Fourier Transform Raman Microscopic Mapping of the Molecular Components in a Human Tooth

Abstract

Fourier transform Raman microscopic mapping was used to examine the distribution of the mineral and organic components in a cross-section of a human tooth. The relative distributions of carbonate and phosphate ions as well as the organic matrix components were plotted using functional group maps. The distribution of organic components was examined using the C–H stretch band between 2880 and 2700 cm-1. The distributions of phosphate and carbonate were determined using their respective symmetric stretching vibrations, νs(PO) at 961 cm-1 and νs(CO) at 1070 cm-1. Maps of the enamel–dentine junction at a high resolution of 10 μm showed that the amount of phosphate is lowest in this region. A series of spectra at 2 cm-1, ca. 20000 scans, used for curve fitting of the νs(CO) band was used to show that the concentration of carbonate ions in B-hydroxyapatite positions increases on going from the outside of the enamel towards the enamel–dentine junction. The results reveal that the deconvolution of the band envelope of νs(CO) and νas(PO), the antisymmetric stretching vibration of phosphate is more complicated than previously reported. The advantage of functional group Raman mapping is that, in addition to identifying the chemical constituents, valuable microstructural information is obtained including species distribution across the surface, and in particular at the enamel–dentine interface. Minimal, non-chemical sampling preparation means that spectral information obtained can be directly related to the physical properties and biological function of such tissues. © 1997 by John Wiley & Sons, Ltd.