the normal periodontium pdl
TRANSCRIPT
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The Normal PeriodontiumIIThe Periodontal Ligaments
Periodontology 1
DENT 371
Dr. Hisham Al-Shorman, PhD
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The periodontium
Gingiva
Periodontal ligaments
Cementum
Alveolar bone
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Physically small,functionally important
Subjected to
continuous mechanical
loading
High turnover rate
Periodont
al
Ligament
The Periodontal Ligament
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Composed of:
Fibers
Cells
ECM
Nerves
blood & lymphaticvessels
The Periodontal Ligament
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Fibers
Most important are the
principal fibers Other fibres are
immature elastic fibres:
Oxytalan Eluanin
Indifferent fiber plexus
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Principal fibres Type I and III collagen :
fibrils form fibers
In type I collagen: fibers
are arranged in bundles
Follow a wavy course
Terminal portionsinserted into cementum
and bone: Sharpeys
fibres
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Fibers
Mechanical strength of PDL is derived from
the molecular structure of type I collagen
AND its arrangementinto fibers
Tensile strength > steel
Unique in that they connect 2 mineralized
tissues
Resemble a stretched fishing net
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Groups of fibres
Transseptal group
Connect adjacent teeth
Alveolar crest group
Resist extrusion, lateral
movements
Horizontal group
Resist lateral movements
Oblique group
Receive the bulk of vertical
forces
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Apical group
Resist intrusion &
extrusion
Inter-radicular group
Furcation areas of multi-
rooted teeth
Groups of fibres
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The PDL is derived from ectomesenchymal cells of
the dental follicle
Sharpeys fibres start to form before cementum and
alveolar bone are mineralised
Fibroblasts produce tropocollagen molecules,
which aggregate into microfibrils, that are packed
together to form fibrils. Fibrils aggregate together
to form fibres, and fibres aggregate to form
bundles. Collagen fibrils are cross-striated
Formation of Principal Fibres
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Collagen Fiber Bundles
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Sharpeys fibers
At insertion, PDL fibers are fully or
partially mineralized
High levels of non-collagenous proteins,
such as osteopontin
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Cells
C.T cells:
Fibroblasts, Osteoblasts, Cementoblasts
Osteoclasts, odonoclasts
Defence cells:
macrophages, mast cells, eosinophils
Sensory cells
Epithelial rests of Malassez:
remnants of HERS
Undifferentiated Cells
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The Fibroblast
The most common cell in
PDL
Formation & remodeling ofPDL fibers
Highly dynamic cell
Their long axis is orientedparallel to direction of
collagen fibers
Signals are partly
mediated by forces
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Epithelial Rests of Malassez
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Ground Substance
60% of PDL by volume
Water (70%)
Glycoproteins: fibronectin, laminin
Glycosaminogycans: hyalurnic acid,
proteoglycans
May contain cementicles
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Functions of PDL
Supportive functionattaches the tooth to
the bony socket and suspends the tooth so
it does not grind on the bone duringchewing
Sensory functiontransmits tactile
pressure and pain sensationsNutritive functionhas blood vessels that
provide nutrients to the cementum and the
bone
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Functions of PDL
Formative functioncontains
cementoblasts that produce the cementum
throughout the life of the tooth
Resorptive functioncontains osteoclasts
that can resorb the bone and the cementum
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Periodontal Ligament Space
Variable in width, (average 0.2 mm)
Reduced in:
Unerupted & non-functional teeth
With age
In permanent teeth
Increased with:
Heavy occlusal stress
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Thank you