the late Cambrian had dentine in their exoskeletons, which may have functioned in defense or for sensing their environments. Dentine can be as hard as the rest of teeth and is composed of collagen fibres, reinforced with hydroxyapatite. Though teeth are very resistant, they also can be brittle and highly susceptible to cracking. However, cracking of the tooth can be used as a diagnostic tool for predicting bite force. Additionally, enamel fractures can also give valuable insight into the diet and behaviour of archaeological and fossil samples. Decalcification removes the enamel from teeth and leaves only the organic interior intact, which comprises dentine and cementine. Enamel is quickly decalcified in acids, perhaps by dissolution by plant acids or via diagenetic solutions, or in the stomachs of vertebrate predators. Enamel can be lost by abrasion or spalling, and is lost before dentine or bone are destroyed by the fossilisation process. In such a case, the 'skeleton' of the teeth would consist of the dentine, with a hollow pulp cavity. The organic part of dentine, conversely, is destroyed by alkalis. See also Animal tooth development Dragon's teeth (mythology) References Sources External links Animal anatomy Speech organs