Mouse molar cell proliferation kinetics in vivo and in vitro

Patterns of cell proliferation kinetics have been examined in mouse first mandibular molars growing in vivo and in vitro. In vitro teeth were cultured on semi-solid medium or on Millipore filters. These conditions led respectively to normal and abnormal cusp formation. Similar cell-compartment specific mitotic activities existed in vivo and in vitro. Intradental control mechanisms exist. In vitro however the duration of cell cycle was lengthened, leading to lower rate of decrease of mitotic indices. The implications of these findings are discussed in the context of tooth morphogenesis and cytodifferentiation.