A monetite/amorphous silica complex for long-term dentine hypersensitivity treatment through the acid stability and mineralization promoting effect of silica

Dentine hypersensitivity (DH) is often related to the exposure of dentin tubules. Mineral particles, such as hydroxyapatite and bioactive glass, can provide calcium and phosphate ions to temporarily block dentin tubules via the biomineralization process, serving as feasible alternatives for DH treatment. However, due to the acidic microenvironment caused by dietary acids, these particles are easily eroded and dissolved, making it difficult to achieve efficient dentin tubule occlusion. Given the significant stability of silica in dietary acids and its excellent ability to bond with calcium and phosphate ions to form mineralized hydroxyapatite, we proposed to develop a micron-sized monetite/amorphous silica complex (MMSi) hydrosol to effectively seal the exposed dentin tubules. In this study, we hypothesized that the MMSi hydrosol could tolerate acid erosion and concurrently provide active sites for the calcium and phosphate ions to promote biomineralization in comparison to a micron-sized monetite (MM) hydrosol. Hence, the composition and microstructure including the surface morphology, silica content and phase composition of MMSi were investigated to verify the presence of silica. The results of the ion release and in vitro biomineralization process indicated that silica did not hinder the calcium and phosphate ion release and the formation of hydroxyapatite via the biomineralization process. The acid-resistant test suggested that the MMSi hydrosol exhibited a significantly slower corrosion rate than the MM hydrosol when treated with citric acid. Notably, the silica in the MMSi hydrosol retained the ability to induce the nucleation and crystallization of hydroxyapatite during de/remineralization processes. Finally, the MMSi hydrosol was mixed with commercialized toothpaste to explore its efficacy in dentin tubule occlusion via cycling de/remineralization processes. As a result, compared to the MM hydrosol, the toothpaste containing the MMSi hydrosol presented excellent acid-resistant ability and dentin tubule occlusion outcomes, which indicated that the MMSi hydrosol could be a potential promise in the long-term treatment of DH. Due to the acid stability and mineralization activity provided by silica, the monetite/ silica complex can effectively seal the dentin tubules under cyclic de-/remineralization conditions that mimic oral envioument, enabling long-term treatment of dentin hypersensitivity.