Scanning electron microscopic observations of casts of human dentinal tubules along the interface between primary and secondary dentine.

A scanning electron microscope cast technique was used to examine the interface between primary and secondary dentine in young and old human teeth. In addition, more traditional methods were used to examine this interface with light microscopy, identical regions being viewed before and after demineralization. No continuity was seen between the tubules in primary dentine and those in irregular secondary dentine in the scanning electron microscope preparations. These preparations did show the tubules to be continuous between primary dentine and regular secondary dentine in young and old teeth. Both the scanning electron microscopic and light microscopic observations suggested that regular secondary dentine becomes highly sclerosed in old teeth.