Rapid structural evolution and bone inducing mechanism of the multilayer coating with silicon-doped hydroxyapatite crystals on the microwave water steaming-hydrothermally treated titania coating

To reveal the formation mechanism of new bone tissues induced by the multilayer titania coating with silicon-doped hydroxyapatite (Si-HA), plasma electrolyte oxidation (PEO) and microwave steam-hydrothermal treatment (MG) were performed to form Si-HA nanorods rapidly on the PEO coating. In the present work, the length and diameter of Si-HA nanorods on the MG-treated PEO coating for 10 min (PEOMG10) were smaller than that those treated for 60 min (PEOMG60). The microstructure of the multilayer coating, including the porous middle layer containing anatase nanocrystal cluster, the middle anatase layer, Si-HA nanocrystals, and the outermost layer that grew Si-HA nanorods, was revealed by transmission electron microscopy (TEM). The in vitro mineralization test indicates that the PEOMG60 sample exhibits excellent apatite-inducing ability because of its high degradation. The in vivo animal experiment showed that the PEOMG10 implant has high interfacial bonding strength and excellent osseointegration interface status. The fracture for the PEOMG10 implant occurred at the interface between the coating and the bone side owing to its good interface status. The present study can expand the widespread applications of the titania-based hydroxyapatite composite materials for repairing hard tissues and teeth filling.