M+O 1 - tooth eruption Flashcards
What “eruptive” movements continue adjusting teeth?
- over-eruption in response to opposing extraction
- compensation for wear
What is active eruption?
bodily movement of the tooth
What is passive eruption?
uncovering of the tooth by apical gingival migration
What does ‘bloodless eruption’ mean?
tooth comes through an epithelial lined channel,no bleeding
When and why does pre-eruptive movement happen?
- 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
What is the eruptive force?
~5-10g force
What is the speed of intraosseous eruption?
1-10um per day
What is the speed of supraosseous eruption?
75um per day
In eruption, what forces is there a balance between?
eruptive forces and resistive forces (overlying tissues)
What issue can be caused by the early loss of primary teeth?
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
What are the ‘push’ theories of eruption?
- root formation
- bone formation
- fluid pressure (from vascular papilla)
What are the ‘pull’ theories of eruption?
PDL
- collagen contraction
- fibroblast contraction
- fibroblast migration
What are the ‘for’ and ‘against’ arguments for the root formation theory of eruption?
for:
- roots normally form during eruption
against:
- some teeth have eruption paths»_space; root length
- impacted teeth with fully formed teeth can erupt if impaction released
- experimental evidence disproves
What are the ‘for’ and ‘against’ arguments for the hydrostatic pressure eruption theory?
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
When collagen formation is disrupted, what happens to eruption?
- slower eruption rate or no change in eruption rate
- root formation continues
- ? collagen synthesis affects eruption rate
- but does the collagen generate the force?
Why does it appear that PDL pull eruption theory is not the case?
- teeth erupt when PDL fibres are not well developed
What is the ‘for’ and ‘against’ argument for the collagen contraction eruption theory?
for:
- collagen can contract in vitro
against:
- no proof that collagen contracts in vivo
What are the ‘for’ and ‘against’ arguments for fibroblast migration/contraction?
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
Is there one accepted theory of eruption?
no, multifactorial
What is eruption likely not due to?
- bone formation
- (more likely a result rather than a cause)
- root formation
What is eruption probably due to?
- pull - by PDL fibroblasts
- push - hydrostatic pressure
What does the coronal follicle produce?
factors that regulate osteoclasts and promote bone resorption
What does the apical follicle promote?
bone formation
- BMP-2 (Bone Morphogenic Protein-2)
What are monocyte precursors recruited by?
- CSF-1: Colony stimulating factor-1
- MCP-1: Monocyte Chemotactic Protein-1
What is the fusion of monocytes to form osteoclasts promoted by?
- RANK and RANKL
What are the stages of a bloodless eruption?
- 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)
What must happen to facilitate successional eruption?
primary tooth must be resorbed
What caused resorption?
pressure of tooth on bone
What are the primary teeth resorbed by?
odontoclasts
- multinucleated osteoclast like cells
- derived from monocytes
What are post-eruptive movements, and when do they occur?
- accommodate for growth
- compensate for occlusal wear
- accommodate approximal wear
- following extraction of opposing teeth
