Unlike rodents, which have gnawing incisors that grow continually, the teeth of shrews wear down throughout life, and they lose their milk teeth before birth. Therefore, they have only one set of teeth for their lifetime. Apart from the first pair of incisors, which are long and sharp, and the chewing molars at the back of the mouth, the teeth of shrews are small and peg-like, and may be reduced in number. The dental formula of shrews is: upper=3.1.1-3.3; lower=1-2.0-1.1.3.