Understanding the Periodontal Ligament

CONTENTS
• Introduction
• Development
• Histology
• Pathological consideration
• Clinical consideration
• Conclusion
• References

INTRODUCTION
• The PDL is a layer of dense fibrous
connective tissue between the tooth root
(cementum) and the alveolar bone.
• Provide support , attachment, nutrition,
synthesis, protection & propioception.
ORAL ANATOMY, HISTOLOGY AND EMBRYOLOGY BY BERKOVITZ pg 180

• Pdl width ranges from 0.15 to 0.38mm
• Pdl is hour glass in shape
• Thinnest being at middle third of root
• Thickness of the Pdl reduces with age
Ten Cate's Oral Histology: Development, Structure, and Function pg no. 256

• Pdl space appear radiolucent space of 0.4 to
1.5mm on radiograph
• Pdl space is decreased in non functional
unerupted teeth and increased in heavy
occlusal stress area.
• Pdl space of permanent teeth is narrower
than deciduous teeth.
Ten Cate's Oral Histology: Development, Structure, and Function pg no. 256

DEVELOPMENTOFPDL
• Begin with root formation ,prior to tooth
eruption
• Continues proliferation of the inner and
external enamel epithelium forms cervical
loop of tooth bud.
• This sheath grows apically, in the form of
HERS between dental papilla and dental
follicle.
ORBANS ORAL HISTOLOGY AND EMBRYOLOGY (12TH ED) pg no. 156

• HERS forms a circumferential structures
encompassing dental papilla, separating it
externally from dental follicle cells.
• Dental follicle cells located between
epithelial root sheath and alveolar bone are
composed of two subpopulation
• Mesenchymal cells of dental follicle
proper
• Perifollicular mesenchyme.

• Mesenchymal cells are bounded by dental
follicle and developing alveolar bone are
stellate shaped , small and randomly
oriented .
• Perifollicular cells are more widely
separated , contain euchromatic nucleus,
very little cytoplasm.
• Long thin cytoplasmic process.

• As the root formation progresses ,cells of
perifollicular mesenchyme gain polarity
and cellular volume & their synthetic
activity increases.
• As a result, there is active synthesis and
deposition of collagen fibrils and GAG in
developing PDL .

• The developing PDL and mature PDL
contain undifferentiated stem cells which
has potential to differentiate into
osteoblasts, cementoblasts & fibroblasts.

• Immediately before tooth eruption ,active
fibroblast adjacent to cementum of coronal
third of root, appears to align themselves
in oblique direction to long axis of tooth .
• These act as the precursors of the alveolar
crest fiber bundle group.
ORBANS ORAL HISTOLOGY AND EMBRYOLOGY (12TH ED) pg no. 156-7

• On examination of root surface reveals fine
brush like fibers extending from
cementum.
• Later , similar fibers are observed on
adjacent osseous surface of developing
alveolar process.
• Both set of fibers, continue to elongate
towards each other , ultimately to meet
each other as covalent bonding and cross
linking of individual collagen molecular
units occur. ORBANS ORAL HISTOLOGY AND EMBRYOLOGY (12TH ED) pg no. 156-7

• By the time of first occlusal contact of tooth
with its anatogonist.
• Horizontal group is almost completely
developed (coronal third)
• Oblique fibers are still being formed
(middle third)
• With the formation of apical fiber group
definitive PDL architecture is established.

PERIODONTAL
LIGAMENT
CELLS
FIBERS
GROUND
SUBSTANCE

SYNTHETICCELLS
• Transcribe RNA
• Synthesize ribosomes in nucleolus
• Transport them to cytoplasm
• Increase its complement of RER
• Golgi membranes for translation and
transport of the protein
• Means to produce adequate supply of
energy

FIBROBLASTS
• Principal cells of PDL
• Origin in part from ectomesenchyme of
investing layer of dental papilla & dental
follicle.
• Is different when compared to other cells
in connective tissue.

