Histatin-1 does not reduce hydroxyapatite pellet artificial caries demineralisation

Objectives: Histatins (e.g. Histatin-1, HTN1) are low molecular weight salivary proteins which have been suggested to inhibit hydroxyapatite (HAp) secondary precipitation. Their N-terminus is active with respect to adsorption to HAp and therefore may be involved in enamel homeostasis. The aim of this study was to investigate the influence of HTN1 on HAp pellet tooth analogue dissolution.

Methods: HAp blocks (nominal porosity 20%) were located within a scanning microradiography (SMR) cell. The demineralising solution mimicking a carious challenge was 0.1 mol L^-1 acetic acid buffered to pH 4. The demineralising solution was circulating from a 1 L reservoir through the SMR cells for 3 days. Then the HAp blocks were exposed to HTN1 by immersing each block for 24 h in 0.5 mg mL^-1 solution of HTN1 in phosphate buffer. HAp blocks immersed in phosphate buffer without peptide were used as a control. Afterwards, the HAp blocks were further treated with the same demineralising solution for another 3 days. Changes in mineral mass were measured using SMR, and the dissolution rates calculated.

Results: Reductions in mineral mass during exposure of HAp pellets to artificial caries challenges were linear with time. Dissolution rates after treatment with HTN1, (-5.6±0.4)×10^-5 g.cm^-2.h^-1, were not significantly different from those of the control, (-6.0±0.2)×10^-5 g.cm^-2.h^-1.

Conclusion: Unlike statherin, HTN1 does not inhibit HAp dissolution.

Acknowledgment: Barts and The London NHS Trust, RAB05/PhD/03