International Journal of Computerized Dentistry, 01/2013

The digital intraoral impression is a central part in today's CAD/CAM dentistry. With its possibilities, new treatment options for the patient is provided and the prosthetic workflow is accelerated. Nowadays, the major issue with intraoral scanning systems is to gain more accuracy especially for larger scan areas and to simplify clinical handling for the dentist. The aim of this study was to investigate different scanning strategies regarding their accuracy with full arch scans in an in-vitro study design. A reference master model was used for the digital impressions with the Lava COS, the Cerec Bluecam and a powderfree intraoral scanning system, Cadent iTero. The trueness and precision of each scanning protocol was measured. Lava COS provides the a trueness of 45.8 µm with the scanning protocol recommended from the manufacturer. A different scanning protocol shows significantly lower accuracy (trueness ± 90.2 µm). Cerec Bluecam also benefits from an optimal scanning protocol with a trueness of ± 23.3 µm compared to ± 52.5 µm with a standard protocol. The powderfree impression system Cadent iTero shows also a high accurate full-arch scan with a trueness of ± 35.0 µm and a precision of ± 30.9 µm. With the current intraoral scanning systems, full arch dental impressions are possible with a high accuracy, if adequate scan strategies are used. The powderfree scanning system provides the same level of accuracy compared to scanning systems with surface pretreatment. Keywords: accuracy, full arch dental impression, digital impression, CAD/CAM

Intraorale Scansysteme werden in der Qualität immer besser und in der Bedienung immer einfacher und sicherer. Dies eröffnet Möglichkeiten für einen standardmäßigen Einsatz in der Praxis. Ein besonderer Aspekt dabei ist, dass man durch Überlagerung von Kiefersituationen, die zu unterschiedlichen Zeitpunkten aufgenommen wurden, exakte dreidimensionale Differenzanalysen durchführen kann. Auch für verschiedene Fragestellungen in der Zahnmedizin, die einen Soll-Ist-Vergleich erfordern, kann man solche Differenzanalysen vorteilhaft einsetzen. In diesem Artikel sollen die möglichen Indikationen anhand einer neuentwickelten Software vorgestellt, die Funktionsweise der Auswertungsverfahren erklärt und die Voraussetzungen und Grenzen der 3-D-Verlaufskontrolle erörtert werden. Keywords: digital impression, intraoral scanning, 3D-monitoring, diagnostics, difference analysis

The second part of this review of the literature on the clinical significance of surface electromyography (EMG) of the masticatory muscles systematically examines the results of clinical studies in patients with temporomandibular disorders (TMD), preferably randomized controlled trials, investigating relevant aspects of EMG activity during prolonged chewing activity (fatigue effects), during the mastication process, and under the influence of different factors. Studies on the influence of factors such as gender, age, tooth status, orofacial morphology and (acute) pain, the significance of different occlusal relationships during static and dynamic occlusion, and the impact of changes in static occlusion on EMG activity of the masticatory muscles were included in the review. Keywords: electromyography, review, chewing, masticatory muscles, fatigue, maximal voluntary contraction, symmetry, resting activity, splint therapy, oral rehabilitation

This case report demonstrates how two opposing teeth were restored with full crowns using Cerec software version 4.2 (pre-release version). In addition, an anterior tooth was provided with a veneer. The situation was scanned with the Cerec Omnicam. The new virtual articulator was used for the design to obtain correct dynamic contacts. The Cerec Omnicam can scan the entire situation prior to preparation without the help of an assistant, as no surface pretreatment is necessary. The locations of the occlusal contacts can be marked with articulating paper and are indicated on the virtual models. Selective deletion of individual areas allows the prepared teeth to be rescanned, considerably speeding up the workflow. A video demonstration is available of the acquisition and design procedure. Keywords: Cerec, Omnicam, virtual articulator, virtual model, veneer, crown, lithium disilicate

A new type of material consisting of a ceramic substructure infiltrated with a composite material - referred to as a hybrid ceramic - is currently being introduced for dental CAD/CAM use. The characteristic brittleness of ceramic is thus replaced by an elasticity resembling that of natural human dentin. The material features a high fracture load value of 2980 N, and is straightforward to process in CAD/ CAM milling machines. This article presents a case example describing the manufacture of a veneer restoration. Keywords: CAD/CAM, ceramic, hybrid ceramic, feldspar ceramic, minimally invasive, veneer