OB D4: Tooth development 3 Flashcards
what is root development driven by?
Hertwig’s epithelial root sheath
when is the root formed?
as the tooth erupts
what direction does the root proliferate ?
apically
what way does the root disintegrate?
cervically
where does the dental follicle lie?
between enamel organ and bone
what is the origin of the dental follicle?
ectomesenchyme
what forms cementum?
cementoblasts
what forms PDL collagen fibres?
fibroblasts
what forms the alveolar bone?
osteoblasts
what are the 3 layers of the dental follicle?
◦ Inner investing layer – vascular-become cementoblasts
◦ Loose connective tissue layer
◦ Outer layer – lines alveolus with bone
what happens as the tooth erupts?
More deposition as the tooth erupts. Enamel matrix proteins bind to dentine and predentine to form hyaline layer of Hopewell Smith
what are the stages of root development?
1) Hertwigs epithelial root sheath induces odontoblast formation
2) Pre-Dentine then dentine from HERS basal lamina breaks down
3) HERS cells secrete enamel matrix proteins (amelogenins) on to predestine surface
4) Enamel matrix proteins mineralise to form the hyaline layer
5) HERS disintegrates
6) Induction of follicle cells:migrate to root surface and form cemetoblasts
7) Cementoblasts secrete cementum matrix and retreat outwards
8) Cementum matrix mineralises , entrapping PDL fibres
9) Remnants of HERS form cell rests of malaise in PDL - cystic potential
where does the hyaline layer sit?
between dentine and cementum
what is the origin of the matrix from the hyaline layer?
epithelial cells -enamel matrix proteins
what is the role of the hyaline layer?
- induces cementoblast formation
- cements cementum to tooth
what is cementogenesis?
the formation of cementum
what is the cementum?
calcified connective tissue that covers the roots of the teeth, from the root sheath
what are the two types of cementogenesis?
- acellular (primary)
- cellular (secondary)
where are cementoblasts derived from?
dental follicle
what do cementoblasts do?
deposit matrix (pre cementum) :
- collagen
- ECM matrix containing GAGs and PGs
what type of cementogensis is slow to increase in thickness?
acellular
what happens to PDL collagen fibres?
become trapped in cementum and mineralise
how do root dentine and coronal dentine differ?
in bundles of collagen type I produced by root odontoblasts
what is the alveolus`/
as teeth develop bone extends around the tooth germ
where does the alveolar bone come from?
outer layer of condensed mesenchyme
what happens to the bone when the tooth erupts?
resorption of bone to allow tooth through
what does HERS cells cause?
osteogenic differentiation to form bone cells
what are gubernacular canals?
area between apex of deciduous and permanent tooth germ. Connective tissue through the alveolus bone
what is the periodontal ligament?
connective tissue located between the cementum and the alveolar bone which is part of the perdontium tissue complex participating in the support of the tooth
what does the periodontal ligament contain?
specialised connective tissue fibres that attach the mineralised tissue covering the root dentin (cementum) to the alveolar bone
what does the periodontal ligament produce?
- masses of collagen fibres
- hyaluronan
- growth factors
what controls the number of roots?
dental papilla
what is the origin pf the periodontal ligament?
fibroblast
