Quantitative laser (light) fluorescence method
A method that is related to EFF and is attracting considerable interest is the quantitative laser fluorescence technique. At present, QLF can assess only accessible smooth surfaces and is limited to part of the enamel thickness.
The principle for the QLF method is shown in Fig 199. The excitation is performed with blue-green light (488 nm) from an argon ion laser. The fluorescence in the enamel, occurring in the yellow region (approximately 540 nm), is observed through a yellow high-pass filter (520 nm) to exclude the tooth-scattered blue laser light. Dark regions characteristic of demineralization are registered visually or on a photographic film.
For the initial smooth-surface enamel lesions it can detect, the QLF method has a sophisticated computer-based method for measuring changes in lesion size, which is valuable for some applications.
Recently, a commercial laser fluorescence system, Kavo-Diagnodent, has been introduced. This system seems to be efficient for the diagnosis of noncavitated enamel and dentin lesions on buccal, lingual, and occlusal surfaces (Lussi et al, 1999). In particular, this system should be useful in longitudinal caries-preventive studies.
Selection
Table 17 reveals that most of the caries-diagnosing methods discussed are subjective, and this compromises the potential to make accurate measurements of disease activity over time. The potentially objective tools are the separation method used with a local impression, computer-aided radiographic diagnosis, the electrical methods, and QLF. These tools also have the potential for quantitative measurement, which can be used to aid the diagnosis and determination of carious activity and thus the prognosis. In the past, many of the diagnostic tools have been used only to support a single, dichotomous decision of the presence or absence of disease. Most methods can be used at either the D1 or the D3 threshold. The two exceptions are conventional epidemiologic examinations, which are undertaken at the D3 (dentin caries) level, and the QLF method, which can detect only enamel lesions.
Figure 200 summarizes the performance of the previously discussed methods, in terms of sensitivity and specificity for occlusal and approximal surfaces at diagnostic thresholds D1 (noncavitated enamel lesion) and D3 (dentin lesion). Clearly, no single method will be sufficient for accurate diagnosis of all kinds of carious lesions (see Table 15).
The relatively poor performance and widespread limitations of the available methods
requires clinicians to seek better and more intelligent ways of using existing methods,
while developing new, more accurate, more appropriate devices.
A target for future investigations would be to explore multiple methods in both
supplementary and adjunctive combinations. To meet the clinical requirements of
most general practitioners, a combination of meticulous clinical visual examination,
radiographs (conventional bitewing radiographs or digitized radiographs), and fiberoptic
transillumination would be adequate.
