Effect of fluorine incorporation on long-term stability of magnesium-containing hydroxyapatite coatings.

Dissolution resistance and adhesion strength are two main concerns for long-term stability of surface coated metal implants. In this study, fluorine ions are incorporated into magnesium-containing hydroxyapatite coatings (MgF(y)HA) via sol-gel method to improve the long-term stability of the implants. Surface and interface are studied in terms of phases, depth profiling and chemical bonds by grazing incidence X-ray diffraction, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. The long-term stability is evaluated by dissolution and pull-off test. The results show that fluorine promotes the incorporation of magnesium in HA lattice. The elemental interdiffusion and chemical bonding take place at the coating/substrate interface. Both the dissolution resistance and the adhesion strength are enhanced by fluorine incorporation, thus the long-term stability of the implant is improved.