Milk tooth. Coloured scanning electron micrograph (SEM) of a human canine milk tooth. Milk teeth, also known as deciduous teeth, are the first set of teeth in mammals. The tooth consists of the crown (white), the visible part of the tooth, and the root (pink). Part of the root of this tooth (top right) is showing signs of resorption. This occurs during exfoliation, the replacement of the milk teeth by the permanent teeth. The permanent tooth presses down on the root of the milk tooth, causing it to dissolve. The dissolved material is then absorbed by the permanent tooth.