A New Imaging Aid: Dental CT

Abstract

Recently, the requests for the preoperative modeling of custom subperiosteal implants as well as for the preoperative planning of endosseous dental implants have been strongly increasing. In the USA, approximately 300000 implantations are expected for the year 1992. Dental implant surgery, however, is still a delicate procedure which calls for exact planning [1–3]. In the past, preoperative radiographic evaluations typically included lateral radiographs of the skull, intraoral films, and panoramic views. More recently, the use of computed tomography (CT) has improved the quality of preoperative information, mostly utilizing direct coronal scans. This technique is very uncomfortable for the patient. Even more disadvantageous is that this procedure suffers frequently from artifacts caused by metallic fillings. Clearly, the results obtained by CT scanning needed improvement [4, 5]. It was the clear clinical need for the development of a new imaging aid: dental CT. This software package was driven first by the question of how can a CT scan provide a complete view of the mandible and be optimized for implant surgery and second by the need, to guide the oral surgeon to locate and avoid such vital parts of anatomy like the inferior alveolar nerve. The program offers the possibility of reconstructing out of the measured images panoramic views (PV) and synthetic transaxial images (STI) of the jaw. The first reconstruction offers the referring dentist the well-known panoramic image without superposition as in plain films. The STI add new information; they are defined to be locally perpendicular to the panoramic views. By this means, small transaxial images of the jaw are calculated, showing quantitatively the size of the wall thickness and the alveolar nerve.