Abstract
The life span of the ameloblasts and the dentin-forming cells was obtained by measuring the total length of the individual enamel rod or dentinal tubule and divid- ing by the experimentally detd. rate of appositional growth. The life span of the ameloblasts ranges from a maximum over the growth center to zero at the eemento-enamel junction. The life span of the dentin-forming cells is relatively constant for a particular tooth.