Effect of human salivary proteins on the precipitation kinetics of calcium phosphate

Abstract

Inhibition of calcium phosphate precipitation in saliva, and prevention of the formation of mineral accretions on tooth surfaces, has been ascribed to the existence of inhibiting salivary macromolecules. Marked reductions in the crystal growth rate of hydroxyapatite (HA) seeds were measured in supersaturated solutions containing either of two proline-rich proteins, PRP1 or PRP3, or statherin; the three macromolecules were isolated from human parotid saliva. The reductions were also observed when the HA seeds were pretreated with solutions of the macromolecules before adding them to the supersaturated calcium phosphate solution. This effect was very similar in the case of the two PRPs and it was directly related to the extent of adsorption site coverage of these proteins on the HA seeds. The effect of statherin was larger than anticipated from its adsorption behavior. However, comparison on the basis of number of moles adsorbed per unit area of HA shows that the PRP are more effective inhibitors than statherin. The macromolecule concentrations used were considerably lower than those in the salivary secretions, therefore these macromolecules could readily prevent mineral accretion on tooth surfaces through their adsorption onto the enamel surface.

Chemical alteration by tooth bleaching of human salivary proteins that infiltrated subsurface enamel lesions —Experimental study with bovine lesion model systems—

“…Most of these bound proteins, however, could be removed using an in-office bleaching agent. More than 40 different proteins and peptides are present in saliva 18) , with certain proteins such as statherin having strong affinity for hydroxyapatite (HA) and inhibiting the growth of apatite crystals [19][20][21][22][23][24] . The concentration of statherin, which has similar proline content as proline rich proteins (PRPs), is sufficient to maintain a stable supersaturated HA solution 25) .…”

The Effect of Fluoride On Apatite Structure and Growth

“…The postulated roles of matrix proteins are diverse: a nucleator by providing certain stereochemical arrangement of charged groups, which is sufficient to lower the activation energy barrier for nucleation of a crystal phase (Glimcher, 1989;Gorski, 1992); or an inhibitor by blocking the growth sites through specific adsorption (Moreno et al, 1979;Termine et al, 1980;Romberg et al, 1986) or by providing spacial constraints as exemplified by the lateral growth of apatitic mineral in calcified turkey tendon (Heywood et al, 1990). Casein phosphoproteins in milk, as cited above, act as a stabilizer of amorphous calcium phosphate in nanometer-sized clusters (Holt et al, 1996).…”

Differential expression of proline-rich proteins in rabbit salivary glands.

“…In humans the proteins are encoded by a small number of genes, probably six, that give rise to about 20 secreted proteins (Kauffman et al, 1991;Maeda, 1985). Acidic PRPs bind calcium and inhibit hydroxyapatite formation, and may be important in maintaining calcium homeostasis in the mouth (Bennick et al, 1981;Moreno et al, 1979). They also bind strongly to hydroxyapatite, the main mineral of teeth, thereby contributing to for-…”