLE. They could be due to her combined modality treatment ofchemo- and radiation therapy. As the patient is still in her early stagesof recovery we do not know about the late effects. However, this casedemonstrates that SLE is not an absolute contraindication for radia-tion treatment. Nevertheless, such patients should be advised of thepossible increased risk of severe toxicity from radiation.

STORAGE PHOSPHOR PLATES: HOW DURABLE ARETHEY AS A DIGITAL DENTAL RADIOGRAPHIC SYS-TEM? Aurelija Bedard, University of Missouri School ofDentistry, Kansas City, Mo

Background. The exclusive use of digital radiography based ona storage phosphor system at the Univeristy of Missouri–Kansas CitySchool of Dentistry raised some questions about the durability of thestorage phosphor plates (SPPs). The digital images acquired fromSPPs that have been repeatedly used seem to demonstrate a lowerquality owing to the appearance of scratches. These scratches some-times render the image completely undiagnostic and may lead to a“ remake” of the radiograph. Our observations indicated that thedurability of this imaging system may be limited, despite the manu-facturer’s claim that the SPPs can be used indefinitely.

Objective. The aim of this in vitro investigation was to evaluatethe durability of storage phosphor plates (SPPs) as a digital dentalimaging system and to detect the factors that may contribute topossible reduced durability.

Methods and materials. One hundred forty new storage phos-phor plates were divided in groups and exposed to the effects of thevarious handling steps during the image acquisition: Group 1 testedthe effect of placement of the plates in protective barriers, group 2 the

This study was sponsored in part by the Southern Association ofOrthodontists.

Abstracts 265ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGYVolume 97, Number 2