Seiten: 273-281, Sprache: Englisch, DeutschArnetzl, Gerwin / Pongratz, D.
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.
Schlagwörter: milling precision Cerec 3D, fitting accuracy of inlayrestorations
Seiten: 283-294, Sprache: Englisch, DeutschLuthardt, R. G./Loos, R./Quaas, S.
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.
Schlagwörter: intraoral digitization, matching, accuracy, one-step puttyand- wash impression
Seiten: 311-316, Sprache: Englisch, DeutschMischkowski, R. A./Zinser, M. J./Kübler, A. C./Hampl, J. A./Zöllner, J. E.
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.
Schlagwörter: computer tomography, magnetic resonance imaging, positron emissions tomography, sonography, image guided surgery, fusion, imaging
Seiten: 325-335, Sprache: Englisch, DeutschNeumann, P./Brausewetter, L.
Die Cerec 3D-Software ist inzwischen in der Lage, sicher und reproduzierbar okklusale Zahnoberflächen zu restaurieren. Bei vorhandener, übernehmenswerter Morphologie und/oder durch Einbeziehung eines Gegenkieferregistrates kann der Anwender mit Hilfe des Korrelationsmodus die zentrischen Kontakte zum Gegenkiefer wieder herstellen. Das setzt jedoch voraus, dass die bestehende Kieferrelation physiologisch ist. Bei der prothetischen Versorgung muss unbedingt zwischen gesunden Patienten und Patienten mit Funktionsstörungen unterschieden werden. Für erstere sind die Möglichkeiten, eine genaue Reproduktion der gesunden Parameter vorzunehmen, vorgegeben und können mit geeigneten Mitteln myozentrisch kontrolliert und korrigiert werden. Beim Vorliegen von Funktionsstörungen jedoch sollte die pathologische Situation nicht als Grundlage für den Neuaufbau dienen. Eine Korrektur und ggfs. Stabilisierung der Funktion ist essenziell. Der Artikel schildert an Hand eines komplexen Patientenfalles, wie Cerec-Restaurationen mit Hilfe der IPR-Technik auch bei Funktionsstörungen chairside korrekt angefertigt werden können.
Schlagwörter: Abrasionsgebiss, Funktionsanalyse, IPR, CAD/CAM, Cerec, Korrelation