Subhash Narayanan, Thomas Shiny Sara, Mallia Rupananda J, Jose Mini
Biophotonics Laboratory, Centre for Earth Science Studies, Trivandrum 695031, India.
Lasers Surg Med. 2005 Oct;37(4):320-8. doi: 10.1002/lsm.20229.
Nitrogen laser-induced fluorescence (LIF) spectra of sound tooth consists of two broad bands centered at 440 and 490 nm, with two apparent side bands on either side. In order to locate the exact peak position of these bands and to effectively utilize the LIF spectral signatures for detection of tooth caries, the LIF spectra were curve-fitted using Gaussian spectral functions and the results were compared with those from diffuse reflectance spectral measurements.
STUDY DESIGN/MATERIALS AND METHODS: The excitation light at 337.1 nm was guided to the sound and caries-affected tooth samples through the central fiber of the fiber-optic probe of a laser-induced fluorescence reflectance spectroscopy (LIFRS) system. Six surrounding fibers of the probe collect tooth fluorescence or diffuse reflectance from the lesion and direct it to a miniature spectrometer. The in vitro spectra were obtained from healthy enamel, dentin, and pulp level tooth caries.
As compared to sound tooth, the caries tooth showed lower fluorescence and reflectance intensities in the 350-700 nm region. The deconvoluted peaks in the LIF spectra of sound tooth were found centered at 403.80, 434.20, 486.88, and 522.45 nm, whereas in the case of pulp level caries, a new peak was observed at 636.78 nm. Curve-fitted parameters, such as peak center, Gaussian curve area, full width at half intensity maximum (FWHM), and their ratios, were also found to vary with the stage of tooth caries. The ratios involving the 435 nm band, such as F405/F435, F435/F490, and F435/F525 ratios derived from curve-fitted areas and amplitudes, were found to be sensitive to discriminate between sound, dentin, and pulp level caries. Among the various diffuse reflectance spectral intensity ratios, the R500/R700 was found to be most sensitive to distinguish between pulp and dentin level caries.
Nitrogen laser-excited fluorescence spectral studies were found to be more suited for detection of caries lesions. The LIF measurement with spectral analysis, done by curve fitting, outscores the diffuse reflectance methodology and shows the potential to screen different levels of tooth decay in a clinical setting.
健康牙齿的氮激光诱导荧光（LIF）光谱由两个位于440和490 nm处的宽带组成，两侧各有两个明显的边带。为了确定这些谱带的确切峰值位置，并有效利用LIF光谱特征检测龋齿，使用高斯光谱函数对LIF光谱进行曲线拟合，并将结果与漫反射光谱测量结果进行比较。
研究设计/材料与方法：337.1 nm的激发光通过激光诱导荧光反射光谱（LIFRS）系统的光纤探头的中心光纤导向健康和患龋的牙齿样本。探头的六根周围光纤收集牙齿荧光或病变处的漫反射光，并将其导向微型光谱仪。体外光谱取自健康牙釉质、牙本质和牙髓水平的龋齿。
与健康牙齿相比，龋齿在350 - 700 nm区域的荧光和反射强度较低。健康牙齿LIF光谱中解卷积后的峰值位于403.80、434.20、486.88和522.45 nm处，而在牙髓水平龋齿的情况下，在636.78 nm处观察到一个新的峰值。还发现曲线拟合参数，如峰值中心、高斯曲线面积、半高宽（FWHM）及其比值，会随龋齿阶段而变化。从曲线拟合面积和幅度得出的涉及435 nm谱带的比值，如F405/F435、F435/F490和F435/F525比值，被发现对区分健康、牙本质和牙髓水平的龋齿很敏感。在各种漫反射光谱强度比值中，R500/R700被发现对区分牙髓和牙本质水平的龋齿最敏感。
发现氮激光激发荧光光谱研究更适合检测龋损。通过曲线拟合进行光谱分析的LIF测量优于漫反射方法，并显示出在临床环境中筛查不同程度龋齿的潜力。
