Chromium-cobalt-molybdenum alloy

The cobalt-chromium alloy belongs to the cobalt-based alloys . It is used in prosthetics , a branch of dentistry , to manufacture dentures . In technical jargon, it is often simply called an NEM alloy . Just as simplistic (and incorrectly) one speaks of a piece of steel in dental technology and means a model cast prosthesis .

Lower jaw prosthesis framework made from a chrome-cobalt-molybdenum alloy. In the higher resolution you can see the very fine modeling that has been poured out very well.

composition

Depending on the manufacturer, the following values differ slightly:

about 62-66% cobalt
approx. 27-31% chromium
approx. 4-5% molybdenum

In addition, the alloys contain in small amounts: carbon , silicon , manganese and iron .

properties

Physical Properties

Density : approx. 8 g / cm³
Melting temperature : approx. 1250 ° C to 1500 ° C (this requires a plaster-free investment material )
Yield strength : approx. 630 N / mm²
Tensile strength : approx. 890 N / mm²
Elongation at break : approx. 10%
Brinell hardness : approx. 365 kg / mm² (for comparison: pure gold: approx. 20 kg / mm², dental (dental) gold alloys: approx. 60–145 kg / mm²)

Advantageous properties for use in dentistry

very fluid, so it enables the finest models to be poured
enormous hardness
enormous elasticity (twice as large as with precious metal alloys)
large bridge spans possible
completely corrosion-free
no discoloration in the mouth due to influences such as saliva or food
good soldering properties (important for prosthesis extensions)
physiological properties:
- When using " biomaterials " such as gold , platinum or titanium , the physiological advantage over conventional non-precious metal alloys is emphasized . However, in the case of gold in particular, economic aspects presumably take precedence over those of patient welfare. Titanium is to be regarded as historical in prosthetics; it is used almost exclusively, and here very successfully, for endosseous implants and their superstructures. Silver-palladium alloys containing platinum are suspected of causing allergies.

literature

Paul Weikart: Materials science for dentists , 4th edition, Carl Hanser Verlag, Munich
Walter Hoffmann-Axthelm : Lexicon of Dentistry , Quintessenz-Verlag, Berlin