The teeth of mammals experience constant wear. However, the details of these wear processes are largely unknown.
Researchers at the University of Zurich, Switzerland, have now demonstrated that the various areas of herbivores’ teeth differ in how susceptible they are to dental wear, describing their findings in the Proceedings of the Royal Society.
The teeth of mammals are exposed to constant wear, but the exact details of this process have long been a mystery. Enamel is actually harder than the parts in the food that erode the teeth. In mammals, these parts are mostly phytoliths, or ‘plant stones’—microscopic structures made of silica and often found in grass.
The surfaces of teeth in herbivores are not only made of enamel. In between the enamel ridges, there is dentin tissue, which is softer.
As a result of these varying degrees of hardness, the chewing surface in the teeth of horses, cattle or guinea pigs develops a surface akin to a grater—with hard ridges protruding from softer tissue.
In a feeding experiment with guinea pigs, the researchers fed the animals three different diets over three weeks: fresh lucerne—which, like clover, contains no phytoliths—normal grass and bamboo leaves. Bamboo in particular has a high silica content. To observe the effects, the researchers used micro-computed tomography, a precise 3D imaging technique that uses X-rays to see inside an object.
“Even without knowing which animal I was surveying on screen, I was able to tell which diet it had been fed,” researcher Louise Martin said. “The animals that had been given bamboo had significantly shorter teeth.”
This was the case despite the fact that guinea pigs have continually growing molars.
Looking more closely, Martin also found the shorter teeth featured dentin surfaces that were disproportionately eroded. “The phytoliths attack the dentin, and once the enamel ridges are very exposed, they’re no longer as stable and experience more wear.”