Human teeth have to serve a lifetime despite being subjected to acid, grinding, and huge forces.
But why teeth are so hardy hasn’t been understood until now.
German scientists studying the structure of dentine – the layer beneath a tooth’s enamel – have found tiny nanostructures in it that stop teeth from cracking.
A team of scientists led by Charite Julius-Wolff-Institute Berlin found mineral particles in dentine are pre-compressed so that internal stresses stop teeth cracking.
It appears that nature uses internal stresses in a similar way to engineers, designing strengthened materials.
Unlike bones, which are made partly of living cells, human teeth are not able to repair damage.
Their bulk is made of dentine, a bonelike material consisting of mineral nanoparticles.
Scientists found mineral particles in dentine (shown above) are pre-compressed so that internal stresses stop teeth cracking
These mineral nanoparticles are embedded in collagen protein fibres.
These fibres are found in every tooth and lie in layers to make teeth tough and damage resistant.
To understand more, experts conducted stress experiments on teeth and analysed the orientation of the mineral nanoparticles using cutting edge imaging technology.
They found that when the tiny collagen fibres shrink, attached mineral particles become increasingly compressed.
‘Our group was able to use changes in humidity to demonstrate how stress appears in the mineral in the collagen fibres,’ Dr Paul Zaslansky explained.
‘The compressed state helps to prevents cracks from developing and we found that compression takes place in such a way that cracks cannot easily reach the tooth inner parts, which could damage the sensitive pulp.
‘In this manner, compression stress helps to prevent cracks from rushing through the tooth.’
They also discovered that dentine can be weakened if it’s heated and mineral-protein links are destroyed.
This causes them to think that the balance of stresses between the particles and the protein is important for the extended survival of teeth in the mouth.
The results of the study may explain why artificial teeth don’t usually work as well as natural teeth do.
Jean-Baptiste Forien said artificial teeth are too passive because they lack the mechanisms found in the natural tooth structures, so they can’t withstand forces as well as natural teeth.
Dr Zaslansky hopes the study will lead to tougher ceramic structures that could be used in artificial teeth.
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