• It is believed that PDL contain variety of
fibroblast cell population with different
functional characteristics.
• Responsible for formation & remodeling
of PDL Fibers

OSTEOBLAST
• Bone forming cell lining the tooth socket.
• Basophilic appearance due to presence of
increased RER
• Active osteoblast contain extensive rough
endoplasmic reticulum
• Cells contact one another by
desmosomes .

CEMENTOBLAST
• Line the surface of cementum
• Rich in cytoplasm & have large nuclei
• Cells depositing acellular cementum do
not prominent cytoplasmic process
• Cells depositing cellular cementum
exhibit
abundant basophilic cytoplasm and
cytoplasmic process.

Fibroblast
• These cells show rapid degradation of
collagen by fibroblast phagocytosis.
• The degradation of collagen may be
expected to occur as a result of
extracellular events and intracellular
events.

OSTEOCLAST
• Cells that resorb bone and tend to be large
multinucleated.
• Howship’s lacunae are area of concavities
formed by resorption of bone.
• The part of plasma membrane lying
adjacent to bone that is being resorbed is
raised in characteristic folds
termed as
Ruffled or Striated borders

CEMENTOCLAST
• Resemble osteoclasts
• Occassionally found in normal functioning
PDL
• Resorption of cementum occur under
certain circumstances, and in these
instances mononuclear cementoclasts /
multinucleated giant cells, often located in
Howship’s lacunae, are found on surface of
cementum.

PROGINETOR CELL
• All connective tissue ,including PDL
contain progenitors for synthetic cells that
have capacity to undergo mitotic division.
• If these are not present there would be no
cells available to replace dying cells at end
of their life span.

• Progenitor cells population appear to be in
highest concentration in location adjacent
to blood vessels.
• Exhibit some classical cytological features
of stem cells including small size,
responsiveness to stimulating factors and
slow cycle time.

• Investigators have found that ,there are
cells with characteristics of mesenchymal
stem cells capable of sustained renewal
and tissue regeneration.

EPITHELIAL CELL REST OF MALASSEZ
• Described by Malassez in 1884
• Found close to cementum
• Are the remnants of HERS
• At the time of cementum formation , the
continuous layer of epithelium that covers
surface of newly formed dentin breaks
into lace like strands

• Network, strands, islands, tube like
structure near or parallel to root surface
• These cells are abundant in furcation area.
• Involved in periodontal repair
• May proliferate to form cyst & tumor's
• Calcify to become cementicles

MAST CELLS
• Small , round having diameter about 12-
15 µm
• Often associated with blood vessel.
• Mast cell histamine plays a role in the
inflammatory reaction.
• Important role in regulating
endothelial & fibroblast cell
population.

MACROPHAGES CELLS
• Predominantly located adjacent to blood
vessel.
• Wandering type of macrophages are are
derived from blood monocyte.
• It plays dual role in PDL
1. Phagocytosing dead cells.
2. Secreting growth factors.

EOSINOPHILS
• Occasionally seen in PDL
• Capable of phagocytosis

CELLBIOLOGY
GROWTH FACTOR
CYTOKINES
•IL-1
•FGF
•PDGF
•TGF
•INTERFERON
–Γ
•MMP’S

FIBERS
• Collagen
• Reticular
• Oxytalan
• Elastic
• Indifferent Fiber
Plexus
• Secondary

COLLAGEN FIBER
• Collagen is gathered to form bundles appx
5µm in dia and are termed as principal fiber
• Subunit of collagen c/s collagen fibrils
•Type I : uniformly distributed in ligament
•Type III: 20% collagen fiber
Found in peripheral
attachment to
alveolar bone.

• Type IV &VII : associated with epithelial
cell rest & blood vessel.
• Type XII : is believed to occur only when
PDL is fully functional

•The principal fiber group is the alvelodental
ligament
•Consist of 5 fiber groups
1. Alveolar crest fibers
2. Horizontal fibers
3. Oblique fibers
4. Apical fibers
5. Interradicular fibers

Alveolarcrestgroup
• Run in oblique direction from cementum
just beneath junctional epithelium to
alveolar crest.
• Resist tilting, intrusive, extrusive ,
rotational forces.

