![]() The staging of tooth formation has been studied histologically and morphologically for centuries. There is also mounting information on the clinical outcomes that result from abnormal ameloblast function related to specific gene mutations, and we will summarize what is currently understood about enamel genotype-phenotype relationships. We will pay particular attention to the proteins comprising the enamel matrix, the role of ameloblast-mediated ion transport and mineralization, and the importance of extracellular pH regulation during enamel formation. In this review, we discuss enamel from its developmental beginnings to its final structure. Traces of EMP peptides are included in the fully formed enamel and are believed to contribute to the final structure, such that the fully formed (mature) enamel has unique morphological and biomechanical properties. The formed enamel has a characteristic prismatic appearance composed of rods, each formed by a single ameloblast and extending from the dentino-enamel junction (DEJ) to the enamel surface, and the interrod enamel located around the enamel rods. It is with a high level of precision that ameloblasts regulate the formation of a de novo hydroxyapatite-based (Hap-based) inorganic material within the enamel space. Enamel matrix proteins are secreted by ameloblasts into the enamel space, and are later degraded and proteolytically removed, also by ameloblasts. The process of enamel formation is referred to as amelogenesis. Among these are ameloblasts, which are primarily responsible for enamel formation and mineralization, and form a monolayer that is in direct contact with the forming enamel surface. The enamel organ is formed by a mixed population of cells. ![]() Enamel forms within an organic matrix composed of a unique grouping of extracellular matrix proteins (EMPs) that show little homology to proteins found in other tissues. In mammals, dental enamel is the only epithelial-derived tissue that mineralizes in nonpathological situations (bone and dentin, the other principal mineralized tissues, are derived from mesenchymal cells). The impact of developmental insults on enamel is critical because, unlike bone, once mineralized, enamel tissue is acellular and hence does not remodel. Because the optical properties of enamel are also derived from its structure and composition ( 205), developmental defects or environmental influences affecting enamel structure are typically visualized as changes in its opacity and/or color. It forms an insulating barrier that protects the tooth from physical, thermal, and chemical forces that would otherwise be injurious to the vital tissue in the underlying dental pulp. In this review, we examine key aspects of dental enamel formation, from its developmental genesis to the ever-increasing wealth of data on the mechanisms mediating ionic transport, as well as the clinical outcomes resulting from abnormal ameloblast function.ĭental enamel is the hardest substance in the human body and serves as the wear-resistant outer layer of the dental crown. Cell death by apoptosis and regression are the fates of many ameloblasts following enamel maturation, and what cells remain of the enamel organ are shed during tooth eruption, or are incorporated into the tooth’s epithelial attachment to the oral gingiva. In many vertebrates, the bulk of the enamel tissue volume is first formed and subsequently mineralized by these same cells as they retransform their morphology and function. In this unique environment, ameloblasts orchestrate crystal growth via multiple cellular activities including modulating the transport of minerals and ions, pH regulation, proteolysis, and endocytosis. ![]() Ameloblasts maintain intercellular connections creating a semi-permeable barrier that at one end (basal/proximal) receives nutrients and ions from blood vessels, and at the opposite end (secretory/apical/distal) forms extracellular crystals within specified pH conditions. These heavily polarized cells form a monolayer around the developing enamel tissue and move as a single forming front in specified directions as they lay down a proteinaceous matrix that serves as a template for crystal growth. Enamel development and mineralization is an intricate process tightly regulated by cells of the enamel organ called ameloblasts. Dental enamel is the hardest and most mineralized tissue in extinct and extant vertebrate species and provides maximum durability that allows teeth to function as weapons and/or tools as well as for food processing.
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