21695718
Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
over 4 years ago
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| Question | Answer |
| When does the cervical loop become Herwig's Epithelial Root Sheath? | Once the tooth crown mineralises, it grows down |
| What are the three functions of HERS? | 1. Map out root sheath and boundaries? 2. Initiate root odontoblast differentiation 3. Disintegrate to initiate cementum/PDL formation |
| When does HERGS map out root sheath? | Late bell stage |
| What do molecules secreted from HERS target to initiate root odontoblast differentiation? | Mesenchyme cells |
| How does disintegration of HERS lead to cementum/PDL formation? | Exposes mesenchyme cells in follicle to dentin Cells differentiate into cementoblasts |
| Acellular cementum is... | Thin, coronal 2/3 of root |
| Cellular cementum is... | Thick, apical 1/3 of root |
| What happens to the remnants of HERS? | Can reactivate/become tumours and cysts in adulthood |
| How is the root apex formed? What is different about it in multi-cusp teeth? | HERS grows in 90 degree angle towards apical foramen HERS will connect in double root teeth to form two roots HERS will separate root into 3 |
| What is the apical foramen? | Where nerve/blood vessels get into dental pulp |
| How does tooth eruption occur in deciduous teeth? | 1. Formation of the PDL 2. Fusion of layers into reduced enamel epithelium 3. Oral epithelium and reduced enamel epithelium forms the dental gingival junction 4. Bone reabsorbed at Gubernacular Cord to allow tooth eruption |
| Which cells secrete what to form the PDL? | Fibroblasts secrete collagen which forms bundles |
| Which layers form the reduced enamel epithelium? | 1. Outer enamel epithelium 2. Stellate reticulum 3. Stratum intermedium 4. Inner enamel epithelium |
| Why is there no bleeding during tooth eruption? | Goes through epithelial cells (only mesenchyme cells are vascularised) |
| What is the main cause of permanent tooth eruption? | Alveolar bone remodelling: -Osteoblasts form bone at tips of roots to PUSH teeth out |
| During permanent tooth eruption what occurs in the coronal 1/2 of the root? | resorption by osteoclasts |
| During permanent tooth eruption what occurs in the basal 1/2 of the root? | bone formation by osteoblasts expression of BMP2 for osteoblast differentiation |
| What controls bone resorption/creation at roots? | Dental follicle by sending signals to recruit osteoclasts/blasts |
| What other factors contribute to permanent tooth eruption? | 1. Root growth 2. PDL may accelerate eruption speed by pulling |
| NF1-C mutant mice | lack roots bc no odontoblast diffrentiation |
| Which disorders have short roots? | Dentin dysplasia type 1: DSPP gene Sponastrine dysplasia |
| What is wrong in OFCD? | abnormally long roots mutation in BCOR gene so mesenchyme keeps being stem cells |
| Taurodontism caused by... | failure of HERS to reorientate at proper level, so roots separate too low |
| EDG (lacking or overexpressed) mutants have... | variable root numbers |
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