Early Tooth Development Flashcards
What are the 3 overlapping phases of tooth development?
- Initiation
- Morphogenesis
- Histogenesis
What 2 things occur during the initiation phase of odontogenesis?
- Site of future teeth established
2. Appearance of tooth germ
What occurs during the morphogenesis phase of odontogenesis?
Shape of teeth are determined by cell proliferation and movement
What occurs during the histogenesis phase of odontogenesis?
Differentiation of cells give rise to all dental tissues
At what age does tooth development begin?
6 weeks in utero
Where are teeth derived from?
Ectoderm and mesoderm with contribution from neural crest cells
What are neural crest cells?
Specialised group of migratory cells which originate from neuroectoderm
What is the main function of NCCs?
Essential for the formation of most of the CT elements found in the head
What is the stomodeum?
Primitive mouth lined by ectoderm
What occurs in the initiation phase at 6 weeks in utero?
Oral epithelium of stomodeum thickens and invaginates to form primary epithelial band
What is the primary epithelial band?
Horseshoe-shaped band which correspond roughly to shape of future dental arches
What does the primary epithelial band divide into?
- Vestibular lamina
2. Dental lamina
What does the vestibular lamina go on to form?
Vestibule between cheek and tooth-bearing area
What does the dental lamina contribute to the formation of?
Teeth
What occurs at 8 weeks in utero during the morphogenesis stage of tooth development?
Dental lamina lengthens and forms swellings of epithelium surrounded by condensation of ectomesenchymal cells
What do the epithelial swelling and ectomesenchymal cells make up?
Tooth germs
What are the 3 stages that tooth germs can be classified into?
- Bud stage
- Cap stage
- Bell stage
What occurs during the bud stage?
Extensive proliferation of dental lamina into buds
What is the term given to the tooth germ once the bud stage occurs?
Enamel organ
How many buds will be present in each arch?
10
What 2 main things occur during the cap stage?
- Proliferation of the cells of the enamel organ
2. Deeper surface of enamel organ invaginates
What 4 major structures are present in the cap stage?
- Enamel organ
- Dental papilla
- Dental sac
- Stella reticulum
What is the enamel organ?
Formation of tooth bud In a cap shape with a deep central impression
What is the dental papilla?
Condensed mass of ectomesenchyme within the concavity of the enamel organ
What is the dental sac?
Condensed mass of ectomesenchyme surrounding the outside of the enamel organ
What is the stellate reticulum?
Cells in the centre of the enamel organ which have separated and accumulated GAGs in between
What 2 things occur during the early bell stage?
- Dental lamina breaks down and enamel organ loses contact with oral epithelium
- Dental lamina between tooth germs degenerate
What are the two types of tissues in the dental papilla during the early bell stage?
- Odontoblasts
2. Primordium of the pulp
What occurs during the late bell stage?
Apposition stage - Formation of hard dental tissues
How do ameloblasts arise?
Internal enamel epithelium lines along basement membrane and differentiates into preameloblasts which in turn differentiate into ameloblasts
How do odontoblasts arise?
Outer cells of dental papilla differentiate into odontoblasts
What are the 6 main bell stage structures?
- Dental follicle
- External enamel epithelium
- Stellate reticulum
- Stratum intermedium
- Internal enamel epithelium
- Dental papilla
At what stage do small blood vessels invade the dental papilla?
Early bell stage
At what stage do nerve fibres form a plexus below the dental papilla?
Cap stage
