Ion-modified nanoparticles induce different apatite formation in cervical dentine

Abstract

Aim: The aim of this research was to investigate if mineral and ultrastructure is modified when cervical dentin is treated with four different nanogels-based solutions for remineralizing purposes. Methodology: Experimental nanogels based on zinc, calcium and doxycycline-loaded polymeric nanoparticles were applied on citric acid etched dentin to facilitate the occlusion of tubules and the mineralization of the dentin surface. Dentin surfaces were studied by X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging and selected area electron diffraction. Results: Crystals at the dentin surface were identified as hydroxyapatite with the highest crystallographic maturity and crystallite size in dentin treated with Zn-NPs based-gel. Texture increased in all samples from 24 h to 7 d, except in dentin surfaces treated with Zn-NPs gel. Polyhedral, plate-like and drop-like shaped apatite crystals constituted the bulk of minerals in dentin treated with Zn-NPs gel, after 7 d. Polymorphic, cubic and needle-like shaped crystals characterized minerals, more amorphous in dentin treated with Ca-NPs gel after 7 d than that found when Zn-NPs were applied. Doxycycline-NPs produced the smallest crystallites with poor crystallinity, maturity and chemical stability. Conclusions: Crystalline and amorphous phases of hydroxyapatite, described in both type of dentin treated with Zn-NPs as well as Ca-NPs gels, delayed the effect of erosion and contribute to improve the biomedical properties of cervical dentin after remineralization. Doxycycline-NPs based-gel are not recommended to treat dentin hypersensitivity.