Tooth development Flashcards
(43 cards)
What are the 8 stages of tooth development in early intra-uterine life?
1) Primary epithelial band
2) Dental lamina formation
3) Bud stage
4) Cap stage
5) Early bell stage
6) Late bell stage
7) Root sheath and root formation
8) Root formation and formation of periodontal ligament and alveolar bone
At the beginning of week 6 what is the primitive mouth lined by?
Ectoderm
How does the primary epithelial band form?
Thickening of the embryo’s oral epithelium which lies above mesenchyme
What are the two primary epithelial bands shaped like?
Horse shoe
What is ectomesenchyme derived from?
Neural crest cells that have migrated to the region from neuroectoderm of the embryo
What is the primitive oral cavity called?
Stomodeum
How is the dental lamina formed?
Further thickening and growth of the arch shaped epithelial band into the underlying ectomesenchyme.
Where does the dental lamina begin to form?
Initially in the midline then progresses posteriorly
What are the two processes that the primary epithelial band divides into?
1) Buccal placed vestibular lamina - lips, buccal sulcus, cheeks
2) Lingual placed vestibular lamina - development of the teeth is ARCH shaped
What is initiation?
The development of individual tooth sites along the dental lamina with 10 deciduous tooth germs developing sequentially along each arch
What is morphogenesis?
The process that gives rise to the individual tooth shape under the influence of genetic programming and cell signalling from interactions between the epithelial and mesenchymal cells
What is histogenesis?
Differentiation of different cell types (ameloblast/odontoblast) to give rise to either mineralised tissue - enamel, dentine or cementum or non-mineralised such as pulp and periodontal tissues
What do oral epithelium signal to underlying mesenchyme via?
Bone morphogenic factors and fibroblast growth factors - these regulate gene expression
What do bone morphogenic factors induce?
The expression of mesenchymal homeobox gene transcription factors Msx 1 and Msx2 - Msx1 is found in the bud stage epithelium and Msx2 possibly a regulator in morphogenesis
Where do bioactive signalling molecules pass between?
Epithelium and mesenchyme, where they bind to cell receptors and set of a series of intracellular cascades that regulate gene expression thereby altering cell behaviour
In the superficial layer of the adult oral mucosa what are cells like?
Large and flattened
In the intermediate layer of the adult oral mucosa what are cells like?
Start to enlarge and become flattened in shape
In the basal layer of the adult oral mucosa what are cells like?
Cells are tall columnar, actively reproducing and cells move over the superficial layer over time
What cell layers make up the embryonic oral epithelium/?
Superficial and basal
What creates the primary epithelial band?
Multiplication of basal and superficial cells to increase tissue thickness and complex cell signalling and gene expression
What characterises the early bud stage?
- Spherical condensation of epithelial condensation surrounded by mesenchyme
- No morphodifferentiation visible
- No histodifferentiation visible
- Ectodermal tissue origin
What does the oval mass in the early bud stage penetrate into?
Surrounding ectomesenchyme which surrounds the enamel organ and is growing and condensing
What characterises the cap stage?
Enamel organ looks like a cap
Morphodifferentiation is still not visible
- Early histodifferentiation is visible with recognisable:
Stellate reticulum
Outer enamel epithelium
Inner enamel epithelium
What is the stellate reticulum?
Star shaped cells derived from the superficial cell layer
