Precipitation of octacalcium phosphates on artificial enamel in artificial saliva.

The natural saliva samples were collected from 30 Japanese men and women aged between 20 and 30, and the inorganic components in the saliva were analyzed chemically. Artificial saliva (AS) was prepared based on the chemical analysis using chemical reagents. The calcium/phosphate molar ratio of the AS was 0.28 with pH=7.0. Artificial enamel (AE) was prepared by sintering hydroxyapatite powder at 1,200 degrees C. The AE was placed in the AS at 37 degrees C. XRD, SEM and EDX investigated precipitation on the AE. The precipitation was always identified as being OCP. As decrease in the pH of the surface of the AE and increase in the concentration of phosphate ions were observed by chemical analysis, it was concluded that the OCP occurs by the pH decrease and phosphate ion concentration increase on the surface of AE.