International Journal of Computerized Dentistry, 04/2005

The milling accuracy of the Cerec Scan system was examined under standard practice conditions. For this purpose, one and the same 3D design similar to an inlay was milled 30 times from Vita Mark II ceramic blocks. Cylindrical diamond burs with 1.2 or 1.6 mm diameter were used. Each individual milled body was measured exactly to 0.1 µm at five defined sections with a coordinate measuring instrument from the Zeiss company. In the statistical evaluation, both the different diamond bur diameters and the extent of material removal from the ceramic blank were taken into consideration; sections with large substance removal and sections with low substance removal were defined. The standard deviation for the 1.6-mm burs was clearly greater than that for the 1.2-mm burs for the section with large substance removal. This difference was significant according to the Levene test for variance equality. In sections with low substance removal, no difference between the use of the 1.6-mm or 1.2- mm bur was shown. The measuring results ranged between 0.053 and 0.14 mm. The spacing of the distances with large substance removal were larger than those with low substance removal. The T-test for paired random samples showed that the distance with large substance removal when using the 1.6-mm bur was significantly larger than the distance with low substance removal. The difference was not significant for the small burs. It was shown several times statistically that the use of the cylindrical diamond bur with 1.6-mm diameter led to greater inaccuracies than the use of the 1.2-mm cylindrical diamond bur, especially at sites with large material removal. Keywords: milling precision Cerec 3D, fitting accuracy of inlayrestorations

The achievable accuracy is a decisive parameter for the comparison of direct intraoral digitization with the conventional impression. The objective of the study was therefore to compare the accuracy of the reproduction of a model situation by intraoral digitization vs. the conventional procedure consisting of impression taking, model production, and extraoral digitization. Proceeding from a die model with a prepared tooth 16, the reference data set of the teeth 15, 16 and 17 was produced with an established procedure by means of extraoral digitization. For the simulated intraoral data acquisition of the master model (Cerec 3D camera, Sirona, Bensheim), the camera was fastened on a stand for the measurement and the teeth digitized seven times each in defined views (occlusal, and in each case inclined by 20°, from the mesio-proximal, disto-proximal, vestibular and oral aspect). Matching was automated (comparative data sets B1-B5). A clinically perfect one-step putty-and-wash impression was taken from the starting model. The model produced under defined conditions was digitized extraorally five times (digi- SCAN, comparative data sets C1-C5). The data sets B1-B5 and C1-C5 were assigned to the reference data set by means of best-fit matching and the root of the mean quadratic deviation (RMS; root mean square) calculated. The deviations were visualized, and mean positive, negative and absolute deviations calculated. The mean RMS was 27.9 µm (B1-B5) or 18.8 µm (C1-C5). The mean deviations for the prepared tooth were 18 µm/-17 µm (B1-B5) and 9 µm /-9 µm (C1-C5). For tooth 15, the mean deviations were 22 µm/-19 µm (B1-B5) and 15 µm/ -16 µm (C1-C5). The intraoral method showed good results with deviations from the CAD starting model of approx. 17 µm, related to the prepared tooth 16. On the whole, in this in-vitro study, extraoral digitization with impression taking and model production showed higher accuracy than intraoral digitization. Since the inaccuracies in the conventional impression under real clinical conditions may be higher than the values determined above, a comparison under clinical conditions should be performed subsequently. Keywords: intraoral digitization, matching, accuracy, one-step puttyand- wash impression

The application of modern software algorithms allow for volumetrically accurate fusion of relevant image data, which may be used for planning purposes and for intra-operative guidance in maxillofacial surgery and related specialties. This study evaluates the feasibility and accuracy of different fusion modes and the application of image fusion for image guided surgery (IGS). Within the study, the IGS system VectorVision (BrainLAB, Heimstetten, Germany) was used. The platform currently supports the fusion of the following imaging methods: CT, MRI, Angio-MRI, PET, Sonography, SPECT, Fluoro- Radiography. The most frequently performed fusion was CT in bone windowing with CT in soft tissue windowing in 82.8% of all cases followed by CT/MRI, CT/Angio-MRI and MRI/Angio-MRI. Increasing significance gains the usage of PET data. The fusion of relevant image data, which can now be performed fully automatically, improves the planning and the realization of especially complex procedures in maxillofacial surgery. Keywords: computer tomography, magnetic resonance imaging, positron emissions tomography, sonography, image guided surgery, fusion, imaging

Cerec 3D software is now able to restore occlusal tooth surfaces safely and reproducibly. With an existing morphology worth adopting and/or by making use of an opposing bite registration, the user can reproduce the central contacts to the opposing jaw with the aid of the correlation mode. However, this assumes that the existing maxillo-mandibular relation is physiological. In prosthetic treatment, it is essential to differentiate between a healthy patient and patients with functional disorders. In the first case, the possibilities of performing an accurate and exact reconstruction of the healthy parameters are given and can be myocentrically controlled and corrected with suitable means. However, in the presence of functional disorders, the pathological situation should not serve at the basis for the reconstruction. Adjustment and, if necessary, stabilization of the function is essential. The following article illustrates by reference to a complex patient case how Cerec restorations can be produced correctly chairside with the aid of the IPR technique even in the case of functional disorders. Keywords: abraded dentition, functional analysis, IPR, CAD/CAM, Cerec, correlation