Ultrastructural changes in developing hamster molars during vitamin C deficiency in vitro.

: Second day maxillary molars of hamsters were cultured during 4, 8 and 10 days in the presence or absence of 250 micrograms/ml vitamin C. After 8 days of culture without vit. C the basal lamina in the cervical loop region (proliferation zone) was locally disrupted; after 10 days it was completely absent or only remnants of it could be found. In the differentiation zone an abnormal amorphous predentine matrix was found during vit. C deficiency; from the 4th day on the basal lamina had changed in structure or ruptured prematurely. A role of the basal lamina in directing odontoblast differentiation is possible but was not actually demonstrated. It is suggested that the failure of the pre-ameloblasts to differentiate was due to changes in the extracellular matrix. The observations support a cell-matrix type of interaction for the differentiation of the ameloblast.