(June 10, 2015) Human
teeth have to serve for a lifetime, despite being subjected to huge forces. But
the high failure resistance of dentin in teeth is not fully understood. An
interdisciplinary team led by scientists of Charité – Universitätsmedizin
Berlin has now analyzed the complex structure of dentin. At the synchrotron
sources BESSY II at HZB, Berlin, Germany, and the European Synchrotron
Radiation Facility ESRF, Grenoble, France, they could reveal that the mineral
particles are precompressed. The internal stress works against crack
propagation and increases resistance of the biostructure.
Engineers use internal stresses to strengthen materials for
specific technical purposes. Now it seems that evolution has long ‘known’ about
this trick, and has put it to use in our natural teeth. Unlike bones, which are
made partly of living cells, human teeth are not able to repair damage. Their
bulk is made of dentin, a bonelike material consisting of mineral nanoparticles.
These mineral nanoparticles are embedded in collagen protein fibres, with which
they are tightly connected. In every tooth, such fibers can be found, and they
lie in layers, making teeth tough and damage resistant. Still, it was not well
understood, how crack propagation in teeth can be stopped.