7-Tooth Histology Flashcards
Enamel
Acellular avascular non-innervated non-dynamic de/remineralization on the surface
Which parts of teeth change?
Dentin, pulp and peridontum change
while enamel wears down
Is enamel thickness even?
No it varies along its surface
Enamel composition (general)
90-92% inorganic
1-2% organic
4-6% water
Major structural part of the enamel
enamel rod
How many enamel rods per tooth?
5-12 million
Enamel rod shape
Waavy and diameter gets 2-3x larger as it goes drom DEJ to tooth surface
and is slightly tall on one end(cross-sectionally)
They don’t have interruptions or branches
Space between the rods
Inter-rod substance aka rod sheath
Rod sheath composition
Water and trace proteins
what are the rods made of
Apatite crystals
At what angle do enamel rods meet the tooth surface and DEJ?
90˚
Amelogenesis
Formation of enamel
Where does amelogenesis start and when does it end?
Starts at DEJ and ends before tooth eruption
Dentinogenesis
Formation of dentin
Can enamel repair itself?
NOOOOO
Dentin function
Resilient support for enamel(like wood under glass) and restorations
-Most of the tooth structure
Dentin properties
Sensitive & conducttive
Very porous
very dynamic
pulp’s partner
Is enamel permeable?
Yes which is what causes stains and allow for whitening
Dentin structures
Dentinal tubules
Peritubular dentin
Intertubular dentin
Dentinal tubules structure
Can branch and communicate with other tubules
Gets smaller in diameter going from pulp to DEJ
Peritubular dentin vs intertubular dentin
Peritubular is more mineralized.
Forms outline for dentinal tubules
intertubular dentin composition
- Type I collagen
- Small hydroxyapatite crystals
- Water
What is in dentinal tubules
Water/dentinal fluid and cellular process of the odontoblasts
What is the odontoblast process called?
Tomes fiber
dentin chemistry
Heterogenous
50% inorganic(apatite crystals)
5-25% water
5-25% organic(collagen)
Primary dentin
Dentin made before eruption
Secondary dentin
Dentin is still made after eruption but slows down and is more irregular
Physiological secondary dentin
This is made slowly and continuosly with age
Reparaitive dentin
secondary dentin caused by trauma. Made in dentin and the peritubular dentin
Sclerotic dentin
When peritubular dentin gets thicker and close off.
Dentin response to insult
- Dentin is injured(reversible?)
- tubules sclerose
- reparative dentinogenesis
- pulpal inflammation
- pulp recovery or necrosis
Pulp properties
Arterioles and venules enter/leave via small foramina
no collateral circulation
no space for expansion
collagen and ground substance
defense and formative cells
sensory and motor(for vasodilation) innervation
Nerves in pullp
C, A-alpha, and A-delta fibers
-Pain only
C-fibers
Dull throbby pain
respond to inflammation
A-fibers
Respond to quick sharp pain
on the walls by the dentin and odontoblasts
Zone of Weil
Right under the odontoblast layer
Cementum
Covers clinical root -Acellular mostly fibers cellular(apical third) -hardness like bone -thickness varies -attached PDL to tooth
Supportive hard tissues
- Cenemtum
- Principle fibers
- Sharpey’s fibers
- periodontal ligament
- alveolar bone
- cortical bone
- cancellous bone
