[Insolubilization of deciduous tooth enamel by the two-step method with fluoride and lanthanum treatment].

The acid-resistance of the tooth surface is strengthened to form noncrystal lanthanum fluoride on its surface by the two-step treatment (F-La treatment) with acidulated-phosphate fluoride and lanthanum chloride solutions as previously reported by Fujiwara, Negishi, Miyagi et al. This study has been made to examine some clinical applications of the treatment. The acid-resistance effect and the actual condition of the F-La treatment were investigated on the extracted human deciduous dentin. Analysis was made using the electron probe X-ray microanalyzer before and after the acid solubility test. The results were as follows: 1) With F-La treatment, the acid-solubility of deciduous tooth dentin was reduced to about one-third of that without treatment, and to about two-third compared both with F-treatment and with diamine silver fluoride application. 2) Applications of 3 to 5 minutes with F and 3 minutes with 0.5 to 1.0% La sufficed for this F-La treatment. 3) An etching procedure was not necessary previous to the treatment in contrast with the application to the enamel. 4) Fluorine and lanthanum penetrated up to approximately 10 microns from the dentin surface with this treatment. Even after the acid-solubility test, a sufficient quantity of the stated chemicals remained, thus protecting the tooth substance. 5) The acid-solubility of the deciduous dentin was higher than that of the deciduous enamel. After the F-La treatment, however, the former diminished more markedly than the latter. Based on these experimental results, one can confirm the fact the chemical reactivity of the deciduous dentin is higher than that of the deciduous enamel.