CoCr Alloy (cocr + alloy)

Distribution by Scientific Domains


Selected Abstracts


Mechanical Surface Properties of CoCr Alloys After Nitrogen PIII

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Inga-Maria Eichentopf
Abstract Initial experiments were performed to improve the mechanical surface properties of CoCr alloys by nitrogen plasma immersion ion implantation (PIII). Fast thermally activated diffusion with an activation energy of 0.6 eV was observed. A detailed investigation of the phase formation by X-ray diffraction revealed a variable phase composition with CrN and Cr2N being dominating at higher temperatures and additional fcc phases being present. The hardness of the surface layer increased from about 300 HV by a factor of 3,5 while the wear rate was reduced by a factor of up to ten as a result of the PIII treatment. [source]


Comparison of cobalt chromium, ceramic and pyrocarbon hemiprostheses in a rabbit model: Ceramic leads to more cartilage damage than cobalt chromium

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008
Martin Jung
Abstract Cartilage wear after hemiarthroplasty remains a problem in orthopedic surgery. The main cause of cartilage wear, apart from incongruency of the joint partners, is generally considered to be the tribology of the material surfaces. This study evaluates in 27 rabbits the degree of cartilage wear of the tibia plateau after hemiarthroplasty with proximal interphalangeal prostheses made of three different materials [cobalt chromium (CoCr), pyrocarbon (PyCa), and ceramic (Cer)]. Three months after hemiarthroplasty, the articulating tibial cartilage was histomorphologically examined and degenerative damage was graded using the modified Mankin score. The mechanical capacity of the cartilage was assessed by stress relaxation testing. The biomechanical properties of the cartilage were significantly superior in the CoCr group as compared with the Cer group (p < 0.03), indicating less damage to the articulating cartilage surface. The Mankin score showed significantly lower values in the CoCr compared with Cer group (p = 0.011), whereas no differences were found between PyCa and CoCr or PyCa and Cer. In contrast to earlier reports, in this hemiarthroplasty model, the CoCr alloy showed less cartilage damage than a ceramic surface. Further, in vivo experiments are necessary to elucidate the controversial issue of the most suitable material for hemiarthroplasty. 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source]


Hypoxia-like effect of Cobalt Chromium alloy micro particles on fibroblasts in vitro

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2010
Bernadette K. Madathil
Abstract Periprosthetic osteolysis leading to asceptic loosening remains the primary cause of failure of joint replacement. Although many inflammatory cell types have been implicated, the exact pathomechanisms of asceptic loosening have not been delineated. In the present study we have adopted a proteomic approach to elucidate the initial signals that are expressed to particulate material, using an in vitro cell culture system. Human lung fibroblasts MRC-5 were cultured with Cobalt Chromium (CoCr ASTM F-75, 1,7,m) particles. Cells were harvested after 72,h incubation and total cellular proteins extracted for downstream analysis via 2D Gel Electrophoresis and tandem mass spectrometry using MALDI-TOF-TOF-MS. Thirteen protein spots showed greater than twofold increase, following 72,h incubation of fibroblast with CoCr particles. Four of these proteins were identified by tandem mass spectrometry. These were Annexin II, Pyruvate kinase, Triose phosphate isomerase, and N-myc downstream regulated gene 1 protein. Cobalt is a hypoxia mimicking agent and N-myc downstream regulated gene 1 protein, Triose phosphate isomerase, Pyruvate kinase, and Annexin II are important hypoxia regulated gene products that are found to be over expressed in cellular oxidative stress response. Our data indicates that exposure of fibroblast to CoCr alloy induces the transition of these cells into a hypoxia like state and oxidative stress even in normoxic culture conditions. The study reflects the possibility of the presence of a hypoxic environment in the periprosthetic tissue surrounding metallic implants. Published by Wiley Periodicals, Inc. J Orthop Res 28:1360,1367, 2010 [source]


Effect of Ion Bombardment on the Characteristics of Ti Based Biocompatible Coatings

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Alina Vladescu
Abstract TiN and TiAlN coatings were deposited on CoCr alloy, 316L stainless steel, and Si substrates by cathodic arc method. Various ion bombardment conditions were obtained by different DC and pulsed bias voltages applied on the substrates. A comparative analysis of the coating characteristics for different substrate biasing conditions was performed. [source]


Retrievability of implant-retained crowns following cementation

CLINICAL ORAL IMPLANTS RESEARCH, Issue 12 2008
Christian Mehl
Abstract Objectives: The purpose of this study was to assess the retrievability of cemented implant crowns using two different removal devices. The influence of five cement types and two cement application techniques was evaluated. Methods: Forty copings were cast from a CoCr alloy for 40 tapered titanium abutments (5 taper, 4.3 mm diameter, 6 mm height, Camlog, Germany). Twenty copings were modeled as single crowns, whereas 20 copings were modeled with an extension to simulate fixed partial dentures (FPDs). Before cementation, the inner surfaces of the copings were air-abraded (50 ,m Al2O3 particles at 2.5 bars), while the abutments were used as delivered with machined surfaces. Copings were cemented with eugenol-free zinc oxide (Freegenol), zinc phosphate (Harvard), glass ionomer (Ketac Cem), polycarboxylate (Durelon) and so-called self-adhesive resin (RelyX Unicem) cement. Cement was applied in a thin film band of 1 or 3 mm to the cervical margin of the inner surface of the copings, respectively. After cementation, specimens were stored in saline solution for 24 h. The Coronaflex and a standardized custom-made removal device were used to remove the copings from the abutments. Results: Using the same cement, no statistically significant influence with regard to the type of restoration (crown/FDP), cement application mode and device was detected (P>0.05). Therefore, data of specimens cemented with the same cement were pooled. Median attempts to remove the copings were: zinc oxide: 3, self-adhesive resin: 3, zinc phosphate: 5, glass ionomer: 16 and polycarboxylate: 58. Four levels of significance (P<0.0001) were found: (1) zinc oxide/self-adhesive resin; (2) zinc phosphate; (3) glass ionomer; and (4) polycarboxylate. Conclusions: Zinc phosphate and glass ionomer cement might be suitable for a so-called ,semipermanent' (=retrievable) cementation, while polycarboxylate seems to provide the most durable cementation. [source]


PIII nitriding of fcc-alloys containing Ni and Cr

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
Johanna Lutz
Abstract Face-centred cubic (fcc) alloys such as austenitic stainless steel, Ni base alloys and Co base alloys are important materials with a high corrosion resistance. Nitrogen insertion by PIII into all these alloys at moderate temperatures leads to the formation of an expanded austenite structure. A similar activation energy for the thermally assisted diffusion of about 0.75 eV was found for steel and CoCr alloys with CrN precipitates beyond 400 C in both systems. However, a double layer structure was observed for CoCr, similar to Ni alloys, in contrast to a single layer for austenitic steel. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Mechanical Surface Properties of CoCr Alloys After Nitrogen PIII

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Inga-Maria Eichentopf
Abstract Initial experiments were performed to improve the mechanical surface properties of CoCr alloys by nitrogen plasma immersion ion implantation (PIII). Fast thermally activated diffusion with an activation energy of 0.6 eV was observed. A detailed investigation of the phase formation by X-ray diffraction revealed a variable phase composition with CrN and Cr2N being dominating at higher temperatures and additional fcc phases being present. The hardness of the surface layer increased from about 300 HV by a factor of 3,5 while the wear rate was reduced by a factor of up to ten as a result of the PIII treatment. [source]