Histology of the Teeth

Tooth Development and Differentiation
into Various Types
https://www.ncbi.nlm.nih.gov/books
/NBK27071/

Mammalian teeth develop from oral ectoderm and neural crest derived mesenchyme, also known as embryonic tissue (Thesleff et al., 2009). From this embryonic tissue it continues to differentiate into the various different components of the teeth. First, the oral epithelium thickens and becomes the primary dental lamina which can be seen at the base where the future tooth will lie. Dental placodes will form along the dental lamina (Thesleff et al., 2009).

The hard tissues of the teeth - the enamel and dentin - are secreted by ameloblasts and odontoblasts that differentiate at the junction between the oral epithelium and the mesenchyme.

Following the development of the crown, root formation will occur and cementoblasts (differentiated from dental follicle mesenchyme) secrete cementum.

However, once teeth have matured most of the epithelial tissue has been lost (Thesleff et al., 2009). FUN FACT!!!: some rodents have continuously growing incisors due to epithelial stem cells that are maintained in the cervical loop. Since they are always gnawing on their food, this ensures that the incisors never wear down too far!

Dried, Non-Decalcified and Unstained Tooth
Atlas of Histology

This image shows the sections of a dried, non-decalcified and unstained tooth. The cementum contains lacunae with cementocytes and their connecting canaliculi. It also shows the pulp cavity which contains connective tissue, blood vessels, fibroblasts, histiocytes and odontoblasts (Eroschenko et al., 2013). The edge of this pulp cavity is composed of the secondary dentin secreted throughout life by the odontoblasts. The base of the tooth contains external and internal enamel epithelium, the latter will grow downwards and form the epithelial root sheath.

Developing Tooth 1
Atlas of Histology

These next two images show a tooth that is still developing. They show the rows of columnar ameloblasts and sections of enamel that contains calcified enamel rods. They also show the columnar odontoblasts that will secrete the
predentin, which can then calcify to form dentin
(Eroschenko et al., 2013).

Developing Tooth 2
Atlas of Histology