Co-operativity of Statherin and Histatin in Demineralisation of Carious and Erosive HAp Model

Objectives: One aim of preventive and minimal invasive dentistry is to alter the oral environment to a less demineralisation setting which may allow early caries and erosive lesions to be reversed. Salivary proteins such as statherin (StN43) are known to be involved in de-remineralisation. The active N-terminal is involved in inhibition of precipitation and responsible for binding with Ca²⁺. StN21 is an analogue peptide that contains the N-terminal 21 residues similar to StN43. Histatin-1 (HtN38), similar to salivary proline-rich proteins, is also understood to inhibit crystal growth of calcium phosphate salts, but does not inhibit spontaneous precipitation.
The objective of this study was to measure the effect of these test peptides (StN21 and HtN38 individually and in combination) on the demineralisation rate of previously demineralised hydroxyapatite discs (HAp) using scanning microradiographic (SMR).
Methods: HAp discs were mounted within SMR cells. Three scanning positions were located on each disc for the measurement of the rate of mineral loss (RD_HAp). The discs were exposed to demineralising solutions (pH 4.0, 0.1M acetic acid) for 3 days. After this preliminary acidic exposure, the HAp discs were rinsed thoroughly with distilled water and then exposed to 2.0ml of the test solution containing the peptides dissolved in phosphate-buffered saline (PBS) at a concentration of 0.2mM. After 24hrs the HAp discs were then exposed to the acidic demineralisation solution for a further 3 days. A HAp disc exposed to PBS was used as a negative control. RD_HAp was measured continuously using real-time SMR.
Results: StN21 and HtN38 reduced the RD_HAp by 40.0±3.2% and 39.2±2.9% respectively compared to the control. The peptides in combination reduce the RD_HAp by 52.6±2.2%.
Conclusions: This study has shown that StN21 and HtN38 have considerable effect in reducing HAp demineralisation under caries/erosive simulation conditions. Their increase in efficacy in combination suggests a cooperative action. This suggests that StN21, HtN38, and a combination of both can be used as a therapeutic agent for preventive treatment of enamel demineralisation.