A functionally graded titanium/hydroxyapatite film obtained by sputtering.

Area of Science:

• Biomaterials Science
• Materials Engineering
• Orthopedic Research

Background:

• Titanium and hydroxyapatite (HA) are widely used in orthopedic implants due to their biocompatibility and osteoconductivity.
• Improving the interface bonding strength between implant materials and bone is crucial for long-term implant stability and success.
• Existing coating methods like plasma spraying have limitations in achieving optimal adhesion and functional grading.

Purpose of the Study:

• To develop and characterize a functionally graded titanium/hydroxyapatite (HA) film on a titanium substrate using radio frequency magnetron sputtering.
• To evaluate the bonding strength and mechanical properties of the graded HA film.
• To assess the in vivo performance and bone integration of implants coated with the graded HA film.

Main Methods:

• A functionally graded titanium/HA film was fabricated on titanium substrates using radio frequency magnetron sputtering, controlling the Ti:HA ratio via a target shutter.
• The film, approximately 1 micrometer thick with graded composition (HA-rich surface, Ti-rich substrate interface), was characterized for bonding strength using pull-out and scratch tests.
• Titanium columns coated with graded HA or pure HA films were implanted into canine femora, and push-out tests were conducted at 2, 4, and 12 weeks post-implantation.

Main Results:

• The functionally graded Ti/HA film exhibited significantly higher bonding strength (15.2 MPa pull-out, 58.85 mN scratch load) compared to pure HA sputtered films (8.0 MPa, 38.47 mN) and pure HA plasma spray coatings (10.4 MPa).
• In vivo, after 12 weeks, the graded HA coated implants showed the highest push-out strength (3.7 MPa) compared to pure HA coated implants (3.5 MPa) and uncoated controls (1.0 MPa), indicating enhanced osseointegration.
• The graded film structure, with HA concentrated near the surface, contributed to improved interfacial adhesion and biological response.

Conclusions:

• Functionally graded titanium/hydroxyapatite films prepared by magnetron sputtering offer superior bonding strength and mechanical stability compared to conventional HA coatings.
• The graded HA coating demonstrates enhanced osseointegration and implant fixation in a canine model, suggesting potential for improved clinical outcomes in orthopedic applications.
• This sputtering technique provides a viable method for creating advanced biomaterial coatings with tailored properties for orthopedic implants.