Infiltration of demineralized dentin with silica and hydroxyapatite nanoparticles.

OBJECTIVES: The management of demineralized dentin resulting from dental caries or acid erosion remains an oral healthcare clinical challenge. This paper investigates, through a range of studies, the ability of colloidal silica and hydroxyapatite (HA) nanoparticles to infiltrate the collagen structure of demineralized dentin. METHODS: Dentin samples were completely demineralized in 4 N formic acid. The remaining collagen matrix of the dentin samples was subsequently infiltrated with a range of nano-particulate colloidal silica and HA solutions. The effectiveness and extent of the infiltration was evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). RESULTS: Silica nanoparticles have the ability to penetrate dentin and remain embedded within the collagen matrix. It is suggested that particle size plays a major role in the degree of dentin infiltration, with smaller diameter particles demonstrating a greater infiltrative capacity. The infiltration of demineralized dentin with sol-gel HA nanoparticles was limited but was significantly increased when combined with the deflocculating agent sodium hexametaphosphate. The use of acetone as a transport vehicle is reported to enhance the infiltration capacity of sol-gel HA nanoparticles. SIGNIFICANCE: Collagen infiltrated with HA and silica nanoparticles may provide a suitable scaffold for the remineralization of dentin, whereby the infiltrated particles act as seeds within the collage matrix and given the appropriate remineralizing environment, mineral growth may occur.