Horizontalgroup
• Run at right angle to long axis of tooth from
cementum to alveolar bone.
• Roughly parallel to occlusal plane of the arch.
• Limited to coronal 1/4th of PDL space
• Resist horizontal & tipping force.

Obliquegroup
• Most numerous
• Occupy nearly 2/3rd of ligament
• Insert into alveolar bone at position coronal
to their attachment to cementum, resulting
in oblique direction in PD space.
• Resist vertical & intrusive forces

Apicalgroup
• Run from cementum at root tip.
• Fibers of apical group radiates through PD
space to become anchored into fundus of
bony socket.
• Resist forces of luxation , prevent root
tipping.
• Not present in incompletely
formed roots.

Interradiculargroup
• Inserted into cementum from crest of
interradicular septum in multirooted tooth.
• Resist tipping, torquing , luxation

SHARPEY’S FIBERS
• Collagen fiber are embedded into
cementum on one side & into alveolar bone
on other side of PD space .
• These embedded fibers are termed as
SHARPEY’S FIBER
• They are numerous but smaller at their
attachments into cementum
and alveolar bone.

• The mineralized part of Sharpey’s fiber in
alveolar bone appears as projecting stubs
covered with mineral cluster.
• Mineralization occur at right angle to the
long axis of fibers, indicating that in
function , the fibers are subjected to
tensional forces.
• Few Sharpey’s fiber pass uninterruptedly
through bone known as Transalveolar
fibers.

Intermediateplexus
• Earlier it was believed that , the periodontal
fiber follow a wavy course from cementum
to bone and are joined in mid region of
periodontal space giving rise to zone of
distinct appearance , called as intermediate
plexus.
• The recent concept is that, fibers cross the
entire width of PD space , but branch en
route and join neighboring fibers to form a
complex three dimensional network.

ELASTIC FIBER• MATURE ELASTIC FIBERS/ELASTIN:
Consist of microfibrillar component
surrounding the amorphous core of
elastin protein.
Observed only in walls of afferent blood
vessel.
• ELAUNIN :
Bundles of microfibrils
embedded in relatively
small amount of amorphous
elastin.

Oxytalanfibers
• Type of immature elastic fibers
• Consist of microfibrillar component only.
 0.5-2.5µm diameter
 They run in axial direction
 One embedded in cementum and other
in alveolar bone

• RETICULAR FIBER:
 Fine immature collagen fibers
 Related to basement membrane of
blood vessels & epithelial cell which
lie within PDL
• SECONDARY FIBERS:
 Represent newly formed collagenous
elements
 Relatively non directional and
randomly oriented
 These fiber appear to transverse the
PDL space corono-apically.

• INDIFFERENT FIBER PLEXUS:
 Small collagen fiber associated with large
principal fibers
 Run in all direction forming plexus

GROUNDSUBSTANCE
• Contain 70 % water and thought to be
significantly effective on tooth’s ability to
withstand stress load.
• Gel like matrix in which cellular and
fibrous component are embedded
• It accounts for 65% of the volume of PDL

• Consist of hyaluronate , GAG,
proteoglycan & glycoprotein.
• Proteoglycans are compound containing
anionic polysaccharides covalently attach
to protein core.

• 2 types of PROTEOGLYCAN :
1. Proteodermatan sulphate
2. Proteoglycan containing chondroitin
sulphate/dermatan sulphate hybrids
that has been designated PG1.
• GAG:
 Linear polymer of disaccharides
 Contain hexosamine, heparin sulfate &
hexuronic acid.

