Synthesis and Characterization of Magnesium Hydroxyapatite Nanopowders for Enamel Remineralization of Initial Caries Lesions

Hydroxyapatite (HA) and magnesium hydroxyapatite (MgHA) were successfully prepared and its ability to enhance the remineralization of initial enamel lesions was investigated in this study. For this purpose, the nanoparticles were prepared by the wet chemical synthesis. XRD and FTIR were applied to characterize phase structure and chemical species in the prepared samples. The crystallite size and crystallinity index of HA and MgHA samples were 43.88 and 29.59 nm and 46.15 and 26.67% respectively, which were calculated using XRD data and compared with stoichiometric HA sample. SEM was used to investigate the morphology and mean size of the nanoparticles. According to the results of physicochemical characterization, magnesium was detected in the crystal structure of the nanoparticles and nanoparticles of HA with mean particle size of 55.79 nm, MgHA with mean particle size of 39.52 nm were successfully synthesized. In addition, it is revealed that substitution of magnesium in the crystal structure of HA results in the reduction of crystalline and particle sizes, and also, reduce the crystallinity. A pH-cycling regime was used to simulate the dynamic demineralization-remineralization conditions and performance of the prepared materials in enamel remineralization was characterized by surface microhardness (SMH) measurement. Finally, surface of the enamel samples was further characterized by SEM investigations. According to the results of experiments, HA and MgHA can strongly adsorb on the enamel surface and improve the SMH of the substrate due to improvement of the dental remineralization. The improvement of dental remineralization can be attributed to the development of a new biomimetic apatite mineral deposition which progressively fills the surface scratches. According to the results of the present research work, MgHA shows 12% higher remineralization ability compared to that of HA and can be effectively used as remineralization agents in dental hygiene products such as toothpaste, mouthwashes, and oral health compounds.