What are the stages of amelogenesis?
Pre-secretory
Secretory
Maturation
What part of the tooth germ differentiate into ameloblasts?
IEE
What occurs in the pre-secretory stage of amelogenesis?
-differentiation of pre-ameloblasts (cubodial -> columnar cells)
-odontoblasts secrete pre-dentine matrix which signals for ameloblasts to start secretion
What occurs in the secretory stage of Amelogenesis?
-Fully differentiated w. Tomes process
-tomes process secrete enamel matrix
-columnar cells
-finishes when full thickness of enamel is reached
Name the enamel proteins.(4)
Amelogenin
Ameloblastin
Enamelin
Tuftelin
Describe the maturation stage of Amelogenesis.
- majority of amelogenins removed
- enzymes break down amelogenins soon after secretion of enamel matrix
- loss of tomes process
- bulk water removal -> mature enamel
- via smooth ended and ruffled ended ameloblasts
what’s the significance of the tomes process in ameloblasts?
Secreates the initial enamel matrix
How does immature enamel differ from mature enamel?
- mature enamel has:
- less water (from bulk water removal)
- more mineral content.
What’s the final stage of Amelogenesis?
- formation of hydroxyapatite crystals
- apoptosis of ameloblasts
At what stage of tooth development does the differentiation of odontoblasts occur?
Bud/cap stage
Where are odontoblasts originated?
Peripheral cells of the dental papilla
What stimulates the differentiation of odotoblasts?
Inductive signals from pre-ameloblasts
What shape are pre-odontoblasts?
Columnar
What’s the role of pre-odontoblasts?
Develops odontoblast processes
Secretes extracellular dentine matrix
Describe the maturation process of the dentine matrix.
-Calcium and phosphate ions deposited into matrix
- mineralising it
-pre dentine -> mature dentine
-formation of hydroxyapatite crystals
-odontoblast processes form dentinal tubules
What are the types of dentine and when are they deposited?
Primary = in tooth development
Secondary = throughout life
Tertiary (reparative/reactionary) = in response to assault
Compare mineralisation of dentine and enamel.
ENAMEL
- instantaneous
DENTINE
- lags begins
State the similarities between Dentinogenesis and Amelogenesis. (2)
- elongated columnar cells
- both form hydroxyapatite crystals
Where does the pulp originate from?
Dental papilla
What occurs in root development?
- dentine deposition ‘outlines’ pulp chamber
- IEE and OEE fuse to form double layered HERS
- HERS completes outline of root canals + enclose dental papilla
- root sheath disintegrates
What’s unique about the growing patterns of HERS?
- root sheath always remains the same size
- downgrowth/degeneration = proliferation
Describe development of root dentine.
- mesenchymal cells in dental papilla located between HERS layers differentiate into odontoblasts
- secrete pre-dentine
- mineralisation of dentine via deposition of hydroxyapatite
- dentinal tubule formation (from odontoblasts processes)
What’s the process in the development of primary cementum (acellular)?
-at time of tooth eruption
- extomesenchymal cells from dental follicle between layers of HERS differentiate into ‘cementoblast-like cells’
- cementoblasts secrete unmineralised cementoid + cementoblasts become embedded in it
- hydroxyapatite deposition =mineralise
what’s the process in the development of secondary cementum (cellular)?
- after tooth eruption
- external stimuli stimulate cementoblasts to deposit secondary cementum (between cementum and PDL)
