CORDIS proporciona enlaces a los documentos públicos y las publicaciones de los proyectos de los programas marco HORIZONTE.
Los enlaces a los documentos y las publicaciones de los proyectos del Séptimo Programa Marco, así como los enlaces a algunos tipos de resultados específicos, como conjuntos de datos y «software», se obtienen dinámicamente de OpenAIRE .
Resultado final
Whilst contributing to the Ortholaser project Cybamatic realised that it was possible to use the machine and software system they had developed in reverse. By adding a digitising probe to the machine, a component placed upon the machines table could have its 3D surface data shape captured directly into CAD. Since the captured data related to the machine datum when imported into the CAD and displayed in the same relation to the CAD datum.
The result was the ability to reverse engineer the component by generating an exact replica of the scanned part. The primary method of generating the component was through the machining process. However, it has been demonstrated outside this project that the laser deposition process for the Hydroxyapetite can be modified to deposit metal powder and by these means cast metal parts may be built in minutes directly from their computer model.
The hard tissue damage is a normal occurrence in the world requiring large amount of substitute materials, medical and surgical interventation with high costs and resulting in loss of human resources and patient pains. The problem of bone substitution has been known and studied for some considerable time, but no completely effective solution found. It concerns the field of reconstructive surgery in orthopaedy, neurosurgery, dentistry and maxillo-facial surgery.
In orthopaedic surgery, the largest market, bone grafts are widely used in hip and knee artroplasty (osteoarthritis, osteoporotic and traumatic fracture, reumatoid arthritis), neoplastic surgery, osteomyelitis (hematogenic, open fracture, metal implants), spine surgery (disc herniation, tumors, spondilo-discitis)
Autograft has the advantages of not being immunogenic and, even more importantly, it is best for inducing new bone formation in the host. The disadvantages of autograft are the limited quantity available and the strength, shape, and form, which cannot precisely duplicate the bone being replaced. They require additional surgery, more pain for the patient, risk of infection, and additional cost for longer time of surgery.
Allografts, on the other hand, are available in quantity, can be strong, and can duplicate the deficit. Allograft bone has certain biologic problems: unfortunately, however, they are immunogenic and are not as osteoinductive as autograft bone and non-union may result. The problems of disease transmission are well documented (HIV, Hepatitis).
To overcome the previous problems synthetic materials with biological, chemical, morphological and mechanical characteristics similar to the bone have received an increased interest. Synthetic Ca/P materials, such as Hydroxyapatite and Tricalcium Phosphate, which are containing Calcium and Phosphorus as chemical elements similar to the natural bone chemistry, are still increasing as bone substitute biomaterials.
The scientific output from the present project is consisting in the availability for the Public Health Service of a bioactive material be used in the production of Medical Devices (Class 2B) in the bone defects due to patological conditions such as traumatic and infiammatory lesions for the reconstruction and substitution of the bone tissues in the orthopaedic, maxillo-facial, odontoiatric, cranial and neuro surgeries. The technological output is consisting in the availability of a bioactive Ca/P material tailored for bioactive coatings with laser processing.
The up to date production technology of the Hydroxyapatite powder at laboratory scale is giving an indication of production costs at the same level of the competing producers with a consequent competitiveness of the product in the market depending mainly from the commercial strategy.
The aim of our study was to analyse the osteointegrative capacity of titanium cylinders, some uncovered, others covered with calcium phosphate using two different techniques, namely plasma spray and laser technique.
Calcium phosphate covering has been shown to have advantages for implants, since it is capable of achieving good adaptation between the implant and the bone, and also reduces the interface surface between the two.
The two techniques used for covering the implant, that is, plasma spray and laser, produce different results. While the plasma spray covering causes integration of the bone, which forms fingers that invade the covering, the laser covering causes detachment of particles, which are eliminated and replaced by bone.
There are a large number of industrial activities in which the injection of a material in the form of powder is required. Applications such as the production of coatings by laser cladding, rapid prototyping, powder metallurgy, welding with filler powder or cleaning by powder blasting are demanding devices to handle a stream of powder in a controllable and accurate manner.
The Applied Physics department at the University of Vigo has developed a new nozzle, which presents the following advantages in comparison to the existing technology:
- The device allows to focalise the powder and to adapt the size of the powder jet spot to the requirements of a specific application.
- It is possible to change the diameter of the powder jet and the focal distance without changing the nozzle.
- It is possible to align independently the position of the focus and the direction of the powder jet.
- The nature of the shrouding gas can be independent of the powder carrier gas in order to establish either an inert or reactive atmosphere around the working area.
Anatomic tibial plates, with four right sizes and 4 left sizes, which cover any necessity, in reference with different tibia dimensions, to avoid plunging in cortical areas, which is the most frequent reason of failures in tibia prostheses.
Joint between Titanium Plate and Polyethylene plate, by means of a perimetral area and an orientation central pivot, that allows coupling the joint manually. This guarantees a perfect adjustment of the plates without using any type of instrumental, and without making any pressure for the coupling in the operating area.
