PNNL

Abstract

The enamel of mammalian teeth, a highly mineralized tissue that must endure a lifetime of cyclic contact, is serving as a source of inspiration in the development of next-generation engineering materials. Attempts to implement enamel-inspired structures in synthetic materials have had limited success, largely due to the absence of a detailed understanding of its microstructure. The present work develops quantitative descriptions of the three dimensional microstructure for the first time, as derived from synchrotron phase-contrast microCT imaging of the enamel from four mammals, including Lion, Gray Wolf, Snow Leopard, and Black Bear. Results of image analysis revealed that the decussation pattern of enamel consists of discrete diazone (D) and parazone (P) bands of rods organized with stacking arrangement of D+/P/D-/P in all mammals evaluated. Furthermore, the rod orientations in the bands can be described in terms of two principal angles, defined here as the pitch and yaw. While the pitch angle increases from the outer enamel to a maximum (up to ˜ 40°) near the dentin enamel junction, minimal spatial variations are observed in yaw across the enamel thickness. These results suggest that the decussation parameters in enamel are modulated across species to achieve an appropriate fracture resistance as necessary to fulfill the structural demands placed on their teeth. The rod pitch and band width appear to be the primary design parameters and were found to be correlated with bite force quotient.