At last: a stiff, strong artificial tooth enamel analog

Delivering what has been so challenging to produce, researchers present an engineered analog of tooth enamel – an ideal model for designing biomimetic materials – designed to closely mimic the composition and structure of biological teeth’s hard mineralized outer layer. It demonstrates exceptional mechanical properties, they say. Natural tooth enamel – the thin outer layer of our teeth – is the hardest biological material in the human body. It is renowned for its high stiffness, hardness, viscoelasticity, strength, and toughness and exhibits exceptional damage resistance, despite being only several millimeters thick. Tooth enamel’s unusual combination of properties is a product of its hierarchical architecture – a complex structure made up of mostly hydroxyapatite nanowires interconnected by an amorphous intergranular phase (AIP) consisting of magnesium-substituted amorphous calcium phosphate. However, accurately replicating this type of hierarchical organization in a scalable abiotic composite has remained a challenge. Here, Hewei Zhao and colleagues present an engineered enamel that contains the essential hierarchical structure at multiple scales. The artificial tooth enamel (ATE) was produced using AIP-coated hydroxyapatite nanowires, which were aligned using dual-directional freezing in the presence of polyvinyl alcohol. According to the authors, this allowed the engineered structures to have an atomic, nanoscale and microscale organization like natural enamel. In a series of tests, Zhao et al. demonstrated that the ATE nanocomposite simultaneously exhibited high stiffness, hardness, strength, viscoelasticity, and toughness, exceeding both the properties of enamel and previously manufactured materials.