Tooth resorption cell. Coloured scanning electron micrograph (SEM) of an odontoclast, a cell that facilitates the process of resorption of milk teeth roots. Resorption 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 via odontoclasts. Milk teeth, also known as deciduous teeth, are the first set of teeth in mammals.