We study the propagation of cracks and crack-arrest mechanisms across the interface between tooth dentine and root cementum. We use freshly extracted porcine teeth as they have diet and eating habits that can be compared to young adult human teeth, which we cyclically load in the lab. We apply for an imaging experiment, using high energy (70 keV +) with phase contrast, to reveal cracks and inclusions in the still-hydrated samples, as we need to distinguish between drying cracks and cracks induced by fatigue. Results from this experiment will help us elucidate design principles of a naturally grown bilayer composite that is designed to function for decades of cyclic loading in the living animal.