Characterization of dental caries by LIF spectroscopy with 404-nm excitation

Biophotonics Laboratory, Centre for Earth Science Studies, Trivandrum, India.
Lasers in Medical Science (Impact Factor: 2.49). 05/2011; 26(3):299-305. DOI: 10.1007/s10103-010-0771-3
Source: PubMed


The potential of laser-induced fluorescence (LIF) spectroscopy for the characterization of different stages of dental caries using 404-nm diode laser excitation was investigated. In vitro spectra from 16 sound, 10 noncavitated carious and 10 cavitated carious molar teeth were recorded on a miniature fibre-optic spectrometer. The areas under the receiver operating characteristics (ROC-AUC) were calculated and one-way analysis of variance (ANOVA) was performed. The LIF spectra of the carious teeth showed two peaks at 635 and 680 nm in addition to a broad band seen at 500 nm in sound teeth. The fluorescence intensity ratios, F500/F635 and F500/F680, in carious teeth were always lower than those in sound teeth. The ROC-AUC for discriminating between carious and sound teeth was 0.94, and for discriminating between noncavitated and cavitated carious teeth was 0.87. Statistically significant differences (p<0.001) were seen between sound, noncavitated carious and cavitated carious teeth. The results showed that LIF spectroscopy has the potential to be useful for characterizing different stages of caries in a clinical setting.

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    • "Caries shows additional red fluorescence at around 630 nm because of porphyrin emissions in oral bacteria [10]. Different parameters based on the spectral ratio of two specific peaks [7] [11] or the integrated intensity in two fluorescence spectral bands [6] [12] have been recommended as diagnostic tools to discriminate carious stages. Fluorescence cameras, which were developed to obtain digital images of the tooth surface, have also been extensively investigated [13] [14]. "
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    ABSTRACT: A quantitative method to discriminate caries lesions for a fluorescence imaging system is proposed in this paper. The autofluorescence spectral investigation of 39 teeth samples classified by the International Caries Detection and Assessment System levels was performed at 405 nm excitation. The major differences in the different caries lesions focused on the relative spectral intensity range of 565-750 nm. The spectral parameter, defined as the ratio of wavebands at 565-750 nm to the whole spectral range, was calculated. The image component ratio R/(G + B) of color components was statistically computed by considering the spectral parameters (e.g. autofluorescence, optical filter, and spectral sensitivity) in our fluorescence color imaging system. Results showed that the spectral parameter and image component ratio presented a linear relation. Therefore, the image component ratio was graded as <0.66, 0.66-1.06, 1.06-1.62, and >1.62 to quantitatively classify sound, early decay, established decay, and severe decay tissues, respectively. Finally, the fluorescence images of caries were experimentally obtained, and the corresponding image component ratio distribution was compared with the classification result. A method to determine the numerical grades of caries using a fluorescence imaging system was proposed. This method can be applied to similar imaging systems.
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    ABSTRACT: The validity of laser induced fluorescence spectroscopy for early diagnosis of occlusal caries irradiated by 403 nm diode laser compared to commercial device DIAGNOdent pen was investigated. The quantitative evaluation parameter based on the fluorescence intensity area ratio of different bands F(440–480 nm)/F(540–700 nm) was built. And the linear correlation analysis between fluorescence result and corresponding DIAGNOdent reading is performed to be r = −0.9085. Moreover, the factors of irradiation laser power and excited site influencing the fluorescence distribution was experimentally investigated. The result shows that the fluorescence spectra at different site of sound occlusal surface is different and the higher laser power will lower the sensitivity of evaluation parameter based on the red fluorescence region increasing. The work is of great significance for practical application of laser induced fluorescence at 403 nm.
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