Tooth eruption

Question 1

What is tooth eruption

Answer 1

The process boy which a tooth moves from its developmental position within the jaw to its functional position within the oral cavity

Question 2

Name the 3 phases of tooth eruption

Answer 2

1. Pre eruptive (pre eruptive)
2. Pre functional (eruptive)
3. Functional (post eruptive)

Question 3

What is the first phase of tooth eruption

Answer 3

Pre eruptive

Question 4

What does the pre eruptive refer to

Answer 4

Refers to the movements of the developing tooth arising from growth of the tooth germ itself or from growth changes in the surrounding bone

Question 5

Name the second stage of tooth eruption

Answer 5

Pre functional or eruptive

Question 6

What does the pre functional/ eruptive phase of tooth eruption refer to

Answer 6

Refers to the active phase of movement of the tooth into its functional position following crown completion

Question 7

Name the 3rd stage of tooth eruption

Answer 7

Functional or post eruptive

Question 8

What does the 3rd phase of tooth eruption refer to

Answer 8

Refers to the constant slow outward movement of the teeth to accommodate for the loss of enamel due to occlusal wear

Question 9

State the formal tooth eruption is depend on

Answer 9

Net eruptive force= generated force - resistance

Question 10

What does the net eruptive force formula mean in words

Answer 10

If the fore pushing or pulling the tooth out is greater than the resistance to the movement then the tooth will erupt

Question 11

What is a lack of eruption usually due to

Answer 11

Caused by either a reduced force or an increased resistance

Question 12

What happens to the tooth once it enters the oral cavity

Answer 12

Occlusal forces will start to impinge and will provide a large component of any resistance to eruption

Question 13

Give an example of a tooth without a predecessor

Answer 13

human permanent molar or a deciduous tooth

Question 14

What is the major source for a tooth that has no predecessor

Answer 14

The overlying bone and gingiva

Question 15

What needs to happen to the overlying bone and gingiva covering teeth with no predecessor

Answer 15

They need to be removed before eruption

Question 16

How is the overlying bone and gingiva covering teeth with no predecessor removed

Answer 16

1. The reduced enamel epithelium which covers the enamel proliferates into the overlying gingival connective tissue and released enzymes which start to degrade the connective tissue matrix
2. It also releases cytokines
3. it prevents the simultaneous action of osteoclasts on the enamel which of course is subjected to the same pressure

Question 17

What do the cytokines released by the reduced enamel epithelium do

Answer 17

1. Trigger the adjacent fibroblast to also release degrading enzymes
2. Starts the cascade of events which lead to the recruitment of osteoclast and subsequent bone removal

Question 18

Other than enamel epithelium what else can stimulate osteoclasis

Answer 18

Pressure from the upward movement of the crown

Question 19

What happens as the cusps of the tooth approach the gingival epithelium

Answer 19

1. Remaining connective tissues becomes ischemic and necrotic
2. Where the reduced enamel epithelial meets the oral epithium they fuse and continued pressure results in degradation of the fused epithelium above the cusp

Question 20

What happens as the remaining connective tissue becomes ischemic and necrotic

Answer 20

It triggers an inflammatory reaction- redness, sourness and raised temperature

Question 21

What does the fusion of the oral epithelia and enamel epithelium result in

Answer 21

Results in a channel being formed through which the tooth can erupt

Question 22

What is the effect of the fusion of the oral epithelia and enamel epithelium

Answer 22

a continuous and intact epithelial barrier is maintained meaning underling connective tissue is never exposed

Question 23

What forms the initial junctional epithelium

Answer 23

Derived from the remnants of the reduced enamel epithelium

Question 24

List the 5 criterias that must be fulfilled to be able to explain what generated the eruptive force for tooth eruption

Answer 24

1. The proposed system must be capable of producing a force under physiological conditions which is sufficient to move a tooth in the required direction
2. Experimentally induced changes in the system should cause predictable changes in eruption
3. The system myst have characteristics which allow it ti sustain eruptive movements over long periods
4. The biochemical and physiological characteristics of the system should be consistent with the production of an eruptive force
5. The morphological features associated with the system should be consistence with the production of the eruptive force

Question 25

Describe the 2 ideals that have been suggested for the eruptive force

Answer 25

1. It involves the periodontal ligament
   OR
2. It doesn’t involve growth in and around the developing root

Question 26

What does fundic bone deposition mean

Answer 26

It encapsulates the idea that as new bone was laid at the base of the sockets the tooth would be pushed out

Question 27

Is the fundic bone deposition theory accepted? why?

Answer 27

A close study of the sockets has shown that bone may be resorbed in this area as well as formed but eruption continues regardless so this idea may not be accurate

Question 28

What is the idea behind pulp cell proliferation

Answer 28

The pulp cell population at the base of the forming root is increasing rapidly by cell division and this increase in bulk can only be accommodated by movement of the tooth outwards

Question 29

Name the 3 theories explain tooth eruption forces

Answer 29

1. fundic bone deposition
2. Pulp cell proliferation
3. elongating root pushes the tooth oUT

Question 30

Why is the elongating root pushing the tooth out not an accepted idea

Answer 30

1. If artificial stainless steel crowns are implanted within the follicle they will ‘erupt’ just as a natural tooth would but obviously they don’t have roots or pulp. 2. studies using the continuous erupting teeth of rodents suggest that the generator of the eruptive force must lie within the periodontal space

Question 31

Evidence suggests that the eruptive forces for teeth resides where?

Answer 31

resides around the tooth in the periodontal space

Question 32

Which parts of the periodontal ligament are the key candidates to be causing the eruptive forces if the forces are coming from the peritoneal ligament

Answer 32

1. Periodontal fibroblast migration

2. Contraction or vascular or tissue fluid pressure

Question 33

How might periodontal fibroblast migration aid in the eruption of teeth

Answer 33

When the periodontal fibroblasts migrate through the periodontal matrix they either:

1. Pull out the tooth
2. Act in a contractile fashion contracting the matrix and pulling the tooth out

Question 34

Describe the vascualr/tissue fluid pressure hypothesis

Answer 34

The periodontium acts a little like a tooth paste tooth where by if pressure is applied to anyway on the sides of the time the paste comes out of the top causing the tooth to be pushed out

Question 35

Where does the pressure build up come from to support the vascualr/tissue fluid pressure hypothesis

Answer 35

Thought to arise from either peripheral vascular pressure or tissue fluid pressure

Question 36

Which animal do we often look at when studying tooth eruption

Answer 36

Rodents

Question 37

What evidence do we have that goes against the idea that fibroblasts blast migration drives tooth eruption

Answer 37

The fact that measurements of mitochondria (needed for energy production for migration) and actin filaments (needed for movements and contractility of fibroblasts) in adult and young mice is almost the same
Suggesting active movement or contraction of fibroblast is not needed to generate the eruptive force

Question 38

It is said that possible the teeth erupt in time with what?

Answer 38

Heart beat (pulse)

Question 39

How might the erupt in time with a heart beat?

Answer 39

As blood pressure rises and blood flow increases the tooth is extruded and as pressure drops and blood pressure decreases it falls back into the socket.