Concise Review: Cellular and Molecular Mechanisms Regulation of Tooth Initiation.

Development of teeth depends on the reciprocal interactions between the surface epithelium (ectoderm) and the underlying neural crest-derived mesenchyme. These interactions are facilitated by the conserved signaling pathways, which build a complex network of signals and transcription factors. Tooth development starts at specific and predetermined loci in the oral ectoderm and is described as a morphologically distinct thickening of oral ectoderm, named dental lamina. Cells within the dental lamina invaginate into the underlying mesenchyme, generating placodes that mark the onset of individual tooth development. In the following stages of development, the tooth epithelium buds and folds transitioning through various shapes, including bud, cap, and bell shapes, which also identify the specific stages of tooth development. Although much of the molecular regulation of tooth development has been unraveled, the regulation of the initial stages of tooth development, as well as the cellular mechanisms that govern tooth development remain largely unknown. This review provides a systematic overview of the current knowledge on the molecular and cellular mechanisms that guide initial stages of tooth development and outlines the challenges which temper the progress. Stem Cells 2019;37:26-32.