The effect of strontium-substituted hydroxyapatite coating on implant fixation in ovariectomized rats

This study was designed to investigate the effects of strontium-substituted hydroxyapatite coatings with 10 mol% Ca(2+) replaced by Sr(2+) (10% SrHA) on implant fixation in ovariectomized (OVX) rats. Coatings of HA and 10% SrHA were prepared on the surface of titanium implant using sol-gel dip methods, and then characterized by Scanning Electron Microscope, Atomic Force Microscope, X-ray diffraction, X-ray Photoemission Spectroscopy, and an automatic scratch tester. Twelve weeks after bilateral ovariectomy, twenty OVX rats accepted implant insertion in the proximal tibiae, half with HA-coated implants and the other half with 10% SrHA coated implants. After 12-week healing period, 10% SrHA coated implants revealed improved osseointegration compared to HA, with the bone area ratio and bone-to-implant contact increased by 70.9% and 49.9% in histomorphometry, the bone volume ratio and percent osseointegration by 73.7% and 45.2% in micro-CT evaluation, and the maximal push-out force and ultimate shear strength by 107.2% and 132.9% in push out test. These results demonstrated that 10% SrHA coatings could enhance implant osseointegration in OVX rats, and suggested the feasibility of using SrHA coatings to improve implant fixation in osteoporotic bone.