A Fundamental Study on Lanthanum as a Preventive of Dental Caries

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  • SHIMANO Ryoyu
    Laboratory of Chemistry, Department of General Education, Aichi-Gakuin University

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  • う蝕予防剤としてのランタンに関する基礎的研究
  • ウショク ヨボウザイ トシテノ ランタン ニ カンスル キソテキ ケンキュウ

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Lanthanum inhibits dental caries in experimental animals. The question of how lanthanum is absorbed by the enamel surface still leaves much to be studied.<BR>The items of this study were as follows:<BR>1) the relation between the concentration and the time of action of lanthanum when it is absorbed by the enamel surface;<BR>2) the concentration of lanthanum in experimental caries control and its distribution in internal organs when it is prescribed;<BR>3) quantitative analysis of the three elements La, Ca, and P by electron probe X-ray microanalyser and X-ray fluoressent spectrometer;<BR>4) various lanthanum phosphates in enamel surface seen by X-ray diffractometory.<BR>An exchange reaction of Ca and La in enamel surface occurred when an extracted human tooth was dipped in lanthanum solution and the surface become coated with lanthanum phosphate (LaPO4).<BR>After 3 days of immersion of a tooth in 2-8% of lanthanum solution, about 65% of the Ca was replaced and an equilibrium was reached. But in lanthanum solution of less than 1% replacement was slow, and in solution of 0.001% no reaction was detected.<BR>The lanthanum compounds in the enamel surface were aciduric.<BR>When lanthanum solution was given to a hamster, caries decreased clearly and 0.1%-0.01% of lanthanum solution (La: 312-31.2μg/ml) was most effective in preventing dental caries.<BR>In an acute toxicity test, La was accumulated in all the internal organs when solution of more than 1.5% were used.<BR>From this study I conclude that lanthanum fortifies the acid resistance of the teeth, that it is only slightly toxic, and that it is only slightly accumlated in internal organs.

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