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At least 19 recordsLinked to original sources
PubMed1994

Bond strength of adhesive resin to three nickel-chromium alloys with varying chromium content.

This in vitro study evaluated the influence of chromium content on bond strength and durability between nickel-chromium alloys and an adhesive resin that contained 4-methacryloxyethyl trimellitate anhydride. Three nickel-chromium alloys with different chromium content, as well as pure chromium and pure nickel metals, were bonded and tested for shear strength. After repeated thermocycling, shear bond strength decrease was lower in alloys containing high chromium content. Pure chromium metal demonstrated a 15.2% decrease, whereas pure nickel metal demonstrated the greatest (53.7%) decrease. The results suggest that nickel-chromium alloys with higher chromium content are desirable for 4-methacryloxy-ethyl trimellitate anhydride resin-bonded restorations.

Acrylic Resins↗
PubMed2005

[Metallurgical differentiation of cobalt-chromium alloys for implants].

BACKGROUND: Cobalt Chromium alloys are used in cemented total hip or knee arthroplasty as well as in metal-on-metal bearings in total hip arthroplasty. An increasing number of publications report about (allergic) reactions to wear particles of Cobalt Chromium alloys. Reactions to nickel are more frequent in comparison to Cobalt or Chromium particles. It is well known that different kinds of Cobalt Chromium alloys contain different amounts of alloying elements; nevertheless. The aim of the current work was to compare the different Cobalt Chromium alloys according to ASTM F or ISO standards in respect to the different alloying elements. MATERIAL AND METHODS: Co28Cr6Mo casting alloys according to ASTM F 75 or ISO 5832-4 as well as forging alloy types according to ASTM F 799 and ISO 5832 such as Co20Cr15W10Ni, Co35Ni20Cr, Fe40Co20Cr10Ni, Co20Cr20Ni, and Co28Cr6Mo were analyzed in respect to their element content of Co, Cr, Ni, Mo, Fe, W, and Mn. RESULTS: In 1935 the Cobalt based alloy "Vitallium" Co30Cr5Mo basically used in the aircraft industry was introduced into medicine. The chemical composition of this alloy based on Cobalt showed 30 wt.% Chromium and 5 wt.% Molybdenum. The differentiation using alloy names showed no Nickel information in single alloy names. CONCLUSION: The information given about different alloys can lead to an unprecise evaluation of histopathological findings in respect to alloys or alloying constituents. Therefore, implant manufacturers should give the exact information about the alloys used and adhere to European law, Euronorm 93/42/EWG.

Chromium Alloys↗
PubMed1980

Galvanic cells including cobalt-chromium alloys.

Galvanic cells may be created when dentures made of cobalt-chromium alloys are placed on teeth with metallic restorations. The power of such cells was evaluated in an in vitro galvanic using amalgams, gold alloy, and nickel-chromium alloys. The amalgams and one of the nickel-chromium alloys revealed high corrosion currents when placed in contact with cobalt-chromium alloy, the conventional amalgam showing the highest values. The gold alloy and another nickel-chromium alloy exhibited low corrosion currents and they were noble with respect to cobalt-chromium.

Chromium↗
PubMed1983

Release and uptake of cobalt from cobalt-chromium alloy implants.

Cobalt-chromium alloy implants were placed subcutaneously in the neck region of mice, and the animals were killed after 8 weeks. The cobalt concentration was high in the connective tissue of the capsule formed around 5 out of 10 cobalt-chromium implants. In nine other tissues analyzed no statistically significant increases in the cobalt concentration were detected. The surgical procedure and the carrying of an implant did not influence the weight increase of the animals during the period of the experiment.

Animals↗
PubMed1998

Osseointegration of surface-blasted implants made of titanium alloy and cobalt-chromium alloy in a rabbit intramedullary model.

