An experimental study on the behavior of enamel-dentin in human teeth at low strain rates

Human teeth function as nature's cutting and grinding tools and represent a remarkable biocomposite. This study investigates the rate-dependent mechanical behavior of the enamel-dentin (ED) complex at low strain rates. High-precision ED specimens were prepared from healthy human premolars and tested under uniaxial compression using a universal testing machine at strain rates ranging from 0.0005 to 2.5 s^-1. The results demonstrated that, with increasing strain rate, the maximum stress and elastic modulus increased by 17.0% and 24.7%, respectively, while the maximum strain decreased by 12.5%. One-way ANOVA with Tukey's HSD post-hoc testing indicated that strain rate had a statistically significant effect on all three mechanical properties (p < 0.01 for each). This rate sensitivity is attributed to the hierarchical structure and complex organic-inorganic composition of the ED biocomposite. Based on the experimental findings, quantitative relationships were proposed to describe the maximum stress, elastic modulus, and maximum strain as functions of strain rate. These results highlight that the mechanical properties of the ED complex are sensitive to strain rate even within the low rate regime. The present findings can contribute to computational simulations of dental structures, the development of restorative materials, and the design of tissue-engineered artificial teeth.