The Effects Of Functionalized Titanium Screws On Osteointegration At The Bone-implant Interfaces In Osteoporotic Rats

Objective:To generate an ovariectomized rat model of osteoporosis to assess bone lossMethods:56 8-10 weeks old Wistar rats are randomly separated into the control and overiectomized groups.Control group includes 6 rats and the overiectomized group includes 50 rats.The bone density and structure are scanned and assessed by Micro-CT after 8 weeks.Results:The images of high resolution from Micro-CT scanning have shown that bone volume,bone mineral density,mean connective density,trabecular number and thickness are significantly decreased in the femoral condyle in the overiectomized rats compared with the controls.However,trabecular separation is markedly increased in the overiectomized rats.Taken together,these results indicate that bone mass is lost and osteoporosis occurs in these rats.Conclusion:An adult rat model of osteoporosis is well established 8 weeks after ovariectomy.This model is a useful tool for the studies of osteoporotic pathogenesis,prevention and clinical treatment.Objective:To asess the effects of functionalized titanium screws on osteointegration at the bone-implant interfaces in osteoporotic rats.Methods: The surface of titanium screws is functionalized by treatment with RGD,OGP or both RGD and OGP.25 titanium screws from each treatment or without treatment were randomly implanted into 50 overiectomized rats.The femoral bones with implants were taken out after these rats were raised for 8 weeks.The bone density and structure are scanned and assessed by Micro-CT and electronic microscope.The elements of the bone tissues were analyzed and quantified by energy dispersive spectrometer(EDS).The anchorage force of the Ti screws was evaluated by a biomechanical pull-out testing.The histological images of titanium screws were also observed by optical microscope.Finally,the effects of functionalized titanium screws on osteointegration at the bone-implant interfaces are determined by analysis of the bone volume and the bone-implant contact.Results:Trabecular number and bone mineral density were increased significantly in the femoral bones from overiectomized rats after the titanium screws functionalized with RGD and OGP were implanted.The calcium and phosphorus contents were increased markedly in the surface of the functionalized titanium screws compared with the conventional titanium screws.Further,the functionalized screws are more stable and have greater pull-out strength than the conventional titanium screws.Bone apposition on the functionalized titanium screws are more at the bone-implant interfaces.Importantly,titanium screws functionalized by treatment with both RGD and OGP indicated an enhanced synergism on osteogenecity and show better effects on osteointegration at the bone-implant interfaces than those treated with either RGD or OGP.Conclusion:The functionalized titanium screws promote osteointegration at the bone-implant interfaces in osteoporotic rats.