Rott and periodontium development

Question 1

By what mechanism does the root develop

Answer 1

Indiction of odontoblasts but not ameloblasts

Question 2

What is the root sheath of Hertwig

Answer 2

It is a down growth of the inner and outer epithelia from the enamel organ to form a bilaminar strip

Question 3

What is the toor diaphragm

Answer 3

The part of the root sheath that runs across the papilla at right angles to the orientation of the tooth

Question 4

What makes the root sheath unique

Answer 4

It does not normally have a component derived from either stellate reticulum or stratum intermedium

Question 5

In what direction does the epithelium proliferate

Answer 5

Proliferate in a downwards direction

It does NOT proliferate at its ends and does not increase in length inwards

Question 6

Where do odontoblasts differentiate from

Answer 6

The outer cells of the papilla

Question 7

What do the inner row of cells in the root sheath do

Answer 7

They induce the papilla cells to stop dividing and terminally differentiate into odontoblasts

Question 8

What happens to some of the root sheath cells as dentine is being laid down

Answer 8

Some cells die and other migrate away to form clusters of epithelial cells within the follicle called the rests of Malassez

Question 9

What might explain the lack of ameloblast differntiation in the root

Answer 9

May be due to the lack of stratum intermedium derivative within the root sheath structure

Question 10

What happens in areas of the sheath where small pockets of stratum intermedium do occur?

Answer 10

Ameloblasts form and crate small pearls of enamel on the root

Question 11

What heppens once the root sheath has broken up

Answer 11

The follicle becomes exposed to newly formed dentine which then induces the differentiation of cementoblasts from cells within the follicle that secrete cementum

Question 12

What does the formation of dentine induce in the root

Answer 12

The differentiation of cementoblasts

Question 13

What do cementoblasts do

Answer 13

They secrete cementum

Question 14

Does the root sheath get bigger, smaller or remain the same size

Answer 14

Remains the same size

Question 15

How does the root remain the same size

Answer 15

Because the breakup of the root sheath and the rate of proliferation and downgrowth are in synchrony

Question 16

What is the current idea of how root morphology is controlled

Answer 16

Based on the morphology of the vascular bed entering the papilla

Question 17

How is the root diaphragm inhibited from growing across the papilla

Answer 17

Due to the vasculature such that is a single central capillary bed would uniformly inhibit the ingrowth thereby producing a single tubular root

Question 18

How do accessory root canals form

Answer 18

Can form when the root sheath breaks up before odontoblast differentiation has been initiated
This means dentine will never form in this area and a channel will remain through th dentine between the follicle and papilla

Question 19

Other than being the source of cementoblasts what else does the follicle do

Answer 19

Is the source for periodontal fibroblasts and a significant number of osteoblasts on the surface of the alveolar bone