抄録
1. The solubility of zinc phosphate cement
From the experimental results, it is proved that the solubility of zinc phosphate cement becomes largest in buffered solution pH 4, the solubility of Zn and Mg amounting to 1440-1580μg/cm2. But, in artificial saliva and buffered solution pH 9, both Zn and Mg show small values. Especially, the solubility proves to be small in alkaline solution. Again, all 3 kinds of cement show similar values in solubility.
The solubility shown above proves to be very large, as compared with those obtained in the case, soaked in the distilled water for a day [1], though in buffered solution pH 9, both Zn and Mg respectively show the values similar to those in the distilled water. Again, it is proved that H3PO4 in zinc phosphate cement is slightly soluble in buffered solution pH 4 [3], but not determinable.
2. The solubility of carboxylate cement
As shown in Figs. 3 & 4, the solubility of Zn and Mg of both kinds of cement becomes largest in buffered solution pH 4, Zn and Mg amounting to 1210-1465 μg/cm2, a value similar to that of zinc phosphate cement. The solubility proves to be comparatively large both in artificial saliva and buffered solution pH 9, too. Especially in buffered solution pH 9, both Zn and Mg show 15.0-45.5μg/cm2, and it is presumed that the solubility of this kind of cement is large in alkaline solution. Again, it is proved that in any solution the solubility is very large, as compared with those obtained in the distilled water. On the other hand, -COOH of this cement is not detectable in any solution but in buffered solution pH 4 [4].
3. The solubility of silicate cement
The solubility of Si and Al of this cement shows comparatively a large value, especially, Al, approximately 305μg/cm2. But in artificial saliva and buffered solution pH 9, Al is not detectable, though Si shows 14.0 and 26.0μg/cm2 in the respective solutions.
The above-shown values, in comparison with those obtained by 7-day soaking in the distilled water, prove that Si shows small values in any solution, and Al, which shows a large value in buffered solution pH 4, is not detected in both buffered solution pH 9 and artificial saliva. The presumption, then, is that silicate cement, soluble in buffered solution pH 4, is hardly soluble in both artificial saliva and buffered solution pH 9, though the reason for this is not traceable.
In any case, it is proved that the solubility of zinc phosphate, carboxylate and silicate cement is large in the acid region. Again, Mg of zinc phosphate and carboxylate cement shows very large solubility, considering their composition shown in Table 1. Especially, carboxylate cement proves to have large solubility in the alkaline region. As to silicate cement, the solubility of Na is proved to be large.
