A constant composition kinetics study of the influence of salivary cystatins, statherin, amylase and human serum albumin on hydroxyapatite dissolution

The influence of salivary cystatins, statherin, amylase and human serum albumin on the dissolution kinetics of hydroxyapatite has been investigated using the constant composition method. At a pH of 6.0, salivary cystatins and statherin all decreased the dissolution rate by about 30% at a surface concentration of 5.0 × 10^-8 mol m^-2. Although little difference between neutral cystatin SN and acidic cystatin S was seen at pH 6.0, when the reaction was performed at a similar degree of undersaturation at neutral pH (6.95), cystatin S was the more efficient inhibitor. At a surface concentration of 5.0 × 10^-8 mol m^-2, cystatin SN and cystatin S decreased the rates of dissolution by 35% and 30% at pH 6.0 and by 40% and 65% at a pH of 6.95 respectively. Human serum albumin and amylase were more efficient dissolution inhibitors than either of these salivary cystatins at pH 6.0 and 4.8. Moreover, in all cases the influence of the adsorbed proteins increased with extent of reaction.