Embryology of the tooth

Question 1

what are tooth development based on?

Answer 1

overlying oral epith and the underlying mesenchyme derived from the neural crest cells

Question 2

Dental lamina formation stage

Answer 2

6th week
basal layer of the oral epith lining the upper and lower jaw

8th week
lamina grows into the neural crest mesenchyme = dental bud (10 each jaw)

10th week
buds invaginate resulting into the capping stage

Question 3

Capping stage

Answer 3

outer layer - outer dental epith
inner layer - inner dental epith
stellate retinaculum - central core of loosely woven tissue
-at this stage the dental papilla arises form the mesenchyme of the neural crest and proliferate into the enamel organ

Question 4

Bells stage

Answer 4

at 3 month
- dental papilla invagination deepens –> bell shape
1. dental papilla mesenchyme cells –> odontoblasts to form dentin
- Form tomes fibers (dental processes –> dentin layer thicken and the odontoblasts will retreat into the papilla
*provide predentin
- remaining cells of the papilla form the Pulp

Question 5

Bells stage pt 2

Answer 5

inner dental epithelium will diff into ameloblasts –> enamel
- enamel knot (clusters of the cells) ; signaling center for the early development of the tooth ( diff of the dental cap into enamel organ)
Dental cuticle- enamel thickens and the ameoblasts retreat into the stellate retinaculum

ameloblasts - odontoblasts - dentin - enamel

Question 6

Root formation

Answer 6

Both layer of dental epith penetrate into the underlying mesnchyme cells –> epith root sheath (Hartwigs sheath)
continuation of the dentin causes the narrowing of the pulp chamber = canal with the vessels and nerves

Question 7

Cementum formation

Answer 7

dental –> condensation of the mesenchyme cells surrounding the primordial tooth
- inner sac diif into cementoblasts –> cementum (specialized bone)
- outer sac diff into the periodontal ligament (hold the tooth and shock absorber)

Question 8

Dentition

Answer 8

prenatal - tooth crown
birth - 4 years - milk teeth and the finishing root
6-12 y - mixed dentition

Question 9

Deciduous teeth

Answer 9

6-24 month
Central incisors, lat incisors, first molar, canines, second molar
mandibular before the maxillary
–> finished at 33 month
root reabsorption by the osteoclasts and sheds forming the permanent tooth

Question 10

Permanent tooth

Answer 10

Bud grows at the 3rd month but remains dormant until 6 year
- bud outgrows the dental lamina and push the milk teeth
incisors, canines, premolar - deciduous predecessors
molar - no deciduous predecessors