| Objective: To study the constitution and structure of the extrinsic tooth discoloration (dental stain). Methods: The scanning electron microscope (SEM) was used to survey the thickness and structural of the stain. The constitution of the stain was studied by Energy Dispersive Spectrometer (EDS), Fourier transform spectroscopy(FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray Diffraction (XRD) observations. Results: It showed that these stains were highly calcified and contained a significant amount of organic matter (C, N, O, S), with traces of P,Fe and Ca,and exist in the form to calcium phosphate. The crystal of the calcium phosphate is lamellar on the tooth surface, and the structure of the crystal is different from the hydroxyapatite crystals. As the result of the spectroscopy, in addition to containing the PO43-,CO32-,OH- , the stain contains the characteristics absorption peaks of the benzene and amino acid. Conclusion:The results suggest that the dental stains probably include high molecular weight organic materials together with small amounts of calcium phosphate. Through analyzing functional groups of the stain, which was on the natural tooth surface, it shows that the stain may contain not only calcium phosphate, but also contain some composition of polyphenol and proteins. The characteristic absorption peaks of the phenol component in the stain material are similar to the peaks of the tea powder composition, but the difference in absorption peak intensity merely. We may deduce that the polyphenols and the proteins participate in the formation of the stain. Once the stain adsorbed on the tooth surface, the proteins adsorbed up immediately in a short time and formatted the protein films, and then were combination with the polyphenols in food, again and again. It may be the causes that the structure of the stain just be layer-by-layer in images of the scanning electron microscope. The pellicle takes part in the whole process of the formation of stain. |
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