Structure, property, and function of sheepshead (Archosargus probatocephalus) teeth.

OBJECTIVES: This paper studies A. probatocephalus teeth and investigates the mechanical properties and chemical composition of the enameloid and dentin. DESIGN: Nanoindentation tests with a max load of 1000 µN and X-ray Energy Dispersive Spectroscopy (EDS) were performed along the diameter of the polished sample. Microstructural analysis of the dentin tubules was performed from SEM images. RESULTS: From nanoindentation testing, the dentin of the sheepshead teeth has a nanoindentation hardness of 0.89 ±â€¯0.21 (mean ±â€¯S.D.) GPa and a reduced Young's modulus of 23.29 ±â€¯5.30 GPa. The enameloid of A. probatocephalus has a hardness of 4.36 ±â€¯0.44 GPa and a mean reduced Young's modulus of 98.14 ±â€¯6.91 GPa. Additionally, nanoindentation tests showed that the enameloid's hardness and modulus increased closer to the surface of the tooth. X-ray Energy Dispersive Spectroscopy (EDS) data further suggests that the gradient may be a result of the wt% fluoride within the enameloid, where an increase in fluoride results in an increase in reduced Young's modulus and hardness. CONCLUSION: The microstructural characterization of the number density and area of the dentin tubules were used to address the porosity effect in the dentin to achieve the experimentally validated microhardness. The mechanical properties of the sheepshead teeth were also compared with previous nanoindentation tests from other aquatic species. The sheepshead teeth exhibit a greater reduced Young's modulus and hardness compared to shark and piranha teeth.