3 Periodontal Ligament

7/31/2019 3 Periodontal Ligament

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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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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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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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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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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

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3 Periodontal Ligament