• Fibronectin:
 Promote attachment of cells to
substratum, especially to collagen
fibrils.
 Involved in cell migration & orientation.
• Tenascin:
 Commonly found in attachment zone
located near cementum & alveolar bone
 Act to transfer forces of mastication &
stresses of tooth support to specific
protein structures

STRUCTURESPRESENTINCONNECTIVETISSUE
• Blood vessels
• Lymphatics
• Cementicles
• Nerves

Bloodsupply
• Inferior & superior alveolar arteries reach
PDL from 3 sources.
1. From apical vessels that supply the
dental pulp
2. From intra alveolar vessels run
horizontal , penetrate alveolar bone to
enter PDL
3. From gingival vessel enter
PDL from coronal direction.

BLOOD VESSELS
• The PDL has some specialized feature in
vasculature namely, presence of large
number of fenestrations in capillaries and
a cervical plexus of capillary loops.
• The fenestration capillary beds have a
increased capacity for diffusion and
filteration.

LYMPHATIC DRAINAGE
• Network of lymphatic vessel following
path of blood vessel provide lymph
drainage of PDL .
• The flow is from ligament towards and
into adjacent alveolar bone.

NERVE SUPPLY

NERVES
• 2 types of nerves
1. Sensory: touch, pressure, pain,
proprioceptive sensation
2. Autonomic : associated with PDL
vessels.

CEMENTICLES
• These are the calcified bodies found in
PDL
• Remnants of HERS
• Are seen in older individuals
• They may remain free , fuse to large
calcified masses, or join to cementum
• When adherent to cementum
k/s excementoses

FUNCTIONs
• Supportive
• Sensory
• Nutritive
• Eruptive

TRAUMATICINJURIES
• Concussion
• Subluxation
• Extrusive luxation
• Intrusive luxation
• Lateral luxation
• Avulsion

CONCUSSION
• Injury to tooth supporting structure
• Without Abnormal
loosening/displacement
• Pdl changes after 1 hour of trauma
Hemorrhage
Stretched torn / compressed pdl fibers
Cell destruction & edema.
Textbook & color atlas of traumatic injuries to teeth 4th edition pg 372

CONCUSSION
• After 1 day cell free zone could be seen in
pdl , bordered by zone of inflammation.
• Marked reaction to percussion

SUBLUXATION
• Loosening of tooth without clinical or
radiographic displacement of tooth
• Laceration of PDL fibers.

EXTRUSIVELUXATION
• Peripheral displacement / partial avulsion
following axis of tooth out of socket but
without leaving socket.
• Complete rupture of pdl fibers.

EXTRUSIVELUXATION
• After 3 days – split in pdl
• After 2 weeks – newly formed collagen
fibers are seen
• After 3 weeks – pdl appears normal.

LATERALLUXATION
• Eccentric displacement of tooth.
• Increase in periodontal width space.
• Rupture / compression of PDL fibers.

INTRUSIVE LUXATION
• Central dislocaton.
• Deeper into alveolar bone
• Fracture of alveolar bone
• Decrease in PDL space
• Crushing injury to PDL

INTRUSIVE LUXATION
• After 3 mths - some show ankylosis
• Others may show surface resorption/
normal pdl

AVULSION
• Total removal of tooth from socket
• Tearing of PDL
• Some of the viable cells leaves viable PDL
on root surface.

• Cell and tissue culture solutions like
Hbss
 Saliva
Bovine milk and its variation
Green tea
Egg white
Coconut water
Braz Dent J. 2013 Sep-Oct;24(5):437-45]

ROOTRESORPTION
• Late complication of luxation injuries
• It of 3 types
1. Surface (repair related resorption)
• Occurs as a result of localized
injury to the PDL
• Self limiting and spontaneous
repair
Textbook & color atlas of traumatic injuries to teeth 4th edition pg 386-390

1. Ankylosis (replacement resorption)
• Disappearance of PD space
• Union between bone and root substance
2. Inflammatory resorption
• Apparently related to presence of
infected necrotic pulp tissue in root canal.
• Bowel shaped resorption concavities in
cementum & dentin.
• Numerous lymphocytes ,plasma cells ,
PMN leukocytes.
Textbook & color atlas of traumatic injuries to teeth 4th edition pg 386-390

