EDTAによる歯牙の脱灰過程の研究―殊にカルシウムと燐酸について

Abstract

As the basic investigation of decalcification by EDTA, the author has observed how calcium ion in various materials, e. g., triturated human teeth, bovine bone, marble and fluoroapatite, is removed at varied pH of decalcifying media.Phosphorus which dissolves simultaneously in the decalcifying media has been also determined.In summary, the following results were obtained.1) The modes of the reaction are found to be different in the decalcifying media of varied pH; i. e., second-order reaction in the weakly acid medium (pH 4.3), the first-order reaction in the neutral and weakly basic media (pH 7.0-10.3) . But dentin and bovine bone in these media do not behave as the above unless their organic matrices are eliminated.From these findings, it is deduced that the decalcifying action of EDTA is disturbed mechanically by the organic matrices in dentin or bovine bone.Author's conception about the different modes of reaction mentioned above is that EDTA in the weakly acid medium reacts with calcium ion which dissolved out of materials through the acidity of medium, and in the neutral or weakly basic medium it directly attacks calcium on the grains of metarials.2) In the case of the first-order reaction in the neutral and weakly basic media, the velocity constants of marble, dentin and bovine bone free of their organic matrices, are much greater than those of enamel and fluoroapatite.In the case of the second-order reaction in the weakly acid medium, the velocity constants of marble and dentin are also greater than that of enamel.3) In the neutral and weakly basic media, the lower its pH is, the faster the decalcifying velocity becomes. And the weakly acid medium gives a faster velocity, but in this case acid could have the decalcifying action by itself.4) As to the ratio of removed calcium and phosphorus, it seems that other calciumm salts than calcium phosphates, e. g., calcium carbonate or organic calcium salts, are more soluble than calcium phosphates in the early period of the decalcification.