OCB02-1013 Root development and Eruption Flashcards
What does HERS stand for?
Hertwig’s epithelial root sheath
What is HERS?
A proliferation of cells in the cervical loop where IEE and OEE meet, without the involvement of stellate reitculum
Why direction does HERs grow in single roots teeth?
Down vertically
Why direction does HERs grow in multi-root teeth?
Grows horizontally
How do HERS initiate odontoblast differentiation?
HERS secretes signals to the dental papilla which induces differentiation of mesenchymal cells into odontoblasts
What do odontoblasts do?
Secrete pre-dentin which mineralises to form dentin
What happens to HER as dentin is laid down? how does this affect the dental follicle?
HERS begins to break down, which allows cells from the dental follicle to come in contact with the root dentine, which allows the formation of the periodontal ligament and some ells to differentiate into cementoblasts to form cementum
What are the cell rests of Malassez? and what can they cause?
remnants of HERS within the periodontal ligament
Can cause cysts often in unerupted teeth which can lead to fracturing of the jaw
At what point does HERS change direction?
When the root is at its final length
What forms when HERS grows at a right angle?
The epithelial diaphragm, which leaves an opening in the apex of the root
What is the opening in the apex of the root called?
Apical foreamen
What is the purpose of th apical foreman?
The tooth can be innervated
What does the OEE, IEE, Stratum intermedium and stellate reticule form?
Reduced enamel epithelium
What happens once the bone is removed between the developing tooth germ and oral cavity?
The REE fuses with the oral epithelium and the cells within the centre of the oral epithelium and an epithelial canal is formed
What forms to dent-gingival junction?
REE and oral epithelium
What happens to odontoblasts and ameloblasts on eruption?
The ameloblasts have disappeared
Odontoblsta will always remain to repair dentin
How does the secondary dentition erupt?
Firstly, the roots of the decidiuous teeth are resorbed by odontoclasts
The deciduous crowns are then shed, which leaves space fo the permanent tooth to move axially into the oral cavity
What forces pull the tooth upwards?
Tension from the periodontal ligament
What forces push the tooth upwards?
Root growth and alveolar bone remodelling
What resorbs the alveolar bone above the tooth?
Osteoclasts
What do osteoblasts do one the tooth has erupted?
Deposit bone on the apical site of the root
What occurs when the coronal part of the dental follicle is removed?
no bone resorption
What occurs when the basal part of the dental follicle is removed>
There is no bone formation
What are the effects of short roots?
Loss in permanent dentition as the teeth are not properly anchored into the jaw
What is taurodontism?
The failure of HERS to for the epithelial diaphragm at the correct horizontal level
What are the effects of taurodontism?
Leads to larger pulp chamber and smaller roots in must teeth
What gene mutations cause variable root numbers?
Eda gene
