21671607
Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
about 4 years ago
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| Question | Answer |
| What are the 5 main stages of tooth development? | 1. Initiation 2. Bud Stage 3. Cap Stage 4. Bell Stage 5. Eruption |
| What 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) |
| Where does dental tissue originate from? | 1. Frontonasal process 2. The 1st brachial arch 3. 2nd brachial arch |
| Where do the oral epithelium cells originate from, and what does they become? | Originates from the ectoderm, becomes enamel |
| Where 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 |
| Where are neural crest cells found? | At the neural fold |
| What 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) |
| Which transcription factors are present in the epithelium? Which are present in the mesenchyme? | Epithelium: PITX2 Mesenchyme: BARX1, PAX9, LHX5,6 |
| What 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 |
| What is the primary epithelial band? | Thickened band of oral epithelium along oral side of maxilla/mandible |
| What is the dental placode? | Swellings on the dental lamina that correspond to a future tooth |
| What occurs during the bud stage? | 1. Placode proliferates into bud shape 2. Mesenchyme around epithelial band CONDENSES |
| During the cap stage, what determines the shape? | 1. Unequal proliferation of cells |
| What are the cell types in the enamel organ? | 1. Outer enamel epithelium 2. Inner enamel epithelium 3. Stellate reticulum 4. Stratum intermedium |
| Where 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 |
| What 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 |
| What growth factors does the PEK secrete? | BMPs Fibroblast Growth Factor (FGFs) Wnts Sonic Hedgehog (Shh) |
| What happens to the PEK eventually? What signals this? | Dies via apoptosis Signalled by BMP4 |
| What does the PEK mark? | The first buccal cusp |
| In 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 |
| What are the 3 layers of the dental follicle? | Inner layer Loose connective layer Outer layer |
| What 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 |
| When does tooth buds for permanent teeth form? How does this happen? | Occurs during the late bell stage Backward extension of the dental lamina |
| What is the difference between a successional and an accessional tooth? | Successional: Has predecessor Accessional: Has no predecessor (eg. PM1, PM2, PM3) |
| What activates tooth generation? | Wnt |
| What 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 |
| When does hard tissue (ameloblasts/odontoblasts) start forming at the tip of cusps? | Late bell stage |
| Where 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 |
| Where are odontoblasts first located? How do they move? What do they lay down? | Periphery of dental papilla Move INTO pulp Lay down dentin |
| Do ameloblasts or odontoblasts differentiate first? What do they secrete? | Odontoblasts Predentin which signals preameloblast to become ameloblast |
| Does dentin or enamel form first? | Dentin |
| How is tooth type determined? | The homeobox code-different levels of gene expression in different areas |
| Where is the homeobox code located? | In the mesenchyme, precedes tooth development |
| What limits the growth of teeth? | Alveolar bone |
| What 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 |
| What are some EDA defects? | Defective PEK/SEK leading to: -Cusp/enamel flattening -Reduced PEK-->defective SEK-->lower number of cusps |
| What is hypohidrotic ectodermal dysplasia? | Reduced teeth and flattening cusps |
| What occurs with overexpression of EDAR? | Formation of extra cusps |
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