Dentin is one of the most durable biological materials in the human body. Researchers from Charité–Universitätsmedizin Berlin were able to show that the reason for this can be traced to its nanostructures. Measurements performed showed that it is the mechanical coupling between the collagen protein fibres and mineral nanoparticles which renders dentin capable of withstanding extreme forces.
As part of their experiments, the researchers increased the compressive stress inside the dentin samples. Huge stress was exerted on the nanoparticles. They had the ability to withstand forces of up to 300 megapascals (MPa) of pressure. This is equivalent to the yield strength of construction grade steel.
In humans, teeth come into contact almost 5,000 times per day under normal use. In spite of this it is surprisingly rare for healthy teeth to break. The secret to this strength lies in the structural details.
Dentin is a bone-like substance, which is composed of mineral nanoparticles, collagen and water. While both enamel and dentin are composed of the same mineral, dentin represents a complex nanocomposite material.
Compression stress found within the material can explain why damage in enamel does not extend catastrophically into the dentin bulk. As part of the new findings, samples of human teeth were used to measure how nanoparticles and collagen fibres interact under humidity-driven stress.
In order to gain insights into the performance of the nanostructures involved, the researchers used both laboratory experiments and measurements obtained using a device that produces radiation frequencies ranging from terahertz to hard x-rays.