Quantified light-induced fluorescence, review of a diagnostic tool in prevention of oral disease

Abstract

Diagnostic methods for the use in preventive dentistry are being developed continuously. Few of these find their way into general practice. Although the general trend in medicine is to focus on disease prevention and early diagnostics, in dentistry this is still not the case. Nevertheless, in dental research some of these methods seem to be promising for near future use by the general dental professional. In this paper an overview is given of a method called quantitative light-induced fluorescence or (QLF) in which visible and harmless light excites the teeth in the patient's mouth to produce fluorescent images, which can be stored on disk and computer analyzed. White spots (early dental caries) are detected and quantified as well as bacterial metabolites on and in the teeth. An overview of research to validate the technique and modeling to further the understanding of the technique by Monte Carlo simulation is given and it is shown that the fluorescence phenomena can be described by the simulation model in a qualitative way. A model describing the visibility of red fluorescence from within the dental tissue is added, as this was still lacking in current literature. An overview is given of the clinical images made with the system and of the extensive research which has been done. The QLF™ technology has been shown to be of importance when used in clinical trials with respect to the testing of toothpastes and preventive treatments. It is expected that the QLF™ technology will soon find its way into the general dental practice.

Is the red fluorescence of dental plaque related to its cariogenicity?

“…1,5 Several tools proposed to support the clinicians in caries diagnosis process are based on the quantification of the fluorescence emitted by the carious tissue. 2,7 Another use of these devices is the possibility of quantifying the red fluorescence of dental plaque in the oral environment. 6,[8][9][10] One of those devices is the quantitative light-induced fluorescence (QLF), which emits a blue light at 405 nm and collects the fluorescence at the green and red spectra.…”

“…6,[8][9][10] One of those devices is the quantitative light-induced fluorescence (QLF), which emits a blue light at 405 nm and collects the fluorescence at the green and red spectra. 7 With regard to the dental plaque, the researchers have first focused on the investigation of individual microorganisms responsible for the emission of the red fluorescence. The authors observed that obligate anaerobic bacteria were the main source of red fluorescence, including microorganisms usually present in thicker plaque and in dentin caries lesions.…”

Clinical performance of fluorescence-based methods for detection of occlusal caries lesions in primary teeth

“…This difference between carious and sound sites are presented as percentage of increase of red fluorescence. 3,8,11,14 Therefore, these differences between the two devices can explain the different performance observed in our study.…”

“…Moreover, an objective method could be less influenced by examiner's experience than would visual inspection. 4 Considering that LFpen and QLF (red fluorescence measurement) are methods based on the fluorescence emitted by microorganisms present in the caries lesions, 9,11,15 and since active caries lesions are more infected than inactive ones, 16 this possibility would be plausible. The old version of the LF method used with different drying times had been tested for this purpose previously, 28 but this methodology was not compared with visual inspection.…”

“…8 10 Another FBM is quantitative light-induced fluorescence (QLF), in which a blue light is emitted, capturing the back-scattered fluorescence in the green and red spectra. 11 Loss of green fluorescence is observed in initial enamel carious lesions, and the QLF device translates this fluorescence into a quantitative value. Therefore, this method is appropriate for detecting the early signs of carious lesions and for monitoring the arrestment of these lesions after non-operative treatments, mainly on free smooth surfaces.…”