Comparative fluorescence spectroscopy of root caries lesions

Abstract

In this study, the light-emission properties of carious and sound root surfaces were investigated under a wide range of excitation wavelengths. Human molar teeth with exposed root surfaces containing light- and dark-discolored root caries (n = 3 of each) were selected. Emission spectra were recorded from carious and corresponding sound root surface areas from each tooth by using a fluorescence spectrophotometer at excitation wavelengths from 360 nm up to 580 nm, in steps of 20 nm. The spectra were corrected for fluctuations in detector sensitivity and excitation light intensity, and normalized to peak intensity. Excitation spectra were recorded for selected emission wavelengths that showed maximum intensity. Light- and dark-discolored root surface caries showed distinct fluorescence emission bands between 600 and 700 nm that were not present in sound root surface areas. These bands were strongest for excitation wavelengths between 390 and 420 nm. The excitation spectra of root caries revealed maximum excitation at around 405 nm, which is equivalent to the Soret band of porphyrin compounds. The emission spectra of both types of root caries lesions were shifted towards longer wavelengths (red shift at half maximum) when compared to the spectra of corresponding sound root surfaces. The red shift for dark-discolored root caries was higher than for light-discolored lesions at all excitation wavelengths.