The extreme wear tolerance of the sea urchin tooth

The sea urchin tooth, a natural grinding tool, exhibits prominent wear resistance during food biting and rock boring, while being almost entirely composed of intrinsically brittle CaCO3. Revealing its underlying wear tolerance mechanisms may provide significant inspiration for the potential application of low-cost, brittle structural materials (e.g., ceramics). To this end, the present study investigated the mechanical and wear behaviour of the stone in Glyptocidaris crenularis tooth using nanoindentation, scanning electron microscopy and transmission electron microscopy. The results show that the stone exhibits superior wear resistance than geological calcite and dolomite though moderate in hardness. Owning to its sophisticated fiber-reinforced architecture, confined damage is achieved via multiple deformation mechanisms, thus maintaining the structural and functional integrity of the tooth.