CFD 15 - odontogenesis 2b Flashcards
What is tooth shape determined by?
- differential rates of cell division/maturation
- NOT by forced within the papilla, however…
- signal for tooth shape from the dental papilla
- (evidence from recombination studies)
What produces the signals for tooth shape?
the dental papilla (mesenchyme)
In terms of tooth shape determination, what does the IEE do?
- IEE proliferates down to form root tissues
- certain IEE cells start to mature, and the type of tooth being formed determines how quickly they mature, and where and when they mature
i.e. incisor - one area will mature, molar - multiple areas will mature (think of cusps)
What transcription factors determine what sort of tooth is found where?
MSX-1, MSX-2, Dlx1/2, Bart-1 and Alx-3
What transcription factor MUST be switched on for tooth development to occur?
PITX2
What transcription facts are in excess out towards the edge of the jaw?
things such as Dlx-1/2 of Barx-1
What transcription facts are in excess towards the centre of the jaw?
MSX-1, MSX-2 and a bit of Alx-3
Expression of what transcription factor drives incisor development?
MSX-1
Expression of what transcription factor drives molar type development?
Barx-1 and Dlx-1/2
What happens if Dlx-1/2 is knocked out?
no maxillary molars
What happens if Barx-1 is over-expressed?
whole jaw covered in molars
If Shh gene is over-expressed, what is this a major determinant of?
where teeth will develop
- over-expressed in areas of thr dental epithelium and controls a lot of what happens within the epithelium
- doesn’t really effect what happens within the dental ectomesenchyme - this is usually left to things like Wnt
When will Wnt signalling get switched on?
at a later point during bud to cap stage
What is the importance of Wnt during the bud to cap stage?
important as tooth shape is determined between bud and cap stage- will know tooth being formed by the end of cap stage
- Wnt signalling very important during this process
What does inhibiting activity of one of the Wnt signalling pathways lead to?
the arrest of tooth morphogenesis
What can happen if Wnt is over-stimulated via use of Beta catenin?
can get stimulation in the oral epithelium (not the dental epithelium), which results in dozens of extra teeth being formed
What do secondary enamel knots lead to?
the maturation and decreasing the proliferation within the cells
What are the important growth factors in tooth development?
- BMP
- Shh: within the epithelium
- Wnt: within the mesenchyme which is going to affect the way that the cells differentiate and mineralise
When does the reduced enamel epithelium form?
when enamel formation is complete
What is the reduced enamel epithelium derived from?
- reduced ameloblasts
- other remnants of the enamel organ:
- OEE, SR, SI
When the ameloblast later, stellate reticulum, stratum intermedium, and outer enamel epithelium start to fuse, what is this now referred to as?
the reduced enamel epithelium
What does the reduced enamel epithelium secrete?
proteases that facilitate the break down of the connective tissue to form an eruption pathway during the early signalling of eruption
What do the reduced enamel epithelium and the dental follicle interact to do?
recruit monocytes that differentiate into osteoclasts, and subsequently can accelerate connective tissue degradation and bone resorption as the tooth erupts
What do the reduced enamel epithelium and dental follicle play key roles in?
bone resorption during an eruption
- the coordinated molecular mechanisms between these tissues are not well understood
What are the 3 roles of the reduced enamel epithelium?
- protection of enamel surface from:
- resorption
- prevention of cementum formation - provide an epithelial lined pathway for eruption
- forms initial junctional epithelium
What happens to the reduced enamel epithelium as the tooth moves towards eruption?
- the reduced enamel epithelium fuses with the oral cavity basal lamina
- there will be cell death, and then the reduced enamel epithelium forms the junctional epithelium
- this is probably why the junctional epithelium is quite leaky
Why is there no bleeding during tooth eruption?
due to the fusion between the different epithelial cells
What are the successional dental laminae?
- secondary dentition is going to from behind the primary dentition
- the primary tooth is forming, and the permanent tooth is also going to come off that dental lamina
What side of the primary tooth do the successional dental laminae usually go to?
usually goes to the lingual side of the tooth
- if it goes to the labial side it is known as a tooth gland lamina and it’s probably a vestige of reptilian venom glands
What dental developmental disturbances can occur during the initiation stage of tooth development?
- anodontia (teeth missing)
- supernumerary tooth/teeth (extra teeth)
What dental developmental disturbances can occur during the bud stage of tooth development?
microdontia or macrodontia
What dental developmental disturbances can occur during the cap stage of tooth development?
- Dens in dente
- fusion
- germination
What is hypodontia?
tooth loss (except third molars)
What is oligodontia?
more than 6 teeth missing
What i anodontia?
all teeth missing (extremely rare)
What is dens in dente?
- when enamel organ invaginates into the dental papilla
- commonly effects the permanent maxillary lateral incisor
What is fusion?
union of 2 adjacent teeth resulting in 1 large tooth
What is germination?
1 tooth tries to divide, giving 1 large single rooted tooth with a one pup cavity and 2 ‘teeth’