TRAUMAFROMOCCLUSION
• The effect of occlusal forces on the
periodontium is influenced by the
magnitude, direction, duration, and
frequency of the forces.
• If pressure is slightly excess results in
widening of PDL
• If pressure greatly excess results in
compression and hyalinization of PDL
fiber , PDL necrosis.
Newman M. trends in clinical periodontology and implant dentistryNewman M. trends in clinical periodontology and implant dentistry

TRAUMAFROMOCCLUSION
• If tension is slightly excess elongation of
periodontal fibers
• If tension is greatly excess results in
widening of PDL , tearing of PDL.
Newman M. trends in clinical periodontology and implant dentistry

CHRONICPERIODONTITIS
• The fibers of the PDL become
disorganized, and their attachments to
either the alveolar bone proper or
cementum through Sharpey fibers are lost
because of the resorption of these two
hard dental tissue.
Illustrated Dental Embryology, Histology, and Anatomy, Bath-Balogh and Fehrenbach, Elsevier,
2011, page 184.

PERIODONTITISOBSERVEDASAMANIFESTATIONOFSYSTEMIC
DISEASES:
1. Hematologic disorders
a. Acquired neutropenia
b. Leukemias
James E. Hinrichs and georgios kotsakis Carranza’s clinical periodontology, chapter 3, 45-67.

2. Genetic disorders
a. Familial and cyclic neutropenia
b. Down syndrome
c. Leukocyte adhesion deficiency syndromes
d. Papillon–Lefèvre syndrome
e. Chédiak–Higashi syndrome
f. Histiocytosis syndromes

g. Glycogen storage disease
h. Infantile genetic agranulocytosis
i. Cohen syndrome
j. Ehlers–Danlos syndrome (types IV and VIII,
autosomal dominant)
k. Hypophosphatasia
l. Cyclical neutropenia
m. Francoies syndrome: Absence of PDL

ORGANSYSTEMSANDCONDITIONSPOSSIBLYINFLUENCEDBY
PERIODONTALINFECTION
• Cardiovascular System
• Atherosclerosis
• Coronary heart disease
• Angina
• Myocardial infarction

• Endocrine System
• Diabetes mellitus
• Reproductive System
• Preterm low birth weight infants
• Respiratory System
• Chronic obstructive pulmonary disease
• Acute bacterial pneumonia

PERIODONTAL AND PERIAPICAL ABSCESS

Features Periapical abscess Periodontal abscess
Cause Pulpal problem Periodontal Pocket
Clinically Accumulation of pus
at root of infected
tooth
Edematous red and shiny
gingiva
Radiographically Slight thickening of
PDL space
Radiolucent area at
apex of root
Discrete radiolucency on
lateral aspect of root.
Bone loss is seen
Percussion +ve on VP +ve on LP
Pulp vitality Non vital vital

ENDOPERIOLESION
• Persistent infection in the pulp tissue leads
to secondary infection and breakdown of
tissues in the periodontium.
• Conversely, severe periodontal disease
may initiate or exacerbate inflammatory
changes in the pulp tissue.
Kenneth C. Trabert and Mo K. KangCarranza’s Clinical Periodontology, Chapter 43, 470-479.

• This mutuality of infection between pulp
and periodontium is mediated through
physical routes, allowing for
communication between the two structures.
• The main and obvious route of
communication is the apical foramina.

• Retrograde periodontitis ,it represents the
periodontal tissue breakdown from an
apical to a cervical direction and is the
opposite of orthograde periodontitis that
results from a sulcular infection.
• Alternatively, lateral or accessory canals
may also be the route of periodontal and
pulpal communications.

