Development of hydroxyapatite coating method on titanium using plasma spray and mesh masking

Summary form only given. Titanium and its alloys have been used with some success in several implant applications. However, they can suffer certain disadvantages, such as poor osteoinductive properties and low corrosive-wear resistance. Attempts to overcome the former have involved with coating the metal with bioceramic materials like hydroxyapatite. The hydroxyapatite(HAp, Ca/sub 10/(PO/sub 4/)/sub 6/(OH)/sub 2/) is preferred in general for its ability to interact with living bones, resulting in improvement of implant fixation and faster bone healing. Of the various coating methods, the plasma spraying technique is the primary one currently used commercially to produce HAp coatings on metallic implants with its application increased significantly in recent years due to high tolerance of surgical inaccuracies and fast fixation of the implants in bone as well as firm attachment of implant to bone. Some of the bioactive properties of HAp are degraded during plasma spraying because of high temperature. Control of the composition change is necessary and the crystalline structure of HAp layer will have to increase to eliminate these drawbacks of HAp plasma spray. However, these conditions have opposite relation to each other and are difficult to satisfy at the same time. The purposes of this study are to enhance adhesiveness of initial stage strength and to work out a countermeasure about the absorption of HAp coating layer in human body. Surface porosity is utilized using TiO/sub 2/ blast and HAp plasma spray coating by masking method. The HAp coating layer appears to ensure bonding strength at the initial stage. Separation and/or absorption of HAp may also occur between implant and bone after inserting the implants. The combination between porous surface and grown-up bone can be successfully used to maintain adhesive strength. Screws of pure titanium are made for testing and then HAp coating group is separated using plasma spray, porous surface group using TiO/sub 2/ - last and HAp coating and porous surface group using mesh masking respectively. Screws of each group will be implanted in the femurs of rabbits. After 4 weeks, 8 weeks and 12 weeks, screws of each groups are withdrawn from rabbit´s femur and examined for the adhesive strength with torque meter and tissue condition between implant and bone.