Measurement of the efficacy of calcium silicate for the protection and repair of dental enamel

ABSTRACT Objectives To investigate the formation of hydroxyapatite (HAP) from calcium silicate and the deposition of calcium silicate onto sound and acid eroded enamel surfaces in order to investigate its repair and protective properties. Methods Calcium silicate was mixed with phosphate buffer for seven days and the resulting solids analysed for crystalline phases by Raman spectroscopy. Deposition studies were conducted on bovine enamel surfaces. Acid etched regions were produced on the enamel surfaces using scanning electrochemical cell microscopy (SECCM) with acid filled pipettes and varying contact times. Following treatment with calcium silicate, the deposition was visualised with FE-SEM and etch pit volumes were measured by AFM. A second set of bovine enamel specimens were pre-treated with calcium silicate and fluoride, before acid exposure with the SECCM. The volumes of the resultant acid etched pits were measured using AFM and the intrinsic rate constant for calcium loss was calculated. Results Raman spectroscopy confirmed that HAP was formed from calcium silicate. Deposition studies demonstrated greater delivery of calcium silicate to acid eroded than sound enamel and that the volume of acid etched enamel pits was significantly reduced following one treatment (p < 0.05). In the protection study, the intrinsic rate constant for calcium loss from enamel was 0.092 ± 0.008 cm/s. This was significantly reduced, 0.056 ± 0.005 cm/s, for the calcium silicate treatments (p < 0.0001). Conclusions Calcium silicate can transform into HAP and can be deposited on acid eroded and sound enamel surfaces. Calcium silicate can provide significant protection of sound enamel from acid challenges. Clinical Significance Calcium silicate is a material that has potential for a new approach to the repair of demineralised enamel and the protection of enamel from acid attacks, leading to significant dental hard tissue benefits.