The type, origin and function of the odontogenic cells of continuously growing guinea-pig molars

Little is known about which cell types act as the origin of odontogenic stem cells and how these stem cells differentiate to become functional. In the present study 3-day-old guinea-pigs were injected with tritiated thymidine, killed at intervals and their molars studied. The odontogenic cells were found to originate from the stem cells which by autoradiography were shown to be slow cycling and lightly labelled. As they differentiated they became heavily labelled and were designated transit 'dividing cells'. With further differentiation the cells were unlabelled and were designated 'simple transit cells'. It was concluded from the present study that outer enamel epithelium functioned as the source of all odontogenic epithelium; that primitive mesenchyme around the cervical loop functioned as the source of all odontogenic mesenchyme and that all of the transit cells which differentiated to become functional migrated coronally.