Fluorescence characterization of dental plaque by hyperspectral imaging
The buildup of dental plaque is the first step towards the oral diseases caries and periodontitis. Identification of pathogenic substances and matrix components is of importance when choosing an appropriate treatment plan. Hyperspectral imaging combines spectral and spatial information, providing new possibilities for precise optical characterization of biological tissue [1,2], including dental plaque.
A line scanning camera (1600 pixels across the field of view; λ resolution: 3.7 nm (400–1000 nm: spectral direction); close-up lens; spatial resolution at sample surface: ~30 μm; integration time: 21 ms × 5) was used with a light emitting diode (λmax: 365 nm). The corresponding hyperspectral images were characterized using statistical image analysis and evaluation of fluorescence spectra (average:10 × 10 pixels). The fluorescence data was radiometrically calibrated to radiance. Fluorescence spectra were obtained from 5–8 areas of three sides of two extracted lower central incisors from a 36-year old male with diagnosis “localized, aggressive periodontitis”. Plaque had been collected for nine days prior to extraction during which a temporary restoration for the extracted teeth was produced. A plaque-free premolar (tooth bank species) was used for comparison.
The fluorescence spectra of different plaque areas differed in number of peaks and intensity. Spectra with the highest intensity and number of peaks were obtained from the plaque areas closest to the gingival border. Areas without or with little plaque as well as the plaque-free tooth generally displayed spectra with one major peak and one minor peak/shoulder. Spectral peaks of tooth tissue, independent of the presence of plaque, appeared in the range 470–740 nm. Hyperspectral imaging is a promising tool in fluorescence charactrization of dental plaque.