[Three-dimensional imaging with computerized tomography. Etiologic considerations and methods for studying temporo-mandibular joints].

INTRODUCTION: The temporomandibular joint (TMJ) had always been studied with conventional tomography and, more recently, with Magnetic Resonance Imaging. Computed Tomography (CT) can demonstrate periarticular soft tissues only. Recently, the introduction of three-dimensional (3D) CT reconstructions with dedicated softwares permitted to demonstrate functional changes in the TMJ with a simple and accurate measurement system. MATERIAL AND METHODS: We examined 347 patients with TMJ disorders using two different 3rd generation CT units and acquiring two series of scans, with the mouth closed and in maximum opening. 3D reconstructions on predefined planes were obtained with a dedicated software and integrated with the electronic measurements of the following morphologic and functional parameters: zygomatic tubercle height, axis of sagittal inclination of the mandibular condyle, TMJ movement range and changes in torsion/dislocation of condylar angle. RESULTS AND DISCUSSION: CT showed the TMJ easily. This examination lasts about 10 minutes, plus 10-15 more minutes for 3D reconstructions. Some artifacts were found on 3D images--thresholding artifacts, defined as pseudoforamina and pseudocalcifications. Neverthless, 3D imaging can easily demonstrate an articular district which is very complex in both morphology and function, supporting or replacing similar subconscious processes made by radiologists themselves. This technique was well accepted by all our patients and functional results were always in agreement with clinical findings. Moreover, CT is the only technique showing both TMJ sides at the same time. Our measurement system was easy to perform, repeatable and comparable also thanks to its potentials of standardization on different CT units. CONCLUSIONS: CT with 3D reconstructions appears the gold standard technique for functional TMJ studies. Even though it provides no information on the joint disk--which MRI does--3D CT permits easy and accurate measurements of both TMJ sides which can support clinical findings.