On the chipping and splitting of teeth.

One of the most frequent fracture modes in teeth is chipping. It can lead to deterioration and ultimate loss of tooth function. Chips in enamel can also be used to gain insight into the evolutionary history of extant animal and fossil hominin species. In this study, chipping tests are performed on the surfaces of as-received or flattened human molars using hard indenters. The chips exhibit a characteristic scallop shape, with some influence from tooth curvature as well as from enamel anisotropy and inhomogeneity. Chipping fracture tends to follow easy interprism pathways, but inevitably involves breakage of bundles of mineralized prisms in the last stages of spallation. A simple relation describes how critical loads for chipping scale with distance of the occlusal contact from the specimen edge. Measured loads fall well within the range of biting forces exerted during normal oral function. A transition from chipping to splitting occurs at higher loads for contacts nearer the central axis of the tooth.