Exposure to mercury from dental amalgams, with possible negative health effects, has generally been considered to occur via either erosion or evaporation directly from the surface of fillings, followed by ingestion. The aim of this study was to determine the relative importance of the direct migration of mercury through the tooth as an alternative exposure pathway. X-ray fluorescence imaging has been used to determine quantitatively the spatial distribution of Hg, Ca, Zn and Cu in sections of human teeth that had been filled with amalgam for more than 20 years. X-ray absorption near-edge spectroscopy (XANES) was also employed to gain chemical information on the mercury present in the teeth. Hg (up to approximately 10 mg g(-1)) and Zn (>100 mg g(-1)) were detected in the teeth several millimetres from the location of the amalgams. At high resolution, Hg showed higher concentrations in dentinal tubules while Zn was generally evenly distributed. XANES showed that the chemical form of Hg that had migrated into the tooth had been altered from that present in the amalgam. The differing spatial distributions of Hg and Zn suggest distinct transport mechanisms for the two metals, presumably chemical for Zn and initially physical for Hg. Subsequent oxidation of Hg may lead to a loss of mobility or the development of a secondary transport mechanism. Most importantly the detection of Hg in areas of the tooth that once contained an active bloodstream and in calculus indicates that both exposure pathways should be considered as significant.

No abstract

Quantitative X-ray fluorescence imaging of sections of human teeth revealed an increased concentration of copper and zinc in carious regions of dentine compared with unaffected portions of the tooth. Higher-resolution images provided strong evidence that the copper was transported and localized mainly in the dentinal tubules. While similar levels of zinc were found in these areas and concentrated in the tubules, zinc was also more evident in the hydroxyapatite, and the increase in zinc levels compared with the levels in background (normal) areas was less than that for copper. These results suggest a role for copper and zinc in the formation and progression of dental caries and present a potential point of intervention for treatment.

No abstract