PERIODONTAL
LIGAMENT
Dr. Amit Wadhawan
Dr. Amit Wadhawan, Subharti Dental College, SVSU
DEFINITION
Connective tissue that surrounds the
root & connects it to the bone.
Continuous with the connective tissue of
gingiva & communicates with marrow
spaces of bone.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
GOMPHOSIS
Mammals
ANKYLOSIS
Reptiles, Pisces
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
COMPOSITION
Periodontal fibers
Cellular elements
Extracellular matrix
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
PERIODONTAL FIBERS
Principal Fibers: Collagenous in
nature, arranged in bundles & follow
a wavy course.
Sharpey’s Fibers: Terminal ends
which insert into bone & cementum.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
COLLAGEN
Protein composed of different amino acids: glycine, proline, hydroxylysine & hydroxyproline.
Synthesized by fibroblasts, chondroblasts, osteoblasts & odontoblasts.
Different types according to chemical composition, distribution, function & morphology.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
TYPES OF COLLAGEN
TYPE I - Bone
TYPE II - Cartilage
TYPE III, V - Granulation Tissue
TYPE IV,VI - Endothelial matrix
TYPE X - Hypertrophic cartilage
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
COLLAGEN SYNTHESIS
TROPOCOLLAGEN
FIBRIL
FIBER
BUNDLE
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
GROUPS OF PRINCIPAL
FIBERS
1) TRANSSEPTAL GROUP
2) ALVEOLAR CREST GROUP
3) HORIZONTAL GROUP
4) OBLIQUE GROUP
5) APICAL GROUP
6) INTERRADICULAR GROUP
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
OTHER FIBER GROUPS
Oxytalan Fibers: Contain immature
forms of elastin – oxytalan & eluanin.
Direction : Run parallel to the root
surface in a vertical direction.
Function : Regulate blood flow.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
1) Connective tissue cells: Fibroblasts,
Cementoblasts, Osteoblasts
2) Epithelial rest cells
3) Immune system cells
4) Cells associated with neurovascular
elements.
CELLULAR ELEMENTS
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
Most common cells in the Pdl.
Synthesize collagen & also
phagocytose "old" collagen fibers and
degrade them by enzyme hydrolysis –
regulate collagen turn-over.
Functions such as secretion of collagen
of different types or production of
collagenase.
FIBROBLASTS
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
1) Connective tissue cells: Fibroblasts,
Cementoblasts, Osteoblasts
2) Epithelial rest cells
3) Immune system cells
4) Cells associated with neurovascular
elements.
CELLULAR ELEMENTS
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
Osteoblasts
Osteoclasts
Cementoblasts
Odontoclasts
Seen in the cemental and osseous
surfaces of the periodontal ligament.
OTHER CELLS
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
Appear as either isolated clusters of cells or
interlacing strands.
Are considered remnants of Hertwig's root
sheath, which disintegrates during root
development.
Distributed close to the cementum throughout
the periodontal ligament & are most numerous
in the apical and cervical areas.
EPITHELIAL RESTS OF
MALASSEZ
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
CLINICAL SIGNIFICANCE
Diminish in number with age by
degenerating or undergoing calcification
to become cementicles.
Proliferate when stimulated and
participate in the formation of periapical
cysts and lateral root cysts.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
GROUND SUBSTANCE
Has a high water content (70%). 1.Proteoglycans (Glycosaminoglycans & Decorin, Biglycan),
2. Glycoproteins (Fibronectin & Laminin).
Calcified masses called cementicles, which
are adherent to or detached from the root
surfaces. May develop from :
Calcified epithelial rests;
Around small spicules of cementum or alveolar
bone traumatically displaced into the pdl;
Calcified Sharpey's fibers; &
Calcified, thrombosed vessels within the pdl.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
WIDTH & SHAPE
Normal width : 0.15 – 0.25 mm
Increases during hyperfunction.
