(1) Anatomy and Histology of the Periodontium - cementum Flashcards
What is cementum?
thin layer of calcified tissue covering radicular dentine.
How thick is cementum at the cervical?
10-15µm in thickness.
How thick is cementum cervically?
50-200µm thick
How thick could cementum be at the root apex?
600µm
What does cementum adhere to?
Adheres to dentine and to the periodontal ligament.
What is the name of the dentin at the root?
redicular dentin
What cementum capable of doing?
repair and regeneration
When is cementum formed?
Formed throughout life
Can the cementum detach and reattach to the periodontal ligament?
allowing re- attachment of the periodontal ligament.
as it is formed throughout life
What structure is cementum similar to?
bone
What is the difference between bone and cementum composition?
Similar to bone in composition, but not innervated and avascular
What colour is cementum?
pale yellow and has a dull surface
Where can cementum be easily abraded?
cervically
e.g. gum recession can expose cementum
What are the 2 types of cementum?
cellular
acellular
What does cellular cementum contain?
cementocytes
What does acellular cementum cover?
dentine
Where is cellular cementum located?
apical area
inter-radicular areas overlying acellular cementum
In general what cementum forms first?
acellular
closest to the dentin
What type of section is this?
decalcified
see cells
At what pace does cementum form?
slowly
Name structures A-D and what do the black and white arrows point to?
A) Acellular cementum.
B) Cellular cementum. C) Pre-cementum.
D) Periodontal ligament.
White arrows point to cementocytes.
Black arrows point to cementoblasts.
How do you define acellular cementum?
lines in it from slow growth
shown by A
acellular is always closest to the dentin
How do you differentiate cellular and acellular cementum ?
the cellular cementum has cementocytes
shown by white arrows
Where do cementocytes live?
in cellular cementum
Cementocytes live in the lacunae of cementum,
What is C?
C = pre-cementum
newly formed cementum, not calcified yet
What is black arrow pointing to?
cementoblasts
line the pre-cementum
will form the cementum
What happens when cementoblasts get trapped in their own secretion?
they become calcified and become cementocytes
white arrow
What section is this an example of?
ground section, cementocytes appear black in a ground section.
What type of cementum is shown here?
cellular, decalcified
What is the black substance here?
if there is a space, e.g. lacunae it will appear black
due to the light reflection
In cementum, what direction do the canaliculi of cementum face?
one direction
both the cementoblasts and cementocytes
What is a canaliculi?
a canaliculus is a small passageway
Where do the nutrients for the cementocytes come from?
the periodontal ligament
as the cementum and dentin are unvascularised and not inervated
When the cementum become thicker and thicker, what do the cementocytes do?
they try to extend their processes through longer and longer canaliculi, which are projected in one direction.
towards the periodontium
What side is the periodontal ligament?
to the left
tooth to the right
shown by the direction of the canaliculi
What is the most important function of cementum?
Attachment to the periodontal ligament?
What type of section is this?
decalcified
What type of cementum is attached to the periodontal ligament?
acellular
Name structures A-C
A = enamel space (decalcified enamel)
B= dentin
C = acellular cementum (cervical so thin)
Name structure A
periodontal ligament
What is the periodontal ligament composed of?
principal fibres
What do the fibres of the periodontal ligament connect?
the alveolar bone and the cementum
What are the periodontal ligament fibres called when they insert into the alveolar bone?
sharpeys fibres
How do the fibres of the periodontal ligament insert into the cementum?
precementum forms before it is calcified, the principal fibres insert into the cementum which later becomes fully calcified and anchors Sharpeys fibres into the cementum
What side of the periodontal ligament has coarser sharpeys fibres?
the ones inserted into the alveolar bone
Name structures A-C and the black and white arrows
decalcified section
A = Dentine.
B= Periodontal ligament.
C= Alveolar bone
White arrows point to acellular cementum.
Black arrows point to Sharpey’s fibres in alveolar bone
