In the process of enamel maturation, ameloblasts undergo characteristic cyclical changes in both morphology and function, whereby generating dynamic spatial temporal patterns of cell modulation comprising the cohorts of two different types of ameloblasts designated as ruffle-ended (RA) and smooth-ended ameloblasts (SA). RA and SA are arranged in alternating parallel stripes over the maturing enamel and thought to contribute respectively to calcium acquisition to and paracellular matrix removal from the enamel. Interestingly, the striped patterns of RA and SA areas over the enamel are not static ones but move continuously through the ameloblast layer as the waves of cell modulation. Ample evidence indicates that the cyclical phenomenon in the ameloblast layer generated by the two types of ameloblasts is common feature of amelogenesis in higher vertebrates and hence essential for the establishment of highly mineralized enamel comprising large apatite crystals. However, the mechanisms whereby the dynamic cyclical movements and patterning of the waves of ameloblast modulation are regulated have been largely unknown.
This presentation attempts to summarize current knowledge and update our understanding of the mechanisms of enamel maturation, with an emphasis on the functional significance and regulatory mechanisms of cyclical phenomenon in the ameloblast layer.