OB P8 - tooth eruption

Question 1

what is tooth eruption?

Answer 1

movement of a tooth:
– from developmental position in the jaw
– to its functional position in occlusion in the mouth

Question 2

what do “eruptive” movement continue and give examples.

Answer 2

“eruptive” movements continue adjusting tooth e.g.:
– over-eruption in response to opposing extraction
– compensation for wear

Question 3

why is over eruption a problem?

Answer 3

the teeth are aligned in the occlusal plan which is a gentle curve and not flat and so over eruption disturbs the occlusal plane and forms a step in the occlusion which can alter jaw movement (chewing movements)

Question 4

what is compensation for wear?

Answer 4

gradual over eruption- wear out teeth away so it will compensate by over erupting

Question 5

what is active eruption?

Answer 5

Bodily movement of the tooth

Question 6

what is passive eruption?

Answer 6

uncovering of the tooth by apical gingival migration

Question 7

what is the deciduous eruptive movement called?

Answer 7

Bloodless eruption

Question 8

what is the permanent eruptive movement?

Answer 8

deciduous exfoliation

Question 9

where does the permanent successor start?

Answer 9

at the palatal or lingual side and migrates it way underneath the deciduous

Question 10

What happens in pre-eruptive movement?

Answer 10

• during tooth development
• teeth move as jaw grows
• successional teeth move from a lingual/palatal position:
  ( e.g. lower premolars: start lingually and move between the roots of the deciduous molars)
• bone remodelling

Question 11

what is the eruption movement?

Answer 11

into the mouth and into occlusion

Question 12

what direction is eruption?

Answer 12

mainly axial movement

Question 13

what are the eruptive forces?

Answer 13

5-10g force

Question 14

what are the variable speeds of eruption?

Answer 14

– 1mm in month – upper 1’s
– 4.5mm in 14 months – lower 5’s
– 1mm in 3 months – 8’s

Question 15

what is the balance between in eruption?

Answer 15

• Eruptive forces

- Resistive forces – overlying tissues

Question 16

Name the 4 push eruption theories.

Answer 16

• Root formation
• Pulp proliferation
• Bone formation
• Fluid pressure

Question 17

Name the 3 pull eruption theories.

Answer 17

– collagen contraction
– fibroblast contraction
– fibroblast migration

Question 18

what are the reason for push: root formation?

Answer 18

Roots normally form during eruption

Question 19

what are the reasons against push : root formation?

Answer 19

• Some teeth have eruption paths&raquo_space; root length
• Impacted teeth with fully formed teeth can erupt of impaction released
• Experimental evidence…

Question 20

what happens in the rat experiment (root formation)?

Answer 20

- Rat incisor: 
•continuously erupts 
•remains sharp
- Incisal tip removed:
Proliferating root end removed
- Tooth continues to erupt then exfoliates as root formation
stopped and no bone form

Question 21

what does this rat experiment suggest?

Answer 21

As any push from papilla/pulp or root growth is eliminated, yet eruption continues.
Therefore likely force is a pull from the PDL.

Question 22

what are the reasons for push: bone formation?

Answer 22

Bone forms under an erupting tooth

Question 23

what are the reasons against push : bone formation?

Answer 23

• Root resected teeth erupt

- Bone fills in as tooth moves away

Question 24

what are the reasons for push : hydrostatic pressure?

Answer 24

>  Periodontal vasculature
>  Cervical Sympathetic stimulation: 
– vasoconstriction
– cessation of eruption
– Reversible on cessation 
 > Sympathectomy
– Vasodilation 
– increased tissue pressure 
– Increase eruption rate

Question 25

what are the against push : hydrostatic pressure?

Answer 25

– Root resected rodent incisor erupt normally

Question 26

where is the evidence for pull : role of the PDL fibres?

Answer 26

Evidence from root resection experiments

Question 27

what do PDL fibres do ?

Answer 27

> Disrupt collagen formation:
– no Vitamin C - essential for collagen synthesis
– lathyrogens - prevent cross-linking

Question 28

what is the result of PDL fibres disrupting collagen formation?

Answer 28

• slower eruption rate or no change in eruption rate
• root formation continues
• ? collagen synthesis affects eruption rate
• but does the collagen generate the force?

Question 29

when do teeth erupt?

Answer 29

when PDL fibres are not well developed

Question 30

what are the reasons for pull: collagen contraction?

Answer 30

Collagen can contract in vitro

Question 31

what are the reasons against pull: collagen contraction?

Answer 31

No proof that collagen contracts in vivo

Question 32

what is the theory of pull: fibroblast migration/contraction?

Answer 32

• Forces transmitted along principle oblique fibres

- like scar tissue contraction

Question 33

what are the reasons for pull: fibroblast migration/ contraction?

Answer 33

• Fibroblasts show motility when cultured
• Fibroblasts move cervically on eruption
• Colchicine: - reduces cell motility -> retards
  eruption

Question 34

what are the reasons against pull: fibroblast migration/ contraction?

Answer 34

• PDL fibroblasts don’t have organelles for motility

- No evidence that they can exert eruptive force

Question 35

what is the summary of eruption theories?

Answer 35

multifactorial  
 likely not due:
– to bone formation
• more likely a result rather than a cause
– root formation
  Probably due to:
– Pull - by PDL fibroblasts
– Push - hydrostatic pressure

Question 36

what are the steps of bloodless eruption?

Answer 36

• Oral mucosa
• collagen degrades (REE proliferation)
• Fusion of oral epithelium and REE
• Epithelial cell death
• Epithelial pathway
• REE forms JE

Question 37

Describe deciduous exfoliation.

Answer 37

• Deciduous tooth must be resorbed to facilitate successional eruption.
• Pressure of tooth on bone -> resorption
• Deciduous teeth resorbed by Odontoclasts :
  > multinucleated osteoclast like cells
  > derived from monocytes

Question 38

Describe post-eruptive movements.

Answer 38

• accommodate for growth
• compensate for occlusal wear
• accommodate approxinal wear
• following extraction of opposing teeth