Nothing but the tooth.

This article presents an interview with Martin Nweeia, a marine expert as well as a dentist. As a dentist, naturally he was motivated to solve the puzzle of nature that has baffled scientists for hundreds of years. He brought a portable electroencephalogram with him to the Arctic to measure brain activity when sensory information was introduced to the tusk, for example, when pouring fresh water on it. Fred Eichmiller, director of the Paffenbarger Research Center of the National Institute of Standards and Technology in Washington DC, did stress tests on the narwhal tooth and said he had never seen a material as flexible and strong.