Tooth eruption Flashcards
tooth eruption
– from developmental position in the jaw
– to its functional position in occlusion in the mouth
Active eruption
▪ bodily movement of the tooth
Passive eruption
▪ uncovering of the tooth by apical gingival migration
accessional tooth
erupt on their own (i.e molar - not replacing any tooth)
successional tooth
erupt to resorb a tooth (i.e. incisor - replacing a primary tooth)
Bloodless eruption
First stage of eruption. As the primary tooth moves up, the root forms. Enamel epithelium thins, no breaching/exposed tissue = no blood.
Bone changes a lot from 6 months,
Primary tooth exfoliation
Second stage of eruption. As the permanent tooth makes eruptive movements, primary tooth exfoliates.
Pre-eruptive movements
Occurs 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 primary molars
▪ bone remodelling
Force of tooth eruption
~5-10g force
Eruption moves through
▪ Eruptive forces (pushing/pulling tooth into the mouth)
▪ Resistive forces – overlying tissues
Speed of eruption
– 1-10μm per day intraosseous (inside the bone)
– 75μm per day supraosseous (outside the bone)
early loss of a primary tooth as a result of caries
Extraction of tooth prematurely can result in, overlying cortical bone forms over, so delayed eruption, can cause problems in future.
Eruption theories: push
▪ Root formation
▪ Bone formation
▪ Fluid pressure
Eruption theories: pull
▪ PDL:
– collagen contraction
– fibroblast contraction
– fibroblast migration
Evidence FOR: root formation pushing theory
▪ Roots normally form during eruption
Evidence AGAINST: root formation pushing theory
▪ Some teeth have eruption paths»_space; root length
▪ Impacted teeth with fully formed teeth can erupt of impaction released
▪ Experimental evidence: rat incisors constantly replacing themselves, removal of the root still found eruption occured.
Evidence FOR: hydrostatic pushing theory
▪ Periodontal vasculature
▪ Cervical Sympathetic stimulation: – vasoconstriction
– cessation of eruption
– Reversible on cessation
▪ Sympathectomy
– Vasodilation – increased tissue pressure – Increase eruption rate
Evidence AGAINST: hydrostatic pushing theory
– Root resected rodent incisor erupt normally
Evidence FOR/AGAINST: PDL fibres (collagen contraction) pulling theory
FOR
▪ Collagen can contract in vitro
AGAINST
▪ No proof that collagen contracts in vivo
Evidence FOR/AGAINST: PDL fibres (fibroblast migration/contraction) pulling theory
▪ Forces transmitted along principle oblique fibres ▪ ?like scar tissue contraction
For:
▪ Fibroblasts show motility when cultured
▪ Fibroblasts move cervically on eruption
▪ Colchicine: - reduces cell motility -> retards
eruption
Against:
▪ PDL fibroblasts don’t have organelles for motility ▪ No evidence that they can exert eruptive force
Summary of eruption theories
▪ 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
Cellular mechanisms during resorption of the primary tooth
▪ Coronal Follicle produces factors that regulate
osteoclasts and promote bone resorption
– Monocyte precursors recruited by:
* CSF-1:Colonystimulatingfactor-1
* MCP-1:MonocyteChemotacticProtein-1
– Fusion of monocytes to form osteoclasts promoted by: * RANKandRANKL
▪ Apical Follicle promotes bone formation – BMP-2 Bone Morphogenic Protein-2
Describe how bloodless eruption occurs
Post-eruptive movements
▪ accommodate for growth
▪ compensate for occlusal wear
▪ accommodate approxinal wear
▪ following extraction of opposing teeth
