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PERIODONTAL LIGAMENT
by
Helen R. Hallare, DDM
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P E R I O D O N T A L
L I G A M E N T
Dense fibrousconnective tissueattaching the tooth to thealveolar bone
Functionto supportthe tooth in the alveolus& to maintain thephysiologic relationbetween the cementumand bone
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Characteristics
Its fibers are inserted into the alveolar bone and
into the cementum
Its quite cellular, well innervated, vascular and
contains epithelial aggregates
It occupies the narrow space between the
calcified surfaces of the cementum and alveolus
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Is detectable in radiographsa radioluscent lineparallel to the root surface (lamina dura inradiographsradiodense line that represents thealveolar bone proper
Varies in thickness0.1 - 0.25 mm depending
on age, stage of eruption of the tooth andfunctional characteristics
Thicker in adolescents than in older individuals
Characteristics
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Teeth without antagonists would have thinner
ligaments; with impacted teeth theyre eventhinner
Under normal function tends to be narrowest
near the middle of the root and wider near the
apex
Characteristics
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PRINCIPAL FIBER GROUPS
1. Alveolar Crest Group
radiate from the crest of the alveolar process and are
attached to the cervical cementum Attached to the cementum just below the cemento-
enamel junction and running downward and outward to
insert into the rim of the alveolus
function is to resist vertical and intrusive force and
anchor the tooth to the alveolus
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PRINCIPAL FIBER GROUPS
2. Horizontal Fiber Group
run at right angles to the long axis of the tooth,
from cementum to bone near the crest
immediately apical to the alveolar crest at right
angles to the axis of the tooth
They function to resist horizontal or lateral
pressures applied to the tooth crown
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PRINCIPAL FIBER GROUPS
3. Apical Fiber Group
radiate from the apical region of the tooth to the
surrounding bone
Radiating from the cementum around the apex
of the root of the bone, forming the base of the
socket
It prevents vestibulo-oral tipping
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PRINCIPAL FIBER GROUPS
4. Oblique Fiber Group
are the most numerous and constitute the main
support of the tooth
running from cementum in an oblique direction
to insert into bone coronally
Function is to sustain the occlusal forces, that is
to resist intrusive masticatory forces
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PRINCIPAL FIBER GROUPS
5. Interradicular Fiber Group
Found only between roots of multirooted tooth
and running from the cementum into the boneforming the crest of the interradicular septum
It resists tipping and torque
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Other Fibers
1. Indifferent Fiber Plexus
group appears to course parallel to the root
surface, forming a loose intersecting network
May also be incorporated into the mineralized
matrices
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Other Fibers
2. Oxytalan Fibers
is found interspersed among the collagen fibers,
and is morphologically similar to those ingingiva
run in an occluso-apical direction associated
with blood vessels and nerve fibers They are found more often on the cemental
than on the bony side of the ligament
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Other Fibers
3. Elastic Fibers
this group of fibers are scarce
They are confined to the loose connective tissue
surrounding neurovascular channels
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CELLS
The main function of periodontal ligamentcells is to maintain the normal organization
of the fiber system by synthesizing newfibers and remove old ones
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Fibroblasts
They are shaped like spindles or flat disks andhave long ovoid nuclei and numerous
cytoplasmic processes of various lengths make up the major cellular population of the
ligament (principal cells of the periodontalligament)
Their function is to synthesize collagen, whichaggregates into fibrils and fibers extracellularly
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Cementoblasts
Are observed during the phases of active
deposition of cellular cementum
are ovoid to cuboidal shape and the cytoplasm isbasophilic
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Osteoblasts
Found in the peripheral part of the periodontal
ligament adjacent to bone
Appear only in areas of the periodontal spacewhere alveolar bone is deposited
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Osteoclasts and Odontoclasts
They are multinucleated cells that are
morphologically and functionally
indistinguishable
Osteoclasts work with osteoblasts to remodel
existing alveolar bone
Odontoclasts can resorb mineralized dental
tissue, including cementum
They are usually located within superficial bone
concavities the HOWSHIPS LACUNAE
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Epithelial Cells
They are commonly found in the ligament close
to cementum
They originate from Hertwigs epithelial rootsheath
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Defence Cells
They are few in disease-free
periodontal ligament
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Undifferentiated Mesenchymal Cells or
Progenitor Cells Have a perivascular location within 5
micrometers of blood vessels
A sourceof new cells for the periodontalligament
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Macrophages
Important defense cells because of their
phagocytic activity and mobility
Take up bacteria, dead cells and foreign bodies
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Leukocytes
Individual leukocytes, especially small
lymphocytes and plasma cells may appear in
periodontium when it is stressed by disease
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Vascular Supply
Its main blood supply is from the
SUPERIOR AND INFERIORALVEOLAR ARTERIES
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The periodontal blood system is
supplied from 3 sources:1. BRANCHES FROM THE DENTAL
ARTERY
2. BRANCHES OF THE INTERALVEOLARAND INTERRADICULAR ARTERIES
3. BRANCHES OF THE PERIOSTEAL
ARTERIES
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Functions of the Blood Vessels of the
Periodontal ligament1. Nutritive function.
2. Removal of cellular waste.
3. Acts as a hydraulic shock-absorbing system,
cushioning the tooth against light occlusal
forces
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Nerves
Contains both sensory and autonomic nerve endings
The sensory nerve endings are able to identify pain and
pressureextremely sensitive, able to detect minuteparticles between occluding tooth surfaces
The autonomic innervation that originates from the
superior cervical ganglion is primarily responsible for
the control of smooth muscles associated with the
periodontal vasculature
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Four types of neural termination
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1. Free nerve endings
The most frequent neural termination that
ramifies in a treelike configuration.
They are located at regular intervals along thelength of the root
Such endings are thought to be both
nociceptors and mechanoreceptors
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2. Ruffini Corpuscle
Is found around the root apex, appear dendritic
and end in terminal expansions among the
periodontal ligament fiber bundles their known physiologic function as
mechanoreceptors
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3. Coiled Ending
Found in the midregion of the periodontal
ligament whose function and ultrastructure have
not yet been determined
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4. Encapsulated Spindle Type Ending
The lowest frequency, is found associated with
the root apex and consists of spindle-like
endings surrounded by a fibrous capsule
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Functions of the Periodontal
Ligament1. Formative
2. Supportive
3. Nutritive
4. Hemostatic
5. Sensory
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The End