The purpose of this study was to compare the osseointegration of surface-blasted Ti6A14V and CoCr implants in vivo. Ti6A14V and CoCr rods blasted with 710 microm A12O3 particles were bilaterally press-fit into the medullary space of distal femora of 24 rabbits. Evaluation was made radiographically, histologically, histomorphometrically (3, 6, and 12 weeks after implantation), and mechanically (12 weeks). Both Ti6A14V and CoCr implants demonstrated good biocompatibility radiographically and histologically. Toluidine blue-stained sections revealed an osteoconductive effect of the blasted surface, and fluorochrome labeling analysis showed active bone formation at the bone-implant interface at as late as 12 weeks for both specimens. CoCr showed significantly lower interfacial shear strength than Ti6A14V although the bone contact area with the implant surface was comparable and no intervening soft tissue at the bone-implant interface could be seen for either implant by scanning electron microscopy backscatter analysis. Unmineralized tissue (cartilage and osteoid) was observed more frequently on the CoCr surface than on the Ti6A14V surface. These data show less osseointegration of CoCr implants with this blasted surface for this short period, possibly due to a slight difference in surface roughness and some negative effects of CoCr on bone attachment.

Alloys↗
PubMed1995

Durability of resin bonds to a cobalt-chromium alloy.

Common nickel-chromium-beryllium alloys used for resin-bonded fixed partial dentures have possible health hazards due to leaching of nickel and beryllium. For resin-bonded restorations corrosion resistant cobalt-chromium alloys (CoCr) are a suitable alternative material without sacrificing physical properties. This study evaluated the bond strength and bond durability of new adhesive systems to a CoCr alloy. Plexiglas (acrylic) tubes filled with composite were bonded to CoCr alloy discs. Groups of 24 samples were bonded using six different bonding systems. Subgroups of eight bonded samples were stored in an isotonic artificial saliva solution (37 degrees C) either for 1 day, 30 days or 150 days. In addition the 30- and 150-days samples were subjected to 7500 or 37,500 thermal cycles, respectively. The bond strength of a conventional BisGMA composite (Twinlook) to sandblasted CoCr was significant lower than when using chemomechanical bonding systems and decreased continuously during the storage time of 150 days. The additional use of silane on the sandblasted alloy resulted in an insignificant increase in bond strength. Statistically significant higher and more durable bonds to CoCr alloy were achieved either with the combination of silica coating and use of the conventional BisGMA composite or with the combination of sandblasting and the use of a composite modified with a phosphate monomer (Panavia EX). In the latter systems, the bond strengths were mainly limited by the cohesive strength of the resin composites: partial adhesive failures were only observed for a tribochemical silica coating system. A new composite also containing the active phosphate monomer (Panavia TPN-S) exhibited a significant decrease in cohesive strength over time.

Adhesiveness↗
PubMed1997

Transverse strength, ductility, and qualitative elemental analysis of cobalt-chromium alloy after various durations of induction melting.

PURPOSE: The aim of this study was to compare the transverse strength and ductility of bars cast from cobalt-chromium alloy that had been melted for various lengths of time (n = 5 per group). To determine its elemental composition, the cobalt-chromium alloy was also analyzed qualitatively. MATERIALS AND METHODS: Transverse strength and ductility of the cobalt-chromium bars was measured by a three-point loading test. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to determine the composition of the samples compared with unmelted cobalt-chromium alloy. RESULTS: The transverse strengths of the test bars cast from the cobalt-chromium alloy, which had been induction-melted for various lengths of time, did not differ significantly (p = .056); but the ductility of the test bars was affected by the duration of induction melting of the alloy (p < .001). According to the SEM/EDS analysis, the amount of silicon in the cobalt-chromium alloy decreased with lengthening duration of induction melting of the alloy. CONCLUSIONS: This study supports the previous finding that good resistance to deflection fatigue is correlated with increased ductility of cobalt-chromium alloy and vice versa.

Analysis of Variance↗
PubMed1976

Cast chromium alloy surgical splints.

A cast chromium alloy surgical splint can be fabricated in less than 6 hours. This splint has the advantages of being well fitted, smooth, rigid, and less bulky than prefabricated splints. Other metals can be utilized in a similar manner to fabricate cast surgical splints.

Chromium Alloys↗
PubMed1984

Corrosion resistance of a passivated and non-passivated cobalt-chromium alloy.

The release of cobalt and chromium from a passivated and non-passivated cobalt-chromium alloy in artificial saliva has been measured using nuclear tracer technique. The corrosion resistance of the passivated specimens was improved by a factor of about four compared to the non-passivated specimens with regard to the initial cobalt release. The specimens were exposed to the saline solutions for periods up to about 8 wk. The cobalt release is associated mainly with electrochemical corrosion processes, since particulate matter retained on a filter was only registered to a minor extent. It is suggested that the decrease in release of cobalt and chromium after passivation is connected to the formation of Cr-O and/or Cr-OH bonds in the protective film which impede the movement of cobalt and chromium from the alloy into the saliva.