Shape : Hourglass
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
19 Dr. Amit Wadhawan, Subharti Dental College, SVSU
1) PHYSICAL FUNCTION
2) FORMATIVE & REMODELLING
FUNCTION
3) NUTRITIVE & SENSORY FUNCTION
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FUNCTIONS OF THE PERIODONTAL
LIGAMENT
Dr. Amit Wadhawan, Subharti Dental College, SVSU
1) PHYSICAL FUNCTION
1. Provision of a soft tissue "casing" to protect the vessels and nerves
2. Transmission of occlusal forces to the bone
3. Attachment of the teeth to the bone
4. Maintenance of the gingival tissues in their
proper relationship to the teeth.
5. Resistance to the impact of occlusal forces
(shock absorption) .
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
RESISTANCE TO THE IMPACT OF
OCCLUSAL FORCES
1) TENSIONAL THEORY
2) VISCOELASTIC THEORY
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
When a force is applied to the crown, the
principal fibers first unfold and straighten and
then transmit forces to the alveolar bone,
causing an elastic deformation of the bony
socket.
Finally, when the alveolar bone has reached its
limit, the load is transmitted to the basal bone.
TENSIONAL THEORY
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
Considers the displacement of the tooth to be largely controlled by fluid movements, with fibers having only a secondary role.
The extra cellular fluid passes from the pdl into the marrow spaces of bone through foramina in the cribriform plate.
These perforations are more abundant in the cervical third than in the middle and apical thirds
VISCOELASTIC THEORY
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
After depletion of tissue fluids, the fiber
bundles absorb the slack and tighten. This
leads to blood vessel stenosis.
Arterial back pressure causes ballooning of
the vessels, and passage of blood ultrafiltrates
into the tissues, thereby replenishing the
tissue fluids
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
TRANSMISSION OF OCCLUSAL
FORCES TO THE BONE
The arrangement of the principal fibers is similar to a suspension bridge or hammock.
When an axial force is applied to a tooth, a tendency toward displacement of the root into the alveolus occurs.
The oblique fibers alter their wavy, untensed pattern; assume their full length; and sustain the major part of the axial force.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
When a horizontal or tipping force is applied :
The first is within the confines of the
periodontal ligament,
the second produces a displacement of the
facial and lingual bony plates.
The tooth rotates about an axis that may
change as the force is increased.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
The apical portion of the root moves in a direction opposite to the coronal portion.
In areas of tension, the principal fiber bundles are taut rather than wavy.
In areas of pressure, the fibers are compressed, the tooth is displaced, and a corresponding distortion of bone exists in the direction of root movement
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
In single-rooted teeth, the axis of rotation is
located in the area between the apical third
and the middle third of the root .
The periodontal ligament, which is shaped
like an hourglass, is narrowest in the region
of the axis of rotation.
AXIS OF ROTATION
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
31 Dr. Amit Wadhawan, Subharti Dental College, SVSU
In multirooted teeth, the axis of rotation is
located in the bone between the roots.
In compliance with the physiologic mesial
migration of the teeth, the periodontal
ligament is thinner on the mesial root
surface than on the distal surface.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
2) FORMATIVE AND REMODELING
FUNCTION
Cells of the pdl participate in the formation and resorption of cementum and bone :
physiologic tooth movement
in the accommodation of the periodontium to occlusal forces
in the repair of injuries.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
COLLAGEN TURNOVER
Radioautographic studies indicate a very
high turnover rate of collagen
The rate of collagen synthesis is twice as
fast as that in the gingiva and four times
as fast as that in the skin, as established
in the rat molar.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
3) NUTRITIONAL AND SENSORY
FUNCTIONS
The pdl supplies nutrients to the
cementum, bone, and gingiva by way
of the blood vessels and provides
lymphatic drainage .
The pdl is abundantly supplied with
sensory nerve fibers capable of
transmitting tactile, pressure, and pain
sensations by the trigeminal pathways.
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
Pass into the pdl from the periapical area & through channels from the alveolar bone .
Divide into single myelinated fibers.
Four types of neural termination:
1.Free endings : carry pain sensation
2.Ruffini-like mechanoreceptors, located primarily in the apical area;
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Dr. Amit Wadhawan, Subharti Dental College, SVSU
3.Coiled Meissner's corpuscles, also mechanoreceptors, found mainly in the midroot region;
4.Spindle-like endings for pressure and vibration, which after chronic periapical inflammation, tooth replantation, and occlusal trauma and around embedded teeth
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Dr. Amit Wadhawan, Subharti Dental College, SVSU