Tooth eruption

Question 1

tooth eruption

Answer 1

– from developmental position in the jaw
– to its functional position in occlusion in the mouth

Question 2

Active eruption

Answer 2

▪ bodily movement of the tooth

Question 3

Passive eruption

Answer 3

▪ uncovering of the tooth by apical gingival migration

Question 4

accessional tooth

Answer 4

erupt on their own (i.e molar - not replacing any tooth)

Question 5

successional tooth

Answer 5

erupt to resorb a tooth (i.e. incisor - replacing a primary tooth)

Question 6

Bloodless eruption

Answer 6

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,

Question 7

Primary tooth exfoliation

Answer 7

Second stage of eruption. As the permanent tooth makes eruptive movements, primary tooth exfoliates.

Question 8

Pre-eruptive movements

Answer 8

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

Question 9

Force of tooth eruption

Answer 9

~5-10g force

Question 10

Eruption moves through

Answer 10

▪ Eruptive forces (pushing/pulling tooth into the mouth)
▪ Resistive forces – overlying tissues

Question 11

Speed of eruption

Answer 11

– 1-10μm per day intraosseous (inside the bone)
– 75μm per day supraosseous (outside the bone)

Question 12

early loss of a primary tooth as a result of caries

Answer 12

Extraction of tooth prematurely can result in, overlying cortical bone forms over, so delayed eruption, can cause problems in future.

Question 13

Eruption theories: push

Answer 13

▪ Root formation
▪ Bone formation
▪ Fluid pressure

Question 14

Eruption theories: pull

Answer 14

▪ PDL:
– collagen contraction
– fibroblast contraction
– fibroblast migration

Question 15

Evidence FOR: root formation pushing theory

Answer 15

▪ Roots normally form during eruption

Question 16

Evidence AGAINST: root formation pushing theory

Answer 16

▪ Some teeth have eruption paths&raquo_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.

Question 17

Evidence FOR: hydrostatic pushing theory

Answer 17

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

Question 18

Evidence AGAINST: hydrostatic pushing theory

Answer 18

– Root resected rodent incisor erupt normally

Question 19

Evidence FOR/AGAINST: PDL fibres (collagen contraction) pulling theory

Answer 19

FOR
▪ Collagen can contract in vitro

AGAINST
▪ No proof that collagen contracts in vivo

Question 20

Evidence FOR/AGAINST: PDL fibres (fibroblast migration/contraction) pulling theory

Answer 20

▪ 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

Question 21

Summary of eruption theories

Answer 21

▪ 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 22

Cellular mechanisms during resorption of the primary tooth

Answer 22

▪ 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

Question 23

Describe how bloodless eruption occurs

Answer 23

Question 24

Post-eruptive movements

Answer 24

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