Preliminary in vitro Study on Enhancement of Bone-like Hydroxyapatite Formation on Bio-active Titanium Alloy by Low-intensity Pulsed Ultrasound Waving for Early Bone Bonding

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In this study, we investigated whether ultrasound wave stimulation could accelerate the bone-bonding ability of bio-active titanium alloy in vitro. Titanium alloy (α+β-Ti-6Al-4V) processed in chemical and heat treatments was used as a specimen, and soaked in simulated body fluid (SBF) under pulsed ultrasound wave for the planned time periods. The surface of samples was observed using scanning electron microscopy (SEM), energy dispersive spectroscopy, X-ray diffraction to assess the state of bone-like hydroxyapatite formation. SEM images showed that a richer and finer layer of bone-like hydroxyapatite covered the titanium surface in the ultrasound wave group as compared with the non-ultrasound group. The measurements of mass of specimens also indicated the efficiency of ultrasound waves for hydroxyapatite formation. These findings suggest that the nucleation and crystallization of apatite on bio-active material surfaces might be promoted by micro-moving and cavitation of low-intensity pulsed ultrasound waves. We propose that pulsed ultrasound stimulation has a great potential for further improvement of osseointegration and osteoconductivity for medical bio-active implants.