Flashcards
OCB02-1009-Early tooth development/Late tooth development/Tooth morphogenesis
Cards in this deck (39)
- 1What are the 5 main stages of tooth development?1. Initiation
2. Bud Stage
3. Cap Stage
4. Bell Stage
5. Eruption - 2What are the two parts of the dental lamina?The dental lamina is made of the oral epithelium (oral ectoderm cells) and the mesenchyme (ectomesenchyme cells)
- 3Where does dental tissue originate from?1. Frontonasal process
2. The 1st brachial arch
3. 2nd brachial arch - 4Where do the oral epithelium cells originate from, and what does they become?Originates from the ectoderm, becomes enamel
- 5Where does the oral mesenchyme cells originate from, and what do they become?Originate from neural crest cells, become dentin, dental pulp, cementum, periodontal ligament, alveolar bone sack
- 6Where are neural crest cells found?At the neural fold
- 7What do defects in the neural crest cells lead to?1. Treacher Collins syndrome
2. Defective structures from 1st/2nd brachial arches (eg. ear, teeth, cleft palate, droopy eyes, flat face) - 8Which transcription factors are present in the epithelium? Which are present in the mesenchyme?Epithelium: PITX2
Mesenchyme: BARX1, PAX9, LHX5,6 - 9What occurs during the initiation stage of tooth development?1. Forming of the primary epithelial band from thickening of oral epithelium (Shh)
2. Formation of dental (lingual) +vestibular (buccal) lamina
3. Dental placode develops on the dental lamina - 10What is the primary epithelial band?Thickened band of oral epithelium along oral side of maxilla/mandible
- 11What is the dental placode?Swellings on the dental lamina that correspond to a future tooth
- 12What occurs during the bud stage?1. Placode proliferates into bud shape
2. Mesenchyme around epithelial band CONDENSES - 13During the cap stage, what determines the shape?1. Unequal proliferation of cells
- 14What are the cell types in the enamel organ?1. Outer enamel epithelium
2. Inner enamel epithelium
3. Stellate reticulum
4. Stratum intermedium - 15Where is the dental papilla located compared to the dental follicle?The dental papilla is directly under the enamel bud, while the dental follicle is around it
- 16What creates the bell shape? What are the two mechanisms in which this happens?Primary Enamel Knot
1. PEK cells do NOT divide
2. Meanwhile PEK cells act as signalling centre secreting growth factors
Different rates of cell division lead to shape - 17What growth factors does the PEK secrete?BMPs
Fibroblast Growth Factor (FGFs)
Wnts
Sonic Hedgehog (Shh) - 18What happens to the PEK eventually? What signals this?Dies via apoptosis
Signalled by BMP4 - 19What does the PEK mark?The first buccal cusp
- 20In multicuspid teeth, when does the secondary enamel knots form? What does the number, timing and layout indicate?Early bell stage
# of knots=# of cusps
Timing of SEK initiation=height of cusps
Layout indicates cusp pattern
eg. Cusp of Carabelli caused by large crown area with small cusp distance - 21What are the 3 layers of the dental follicle?Inner layer
Loose connective layer
Outer layer - 22What is the cervical loop? What does the cervical loop become, and what is its function?Where the outer enamel epithelium meets the inner enamel epithelium
Hertwig's epithelial root sheath
For root formation - 23When does tooth buds for permanent teeth form? How does this happen?Occurs during the late bell stage
Backward extension of the dental lamina - 24What is the difference between a successional and an accessional tooth?Successional: Has predecessor
Accessional: Has no predecessor (eg. PM1, PM2, PM3) - 25What activates tooth generation?Wnt
- 26What are the Epithelial Pearls of Serres? What can they lead to?Epithelial cells that persist after dental lamina breaks down
Can cause cysts, odontomas, supernumerary teeth - 27When does hard tissue (ameloblasts/odontoblasts) start forming at the tip of cusps?Late bell stage
- 28Where are ameloblasts first located? How do they move? What do they lay down?First located at inner enamel epithelium
Move AWAY from pulp
Lay down enamel - 29Where are odontoblasts first located? How do they move? What do they lay down?Periphery of dental papilla
Move INTO pulp
Lay down dentin - 30Do ameloblasts or odontoblasts differentiate first? What do they secrete?Odontoblasts
Predentin which signals preameloblast to become ameloblast - 31Does dentin or enamel form first?Dentin
- 32How is tooth type determined?The homeobox code-different levels of gene expression in different areas
- 33Where is the homeobox code located?In the mesenchyme, precedes tooth development
- 34What limits the growth of teeth?Alveolar bone
- 35What is the EDA Signalling pathway and what does it lead to?1. EDA from BUD binds to receptors on Enamel knot
2. Edar turns on Edaradd
3. PEK/SEK formation - 36What are some EDA defects?Defective PEK/SEK leading to:
-Cusp/enamel flattening
-Reduced PEK-->defective SEK-->lower number of cusps - 37What is hypohidrotic ectodermal dysplasia?Reduced teeth and flattening cusps
- 38What occurs with overexpression of EDAR?Formation of extra cusps
- 39—
Information
- Description
- Understand: -basic stages of tooth development, features and timing - define cranial neural crest cells and ectomesenchyme. -origin of epithelium and mesenchyme involved in tooth development -function and fate of the enamel organ, dental papilla and dental follicle.- -location and features of primary and secondary enamel knots. Describe initiation of development of secondary dentition -dental lamina and its fate. Explain cellular origin of odontoblasts and ameloblasts.
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- Evian Chai
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