Time-Gated Raman Microscopy analysis of enamel and dentin

Abstract:A new spectroscopic technique, time-gated Raman microscopy, was utilized to characterize non-carious and carious dentin and enamel.

Objectives: The purpose of this investigation was to perform chemical and structural analyses of non-carious and carious enamel and dentin using time-gated Raman microscopy.

Methods: Seventy human teeth, extracted for therapeutic purposes and exhibiting varying degrees of caries, were utilized for the study. The teeth were sectioned bucco-lingually or mesio-distally parallel to their long axes. They were evaluated for presence of caries under light microscope to obtain 15 non-carious and 15 carious specimens. Magnified images of selected samples were generated. Non-carious and carious enamel and dentin areas were scanned using a novel time-gated confocal Raman microscope which allows a complete separation of Raman signal from the autofluorescence signal.

Results: The time-gated Raman spectroscopy provided measurements superior to those made with fluorescence spectroscopy by providing the information about the tooth chemistry and inhomogeneous structures of dentin and enamel in both non-carious and carious areas as well as those exposed to natural pigments. Such measurements would be of significance in the instances where measurements made with DIAGNOdent are either inconsistent or they show false negative results.

Conclusions: The time gating approach provides the ability to independently measure with high signal-to-noise ratio both the Raman and autofluorescence signal from a selected microscopic area of a tooth and thus allows a better discrimination between non-carious and carious tissues.