Histological Development of Teeth Flashcards
Define odontogenesis
Tooth development
When does odontogenesis of primary dentition form?
Embryonic and fetal period
When does odontogenesis of permanent teeth form?
During the fetal period
What does the inner enamel epithelium (IEE) eventually differentiate into?
Ameloblasts
What makes enamel?
Ameloblasts
What makes dentin?
Odontoblasts
Where do odontoblasts differentiate from?
Outer cells of the dental papilla
When do odontoblasts begin dentinogenesis?
When repolarization occurs away from the basement membrane
Outer cells of the dental papilla are induced by __________ to differentiate into _____________
pre-ameloblasts / odontoblasts
What is dentinogenesis?
Apposition of predentin
Why is dentin thicker than enamel?
Because odontoblasts begin production awhile before amelogenesis occurs
During which stage of tooth development do the odontoblasts begin laying down dentin matrix?
Apposition
What are the 6 stages of odontogenesis and when do they occur?
- Initiation/dental lamina stage (6-7 weeks)
- Bud stage (8th week)
- Cap stage (9th-10th week)
- Bell stage (11-12 week)
- Apposition stage (varies)
- Maturation stage (varies)
What tissue arises from the ectoderm?
Enamel (and epithelial tissue)
Dental sac cells eventually become what?
Cementoblasts
When does cementogenesis occur and what is the first thing that happens?
When HERS disintegrates and the cementoblasts move to cover root dentin they lay down cementum matrix
What is the cementum matrix called?
Cementoid
What happens to cementoblasts that become trapped in the cementoid?
They become cementocytes
What happens when cementoid becomes calcified?
Differentiates into cementum which differentiates into the DCJ
What does the dental sac eventually produce?
The peridontium: PDL (fibroblasts), Cementum (cementoblasts), and alveolar bone or lamina dura (osteoblasts)
What does REE stand for and how does it form?
Reduced Enamel Epithelium. It forms when the layers of the enamel organ are compressed
What does the REE first fuse to?
The oral epithelium
When can the tooth begin to erupt?
As the formation of REE occurs
Explain the process of teething eruption?
The enzymes from the REE disintegrate the fused tissue, forming an epithelial tunnel which gives a path of eruption
Why might newly erupted teeth have extrinsic stain?
The presence of Nasmyth’s Membrane, which is the residue of fused REE and oral epithelium
What does HERS stand for?
Hertwig’s Epithelial Root Sheath
What is the function of HERS?
Shape the root/s and induce dentin formation (odontogenesis) in the root area
True or False: HERS contains stellate reticulum and stratum intermedium
False; HERS lacks these, which is why it induces odontogenesis
What happens when dentin formation is completed?
The basement membrane and HERS disintegrates; these cells may become epithelial rests of malassez
What can epithelial rests of malassez form?
Cysts
Simply explain what happens during the apposition stage
Enamel, dentin, and cementum are secreted in successive layers.
How are the tissues originally secreted in the apposition stage?
Secreted as gel-like matrix that is later calcified with calcium hydroxyapatite to harden
Where do all teeth develop from?
THE ECTODERM AND MESENCHYME***