Detection Of Dental Calculus By Using Laser Induced Fluorescence

The21st century is the century of life science and information science. Opticaldiagnostics is a non-destructive, highly efficient, highly sensitive diagnostic method,and it has broad application prospects. In this paper, we carried out the detection ofdental calculus by using laser induced fluorescence as follows:First, a laser-induced fluorescence diagnostic system was build. By comparingspectral characteristics of fluorescence for normal teeth with dental calculus underdifferent excitation light sources, we want to find a suitable light source for clinicaldiagnosis. Under the excitation of a405nm light-emitting diode, normal teeth anddental calculus showed significantly different fluorescence spectra. Dental calculusshowed obvious fluorescence peak at510nm, which was very weak for normal teeth.Under the excitation of He-Ne laser, fluorescence peak near the680nm was observedfor dental calculus. But normal teeth showed no obvious fluorescence peak at the samewavelength. Under the excitation of a635nm semiconductor laser, normal teeth anddental calculus produced a higherfluorescence peak at680nm. But only dentalcalculus showed much higher fluorescence around700nm band.Second, a sensitive detection method was proposed by the analysis and comparisonof fluorescence spectral characteristics of dental calculus and normal teeth. We candetermine whether dental disease exists by using the ratio(R S(618648)S(650730))of thearea of peak fluorescence (650-730nm) and the area of reflected light (618-648nm).The sensitivity and accuracy is as high as90%.Even if the surface of dental calculuswas covered with pork tissue,93.3%sensitivity and100%accuracy were still observedwhen R=0.9was used as the thresholdAt last, we established dual-color fluorescence imaging method for diagnosis ofdental calculus. A blue LED was chosen as excitation light source according to theexcitation and emission properties of the detection samples. For each sample, thespecial fluorescence images in two special wavelength bands (green and red) wererespectively collected by using a CCD with filters. An algorithm involving these twospecial images was used to increase fluorescence imaging contrast. The detection resultsshow that it is difficult to discriminate dental calculus from healthy teeth according to single red fluorescence image or green one. However, dental calculus could be clearlydelineated from healthy teeth by using the dual-color fluorescence imaging methodproposed. This study will provide a powerful noninvasive detection means for thecomplete removal of dental calculus.