What is the periodontium?
the periodontium is the tissues surrounding and supporting the teeth
What does the periodontal tissues consist of
Cementum
Gingiva
Alveolar bone
Periodontal ligament
What are the functions of the periodontium
Retaining the tooth in its socket
Resisting masticatory loads and transferring them to the bone
As a defensive barrier protecting tissues against threats from the oral environment
What is the junctional epithelium
The physical barrier separating the body tissues from the oral environment
Why is the epithelial attachment in the oral environment unique
It is the only breach in the body’s surface
What is cementum
Cementum is a bone like layer of mineralized tissue which is deposited incrementally on the surface of the root
How is cementum similar to bone
Both have a collagen matrix
Both have a lamellar arrangement
How is cementum different to bone
Cementum has a parallel lamellar arrangement whereas bone has a radial lamellar arrangement
What does cementum cover
root dentine
What does cementum provide attachment for
some periodontal fibres
What is cementum laid down by
cementoblasts
Describe cellular cementum
Contains cementocytes
Later formed
Present in the apical part of the root and furcation regions
Covers acellular cementum
Describe acellular cementum
No cells within it
Usually adjacent to dentine
First formed
Fibres of the PDL terminate here (sharpey’s fibres)
Why is the presence of cellular/acellular cementum clinically relevant?
the responses to treatment will be different and so success rates of treatment is linked to the presence of acellular and cellular cementum
what are the alternative classifications of cementum based on the histological differences
acellular extrinsic fibre cementum
cellular intrinsic fibre cementum
describe acellular extrinsic fibre cementum
has collagen fibres from the PDL - sharpey’s fibres
present on cervical 2/3 of the root
why is acellular extrinsic fibre cementum more successful when it comes to regeneration
it has the ability to produce anchorage which is relevant to the treatment of periodontitis
describe cellular, intrinsic fibre cementum
no sharpey’s fibres
intrinsic collagen fibres parallel to surface
has no role in tooth attachment
may represent a transitional form
what makes alveolar bone different to normal bone
it is dependent for its development and persistence upon the presence of tooth
what does the cortical plate form?
the inner lining of tooth socket
what does the cancellous bone contain
marrow
blood vessels, nerves, lymph etc
what are volksman canals
they are small openings which supply the periodontal ligament with nutrients
what does the periodontal ligament contain
cells extracellular matrix fibres nerves blood vessels
what makes the extracellular matrix special
behaves as a viscoelastic gel - gives it capacity to return to its original shape
what is the extracellular matrix made up of
hyaluronate GAGs
glycoproteins
proteoglycans
what are the glycoproteins in the PDL matrix
fibronectin
what are the proteoglycans in the PDL matrix
proteodermatan sulphate
chondroitin/dermatin SO4 hybrid
what are the cells in the PDL
fibroblasts cementoblasts osteoclasts cementoclasts epithelial cells defence cells
what do fibroblasts do in the PDL
they generate the infrastructure and upkeep it
what are the epithelial cells in the PDL
cell rests (or debris) of malassez
what are cell rests of malassez
they are part of the periodontal ligament cells around a tooth
they are discrete clusters of residual cells from hertwig’s epithelial tooth sheath that did not completely disappear
what are the sensory nerves in the PDL
mechanoreceptors
Nociceptors
what are the mechanoreceptors in the PDL
Abeta and Adelta
they are rapidly or slowly adapting
what do the mechanoreceptors in the PDL provide
proprioception; chewing control
what are the nociceptors in the PDL
Adelta and C fibres
what do the nociceptors in the PDL provide
protective reflexes
inhibit jaw elevator motor neurons (jaw jerk reflex)
what do the autonomous (sympathetic) nerves allow in the PDL
blood vessel control
what is the blood supply of the PDL
inferior and superior alveolar arteries which pass into the PDL from alveolar bone
what is the blood supply of the gingiva
lingual and palatine arteries
what are the 2 types of periodontal fibres
true periodontal ligament
gingival ligament
Where are the gingival ligament fibres found
they are fibres mainly above the alveolar crest including free gingival fibres
what is the periodontal ligament
it attaches tooth to jaw
transmits biting forces to alveolar bone
organized (regular) connective tissue
what is the width of the periodontal ligament
approximately 0.2mm
what are the PDL fibres made up of
collagen
oxytalan
what types of collagen make up the PDL fibres
type 1 and 3
what is the function of collagen in the PDL fibres
to support the tooth; load bearing
what do the principal fibre group consist of
alveolodental ligament
interdental ligament
what are the different fibres in the alveolo-dental ligament
alveolar crest horizontal oblique apical interradicular (multi-rooted teeth)
what do the alveolar crest fibres do
they resist vertical and intrusive forces
what do the horizontal fibres do
resist horizontal and tipping forces
what do the oblique fibres do
resist vertical and intrusive forces
what do the apical fibres do
resist vertical forces
what do the interradicular fibres do
resist vertical and lateral movement
what makes up the interdental ligament
transeptal fibres
what do transeptal fibres do
resist tooth separation and connect tooth to tooth
what do the gingival fibre group do
they support the free gingiva
where are the gingival fibre group present
lamina propria in marginal gingiva
what are the 4 fibres in the gingival fibre group
dentogingival
alveologingival
dento-periosteal
circular
where are the dentogingival fibres
they extend from the cervical cementum into the free and attached gingiva
where are the alveoli gingival fibres
extend from the alveolar crest into the gingiva
where are the dento-periosteal fibres
extend from the cervical cementum into the alveolar crest
where are the circular fibres
surround the teeth
what are the two margins visible on the gingiva
gingival margin
muco-gingival margin
what is the gingiva not attached to any bone called
free gingiva
what is the gingiva attached to bone called
attached gingiva
what does junctional epithelia provide
attachment for the gingiva to the tooth in the cervical area and forms the epithelial lined floor of the gingival sulcus
how does junctional epithelium connect to enamel
through hemidesmosomes
how do junctional epithelium connect to each other
desmosomes
what is the interdental col
the area between two teeth that is protected by the contact point
what is special about the epithelium in col
it is not keratinized due to no masticatory forces
what type of forces is the PDL mostly subjected to
intrusive:
- mastication
- swallowing
- speech
- parafunction
what type of forces are the teeth rarely subjected to
extrusive and horizontal forces:
- sticky foods
- orthodontic forces
