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unknown user
06-12-1997, 11:03 PM
Hello,

1. Resume about Tantalum implants and the usage of them.

Thank you very much to everybody's help.
This first resume isn't complete and has only a few information about
Tantalum and its usage. I will add more, until I got them.

I found some good information on the page of the University of
Sheffield, England (http://www.shef.ac.uk/~chem/web-elements).

The main information about Tantalum (Ta) are:
Used to make alloys with desirable properties such as high melting
point (3293 K), high strength, good ductility, density 16.65 kg/dm3
Carbide graphite composite materials may be some of the hardest
materials ever made
Electrolytic capacitors
Used to fabricate chemical process equipment, nuclear reactors, and
aircraft and missile parts
Immune to body liquids and nonirritating: therefore, widespread use
for making surgical appliances

Biological information

The following gives an indication as to toxicity.
Toxic intake: moderately poisonous by ingestion
Lethal intake: LD50(chloride, oral, rat) = 1900 mg/kg
Levels in humans:
Daily dietary intake: 0.001 mg
Total mass of element in average (70 kg person): c. 0.2 mg

Hazards and Risks
Tantalum compounds are encountered rarely by most people. Tantalum
metal does not normally cause problems but all Tantalum compounds
should be regarded as highly toxic. There are possibilities that
Tantalum compounds cause tumors. The metal dust presents a fire and
explosion hazard.

Medical use: Dental implants, markers (balls, d: 0.5 to 1 mm) for
roentgen Sterophotogrammetric analysis.
I didn't found any information about prosthesis, screws etc. made of
Ta. The FDA had one article about Ta-implants (Dental implant)

Some short information form the Medline:

Laass M et al.,(Dtsch Stomatol, 1991, 41: 12, 511-2)
and
Wexler SA, et al. (Ophthalmology 92 (5): 671-675 (May 1985))
are reporting that, there were some problems with the tissue under
electron emission (x-ray) and Ta. Ta-parts should be removed or not
used.


Issa TK et al, (Am J Otol, 1983 Jul. 5: 1, 40-3)
Conclude that Ta is tolerated by the human ear for temporal bone or
implants


Johansson CB. et al., (Biomaterials 11 (4): 277-280 (May 1990))
did a qualitative interfacial study between bone and Tantalum,
niobium or commercially pure titanium (c.p. Ti). He writes in his
results, that there are more subtle differences between Tantalum and
c.p. titanium than between c.p. titanium and niobium which seems to
be less well tolerated when implanted in bone.


Steinemann SG, (Injury 27 Suppl 3: SC16-SC22 (1996))
Metal implants and surface reactions.
Denatured tissue in contact with the foreign body is the consequence.
But behaviour of metals is variable; gold, stainless steel and most
other metals react while few others like titanium and Tantalum do
not.

I couldn't found jet some basic results about the biocompatibility of
Ta. Several articles compare Ta with Titanium (Ti). The risks with
Ta-compounds in the human body should be clearly examined, before
using Ta-implants (prosthesis, screws) even if they are made of pure
Ta.

Beat Goepfert