International Journal of Computerized Dentistry, 02/2007

The impact of radiographic imaging on the diagnosis and treatment of periodontal disease has essentially remained unchanged for decades. Thus, periodontal diagnosis relies primarly on traditional two-dimensional representation of the alveolar bone. Recently, digital volume tomography (DVT) has been introduced for head and neck applications. Major advantages of the DVT are a markedly reduced radiation exposure and superior image quality when compared to conventional computed tomography (CT). With this device, three-dimensional sectional images in the axial, frontal and sagittal plane can be obtained at one examination with tomographic slices of widths ranging from 0.125 to 2 mm. Clinical applications of this unit have been reported for implant site imaging, orthodontics, and temporomandibular joint imaging. Investigations regarding the usefulness of DVT for periodontal applications are still in progress. Thus, a field of interest for the use in periodontology might be the imaging of periodontal intrabony defects, dehiscence and fenestration defects, periodontal cysts as well as the diagnosis of furcationinvolved molars. Keywords: periodontal disease, alveolar bone loss, threedimensional imaging, computed tomography, digital volume tomography

Purpose: Determinants of mandibular movements, like condylar inclination and incisal guidance, should be considered in the fabrication of restorations in occlusion to prevent posterior excursive occlusal interferences. The aim of this study was to investigate differences in the occlusal morphology of the right mandibular molar resulting from high, average, and low values of settings for determinants of anteroposterior and transverse mandibular movement using a virtual articulation model. Material and Methods: The articulation functionalities of computer integrated restorative technology by imaging and new acquisition (CYRTINA®, Oratio B.V., Zwaag, The Netherlands) were used as a tool to examine the potential effect of determinants of mandibular movement on occlusal molar design. High, average, and low values for condylar guide inclination, incisal guide angle, and intercuspal contact area (antero-posterior determinants) and laterotrusion, mandibular lateral translation and intercuspal contact area (transverse determinants) were introduced and differences in molar morphology studied. The latter was done by comparing mesiodistal and buccolingual sections of the occlusal designs. These interocclusal differences were quantified as differences in frequency of occlusal distance intervals in an interocclusal range of 1 mm, measured from the occlusal surface of the molar model. The vertical distance with which a standard crown in occlusion had to be corrected to avoid interferences was calculated. Results: Among all parameters, the ipsilateral and contralateral mandibular lateral translation, sagittal condylar guide inclination, the ipsilateral laterotrusion and the incisal guide angle give substantial occlusal surface corrections. The high setting for the ipsilateral mandibular lateral translation required most correction. Conclusion: High and low setting values of mandibular movement determinants require considerable adaptation of the occlusal surface of a crown to prevent occlusal disturbances. Keywords: occlusal morphology, virtual articulator, occlusal interferences, dental CAD/CAM, dental restoration, computerized dentistry

Currently, three manufacturers are known who have either presented a computer-assisted impression system at the IDS 2007 in Cologne or claim to have such a system ready for the practice. This would mean that the dental industry is increasingly concerned with the idea of relinquishing conventional impression methods established over the decades.