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New surface alloys developed by directed-energy-beam radiation for dental implants

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The main objective of the project is to develop new corrosion and wear protective metallic alloys on the surfaces of dental implants. To achieve this objective, the surfaces of currently available dental alloys: Co-Cr-Mo, Ti-6Al-4V, Cr18-Ni9-Ti, Co-Cr; Ni-Cr, pure titanium (cpTi>99,5%) and 316L SS specimens will be advanced by laser surface alloying (LSA) or ion implantation. The new fabricated surface alloys should possess the advanced biocompatibility, hardness and several times (2-5) improved corrosion resistance in biological media (artificial saliva, synthetic blood plasma) in comparison with the traditionally coated (plasma sprayed or PVD) implants. It is expected to achieve large passive range and current densities, which are 30-100 times, lower in comparison with uncoated specimens. The advanced properties of the implants should result from the new rapidly self-quenched surface microstructures developed by these directed-energy-beam (DEB) radiation techniques.

It is proposed to develop:
- amorphous (metallic-glass) binary Co(10-55%)-Ti; Au(40-60%)-Ti; Cr(30-50%)-Ti and ternary Ni-Mo-Ti; Ni-Ta-Ti coatings developed by LSA or ion implantation (implant base material is at the last postion);
- extended solid solutions of binary Pd(10-35%)-Ti; Mo(10-30%)-Ti; ternary Mo(10-30%)-Cr-Co, or Mo (10-35%)-316L SS systems by LSA or ion implantation;
- nitridized pulsed laser surface hardening (microhardness values up to 1010 Pa) in nitrogen (at a pressure up to 5x106 Pa) of Ti-based dental alloys (Ti-6Al-4V), accompanied by 400-600 (m TiN layer formation;

The unique types of microstructures will be developed: extended solid solutions, metastable crystalline phases, and metallic glasses. The local area of implant (e.g. influenced by definite biological media) will be alloyed. Corrosion resistance of some areas of the implant will be improved whereas other surfaces areas can reveal advanced wear resistance properties. The choose of the implanted species, the thickness of the alloyed/implanted layer, the energy output parameters and environmental conditions will be critical to reduce the possibility of forming galvanic couples, which lead to localized corrosion. The strict control of the surface finish and uniform distribution of alloyed metals will be achieved resulting in removal of electrochemical microcells on the metal surface.

By using LSA and ion implantation it is proposed to develop coatings which should possess "absolute" value of adhesion strength resulted from intermixing occurred at the coating - substrate interface. It is proposed to optimize parameters of ion implantation (ion energies range 35-150keV; Mo+, Pd+ , Ta+ , Au+; ion doses range 1016-2x1018). For LSA both spatial (from Gaussian to uniform power distribution) and temporal (from nanosecond to millisecond mode) laser ((=1,06() output parameters and environmental conditions (thickness of pre-deposited alloying metal film, ambient gas pressure) for uniform distribution of alloying materials over the modified surfaces. Homogeneity structures by scanning a repeatedly pulsed laser beam on the metal surface, thereby obtaining a uniform surface finish, will be developed. Corrosion resistance will be evaluated from potentiodynamic current-potential (I-E) curves by standard three-electrode system (working electrode as a specimen, reference electrode with a constant potential will be a saturated calomel electrode (SCE) and the counterelectrode is made of vitreous carbon). Pourbaix diagrams (specifying whether corrosion, depending on pH values and oxygen concentrations, will take place) for the most perspective alloys will be also developed
Achievement of scientific results is due to wide variety of chemical and microstructural states which can be retained because of the rapid quench (up to 1011 K s-1). The types of the microstructures will include extended solid solutions, metastable crystalline phases, and metallic glasses. This is not only a new trend in biocompatible materials' surface development, but also a contribution to condensed matter investigations. The correlation between the DEB processes' parameters, macroscopic coupled heat- and mass transfer and required resulting composition and microstructure will be investigated too. At the end of the project, it is expected that at least one prototype of the alloyed/implanted dental implant will be ready for restricted production intended for clinical trials.

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Universite Montpellier 2
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Place E. Bataillon
34095 Montpellier
Frankreich

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Letzte Aktualisierung: 30 Oktober 2002

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Permalink: https://cordis.europa.eu/project/id/INTAS-1997-00681/de

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