Caries, a common and widespread infectious disease, has to be detected as early as possible. Based on the need for an
easy and handy tool for preventing invasive treatment a new fluorescence camera system has been developed. Using this
camera the so-called porphyrins, metabolic products of oral pathogenic bacteria can be visualized. Thereby fluorophores
are excited at a wavelength of 405nm by the built-in GaN-LEDs. Healthy and diseased dental hard tissues fluoresce in
the green and in the red spectral range, respectively, thus allowing differentiation by coulor.
To prove the reliability of this fluorescence camera system, freshly extracted teeth were examined. Three different
methods of analysis were verified and compared to give information about the lesions (sensitivity & selectivity): The
extent of the fluorescence area, the integral of the red/green ratio of the lesion and the maximum red/green ratio in the
area of interest. Histological sections of the teeth served as reference. In addition, the camera was compared to a tip
probe sensor already available on the market.
In total, our results show that regarding the three different algorithms of analysis, the maximum of the red/green ratio is a
preferential method to evaluate carious lesions. Sound tissue, enamel caries and dentin caries can be clearly
distinguished. The new fluorescence camera is a handy, efficient and fast device in order to detect lesions and seems to
be superior to the tip probe sensor regarding the positioning. Further studies are required.
Optical methods for the detection of carious lesions, calculus and plaque have the advantage of being minimally invasive. The use of endogeneous fluorescence markers like porphyrins could simplify the application of fluorescence techniques in the dental practice. It is known that porphyrins are produced by some of the bacterial species that are present in the oral cavity. Since porphyrins have an excitation band at about 400nm they have the potential to be used as fluorescent markers of locations in the oral cavity where the production of bacteria is out of the limits of healthy regions. Further, modern and efficient GaN-based semiconductor diodes emit light in this spectral range and thus make the implementation of fluorescence sensors with excitation at this wavelength easy.
Carious lesions, calculus and plaque have been measured using a self build fluorescence camera using GaN-diodes for illumination at 405nm. Further, emission spectra under this excitation were recorded. For the latter purpose freshly extracted teeth were used. It has been found that already in the case of an initial carious lesion red porphyrin-fluorescence is emitted whereas it is absent in healthy enamel. In already brown coloured carious lesions the emission bands of porphyrin are present but the observed overall fluorescence intensity is lower, probably due to the absorption of the fluorescence by the carious defect itself. In dental calculus, dental plaque and subgingival concrements porphyrin originated luminescence was found as well. Since in these cases the emission spectra differ slightly it can be concluded that they originate from different types of porphyrins and thus also from different bacteria. These results show that this fluorescence technique can be a promising method to diagnose carious lesions, calculus and plaque.
In present work the possibility of use the some alkali halide compounds as storage phosphor for image plates is discussed. For improvement of spatial resolution in digital radiographic systems it is proposed to use the single crystalline image plates prepared by liquid phase epitaxy and by diffusion. The optical luminescence properties of obtained structures are studied. The possible mechanisms of photostimulable luminescence in thin single crystalline KBr:In;Tl, RbJ:Tl, KCl:In;Tl layers are discussed.