Laser-Induced Fluorescence and X-Ray Spectral Analysis of Carious Process in Hard Dental Tissues

Abstract

Morphological and spectral X-ray analysis of carious and noncarious extracted teeth showed the patterns of dentin ossification in caries of different degree. Parietal ectopic ossification of the canal and cavity lumens in stages III and IV dental caries is regarded as a specific structural marker of pathological regeneration. The X-ray spectral analysis showed that the progress of carious process is paralleled by loss of mineral components. Laser-induced fluorescent study of tissues in extracted teeth showed 4 spectral bands corresponding to mineral and protein components of the tooth. The progress of carious process was associated with reduction of the fluorescence intensities of the spectral bands characteristic of dental collagen and mineral components.

Decomposition of multi‐component fluorescence spectra by narrow peak method based on principal component analysis

“…The experiments with optical phantoms consisting of water-dissolved fluorophores showed good results in real life conditions. Below, the above described procedure was used to analyze earlier measured LIF spectra from human dental 16 and aortal tissues. 17 In both papers, the 248 nm KrF excimer laser was used, and the shortwave ultraviolet radiation simultaneously excited several fluorophores with overlapping spectra.…”

“…As a result, broadband spectra with no distinct features were observed and were analyzed only qualitatively. The spectra presented in the above papers 16,17 were uncorrected (raw); in the analysis below they were normalized to the spectrometer's spectral sensitivity, measured with tungsten and deuterium lamps. Intact and caries affected dental tissue LIF spectra (Figure 4A) had one or two local maxima at various wavelengths, with a tendency to decrease in the 380-400 nm region for affected samples.…”

“…With the above discussed discrepancy (dip in the 350-400 nm region), the mineral component spectrum matches this peak. 16 For each component, its contribution into spectra was calculated using linear regression. Since only relative intensities were measured, the contributions of the second and the third peaks were normalized to the contribution of the first, the protein peak.…”