Dental enamel formation and implications for oral health and disease

In mammals, in non pathological conditions, dental enamel is the only epithelial-derived tissue that mineralizes. Ameloblasts are primarily responsible for the formation of enamel, which is essentially a Hap-based material containing less than 5% organic material by weight. It is because of its cellular origins that an extracellular matrix has evolved, comprised of proteins with little homology to any other animal proteins, to be capable of guiding the formation of a unique hierarchical structure with a highly ordered and very repetitive patterning. In normal situations, enamel’s distinctive biomechanical properties allow it to function for the entire lifespan of an animal, despite the amount of wear resulting from mastication, clenching and grinding, and disease such as caries. Ameloblasts have a very short lifespan, relative to the life of the organism, to produce the avascular enamel that, once formed, has no reparative abilities. Amelogenesis involves a large number of activities including the formation of a temporary proteinaceous matrix conducive to mineralization followed by the removal of this matrix by endocytosis, ion transport and pH regulation, and apoptosis. Failure during any one of these stages of amelogenesis may result in pathologies impacting enamel health. We have summarized the literature related to amelogenesis, with a greater emphasis on mineralization events occurring largely during the maturation stage. We have also reviewed enamel pathologies that have been linked to known genes and discussed the role of fluoride-based and biomimetic approaches to enamel repair and conservation.