Studies on the incorporation of lanthanides in dental hard tissues.

Rare earth elements (lanthanides)--known from chrystal-chemistry for the rehardening effect on apatites--have been tested previously for the possibility of their incorporation in dental enamel. From the non-toxic lanthanides cerium was incorporated under in vitro conditions in human dental enamel. In the present study, the incorporation of lanthanum (La), europium (Eu), samarium (Sa), ytterbium (Yb) and neodymium (Nd) in human permanent enamel, dentine and deciduous enamel has been investigated by neutron activation analysis. The lanthanides were incorporated--following the above sequence--in an increasing ratio into enamel and dentine, by forming new, more resistant rare earth elements containing apatite structures.