Early development of the human dentition revisited

Abstract

In this review, classical data on the early steps in human odontogenesis are summarized and updated with specific insights into the development of the upper and lower embryonic jaws to help in understanding some oral pathologies. The initial step of human odontogenesis is classically characterized by two parallel horseshoe‐shaped epithelial laminae. These originate from the oral epithelium and an ingrowth into the jaw mesenchyme: the internal dental lamina gives rise to deciduous tooth primordia, while the external vestibular lamina represents the developmental base of the oral vestibule. However, a more complex situation was revealed by recent studies combining analyses of the dental and adjacent oral epithelia on histological sections and computer‐aided three‐dimensional (3D) reconstructions during the 2nd month of human embryonic development. The dental epithelium forms a mound, where swellings appear later, corresponding to the individual primordia of deciduous teeth. External to the developing deciduous dentition, the 3D reconstructions do not show any continuous vestibular lamina but instead a complex of discontinuous epithelial bulges and ridges. The patterns of these epithelial structures and their relationship to the dental epithelium differ not only between the upper and lower jaws but also between the lip and cheek segments in each jaw. Knowledge of early odontogenesis may help in understanding some oral pathologies. For example, the human lateral incisor has a dual origin: it arises in the area of fusion between the medial nasal and maxillary facial processes and involves material from these two regions. Such a dual origin at the site of fusion of facial processes represents a predisposition to developmental vulnerability for the upper lateral incisor, resulting in its frequent anomalies (absence, hypoplasia, duplication), especially in patients with a cleft lip and/or jaw. Other pathologies, such as a minute supernumerary tooth, desmoplastic ameloblastoma or extraosseous odontogenic cysts are located external to the upper or lower dentition, and might be derived from structures that transiently appear during early development of the oral vestibule in humans.

Activation of Mesenchymal Stem Cells Promotes New Bone Formation Within Dentigerous Cyst

“…The results above highlighted that there were MSCs residing in capsules of DC, and marsupialization improved their osteogenic capacity both in vitro and in vivo, which may provide a novel insight into the mechanism of bone regeneration after marsupialization. DC originates from the overexpression of dental lamina in the embryonic period, which become remnants present in the dental arch after birth (19,20). When under some unknown initiating factors, odontogenic epithelium enters into an active proliferative phase, then dead cells desquamating into the cyst, plus serum's diffusion through cyst wall and intra-cystic secretion, resulting in accumulation of uid and bone resorbing factors (21).…”

Activation of mesenchymal stem cells promotes new bone formation within dentigerous cyst

“…DC originates from the overexpression of dental lamina in the embryonic period, which become remnants present in the dental arch after birth (27,28). When under some unknown initiating factors, odontogenic epithelium enters into an active proliferative phase, then dead cells desquamating into the cyst, plus serum's diffusion through cyst wall and intra-cystic secretion, resulting in accumulation of uid and bone resorbing factors (29).…”

Tooth Morphology Overview

“…This ectomesenchyme layer takes the lead in the formation of the hard tissue in the body that includes bone and teeth. Ectomesenchymal cells congregate deep into the bud, forming an aggregation of cells, which is the initiation of the condensation of the ectomesenchyme [6].…”

“…When the dental lamina starts forming a tooth bud, it is called the bud stage (or initiation stage) (see Figure 8). The dental lamina connects the developing tooth bud to the epithelial layer of the mouth until full separation happens and the tooth forms [6].…”