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Both the Sperm whale and Killer whale have conically shaped teeth with a small amount of enamel at the tips and the rest of the tooth covered by cementum. The cross-sections of the teeth are rounded or oval. A characteristic feature is that the dentin forms in layers that alternate directions giving it a banded appearance. Their teeth are second in hardness to hippopotamus ivory. Sperm whale teeth may grow up to 20 cm (8 inches) in length while the killer whale teeth are slightly smaller. Killer whale teeth show two slight peripheral indentations and may also display a faint rosette pattern in the dentin cross-section.