Study of the influence of plasma oxidation conditions on adhesion strength of new urethanes on biomedical grade metals

Full text: Stainless steel 316 L, titanium and its alloys are the most used building materials for dental braces, wires and implants. In biomedical grade PDMS and polyurethane are polymeric material used in implants, catheters, heart valves, etc. due to its biocompatibility and low toxicity. The hydrophobicity of the PDMS surface causes strong adsorption of proteins when in contact with blood, for example. These surfaces are able to absorb a monolayer of proteins which can mediate tissue attachment. Thus, a PDMS-urethane (PDMSUr) based material can provide combined characteristics of the former PDMS and urethane isolated materials such as anti-corrosion, controlled hydrophobic surface, and also to present features for tissue attachment like fibroblast and osteoclast. Once the resulting PDMSUr cited properties are achieved, the material is applied as coating for dental implants; surfaces of interest to be coated are titanium alloy (TiAlV) and stainless steel (SS316L). The stability of the coating is related to its affinity with the substrates. The use of environmentally friendly low pressure plasma activation is proposed to modify the TiAlV and SS316L surfaces in order to improve roughness forming an oxide layer able to condensate with silanol groups from the coating, i.e. promoting an adhesive bond between substrate/polymer. Different conditions, like voltage and time of plasma oxidation process, will be used to provide surfaces with different roughness and porosity. The PDMSUr is obtained reacting a PDMS precursor with an aminosilane as cross linker and a coating by sol-gel process catalyzed by acid is obtained on TiAlV and SS316L. The efficacy of the surface's roughness on adhesion is measured by Pull-Off-Test comparing substrates activated and non-activated by plasma. In additional, contact angle, XPS and AFM measurements will be used to evaluate properties of the surfaces. (author)