6-Development of the tooth Flashcards
Three main developmental layers
Ectoderm
Mesoderm
Endoderm
Mesoderm develops into
- Connective tissue
- Muscle
- Mesothelium
Ectoderm develops into
Epithelium
-CNS, PNS cells, Neural crest cells, surface ectoderm
What dental tissues develop from neural crest cells?
neural crest cells==>Ectomesenchyme==>
- Dentin
- Cementum
- PDL
- Alveolar bone
What dental tissues develop from ectoderm?
Epithelium/enamel
Endoderm(epithelium) develops into
Gut tube and it derivatives
Primary epithelial band
- day 37 of development
- proliferated epithelium at the site of future dental arches
- Split into dental and vestibular lamina
vestibular lamina
Cells enlarge then degenerate to become the vestibule.
Dental Lamina
- initial fold starting tooth development made of ectoderm(epithelium)
- develops 10 centers of proliferation
Ectomesenchyme location in initial tooth developement
Right under the fold of the dental lamina
3 main stages of tooth development and time of development
Bud stage(8-9 weeks) Cap stage (10-11 weeks) Bell stage(12-14 weeks)
Enamel organ
- Epithelium ingrowth
- Enamel
Dental papilla
Condensed ectomesenchyme
-Dentin
Dental follicle/sac
Condensed ectomesenchyme surrounding enamel organ and the dental papilla
-cementum, PDL, and alveolar bone
Dental organ or tooth germ
Enamel organ, dental papilla, and dental folicle
Bud stage
- Tooth bud grow into the ectomesenchyme.
- Form the deciduous teeth
- cells only proliferate no change in function
Cap stage
- The deep surface of the bud invaginates and becomes cap shaped.
- Peripheral cells become cuboidal and columnar
- matrix of enamel organ is increasing in amount of glycoaminoglycans
- Become hydrated and cells grow but maintain contact
Bell stage regions
1) Outer enamel epithelium
2) Stellate reticulum
3) Stratum intermedium
4) inner dental epithelium
Outer enamel epithelium
thick basement membrane separates it from ectomesnchyme
Stellate reticulum
mechanical role(protects dental tissue and produces signaling molecules)
Stratum intermedium
Flatened cells overlying inner dental epithelium.
-produces and transports proteins ti the inner dental epithelium
Inner dental epithelium
-Columnar shaped cells elongate prior to producing enamel then change polarity to secrete adjacent to the basement membrane
Cervical loop
- Inner and outer enamel epithelium meet here
- Gives rise to the epithelium that will signal root development
early bell stage development
Dental and lateral lamina begin to degenerate
- Developing tooth loses connection to oral cavity
- the tooth cron assumes it final shape
Vasularization of tooth developemtn
- Enamel organ/stellate reticulum avascular
- Dental sac/follicle well vascularized
Ameloblast origin
Inner dental epithelium develop into ameloblasts
Odontoblasts origin
Outer dental papillae develop into odontoblasts
What is starts to work first(ameloblasts or odontoblasts)
Odontoblasts
-amelo- and odontoblasts signal each other to develop normally
Inner enamel epithelium(late cap stage)
Mitotic activity will cease when dentin starts being produced
-Some ectomesenchyme cells can become odontoblasts due to pre-ameloblast
Dentin formation
Pre ameloblast signal cells of the dental papilla into odontoblasts
- Odontoblasts secrete predentin that cacifies into dentin in ~ 1 day
- As calcification occurs the odontoblasts move towards the papilla
Odontoblasts
-Have long processes that span the dentin forming dentinal tubules/canaliculi
Dentin sensitivity theories
1) Nerve runs with the odontoblast processes
2) odontoblast act as a receptor
3) fluid movement stimulates receptors in the pulp
mineralization of enamel
- produced when ameloblasts touched by dentin
- Mineralizes almost immediately
Where do ameloblasts get nourishment?
Blood vessels in dental papilla and surrounding the enamel organ
Stellate reticulum collapses and brings peripheral blood vessels closer to active site of ameloblasts
Where does development start and continue?
Ameloblast and odontoblast produce their respective secretions ameloblast moivng outward odontoblasts move inward creating DEJ
What happens to ameloblasts after they finish enamel production?
they form the reduced dental epithelium with stratum intermedium, stellate reticulum and outer enamel epithelium
Dental follicle
develop supporting tissue of the tooth like cementoblast (create cementum), PDL
PDL(Periodontal ligament)
- derived from dental follicle
- located between alveolar bone and cementum
- CT w/ type I collagen
Tooth eruption
Bone overlying the tooth is resorbed, CT over the tooth breaks down in advance.
Reduced enamel epithelium and oral epithelium fuse
-central epithelial cells degenerate
-Dentinogingival junction formed
