Dentistry Flashcards
How do the teeth begin to develop in utero?
3 clear lines in mouth:
Lips - caudal
Labiogingival groove - space between teeth and cheeks
Dental ridge - thickened oral epithelium
How does a tooth develop?
Bud stage: proliferation of oral epithelium and mesenchyme. Thickening of dental ridge by mesenchymal cells.
Cap stage: epithelial bud enlarges, mesenchymal cells gather to form dental mesenchyme/dental bud, a transient signal center (enamel knot) forms in the epithelium.
Early bell stage: tooth germ consists of all three components (enamel organ, dental papilla and dental follicle).
Late bell stage: amelogenesis and odontogenesis, forms the dentine for the root and ename oaround tooth.
Tooth maturation: a mature tooth is a complex of enamel, dentin and dental pulp with periodontum.
What happens to the dental bud?
The dental bud expands forming the enamel organ. This surrounds the dental papilla (mesenchymal neural crest cells)
Together this forms the deciduous tooth
How do adult teeth get formed?
A small primordium of permanent tooth is formed by a small mass of neural crest cells budding off
What differentation occurs in the enamel organ/dental papilla?
Inner layer of enamel organ - ameloblasts
Dental papillae - odontoblasts
What are ameloblasts?
They form enamel, and are gradually replaced as time moves on
What are odontoblasts?
They form dentine, and are replaced by said dentine
What are cementoblasts?
They produce cementum, which joins tooth to root
What are the signals that develop a diastema?
FGF-3 and -4
BMP-2, and -4 also seem
How does a temporary tooth come through?
Erupts before root is formed, leading some space. The epithelium is continuous with gums on eruption and is gradually worn down
How does a permanent tooth come through?
Moves into the socket left from the temporary tooth. Increasing pressure on said temporary tooth. This resorbs the root of the temporary tooth and is eventually shed.
The permanent tooth moves in through metabolic activity pulling on the periodontal ligament.
What is a polyphydont?
Replace teeth continuously and have a reserve of ameloblasts
What is a monophydont?
One set of teeth for entire life with singple plantation with capacity to grow continuously.
This is from the incorportation of the stem cell reservoir in the labial cervical loop.
What is a diphydont?
Two sets of teeth: deciduous and permanent.
What is the general structure of a tooth?
Crown - tooth above gingiva and meets roots at cemento-enamel junction
Roots - 1+, angle is celled furcation angle and have a foramen for nerves, BV etc
What are the variations in the root foramen?
Single - humans
Multiple canal delta - cats/dogs
Open - herbivores - pem - ruminants or close eventually - horses
What is enamel?
96% inorganic hydroxyapatite
4% water
Fibrous organic material
Formed by ameloblasts, needs enamelins and amelogenins.
Hardest biological material in the body but not replaced.
Thomes Fibres - projections into unmineralised enamel
What is dentine?
70% inorganic hydroxyapatite
30% water, collagen and mucopolysaccharide
Dentine tubules extending from external surface to the pulp (30-40k/mm2)
Formed by odontoblasts, produced continously
What are the three types of dentine?
Primary - forms before tooth eruption
Secondary - after eruption, from odontoblasts living in the pulp and developed as layers
Tertiary - after trauma, with fewer tubules and darkened in colour
What is pulp?
Living tissue in pulp and root canals, giving teeth its senstivity.
Contains ameloblasts, odontoblasts, collagen, nerves, lymph and blood vessels.
-odontoblasts line cavity and branch out into the dentine tubules
Enter via apical delta and accessory canals
What does physical trauma to pulp cause?
Bruising, haemorrhage or pulpitis
When does pulp necrosis cause?
Over heating from polishing and scaling
What does a loss of blood supply cause?
Iscaemic necrosis
What is gingiva?
Adheres tooth to the alveolar socket