The surgical instrumentation is reduced to 50% in the number of pieces with regard other manufacturers, improving the surgeons comfort, reduces the time of surgical intervention. The manufacturing and stocking investments for instrumentation from hospital, distributors and factory are reduced.
The aim of the laser cladding and alloying process is to overlay one material with another to form a sound interfacial bond or weld without dilution (cladding route) or with dilution (alloying route) of the provided material. The advantages of this technique in the metallurgical field are the following:
- Controlled shape of the coating within certain limits.
- Localised heating, which reduces thermal distortion and the size of the heat-affected zone.
- Flexibility of the process.
- Controlled levels of dilution.
- Smooth surface finish, near isotropic mechanical properties, fine quench microstructures and good fusion bonding.
- Minimum surface preparation required.
Experience and know-how achieved in this project allows to extend these laser surface processing technologies to other fields of applications such as corrosion protective coatings, thermal barriers, wear resistant coatings, tribological coatings, etc.
Further research is needed to set up the processing parameters for each specific application and to fully automate the process.
QMUL contributed to this result through provision of FT-Raman spectroscopy of the start powders.
FT-Raman spectroscopy was used to corroborate information gained from FT-IR and XRD (obtained by the university of Vigo and Fin-Ceramica) regarding the level of crystallinity within the hydroxyapatite starting powders and to aid in the identification of any distortion within the crystal lattice through study of the relative predominance of the phosphate vibration modes.
This analysis was essential to ensure that the thermal pre-treatment of the powder did not result in chemical decomposition of the hydroxyapatite powder prior to laser processing.
Characterization of this and many other aspects of the powder (as performed by Fin-ceramic and University of Vigo) were essential to ensure that any thermal pre-treatment of the powder did not result in chemical decomposition or detrimental changes in the physical attributes (such as powder morphology, surface area etc.) of the hydroxyapatite powder prior to laser processing.
Lasers have shown an enormous potential for application in many fields, transforming the telecommunications industry and also the medical practices. Materials processing is by far the field of application in which high power lasers found the largest number of industrial installations. A big portion of these installations corresponds to the 2-dimensional laser processing. On the other hand, 3-dimensional laser processing is reduced to robot-based machines or 2-dimensional machines in which an additional axis is added. Therefore a real 3-dimensional laser-processing machine is still needed to be able to perform industrial tasks, which require the specific use of lasers.
Experience and know-how achieved in the combined usage of the Real-virtual-real capabilities of the Cybaman system with our high power lasers allows envisaging future applications in the field of rapid prototyping, 3-D welding, 3-D cutting and 3-D surface treatment of complex forms.
During the removal after some years of prostheses, such as hip joints, excessive osteointegration (bone ingrowth) which was an apparent advantage in the early stages of implantation can lead to problems. The prosthesis may only be removed along with a significant amount of the surrounding bone. This imperils the success of subsequent hip implants.
Based on the work of the University of Vigo in developing and optimising the laser cladding conditions using a Nd:YAG laser to produce calcium phosphate coatings, the University of Liverpool has shown that localised area coverage of titanium alloy implants can be achieved by the cladding process. This seems to be especially effective if the added material is situated in a premachined groove made in the surface of the substrate material.
If the hydroxyapatite coating is placed in this way only in areas where implant/bone adhesion by osteointegration is required for stability of the implant, successful bonding of the implant to the surrounding bone can be achieved while the problems of excessive osteointegration described above are minimised. This allows easier (and less damaging) subsequent removal of the implant and an increased likelihood of success for further implants to be available for the same patient. In a similar way, other localised surface area treatments of implant surfaces may be beneficial.
The characterization and testing of new materials is a key issue in the development of new products The increasing demand for new materials having better performance in service requires a wide an accurate testing and characterization protocol. The research group of the Applied Physics department at the University of Vigo has over 20 years of experience on the field of materials processing and characterization, with a specific emphasis on the production of coatings by means of lasers. A wide and extensive experience has been acquired in materials characterization, either physico-chemical, optical, mechanical, etc.
Experience and know-how achieved during this project allows to offer the following services:
- In-vitro and cytotoxicity testing of biomedical materials.
- R&D consultancy for biomedical and non-biomedical materials applications.
- Material testing services for biomedical and non-biomedical materials applications: Electron microscopy (SEM, TEM), X-ray Diffraction, FTIR and Raman Spectroscopy, X-ray Photoelectron Spectroscopy, Adhesion testing, Scratch-testing, Atomic Absorption and ICP chemical analysis, Atomic Force Microscopy.
QMUL contributed to this result through provision of FT-Raman spectroscopy, adhesion testing, conventional X-ray diffraction and grazing incidence X-ray diffraction of the laser processed calcium-phosphate coatings.
FT-Raman was also used to corroborate information gained from FT-IR (obtained by the university of Vigo) and XRD regarding the level of crystallinity within the coatings. However, the complex phase composition of the coatings made interpretation of spectra difficult with regard to assessing lattice distortion within the crystal structures of the various titanium-calcium-phosphate phases present.
