Treating a metal implant with a rough surface portion so as to incorporate biocidal material
Inventors
Shawcross, James Timothy • Turner, Andrew Derek • Lewis, David Richard
Assignees
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Publication Number
US-8888983-B2
Publication Date
2014-11-18
Expiration Date
Abstract
Metal implants (10) are treated by anodising the surface (11, 12) in contact with an electrolyte, and then briefly subjecting the anodised surface to a reversed voltage. During a first anodising stage the surfaces are passivated, while during a subsequent anodising stage pits are formed in the passivating surface layer. Rough portions (15) of the surface, in particular portions produced by plasma spraying of metal powder, are sealed with a watertight cover (20) during at least part of the anodising process. After rinsing, biocidal metal ions are subsequently absorbed into the surface of the implant. This provides the implant with biocidal properties. The use of the cover (20) enables a more uniform geometric distribution of biocidal metal ions to be achieved.
Core Innovation
The invention relates to a method of treating a metal implant having different surface regions, including a first part of the surface with a rough metal finish having a surface roughness factor of at least 5 and a second part of the surface with a polished surface having a surface roughness factor of less than 2. The method is configured so as to incorporate a biocidal material in leachable form in the surface by forming a passivated surface layer and a rough-featured integral surface layer and then incorporating the biocidal material by ion exchange.
The method performs a two-stage anodising sequence. An anodising step is carried out at a first voltage for achieving passivation, and the first part of the surface is enclosed with a watertight cover. The metal object is then contacted with an anodising electrolyte and anodised at a second voltage to passivate the second part of the surface by forming an anodised integral surface layer, and the application of the anodising voltage is continued to produce pits through the integral surface layer.
A hydrous metal oxide or phosphate is produced in the surface layer by electrochemical or chemical reduction in contact with an electrolyte or a solution, followed by removing the anodised metal object from that electrolyte or solution and then removing the watertight cover. The resulting anodised metal object is contacted with a biocidal material solution so as to incorporate the biocidal material into the passivated surface of the first part and the integral surface layer of the second part by ion exchange, including incorporation into both rough and polished regions using the covered processing to improve geometric distribution.
The approach is applied to implant surfaces with rough and polished finishes, including rough regions such as plasma-sprayed titanium and polished regions, and it supports incorporation of biocidal metal ions such as silver ions into the treated surface. The disclosed document also addresses implant material scope and medical implant use cases, including hip replacement, dental, maxillofacial, trauma, orthopaedic and related applications, and it describes comparative performance with and without masking during anodising.
Claims Coverage
The document provides one independent claim (clm-00001). It contains the central inventive concept using a watertight cover in combination with a two-stage anodising/passivation and pit-forming sequence, followed by formation of a hydrous metal oxide or phosphate and incorporation of a biocidal material by ion exchange; dependent claims further refine specific options and parameter constraints.
Region-selective anodising using watertight cover and dual voltage passivation/pit formation
A method of treating a metal implant having a first rough surface region (surface roughness factor at least 5) and a second polished surface region (surface roughness factor less than 2), comprising anodising the first part with an anodising electrolyte at a first voltage (maximum between 25 and 30 V) to achieve passivation; enclosing the first part with a watertight cover; then contacting the metal object with an anodising electrolyte and applying a second voltage (maximum between 30 V and 150 V) to passivate the second part by forming an anodised integral surface layer; continuing the application of the anodising voltage at the second voltage to produce pits through the integral surface layer.
Hydrous metal oxide or phosphate formation and biocidal incorporation by ion exchange
Producing a hydrous metal oxide or phosphate in the surface layer by electrochemical or chemical reduction in contact with an electrolyte or a solution; removing or separating the anodised metal object from the electrolyte or solution; removing the watertight cover; and contacting the anodised metal object with a biocidal material solution so as to incorporate the biocidal material into the passivated surface of the first part and the integral surface layer of the second part by ion exchange.
Overall, the independent claim coverage centers on region-selective anodising protected by a watertight cover together with first-passivation and second-passivation/pit formation using different anodising voltage ranges, and on forming a hydrous metal oxide or phosphate followed by incorporating a biocidal material by ion exchange across both rough and polished surface regions.
Stated Advantages
Improved uniform geometric distribution of biocidal ions across rough and polished regions using the watertight cover during anodising.
Documented Applications
Medical use cases for treated metal implants, including hip replacement, dental, maxillofacial, trauma, orthopaedic and related implant applications.
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