Tooth and jaw development Flashcards
On an x-ray what are the first visible signs of a developing tooth
Appear as a number of snow capped peaks
What happens to a tooth as it begins to erupt?
The roots start to grown with very open apical ends
Why can we not see anything on an xray before the snow capped peaks even though the tooth started developing before that?
As there is no mineral involved I early development of a tooth
Name the 3 main developmental processes of tooth formation
- Determination- of position and morphology
- Initiation
- Control- of morphology and histodifferentiation
What is the aim fo the determination process of tooth development?
To map out where teeth will grow in the mouth and which teeth will grow where
Morphology and position
How is tooth development controlled
Via ectodermal and mesenvymal interactions
What can interactions between ectodermal and mesenchymal tissue lead to
can up or downregulate:
- Proliferation
- Differentiation
What happens if ectodermal/ mesenchymal interactions affects proliferation?
Morphogenesis occurs
What is morphogenesis?
Formation of crown and root shape
What happens if ectodermal/ mesenchymal interactions affects differentiation?
Histodifferentation occurs which leads to tissue formation
What is histodifferentiation
The formation of distinct cell populations
Name the 3 morphogenic field
- Incisor field
- Canine field
- Molar field
What does the ectomesencyme control
What type of tissue will form where and the morphology of the tooth
List the recombination experiments that showed the ectomesenchyme controls morphology
Enzymatic separation of the ectoderm and the mesenchyme in both developing molars and canines
They then swapped the mesenchyme tissue so that the molar ectoderm now had canine mesenchyme and canine ectoderm had molar mesenchyme
The result was a canine tooth with molar morphology and molar tooth with canine morphology
State the initial stage of tooth development
The primary epithelial band splits into vestibular lamina and dental lamina
List the stages of of tooth formation once the dental lamina has formed
- Bud stage
- Cap stage
- Bell stage early
- Bell stage late
- Root development
What is significant about the late bell stage
It marks the point at which the first mineral is deposited out the cusp of the tooth
Thus the tooth is first visible at this point on an xray
What does the primary epithelial band determine
It maps out where the upper and lower dental arches will form
As the tooth buds continue to develop what else is happening at the same time?
A plate of bone is forming below the tooth germ- this is the lateral plate of the mandible/ maxilla
Where and how does the bone of the jaw form?
The bone of the jaw forms denovo within the mesenchyme
eventually a second medial plate of bone ill develop to form a trough where the tooth germ is contained
What is bone formation in the mesenchyme called?
Intramembranous bone formation
Name the cartilage found on the mandible
Meckel’s cartridge
What happens to Meckel’s cartridge during formation
It plays no direct part in the formation of the main body of the mandible
It eventually disappears and remnants of it contribute to ear ossicles and the speno-mandibular ligament.
What happens to the trough of bone where the tooth germ is contained?
it will become sub divided by cross plates of bone to form the individual tickets
