Tooth Development Flashcards
What are the 3 stages developmental stages of tooth development?
Initiation
Morphogenesis
Histogenesis
What happens at initiation?
Development of initial tooth site along the dental lamina including (forms series of buds)
- 20 deciduous teeth
- 32 adult/permanent teeth
What happens at morphogenesis?
Processes that gives rise to individual tooth shape
- Incisor/ canine/ premolar /molar
- This occurs under influence of genetic programming and cell signalling between: Epithelial cells & mensenchymal cells
What happens at histogenesis?
Differentiation of different cell types i.e.
Ameloblast/ Odontoblast
To give rise to mineralised tissue such as Enamel, Dentine and Cementum as well as non mineralised tissue such as Dental pulp and the Periodontal tissue
When do stages occur?
Stages do not occur separately, but occur in cohesion as given tooth develops, these processes may occur at roughly the same time
What are the 7 stages of tooth development?
- Primary epithelial band at 6 weeks of intra uterine life
- Dental lamina formation at 7 weeks of intra uterine life
- Bud stage
- Cap stage by the 11th week of intrauterine life
- Bell stage of the 14th week of intrauterine life
- Hertiwig’s root sheath & root formation
- Alveolar bone and periodontal tissue formation
Whats the key difference between the embryonic mucosa and the adult mucosa?
Embryonic oral epithelium consists of superficial layer and a basal layer which are both thin as the child is in the mother and not eating whereas in the adult mucosa there is a basal layer between the layers that replaces the superficial layer of cells when they are shed during eating
What changes occur in the formation of the dental lamina formation at 7 weeks from the primary epithelial band at 6 week of intrauterine life?
Initiation of cell growth starts to occur
There is multiplication of basal layer cells and superficial cells to increase tissue thickness. Complex cell signalling along with genetic coding of cells creates primary epithelial band at 6 weeks.
In cells either side, nothing is happening, but a bulge is seen
The genes in these cells start developing/ reproducing
Dental lamina is formed by selective multiplication of basal cell layers by 7 weeks
Certain points on the dental lamina where development of specific dental buds occur
What are the characteristics of the early bud stage?
Spherical/ oval shape
No morphodifferentiation visible (no recognisable tooth shape)
No histodifferentation visible (no recognisable cell types e.g. ameloblasts)
Ectodermal tissue in origin
Basal layer and superficial layer can still be seen
This tissue is ectodermal (outer surface)
What are the characteristics of the cap stage?
In cross section, it looks like a cap
Mophodifferentiation is not yet visible (tooth shape not recognisable, will begin shortly)
Histodifferentation is visible with recognisable cell types such as
-Stellate reticulum
-Outer enamel surface
-Inner enamel epithelium
Basal cell layer of oral epithelium is continuous with the outer enamel epithelium and the inner enamel epithelium (of ectodermal origin)
The stellate reticulum separates them (these have become from superficial cells)
What changes from the early bud to the cap stage?
stellate reticulum becomes star shaped reticulum which becomes mesh (acts as cushioning + has a nutrient role for cells in inner/ outer epithelium)
inner enamel epithelium becomes ameloblast layer
What are the characteristics of the bell stage?
Morphodifferentiation is visible i.e. start of recognisable tooth shape
Histodifferntation visible i.e. start of cell types differentiation (e.g. internal enamel epithelium cells become tall columnar cells
Development of successional lamina, this produces (after deciduous teeth)
-permanent incisor
-permanent canine and
- permanent premolar teeth develop after the deciduous tooth predecessor
Permanent molar teeth develop directly from the dental lamina,
-not from successional lamina, as there are not deciduous teeth to be replaced
Describe the current structure of the mucosa
Inner surface is ultimately what becomes the developed tooth
Outer enamel epithelium is the cervical loop (in this area, when grown to full extent, the enamel stops and the cementum from the root begins to grow)
Stellate reticulum provides nutrients for ameloblasts (for enamel growth)
What are the characteristics of the hertiwig’s root sheath and root formation stage?
Dental papilla and Dental sac is formed
Morphodifferntiation is visible (recognisable tooth shape)
Both comprised of mesodermal cells (inner)
Dental papilla will differentiate into cells that form the pulp and odontoblast layer (produce dentine and pulp)
Dental sac is made from several layers of “flattened” cells from which will create the Cementum, Periodontal ligament and some alveolar bone.
What are the characteristics of the late bell stage and dental tissue formation?
Morphodifferntiation is visible (incisor tooth shape seen)
Histodifferentiation (Ameloblast development from the inner enamel epithelium cells have an inductive effect upon mesenchymal (inner) of the dental papilla cells to create tall columnar odontoblast layer
Alveolar bone deposition is seen around the developing tooth
