Three-dimensional analysis of the early development of the dentition.
Bottom Line: The combination of in situ hybridization and 3D reconstruction have demonstrated the temporo-spatial dynamics of the signalling centres that reflect transient existence of rudimentary tooth primordia at loci where teeth were present in ancestors.The rudiments can rescue their suppressed development and revitalize, and then their subsequent autonomous development can give rise to oral pathologies.This shows that tooth-forming potential in mammals can be greater than that observed from their functional dentitions.
Affiliation: Department of Teratology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.Show MeSH
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Mentions: During further tooth development, morphogenesis and histogenesis progress in parallel. All morphogenetic mechanisms are involved – differential mitotic activities, apoptosis, cell adhesion and cell migration (segregation), regulated in time and space. Tooth morphogenesis (morphodifferentiation) is a very dynamic process that progressively gives rise to a tooth primordium at bud, cap and bell stages. Histodifferentiation of the dental epithelium ends up with the formation of the inner dental epithelium (IDE), outer dental epithelium (ODE), and a stellate reticulum (SR) at the cap stage (compare to Fig. 16c). The stratum intermedium (SI) becomes distinct at the beginning of the bell stage.54 The histo-differentiation of dental mesenchyme includes several steps (Fig. 4b). Mesenchymal cells condense in proximity to the epithelial thickening and dental lamina. Then, the condensed cells become arranged concentrically around the tooth bud, cap or bell (Fig. 4b). The dental papilla does not arise from a part of condensed mesenchyme which is passively enveloped by the extending margins of epithelial tooth cap. Instead, the papilla exhibits different compartments depending on cell proliferation and migration. The majority of the dental papilla arises from a small population of highly proliferative mesenchymal cells adjacent to the dental epithelium at the cap centre.102 Specific arrangement of the mesenchyme surrounding the enamel organ results in formation of the dental sac with distinct inner and outer layer. Blood vessels start to enter the papilla mesenchyme of the mouse M1 at the cap stage,103–105 then nerves appear about three days post-natally.106–108 Nerve fibres have not been found to grow towards the small (‘D’) rudiments (Fig. 6) in the maxillary diastema.109
Affiliation: Department of Teratology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.