Adhesion testing enabled determination of the adhesive bone strength between the calcium-phosphate coating and the titanium substrate. Through close collaboration with the University of Vigo a protocol was developed, based on the current ASTM standard, but which included post-testing analysis of the fracture surface to correct the data for any variation in application of the adhesive used in the assembly of test pieces, resulting from of plate warpage and the highly textured surface inherent in laser cladded coatings. Within this task several protypes of assembling device were developed and optimised by the University of Vigo. This methodology enabled optimisation of the processing conditions to ensure that coatings with a promising phase composition (as determined by XRD) also had an adhesion strength in excess of 35MPa.
X-ray diffraction was employed to assess coating crystallinity, to identify the crystalline phases present and to assess the relative proportion of calcium phosphate phases present within the coating, as compared to the titanium-calcium-phosphate phases. Patterns were collected using grazing-incidence angles of 0.3-3 degrees, in addition to the conventional 2-theta geometry. Grazing-incidence analysis is usually used in the study of thin films, and enabled the identification of changes in phase composition with depth through the laser processed coating by variation in the grazing incidence angle and thus depth of X-ray penetration and diffraction. Thus, X-ray diffraction analysis enabled selection of processing parameters to control for coating phase composition, where a maximal content of hydroxyapatite and a minimal content of calcium titanate or calcium oxide was sought to promote bioactivity.
Development of a C.N.C. Manipulation/ Machine System and Control / Simulation Software for precisely positioning a component three dimensionally against process tooling by moving the models image of the component in Computer Aided Design Software:
Cybamatic contribution to this project was to develop a machine that could both hold the knee prosthesis which is the subject of this project and position it three dimensionally under computer control in order that an hydroxyapetite coating could be deposited by laser cladding on any facet of its three dimensional surface.
The result was the evolution of a multi-axis CNC positioning system comprising a manipulator whose movements were related to a single three dimensional datum created by the configuration of the manipulators axes. This provides a portal through which the real world of the machine can be linked to the virtual world of the CAD software.
The Cartesian datum of the CAD in effect represents the same point as the machines datum therefore any 3D surface model designed or scanned into the CAD will have a surface that is defined relative to the CAD datum and can therefore be generated on the machine in the same relationship to the machines datum.
A Control Software was developed which comprised the mathematics of the manipulators movement algorithm from which a simulation software was developed that displayed the manipulator, allowed a component shape and a pre-defined process path to be loaded and displayed in an animated sequence.
Calcium phosphate ceramics, especially hydroxyapatite (HA) are currently used as biomaterials for many applications in both dentistry and orthopaedics, because they form a real bond with the surrounding bone tissue when implanted. Nevertheless, due to the poor mechanical properties of bulk HA ceramics, these cannot be used as implant devices to replace large bony defects or for load-bearing applications. In those cases, titanium-based devices find their field of utilization. For this reason, much effort has been devoted in the last decade, towards the application of HA as a coating on metallic substrates, in order to improve fixation and promote osteointegration of cementless titanium-based implant devices.
The plasma-spray (PS) technique is currently the only method commercially available for coating implant devices with HA. But the PS HA coatings, although exhibiting a very good biocompability, present some disadvantages affecting the long-term stability of the implant and, therefore, its lifetime. Among these drawbacks, the most significant are the poor coating-substrate adherence (making it necessary to introduce a grit-blasting surface treatment prior to the coating procedure, in order to guarantee a minimum adhesion of the coating) and the lack of uniformity of the coating from two different points of view: morphology and composition.
Because of these drawbacks, a novel laser cladding technology has been developed to produce calcium phosphate coatings showing good adhesion to the titanium alloy in order to overcome the drawbacks of conventional technology. The research included the two more widely used lasers in the industry: Nd:YAG lasers (work performed by the University of Vigo) and the CO(2) lasers (work performesd by the University of Liverpool). The most successful process has been the Nd:YAG laser surface cladding. A patent has already been granted.
The work performed has delivered a calcium phosphate coating that shows a graded interface layer between the Ti substrate and the coating consisting of calcium titanate, which provides the good bonding. At the outermost surface the coating composition is hydroxylapatite and its glassy phase. Such a well adhered bioactive coating should promote faster and better osteointegration of implants for bone substitution mainly in orthopaedics and dentistry.
Design and Manufacturing of the Femoral Knee in Titanium Alloy Grade 5 = TiAl6V4:
The task was to construct and design the implant in different sizes for future castings and forgings.
The femoral part was designed using CAD of AutoCad 14 and MasterCam using virtual utilities by the co-operation of Joe McLean, Cybamatic Ltd. UK. Besides the necessary tooling for milling and turning of the device the surface and structure of the sliding surface of the device have to be considered. A future coating of the sliding surface has to be provided before laser cladding. Also new surgical procedures are demanded, because a lot of surgeons are not replacing the patella anymore.
Therefore a future change of the front shield of the Femoral Part of the Knee could be or would be necessary.
The titanium alloy is too soft as a sliding surface. State of Art has been PVD = Physical Vapour Deposition, using a titanium nitride or titanium niobium nitride coating.
Buscando datos de OpenAIRE...
Se ha producido un error en la búsqueda de datos de OpenAIRE
No hay resultados disponibles