Thursday, January 5, 2012
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the glass-ceramics are produced according to an exactly specified temperature scheme.
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The
hardest substance in the human body is moved by its strongest muscles:
When we heartily bite into an apple or a schnitzel, enormous strengths
are working on the surface of our teeth.
"What the natural tooth enamel has to endure also goes for dentures, inlays or bridges,"
glass chemist Prof. Dr. Dr. Christian Rüssel says. After all, these are
worn as much as healthy teeth. Ceramic materials used so far are not
very suitable for bridges, as their strengths are mostly not high
enough. Now Prof. Rüssel and his colleagues of the Otto-Schott-Institute
for Glass Chemistry succeeded in producing a new kind of glass-ceramic
with a nanocrystalline structure, which seems to be well suited to be
used in dentistry due to their high strength and its optical
characteristics. The glass chemists of Jena University recently
published their research results in the online-edition of the science
magazine Journal of Biomedical Materials Research.
Glass-ceramics on the basis of magnesium-, aluminium-, and silicon oxide are distinguished by their enormous strength.
"We achieve a strength five times higher than with comparable denture ceramics available today",
Prof. Rüssel explains. The Jena glass chemists have been working for a
while on high density ceramics, but so far only for utilization in other
fields, for instance as the basis of new efficient computer hard
drives.
"In
combination with new optical characteristics an additional field of
application is opening up for these materials in dentistry", Prof. Rüssel is convinced.
To
be considered as dentures, materials are not supposed to be optically
different from natural teeth. At the same time not only the right color
shade is important.
"The enamel is partly translucent, which the ceramic is also supposed to be", Prof. Rüssel says.
To
achieve these characteristics, the glass-ceramics are produced
according to an exactly specified temperature scheme: First of all the
basic materials are melted at about 1.500 C, then cooled down and finely
cut up. Then the glass is melted again and cooled down again. Finally,
nanocrystals are generated by controlled heating to about 1,000 C.
"This procedure determines the crystallisation crucial for the strength of the product",
the glass chemist Rüssel explains. But this was a technical tightrope
walk. Because a too strongly crystallised material disperses the light,
becomes opaque and looks like plaster. The secret of the Jena glass
ceramic lies in its consistence of nanocrystals. The size of these is at
most 100 nanometers in general.
"They are too small to strongly disperse light and therefore the ceramic looks translucent, like a natural tooth", Prof. Rüssel says.
A
lot of developing work is necessary until the materials from the Jena
Otto-Schott-Institute will be able to be used as dentures. But the
groundwork is done. Prof. Rüssel is sure of it.
Colorless and high strength MgO/Al2O3/SiO2 glass-ceramic dental material using zirconia as nucleating agent
SOURCE
