Development and Analysis of Glass & Ceramic Based Coating Material for Orthopaedic Implants to Increase Better Bonding and Stability

ABSTRACRT: Over a period of time a number of biomaterials have been developed and are used for hard tissue and joint replacement those are Stainless steel (SS-316L), Co-Cr alloy, Titanium (Ti) and its alloy, ceramics and Polymer especially Ultra High Molecular Weight Polyethylene (UHMWPE) and Alumina (Al2O3). These biomaterials for its suitable mechanical properties, nontoxic behavior, and bio-compatibility can be used as orthopedic implant materials. Titanium, Ti-6Al-4V (alloy) and SS-316L are widely used as materials for orthopedic implants, due to their advantageous mechanical properties and nontoxic behavior but one of the major drawback of using metallic implants is that they are bio-inert and inside the body they become encapsulated by dense fibrous tissue. This impedes proper stress distribution at the implant bone interface, which can result in an interfacial failure and loosening of the implant and finally lead to crack or fracture in the adjacent bone. Most implants today are made from either titanium-based alloys or alloys made from a mix of cobalt and chromium. Both possess excellent mechanical properties but neither is able to bond with bone. As a result, these metals rub against the bones into which they’ve been implanted, creating wear and tear that shortens implant lifetimes. Bone cement (Poly methyl methacrylate) is used to improve the implant fixation but it may result in deterioration of the adjacent bone and failure. Calcium Phosphates, specially Hydroxy apatite [Ca10(PO4)6(OH)2] have been widely used as coating materials on metallic implants due to its bio-active nature to facilitate bonding with bone. Plasma-spray technique, in particular, has been widely investigated by many researchers and has been proposed as a reasonable coating method. But during the plasma spraying process, high flame temperature is required which may lead to compositional changes and structural transformation of Hydroxy apatite (HA). So, after this procedure the uniformity of physical and chemical properties as well as bio-activity of Hydroxy apatite (HA) could be lost. What has been needed is a coating that adheres to the metal surface of the implant and also promotes the formation of Hydroxy apatite (the inorganic component of bone) and better bonding with better stability. The glass ceramic coating material developed according to Appen, the best agreement between the calculated coefficient of expansion to match the thermal expansion coefficient with the metallic implants and studied is suitable for coating Ti and SS-316L substrates by conventional vitreous enameling technique. The glass ceramic coating upon controlled heat treatment produces a glass ceramic containing wollastonite as crystalline phase. The adherence of coating on Ti and SS-316L metal surface was tested by 3-Point Bending Moment using INSTRON 5500R. The results indicate that the coatings are strongly adhered to the metal substrates. The Surface roughness, surface reflectance and DTA/ TGA analysis of coating showed a very good result as per the requirement. Further the successful implants need a porous coating that can be fabricated by using different pore formers like naphthalene powder or other organic materials. This new coating technique overcomes the disadvantages of the systematic treatment and might potential solution for such treatment in the long run.