Tooth development Flashcards
What are developmental phases of tooth development?
1) Initiation- development of tooth site along dental lamina
2) Morphogenesis- rise to tooth shape
3) Histogenesis - differentiation of cells
What do ameloblasts and odontoblasts give rise to?
Mineralised tissue
non-mineralised tissue
What is Mineralised tissue?
Dentine
ENAMEL
Cementum
What is Non-mineralised tissue?
Pulp
Periodontal tissues
What are the Stages of Tooth development?
1) Primary epithelial band at 6 weeks
2) Dental lamina formation at 7 weeks
3) Bud stage
4) Cap stage by 11th week
5) Bell stage by 14th week
6) mineralised tissue forms at 18th week
7) Hertwig’s root sheath and root formation
8) Alveolar bone and periodontal tissue formation
What does embryonic oral epithelium have?
Superficial and Basal layer
What occurs in the basal layer?
Where cells grow
What is the Adult Oral mucosa have?
Superficial Layer
Intermediate layer
Basal layer
What are superficial layer cells?
Large and flattened
What are intermediate layer cells?
start to enlarge and flatten
What are basal layer cells?
Tall columnar, actively reproducing
Where do basal cells move towards overtime?
Superficial layer
What occurs in Primary epithelial band of intra uterine life?
Multiplication of basal and superficial layer cells to increase tissue thickness
What creates primary epithelial band?
cell signalling and gene expression within cells
How is dental lamina formed at 7 weeks?
Selective Multiplication of basal layer cells only
What happens in early bud stage?
1) ovoid epithelium condensation
2) No Morpho/Histodifferentiation
What surrounds Ovoid epitheloum condensation?
Mesenchyme
What happens at Cap Stage by 11th week?
1) Histodifferentiation occurs
- Stellate reticulum
- Outer enamel epithelium
- Inner enamel epithelium
In Cap stage what are the basal cells continuous with?
Outer and Inner enamel epithelium
What is stellate reticulum?
sic star shape- nutrient role for cells of Inner/outer enamel epithelium
What happens at Bell stage at 14th week?
1) Successional lamina form
2) Morpho differentiation
3) Histodifferentiation -IEE become tall columnar cells
What develops from the successional lamina?
Permanent incisor, canine, pre molar after deciduous tooth
Where do permanent molars develop from?
Dental lamina since no deciduous teeth replaced
What is visible in Bell stage?
OEE is cervical loop- where root cementum grows from
What happens in Hertwig’s Root sheath and root formation?
Cervical loop becomes sheath
What happens at Sheath?
Root dentine and cementum formed
What is part of bell stage?
Dental sac and dental lamina form
What are both dental sac and Papilla composed of ?
Mesodermal/Mesenchymal cells
What do dental papilla cells differentiate into?
Pulp cells and odontoblast layer so pulp and dentine made
What is dental sac composed of?
layers of flattened cells
What are created from cells in dental sac?
Cementum
PDL
Some alveolar bone
When are stellate reticulum no longer present?
once dental sac formed
What happens in Dental tissue formation and late bell stage in 18th week?
Morphodifferentiation- INCISOR SHAPE
Histodifferentiation- AMELOBLAST and ODONTOBLAST develops
Alveolar bone deposited
What is amelogenesis?
Enamel formation
What are amelogenesis stages?
1/2) IEE diff. into columnar secretory cells with nucleus away from dentine
3) Ameloblast w/ initial matrix secreted
4a) Tomes process develops
4b) nucleus comes down and widens
5) Maturation phase- lose Tomes and shrink and enamel matrix removed
6) Post maturation- enamel shrink to form protective layer for enamel
Where do Ameloblasts develop from?
Inner enamel epithelium
What does ameloblast development induce?>
mesenchymal cells of dental papilla to produce ODONTOBLAST layer
What does tomes process have?
Secretory vesicles that deposit enamel matrix protein and minerals to for HAP crystals
When does Maturation phase occur?
When enamels full thickness reached
What will ameloblasts contribute to form later on tooth eruption?
Junction epithelium
What are enamel matrix proteins?
Tuftelin and Amelogenin
What is Dentinogenesis ?
Formation of DENTINE
What stimulated dentinogenesis?
Ameloblast differentiation stimulate mesodermal cell in dental papilla
What are the stages to Dentinogenesis?
1) Pre-odontoblast & daughter cell proliferate
2) pre odont. develop into columnar secretory cells
3) Basal lamina of Ameloblast degrade
4) Dentine matrix strip deposited and mineralises
What does degradal of ameloblast basal lamina cause?
allow cell signalling to odontoblast
What does cell signalling to odontoblast cause?
- Nucleus down cell
- Odontoblastic process develop
- Dentine matrix starts to be laid down
