[The binding of blood plasma proteins and salivary proteins to hydroxyapatite columns and its effect on demineralization in an in vitro system].
Demineralization of hydroxyapatite (HAP) columns by acidic acetate buffer proceeds in two phases. In an initial phase which is characterized by the formation of pH gradient within the HAP sediment, calcium but no phosphate ions are eluted from the column. In the second phase when a low pH value has been established in the pellet calcium and phosphate are eluted in a ratio identical to that of the original HAP. The binding of human blood plasma proteins and saliva proteins to the HAP as well as the effect of the protein binding on HAP demineralization was investigated. The maximum binding capacity of HAP for the proteins of unstimulated mixed saliva is about four times lower than the binding of human serum albumin or blood plasma proteins. However, saliva proteins affect HAP demineralization more markedly than the other proteins. Whereas the pretreatment of HAP with human serum albumin does not alter the the demineralization process. binding of blood plasma proteins inhibits the initial phase of demineralization. Both phases of HAP demineralization are strongly inhibited when saliva proteins are bound to HAP. It is also shown that demineralization modifies the protein binding to HAP.