Short-term bone response to titanium implants coated with thin radiofrequent magnetron-sputtered hydroxyapatite in rabbits

Background: It has been suggested that calcium phosphate (CaP) coatings initiate faster bone growth around implants. A major concern about the viable use of these coatings has been their biologic performance related to the coating characteristics. Purpose: The purpose of this study was to investigate the early bone response to micron‐ and submicron‐thick hydroxya‐patite (HA) coatings in cortical and trabecular bone. Materials and Methods: CaP coatings were manufactured by magnetron sputtering. Heat treatment was subsequently used to increase the crystallinity of the coatings. Coatings were characterized by x‐ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP‐OES), and stylus profilometry. Four types of CaP‐coated implants were used (0.1 urn and 2.0 μm amorphous; 0.1 um and 2.0 μn crystalline); uncoated machined commercially pure titanium implants served as controls. Four hundred eighty implants were randomly placed in 60 rabbits. Ten animals were followed up for 1 week, 10 for 3 weeks, and 40 for 6 weeks. The bone response was histomorphometrically evaluated. Results: Coatings with a CaP ratio very close to that of HA were produced. Crystalline coatings significantly improved the early bone‐implant contact whereas the amorphous‐coated implants behaved similarly to uncoated titanium. Conclusions: Crystalline CaP coatings 100 nm thick on titanium implants elicited an improved early bone response compared with that of uncoated titanium implants. No further improvement in the bone response was observed with 2 μm coatings.