Bioactivity Evaluation of Synthetic Nanocrystalline Hydroxyapatite

Abstract

Background: Bone regeneration in the defects around oral implants using substitutes may improve long-term prognosis of the implant. Hydroxyapatite (HA) is a good candidate for bone substitutes due to its similarity to bone minerals. Nanostructured hydroxyapatite is also expected to have better bioactivity than coarser crystals. The aim of this work was to synthesize and evaluate the bioactivity of HA.

Methods: Nanocrystalline HA was synthesized via mechanical activation method.  Fourier transform infrared spectroscopy (FTIR) was utilized to identify the functional groups of the prepared HA. Transmission electron microscopy (TEM) technique was utilized to evaluate the shape and size of prepared HA powder. The synthesized powder was soaked in stimulated body fluid (SBF) medium for various periods of time in order to evaluate its bioactivity. The changes of the pH of SBF medium were measured. Atomic absorption analysis (AAS) was used to determine the dissolution of calcium ion in the SBF environment and scanning electron microscopy (SEM) was utilized to evaluate the surface morphology of nanocrystalline HA powder after immersion in SBF.

Results: The prepared HA powder had nano-scale morphological structure with the mean crystallite size of 29 nm in diameter and bone-like composition. The ionic dissolution rate of prepared nanocrystalline HA was higher than that in conventional HA and was similar to that of biological apatite of bone. High bioactivity of prepared nanocrystalline HA powder due to the formation of apatite on its surface was observed.

Conclusions: Prepared nanocrystalline HA could be more useful for treatment of oral bone defects in comparison with conventional HA, and could be more effective as a bone replacement material to promote bone formation.

Keyword: Bone substitutes, hydroxyapatite, nano-material, nanostructured material