OCB02-1013 Root development and Eruption

Question 1

What does HERS stand for?

Answer 1

Hertwig’s epithelial root sheath

Question 2

What is HERS?

Answer 2

A proliferation of cells in the cervical loop where IEE and OEE meet, without the involvement of stellate reitculum

Question 3

Why direction does HERs grow in single roots teeth?

Answer 3

Down vertically

Question 4

Why direction does HERs grow in multi-root teeth?

Answer 4

Grows horizontally

Question 5

How do HERS initiate odontoblast differentiation?

Answer 5

HERS secretes signals to the dental papilla which induces differentiation of mesenchymal cells into odontoblasts

Question 6

What do odontoblasts do?

Answer 6

Secrete pre-dentin which mineralises to form dentin

Question 7

What happens to HER as dentin is laid down? how does this affect the dental follicle?

Answer 7

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

Question 8

What are the cell rests of Malassez? and what can they cause?

Answer 8

remnants of HERS within the periodontal ligament

Can cause cysts often in unerupted teeth which can lead to fracturing of the jaw

Question 9

At what point does HERS change direction?

Answer 9

When the root is at its final length

Question 10

What forms when HERS grows at a right angle?

Answer 10

The epithelial diaphragm, which leaves an opening in the apex of the root

Question 11

What is the opening in the apex of the root called?

Answer 11

Apical foreamen

Question 12

What is the purpose of th apical foreman?

Answer 12

The tooth can be innervated

Question 13

What does the OEE, IEE, Stratum intermedium and stellate reticule form?

Answer 13

Reduced enamel epithelium

Question 14

What happens once the bone is removed between the developing tooth germ and oral cavity?

Answer 14

The REE fuses with the oral epithelium and the cells within the centre of the oral epithelium and an epithelial canal is formed

Question 15

What forms to dent-gingival junction?

Answer 15

REE and oral epithelium

Question 16

What happens to odontoblasts and ameloblasts on eruption?

Answer 16

The ameloblasts have disappeared

Odontoblsta will always remain to repair dentin

Question 17

How does the secondary dentition erupt?

Answer 17

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

Question 18

What forces pull the tooth upwards?

Answer 18

Tension from the periodontal ligament

Question 19

What forces push the tooth upwards?

Answer 19

Root growth and alveolar bone remodelling

Question 20

What resorbs the alveolar bone above the tooth?

Answer 20

Osteoclasts

Question 21

What do osteoblasts do one the tooth has erupted?

Answer 21

Deposit bone on the apical site of the root

Question 22

What occurs when the coronal part of the dental follicle is removed?

Answer 22

no bone resorption

Question 23

What occurs when the basal part of the dental follicle is removed>

Answer 23

There is no bone formation

Question 24

What are the effects of short roots?

Answer 24

Loss in permanent dentition as the teeth are not properly anchored into the jaw

Question 25

What is taurodontism?

Answer 25

The failure of HERS to for the epithelial diaphragm at the correct horizontal level

Question 26

What are the effects of taurodontism?

Answer 26

Leads to larger pulp chamber and smaller roots in must teeth

Question 27

What gene mutations cause variable root numbers?

Answer 27

Eda gene