Synthesis and characterization of strontium fluor-hydroxyapatite nanoparticles for dental applications

Being biocompatible, bioactive, having low solubility in a wet environment and showing similarities to mineral part of hard tissue in human's body, hydroxyapatite has so many applications in dentistry and related hard tissue concerns. Fluoride ion being found in bone and enamel can be joined to hydroxyapatite and reduce solubility and also hold biocompatibility relatively like hydroxyapatite. Playing main role in bone regeneration, strontium can be used partially or totally to treat biomaterials and increase biocompatibility and bioactivity. In this study hydroxyapatite and strontium hydroxyapatite were synthesized by chemical precipitation of different percentages of strontium by which substitutes calcium. Additionally, Fluoride was incorporated into the apatite structure, using pH-cycling method and producing Strontium-Fluoride hydroxyapatite. Diammonium phosphate, calcium nitrate, strontium nitrate and sodium fluoride were starting materials and solution of sodium hydroxide and nitric acid were used to control pH. Accordingly, synthesized nano-powders characterized by XRD, FTIR, F-selective electrode, inductively coupled plasma spectroscopy and SEM. Subsequently, biological assessment of fluoride's and strontium's influence on the proliferation and differentiation of MG63 cell line was conducted by MIT and ALP tests. Results of XRD and FTIR showed that nano-crystals of HA, SrHA, FHA and F-SrHA were successfully achieved by this method. SEM images revealed that prepared crystalline powders morphology was nano-size and spherical. Biocompatibility also approved by MIT tests. Also, since the process of calcification of hard tissues (bones and teeth) is effected by alkaline phosphatase enzyme (ALP), the influence of both alone and combined fluoride and strontium on cell differentiation was investigated. Consequently, results represent the ability of these elements to enhance remineralization of tooth enamel.