Effect of zinc ions on improving implant fixation in osteoporotic bone

The application of titanium (Ti) and its alloys in tooth restoration and joint replacement for aged patients with unfavorable conditions is gaining popularity. Therefore, strategies aiming at improving the fixation of Ti-based implants are worth investigating. This study was designed to observe whether modification of Ti implants by zinc (Zn) could enhance the fixation capability in osteoporotic bone. Two kinds of implants, hydroxyapatite (HA) coated Ti and Zn-incorporated HA (ZnHA) coated Ti, were inserted into the femoral metaphysis longitudinally in ovariectomized (OVX) rats. Specimens were harvested and subjected to double fluorescence labeling examination at week 6 after surgery. At week 12, samples were evaluated with histomorphometry, micro-CT (μCT) analysis and biomechanical test. Compared to the HA coated implants, ZnHA coating improved mineral apposition rate (MAR) of peri-implant bone, which was revealed by double fluorescence labeling; bone area ratio (BA) and bone-to-implant contact (BIC) were also higher for the latter group by histomorphometry. μCT images suggested that more bone mass was formed around the ZnHA coated implants as compared to the HA coated implants. Biomechanical push-out test showed that the ZnHA coated implants demonstrated higher strength of osseointegration than the HA group. The current study suggested that Zn ions could enhance bone formation and improve implant fixation in OVX rats.