International Journal of Computerized Dentistry, 04/2004

This paper on quantitative light-induced fluorescence (QLF) covers the main developments, physical principles, and current application areas of this noninvasive opticalmethod for caries detection. Until now, QLF has mainly been used to detect and monitor initial carious lesions on smooth surfaces, whereas few studies have tried to assess its performance on occlusal pits and fissures. Since it is technically difficult to image proximal lesions, the use of QLF for detecting proximal lesions does not seem very promising from today's point of view. There can be no doubt that the method's great potential lies in the longitudinal observation of in vitro, in situ and in vivo demineralization and remineralization processes. Keywords: QLF, fluorescence, dental caries, diagnosis

The holographic facial profile scan is a new technique for creation of high-resolution, three-dimensional, realistic facial computer models which can be used for surgical planning and documentation in maxillofacial surgery. First, a holographic image of the patient is recorded using a pulsed laser system. In a second step, called holographic tomography, the real image of the patient's hologram is reconstructed by means of a continuous-wave laser. By moving a screen through the real three-dimensional image, it is sliced into a series of two-dimensional projections which are captured with a digital camera. The slices containing the specific twodimensional information are superimposed to a three-dimensional surface model using special software. The extremely short exposure time of 35 nanoseconds for taking a holographic image is separated from the time-consuming rendering process of the surface model; thus, the obtained models are not affected by themovements of the patient. Keywords: holography, laser, facial profile analysis, maxillofacial surgery, surgical planning, surgical simulation, surgical models

A possible consequence of light absorption as the interaction of electromagnetic radiation with molecules of the tooth's hard substances is, apart from the emission of heat, fluorescence. It was demonstrated that theemission spectraofenamel,dentin, and caries look alike upon excitation with red light; however, fluorescence increases with the process of carious destruction. Based on that, the DIAGNOdent System was developed, which simultaneously injects red light into the tooth surface and detects the resulting fluorescence. Due to this design, clinical application is currently limited to accessible occlusal and smooth surfaces. For occlusal caries detection, it was shown that validity and reproducibility could be optimized over classical diagnostic tests for deep dentin lesions with seemingly intact surfaces. The detection of root caries does not play a relevant role in the directly accessible areas, but estimation of the lesion's activity and progression rate is a prerequisite for differentiated lesion management. Excellent reproducibility of the laser fluorescence measurements was confirmed for this scenario. Lesions with a soft surface texture show significantly higher fluorescence values than leathery or hard lesions, and values also increase with increasing cavity depth. DIAGNOdent offers the potential to improve follow-ups and estimation of the prognosis and to support clinical management of primary carious lesions. Keywords: laser fluorescence, caries detection, occlusal caries, root caries, validity, reproducibility

The accuracy of working length determination in root canal treatment plays a crucial role in the treatment and prevention of periapical disease. Since the introduction of the first apex locator by Sunada in 1961, new and more accurate devices have been developed. Electronic apex locators reduce the number of radiographs required and may detect root canal perforations and fractures. Third and fourth generation apex locators can operate in the presence of intact or necrotic tissue, blood, inflammatory exudates, and various irrigants. The Raypex® 4 and the Apex NRG® novel apex locators are discussed in detail. Keywords: apex locators, endodontics, root apex, working length, Raypex® 4, Apex NRG®

The use of existing devices for object orientation in 3D CAD applications requires some practice and familiarization. In this article, the development of Cercon ®move, a navigation aid for intuitive control of object movements in dental 3D CAD, is presented. Its navigation concept and ergonomics are tailored for the requirements of dental technicians in computer-aided manufacturing of dental restorations. Keywords: 3D CAD, dental, object orientation, navigation, degrees of freedom, Cercon

In this study, the influence of differently shaded substructures made of Y-TZP from different manufacturers (without, with 0.5 mm or 1.0 mm ceramic veneer with Vita VM9 Base Dentin) on the lightness, the saturation, and the color shade (= value, chroma, and hue) was measured and assessed with a spectral photometer (Easy Shade, Vita) on a clinical case in the mouth and on models of different color. Shading substructures made of Y-TZP facilitated adaptation to the basic shade and reduced the layer thickness of the veneer ceramic required to achieve the desired color. This should be done in the future as a matter of routine. In this way, tooth substance can be better conserved when preparing the teeth, and the esthetic result is not diminished. The material used for the production of the working models (plaster or plastic) should be tooth colored and in terms of lightness - analogous to the shading of the substructure - in order to facilitate clinical color measurement and quality control in the laboratory. Keywords: shading, zirconiumoxide, framework, ceramics