Comparison of mechanical behaviors of enamel rod and interrod regions in enamel

Interrod regions exist between the enamel rods and are known to have different crystallite orientations and a higher organic content compared to the enamel rods (the intrarod regions). This study aims to characterize the mechanical properties of both regions especially the time-dependent properties by using spherical indentation. Despite the very small amount of proteins, the interrod region shows statistically significantly higher inelastic energy dissipation than the intrarod region with increased deformation times. The total displacement under constant load (creep), viscosity, and stress relaxation behavior of both regions are also reported. Similar to the observation of previous studies, the elastic modulus and hardness in the intrarod region are significantly higher than in the interrod region.