Despite numerous studies of human biominerals, some problems still remain concerning the relationship between their composition and their structure. For a better understanding of this problem, full spectra of the internal vibrations of human tooth enamel crystallites were obtained through polarized Raman microspectrometry and these are published for the first time. The micro-Raman technique is nondestructive and enables micrometric-scale examination of all the samples with a minimum of artifacts. The spectra show some variation from the predicted bands and many similarities with fluorapatite spectra. The mineral part of enamel is initiated in an organic environment and contains carbonate ions. Despite the carbonation, the crystal structure is preserved. Based on these results, a new description of the structure of apatite crystal is proposed. A box of Ca2+ ions surrounds and isolates the PO43- ions from one another, decreasing the influence of substitutions.
G. Leroy, G. Penel, N. Leroy, and E. Brès, "Human Tooth Enamel: A Raman Polarized Approach," Appl. Spectrosc. 56, 1030-1034 (2002)