Abstract: The normal teeth involve many weak structures, such as pit and fissure, wedge-shaped defect, and cracked tooth. It remains an issue to be explored how to evaluate the effect of these weak structures on the crack initiation and the fracture of the teeth, due to limited evaluation methods. This paper analyzes the failure modes of the dental crown under static and dynamic loads by experimental and numerical methods. It is shown that the weak structures are the determinative factors of the crown fractures, which are in line with the second strength theory. The results of this study will provide a theoretical basis for clinical diagnoses and treatments.