Chemical Phenomena↗
PubMed2006

[Barrel finishing of cobalt-chromium alloy cast plate--basic study on polishing materials and time].

PURPOSE: This study was designed to establish the optimum grinding condition of barrel finishing for cobalt-chromium alloy. Smoothing of the mucosal surface, reduction of labor, and improvement of the working environment were estimated by the application of barrel finishing to cobalt-chromium alloy. METHODS: Tabular test pieces cast in cobalt-chromium alloy whose surface was standardized by waterproof abrasive papers were used in this study with a centrifugal flow barrel finishing machine. The abrasive that was most suitable for the primary polishing was selected, and proper polishing time was then decided by measuring the surface roughness of the test pieces. The abrasive and polishing time for the secondary polishing were decided in the same manner. Finally, the surface texture of the test pieces, which were finished in this condition by the manufacturer's instruction or by the electrolytic polishing method, were compared. Statistic analysis was performed by one-way analysis of variance and the multiple comparison test. RESULTS: A triangular prism-shape abrasive made of Al(2)O(3) and SiO(2) whose one side or height was 6 mm was selected for the primary polishing, and the same kind of abrasive with one side or height of 4 mm was chosen for the secondary one. The optimum polishing time for the primary polishing and the secondary polishing were 60 minutes and 40 minutes, respectively. The surface roughness of the test pieces that were finished in this condition was significantly smaller than that finished following the manufacturer's indication or that finished by the electrolytic polishing method. CONCLUSION: The optimum polishing condition of barrel finishing for cobalt-chromium alloy was established in this study. For the polished surface of cast dentures, polishing by a rotary cutting instrument after barrel finishing in this condition would be needed, as no luster was observed on the finished surface.

Aluminum Oxide↗
PubMed1982

Release of cobalt from cobalt chromium alloy constructions in the oral cavity of man.

The release of cobalt from a cobalt chromium alloy construction with a major palatal connector (palatal strap) in the maxilla was determined for 10 test subjects. The concentration of cobalt in unstimulated whole saliva and tongue scrapings was estimated 21, 14 and 7 d respectively before and 1, 2, 3, 10, 20 and 30 d after insertion of the cobalt chromium alloy construction. The method used to quantify the cobalt content was flameless atomic absorption spectrophotometry (AAS). The results showed that the median cobalt concentration in saliva and tongue scrapings increased after the insertion of the cobalt chromium alloy construction, with the highest values occurring in the first 2 d after insertion. The tongue scrapings, in general, showed higher cobalt median values than saliva did at all times of estimation. The sampling method described in the present study seems to be useful in long-term investigations in man, where numerous sample collections in the oral cavity are required in order to determine metal content. The risk of negative biologic effects on the human organism caused by the cobalt release from the alloy is discussed.

Adult↗
PubMed1997

Effects of adhesive primers on bond strength of self-curing resin to cobalt-chromium alloy.

PURPOSE: This study evaluated the effects of four adhesive primers on the shear bond strength of a self curing resin to cobalt-chromium alloy. MATERIAL AND METHODS: The adhesive primers Acryl Bond (AB), Cesead Opaque Primer (COP), Metal Primer II (MPII), and MR Bond (MRB) were used. A brass ring placed over the casting alloy disk surface nonprimed or primed with each primer was filled with the self-curing methyl methacrylate polymethyl methacrylate resin. The specimens were stored in water at 37 degrees C for 24 hours and then alternately immersed in water baths at 4 degrees C and 60 degrees C for 1 minute each for up to 20,000 thermal cycles before shear mode testing at a crosshead speed of 0.5 mm/min. RESULTS: All the primers examined improved the shear bond strength between the resin and cobalt chromium alloy compared with nonprimed specimens before thermal cycling. However, after 20,000 thermal cycles, the bond strengths of resin to cobalt chromium alloy primed with COP or MPII primers were significantly greater than those of specimens primed with AB or MRB primers and nonprimed controls. CONCLUSION: This study indicated that COP and MPII are effective primers to obtain higher bond strength between resin and cobalt-chromium alloy.

Adhesives↗