The Effect of Magnesium-Incorporated Hydroxyapatite Coating on Titanium Implant Fixation in Ovariectomized Rats

Purpose: This study compared the effect of magnesium-incorporated hydroxyapatite (MgHA) coating with that of HA coating on implant fixation in ovariectomized (OVX) rats. Materials and Methods: Coatings of HA and MgHA (10 mol% Ca2+ replaced by Mg2+) were prepared on the surface of titanium substrates using the sol-gel dip-coating method, and powders of HA and MgHA were produced by the same method. The two kinds of materials were then characterized by scanning electron microscopy and x-ray diffraction. Twelve weeks after bilateral ovariectomy, 18 OVX rats received implants in the distal femora; half of the implants were HA-coated and the other half were MgHA-coated. After 12 weeks of healing, rats were selected randomly for histomorphometry, microcomputed tomography evaluation, and biomechanical testing. Results: Surface characterization analysis demonstrated that the addition of Mg did not dramatically change the surface topography or apatite patterns of the coating. Histomorphometry revealed higher bone-to-implant contact and bone area ratio for MgHA-coated implants than for HA-coated implants. Microcomputed tomographic evaluation revealed improved trabecular parameters and increased osseointegration for MgHA-coated implants. Biomechanical testing revealed that the MgHA coating increased the maximum push-out force and interfacial shear strength compared to the HA coating. Conclusion: Mg incorporated into an HA coating on titanium implants could improve the biologic fixation of implants in osteoporotic bone.