Chemat Technology, Inc. (Northridge, CA) garnered U.S. Patent 7,649,004 for a process to chemically coat the surface of a medical or dental implant with a colloid comprised of crystalline hydroxyapatite nanoparticles that ensures greater biocompatibility. The average particle size is 20 nanometers. The nanoparticle hydroxyapatite coating promotes osseointegration, say inventors Jiankai Liu, Yuhong Huang and Ichiro Nishimura.
Metal implants are widely used in medical and dental applications, such as in orthopedic hip and knee surgeries and in dental surgery. Over two million orthopedic procedures and over 10 million dental implant procedures are performed in the United States every year. Implants fail because of poor osseointegration between the implant and the natural bone. Implants are typically made of metal materials, with titanium (Ti) and its alloys being favored due to their biocompatibility and mechanical properties.
For the implants to function successfully, a direct chemical bond between the implant and the bone needs to form rapidly and needs to be retained over many years while the implant is loaded. Metal materials, however, do not form a direct chemical bond with bone.
In order to promote osseointegration between the metal implant and bone, Chemcat incorporates a layer of osseointegration promotion material on the implant. Calcium phosphate ceramic materials are an example of coating materials that promote osseointegration. The most popular coating among the calcium phosphate family is hydroxyapatite (HA) due to its chemical stability and osteoconductivity. The implant can be a titanium alloy with crystalline hydroxyapatite nanoparticles. HA nanoparticles can also coat medical implants made with tantalum, cobalt, chromium, and their respective alloys
Since it may be desirable, in one application to insert or embed (implant) the substrate into bone material, the substrate includes a surface coating designed to be in contact with bone or other tissue. The surface coating may include at least two coating layers: a first coating layer having a property such that it will bond or otherwise adhere to the substrate, particularly if it is metal substrate being implanted; and a second coating layer on the first coating layer having a property that promotes osseointegration between the apparatus and bone or other tissue. Bone inducing growth factors may also be added, possibly to the second coating layer.