M+O 1 - tooth eruption

Question 1

What “eruptive” movements continue adjusting teeth?

Answer 1

• over-eruption in response to opposing extraction
• compensation for wear

Question 2

What is active eruption?

Answer 2

bodily movement of the tooth

Question 3

What is passive eruption?

Answer 3

uncovering of the tooth by apical gingival migration

Question 4

What does ‘bloodless eruption’ mean?

Answer 4

tooth comes through an epithelial lined channel,no bleeding

Question 5

When and why does pre-eruptive movement happen?

Answer 5

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

Question 6

What is the eruptive force?

Answer 6

~5-10g force

Question 7

What is the speed of intraosseous eruption?

Answer 7

1-10um per day

Question 8

What is the speed of supraosseous eruption?

Answer 8

75um per day

Question 9

In eruption, what forces is there a balance between?

Answer 9

eruptive forces and resistive forces (overlying tissues)

Question 10

What issue can be caused by the early loss of primary teeth?

Answer 10

can cause bone to heal fully and make it harder for permanent teeth to erupt, leading to delayed eruption, can then cause ortho problems etc

Question 11

What are the ‘push’ theories of eruption?

Answer 11

• root formation
• bone formation
• fluid pressure (from vascular papilla)

Question 12

What are the ‘pull’ theories of eruption?

Answer 12

PDL
- collagen contraction
- fibroblast contraction
- fibroblast migration

Question 13

What are the ‘for’ and ‘against’ arguments for the root formation theory of eruption?

Answer 13

for:
- roots normally form during eruption

against:
- some teeth have eruption paths&raquo_space; root length
- impacted teeth with fully formed teeth can erupt if impaction released
- experimental evidence disproves

Question 14

What are the ‘for’ and ‘against’ arguments for the hydrostatic pressure eruption theory?

Answer 14

for:
- periodontal vasculature
- cervical sympathetic stimulation:
- vasoconstriction
- cessation of eruption
- reversible on cessation
- sympathectomy
- vasodilation - increased tissue pressure
- increase eruption rate

against:
- root resected rodent incisor erupt normally

Question 15

When collagen formation is disrupted, what happens to eruption?

Answer 15

• 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 16

Why does it appear that PDL pull eruption theory is not the case?

Answer 16

• teeth erupt when PDL fibres are not well developed

Question 17

What is the ‘for’ and ‘against’ argument for the collagen contraction eruption theory?

Answer 17

for:
- collagen can contract in vitro

against:
- no proof that collagen contracts in vivo

Question 18

What are the ‘for’ and ‘against’ arguments for fibroblast migration/contraction?

Answer 18

for:
- fibroblasts show motility when cultured
- fibroblasts move cervically on eruption
- colchicine: - reduced cell motility -> retards eruption

against:
- PDL fibroblasts don’t have organelles for motility
- no evidence that they can exert eruptive force

Question 19

Is there one accepted theory of eruption?

Answer 19

no, multifactorial

Question 20

What is eruption likely not due to?

Answer 20

• bone formation
  
  • (more likely a result rather than a cause)
• root formation

Question 21

What is eruption probably due to?

Answer 21

• pull - by PDL fibroblasts
• push - hydrostatic pressure

Question 22

What does the coronal follicle produce?

Answer 22

factors that regulate osteoclasts and promote bone resorption

Question 23

What does the apical follicle promote?

Answer 23

bone formation
- BMP-2 (Bone Morphogenic Protein-2)

Question 24

What are monocyte precursors recruited by?

Answer 24

• CSF-1: Colony stimulating factor-1
• MCP-1: Monocyte Chemotactic Protein-1

Question 25

What is the fusion of monocytes to form osteoclasts promoted by?

Answer 25

• RANK and RANKL

Question 26

What are the stages of a bloodless eruption?

Answer 26

• REE (reduced enamel epithelium) formed
• REE proliferates and collagen degrades
• fusion of oral epithelium and REE
• epithelial cell death
• epithelial pathway formed
• REE forms JE (junctional epithelium)

Question 27

What must happen to facilitate successional eruption?

Answer 27

primary tooth must be resorbed

Question 28

What caused resorption?

Answer 28

pressure of tooth on bone

Question 29

What are the primary teeth resorbed by?

Answer 29

odontoclasts
- multinucleated osteoclast like cells
- derived from monocytes

Question 30

What are post-eruptive movements, and when do they occur?

Answer 30

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