Ceramic Core–Shell Particles : Synthesis and Use within Dentistry

Sammanfattning: Dentin hypersensitivity is one of the most prevalent conditions related to oral health, affecting a large share of the adult population. Shortcomings with the available treatment options are related to non-ideal particle sizes and degradation properties. An improved clinical outcome could possibly be obtained using a bioactive occluding agent that can offer a high, continuous release of ions, as well as having a particle size that allows for penetration into the dentin tubules. The work in this thesis focused on the development and investigation of a synthesis approach for calcium phosphate core–shell particles and the use of those in the treatment of dentin hypersensitivity. The overall aim was to increase the knowledge about the synthesis and to evaluate the in vitro performance of amorphous calcium magnesium phosphate (ACMP) particles when used as an occluding agent. The synthesis of the core-shell particles was based on precipitation reactions in aqueous solutions and the synthesized materials were studied in terms of morphological, structural, and compositional aspects. Resulting particles had diameters ranging from 400 nm–1. 5 µm (depending on reaction conditions), with morphologies and structures that were shown to correlate with the ionic radius and the concentration of the substituting ion. This insight resulted in the possibility to control the outcome of the reaction and to extend the synthesis to other alkaline earth phosphates. The mechanism of formation was suggested to be the simultaneous precipitation of primary nanoparticles (NPs) and the formation of gas bubbles that could function as soft templates.A study of the degradation properties together with a series of in vitro studies, using a dentin-disc model, indicated that the ACMP particles may be a promising candidate for clinical use. The material was shown to offer a rapid and continuous release of Ca2+, Mg2+, and phosphate, aiding surface, as well as intratubular occlusion and mineralization. Additional use of a fluoride toothpaste resulted in incorporation of F– in the mineralized material. This could enhance the in vivo performance due to the known benefits of including F– in dental tissues, e.g. decreased solubility. The ACMP particles were, furthermore, shown to be more efficient in terms of degree of occlusion when compared to other similar products available on the market. The intratubular mineralization was additionally mitigating the effect of an acid attack, which is of importance for a long-lasting effect in clinical use.