Tooth Development Flashcards
What is the dental lamina
- A fold in the developing oral epithelium that gives rise to tooth germs
What are the 5 stages of tooth development
- Bud
- Cap
- Bell
- Crown
- Root
What stages of tooth development happen before mineralisation
- Bud
- Cap
- Bell
Give a super brief description of what happens in the bud stage
1st condensation of mesenchyme around epithelium, characterised by appearance of tooth bud with no clear arrangement of cells
Give a super brief description of what happens in the cap stage
Enamel organ forms “cap” above the dental papilla
This stage begins once the epithelial cells proliferate into the ectomesenchyme of the jaw
Give a super brief description of what happens in the bell stage
Shape of tooth crown begins to emerge in contours of enamel organ
Give a super brief description of what happens in the crown stage
Mineralised crown tissue (dentine and enamel) deposition
Give a super brief description of what happens in the root stage
Crown formation complete, roots grow, and tooth erupts and root apex matures
What is the ectoderm
developmental germ layer that forms skin, oral epithelium, and enamel organ.
What is the mesenchyme
loose, migratory, undifferentiated cells that are important in development of many tissues.
What is the dental papilla
mesenchyme-derived part of tooth germ.
What is the enamel organ
developmental derivative of dental lamina.
What is the stellate reticulum
cellular filling of enamel organ
What happens in the bud stage of tooth development
- marked by growth of epithelium into the mesenchyme
- period of extensive proliferation and growth of the dental lamina
- dental lamina forms into tooth buds that penetrate into mesenchyme
- each tooth bud is surrounded by the mesenchyme
- buds + mesenchyme develop into tooth germ and associated tissues of the tooth
What happens in the cap stage of tooth development
- Dental lamina expands to form cap-like structure called enamel organ, which continues to grow.
- Part of mesenchyme is concentrated under cap as dental papilla.
- Earliest cap stages at 11 weeks.
What happens in the bell stage of tooth development
- Enamel organ tissues begin to differentiate.
- Enamel organ begins to fold into shape of finished crown.
- Dental papilla tissues begin to differentiate.
- First reached at 14 weeks.
In the cap stage what forms the cap/enamel organ
A depression that forms in the deepest part of each tooth bud and forms the cap/enamel organ, produces the future enamel
What forms under the cap in the cap stage
A condensing mass of mesenchyme - the dental papilla - produces the future dentin and pulp tissue
What in the cap stage is the future site of the EDJ
The basement membrane that separates the enamel organ and the dental papilla
In the cap stage what does the remaining mesenchyme surrounding the enamel organ form
It condenses to form the dental sac or the dental follicle
What does the tooth germ consist of
Enamel Organ
Dental Papilla
Dental Follicle
What are the 4 types of cells in the enamel organ
- inner enamel epithelium (IEE)
- outer enamel epithelium (OEE)
- stellate reticulum
- stratum intermedium
What does the dental papilla differentiate into
- outer cells of the dental papilla - forms the dentin secreting cells (odontoblasts)
- central cells of the dental papilla - forms the primordial of the pulp
What is the function of OEE cells
Protective barrier during the enamel production
What do the IEE cells differentiate into
Ameloblasts
What is the shape of the stellate reticulum
Star shaped
What is the role of the stellate reticulum
supports the production of enamel and produce GAGs
What is the role of the stratum intermedium cells
Supports production of enamel
How do the cells of the stellate reticulum become star shaped
- cells in the centre of the enamel organ (enamel knot) begin to synthesize and secrete glycosaminoglycans
- this pulls water into the enamel organ
- increasing amount of fluid, forces the cells apart
- however, they remain connected via cellular processes which makes them star shaped
How can the primordia of the permanent dentition first be seen
during the cap stage the primordial appears as an extension off the developing dental lamina (site of origin = successional dental lamina)
What happens in the appositional stage of tooth development
- Secretion of enamel, dentin and cementum
- these tissues are initially secreted as a matrix that is partially calcified – serves as a framework for later calcification
What happens in the maturation stage of tooth development
- characterized by the completion of mineralization
- Before eruption, the surface of the crown is covered by the reduced enamel epithelium. This later degenerates as the tooth erupts into the mouth.
What does the reduced enamel epithelium
- the reduced ameloblasts that are in contact with the enamel, but are no longer able to undergo cell division
- external cells = mostly stratum intermedium, undifferentiated epithelial cells able to divide and multiply, these external cells eventually = junctional epithelium
What do pre ameloblasts induce
– the pre-ameloblasts induce cells of dental papilla to differentiate
What do the odontoblasts differentiate from
from the mesenchyme of th dental papilla
Give a brief description of the crown stage
1.Defined by beginning of mineralization.
2. Bell stage differentiation continues, away from
cusp tips towards future cervical margin.
3. deposition of dentin followed by enamel
What is the Hertwig’s epithelial root sheath (HERS)
The Hertwig epithelial root sheath (HERS) or epithelial root sheath is a proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth
Briefly describe the process of odontogenesis
- Begins with induction of odontoblasts by ameloblasts.
- Begins before amelogenesis.
- Preodontoblasts secrete mantle dentine.
- Odontoblasts grow long processes, which lengthen
as dentine gets thicker. - Secretory phase: organic matrix laid down as
predentine, which has lots of type 1 collagen. - Mineralisation phase
Briefly describe amelogenesis
- Ameloblasts differentiate, become elongated and deposit enamel matrix.
- Initial enamel is aprismatic, but ameloblasts change shape resulting in prismatic enamel through most of crown.
- Secretory phase: Organic matrix deposited and becomes mineralised almost instantly.
- Maturation phase: hydroxyapatite crystals form and organic matrix largely removed.
Describe what happens in the root stage
- After crown is complete, cervical margins (loop) of enamel organ grow down as root sheath (Hertwig’s root sheath).
- Dental papilla cells differentiate into odontoblasts and deposit dentine.
- Dental follicle cells differentiate into cementoblasts and fibroblasts to create cementum and periodontal ligament.
What is the enamel organ derived from
The dental lamina proliferation
What is the dental papilla and follicle derive from
Mesenchymal neural crest cells
