Investigation of mercury pathways from dental amalgam by micro-PIXE

Mercury amalgams are still widely used in dentistry in many countries. There is considerable concern about uptake of Hg in both the patient and environment. It is an interesting question if the pathway is by Hg diffusion through the tissue of the tooth or dissolution in saliva or direct evaporation through inhaled air into the lung. Our previous study Meesat et al. (2017) of a high-Cu amalgam showed no evidence of diffusion through the enamel. However, a compositional change was observed on the biting surface of the amalgam which is indicative of tribochemical changes. To investigate the above observation in more detail, 17 adult teeth with amalgam fillings were obtained as operation-waste from dental clinics. The samples were embedded and sliced into 1 mm sections in the coronal plane of the tooth using a low/speed diamond saw with water-based cooling. Elemental maps from teeth treated with dental amalgam were measured using micro-PIXE. In common with our previous study Meesat et al. (2017), sharp interfaces between the enamel and amalgam were observed with no strong evidence for Hg diffusion in the enamel. Little evidence exists consistent with the presence of tribochemical alteration by mastication. However, Zn was observed to be localized at different sites in the amalgam/enamel interface.