Composition and structure of dental enamel: elemental composition and crystalline structure of dental enamel as they relate to its solubility.

The same elements, 21 in number, were found in both acid-resistant and acid-susceptible enamel specimens by ion microprobe analyses. However, there were differences in the concentrations of 14 elements between groups. Of the 16 trace elements found in enamel, the concentrations of K, F, and Na in parts per million were the greatest. Enamel surface analyses showed V and Zn were more concentrated in acid-resistant specimens by factors of 7.4 and 6.1 respectively, followed by nine other elements, the last molybdenum, that were just slightly more prevalent in acid-resistant enamel. Four elements were equally concentrated in both groups of samples, and only one trace element, B, was more abundant in the acid-susceptible samples by a factor of ten. Ca and P were predominantly more abundant in acid-resistant speciems, and C, H, and O were more concentrated in acid-susceptible samples. The enamel substance in acid-resistant and acid-susceptible groups was found to be similar by these methods. --Ion microprobe: the same elements were detected in both groups. Four trace elements (titanium, lead, Cl, and lithium) were equally abundant in the two groups. --Electron diffraction: the crystal structure type was the same in both groups of samples. --Infrared absorption: the crystalline substance showed the same spectra in both groups. The enamel substance in the two groups of specimens was found to be dissimilar by these methods. --Ion microprobe: the concentrations of 11 trace elements as well as Ca and P were greater in acid-resistant enamel. The concentrations of C, H, O, and B were greater in acid-susceptible enamel. --X-ray diffraction: crystallites in the acid-resistant specimens were larger by a factor of more than two. Enamel solubility appears not to be related to atomic species but associated with one, some, or all elements quantitatively and also with its physical form (crystallite size and probably density).