• The third route of communication between
the periodontium and the pulp is through
the dentinal tubules.
• Also, bacterial invasion into dentinal
tubules from the periodontal pocket has
been demonstrated, suggesting that
dentinal tubules may allow pulpal
irritation from chronic periodontal
infections

CLASSIFICATION BASED ON ETIOLOGY
OF DISEASE

EFFECT OF PERIODONTAL DISEASE ON
PULP

• Atrophic changes(pulposis):
• Due to interference with blood supply
through lateral canals
• Which lead to death of pulp cells
• Resulting in fewer number of cells
• Increased collagen deposition
• Dystrophic mineralization
Seltzer & bender edi 3rdpg no. 309-314

• Inflammatory changes:
• Chronic inflammatory cells consist
primarily of lymphocytes were seen near
radicular portion of pulp at the level of
lateral canal
• Resorption:
• Frequently found sub-adjacent to
granulation of tissue overlying the roots
Seltzer & bender edi 3rdpg no. 309-314

CLASSVRESTORATION
• Supragingival margin
• Least impact on the periodontium
• Equigingival margin
• More plaque accumulation
• A periodontal viewpoint, both supragingival
and equigingival margins are well
tolerated
Babitha Nugala etal J Conserv Dent 2012 Jan-Mar; 15(1): 12–17

•Subgingival margin
•Restorative margin placement within the
biologic width is unfavorable to periodontal
health and acts as a plaque retentive factor
•A constant inflammation is created and
made worse by the patient's inability to
clean this area.
Babitha Nugala etal J Conserv Dent 2012 Jan-Mar; 15(1): 12–17

CLASSIIRESTORATIONS
• Alteration of the interproximal contact
surface entails food retention, gingival
inflammation, pocket formation, bone loss
and finally dental mobility
Syed Sirajuddin etalOpen Dent J 2015; 9: 217–222

TOOTHSEPARATION
• Slow tooth separation there is less injury to
PDL maintaining the integrity of tooth.
• Rapid tooth separation there are chances of
rupturing pdl fibers accompanied by
soreness and pain.
Textbook of Operative Dentistry By Nisha Garg, Amiit Garg pg no.205-211

INTRALIGAMENTARYANESTHESIA
• Anesthetizing only the tooth being
worked on, eliminating the usual face and
tongue numbness
• Immediately effective
• Eliminate the need for uncomfortable
injections
• Uses only a fraction of the
anesthetic drug
• 2
Hristina L etal Journal of IMAB - Annual Proceeding (Scientific Papers) 2005, vol. 11, book

ENDODONTICCLINICALCONSIDERATION
• Effect of thermal changes during
endodontic treatment
• Root canal sealers
• Root canal irrigants

EFFECTOFRISEOFTEMPERATURE
• Endodontic treatment generates heat
within the dentin of the tooth that might
be transmitted to the attachment
apparatus.
• Thermoplasticized obturation techniques
cause rise in root surface temperature.
Chauhan A et al Indian Journal of Oral Health and Research / Vol. 1 / Issue 2 / Jul-Dec 2015

ROOTCANALSEALERS
• Cytotoxicity to PDL fibroblasts
• Reduction in PDL fibroblasts
Chang MC1 et alInt Endod J. 2010 Mar;43(3):251-7
• Inhibit mitochondrial dehydrogenase
activity of PDL fibroblast .
(Lin CP J Biomed Mater Res B. Appl Biomater.2004Nov;vol.71(2):429-40)

ROOTCANALIRRIGANTS
• Inhibited protein synthesis
• Cellular cytotoxicity
• Inhibitory effect on mitochondrial activity on
human PDL cell
Chang et al ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY 447 Volume 92( 4)

CONCLUSION
• PDL is the fibrous connective tissue with
reparative ,supportive , protective &
sensory characteristic.

REFERENCES
• Orbans oral histology and embryology
(12th ed)
• Oral histology,tencate (5 th edition)
• Oral anatomy, histology and embryology:
berkovitz
• Carranza’s clinical periodontology,10th
edition
• Seltzer & bender edi 3rd
• Bakland & andreasen book of
traumatology

• Hristina L etal journal of IMAB - annual
proceeding (scientific papers) 2005, vol. 11
• Chang M. et al int endod J. 2010
mar;43(3):251-7
• Chang et al oral surgery oral medicine
oral pathology 447 volume 92, number 4
• Christoph A. Ramseier1 periodontol 2000.
2012 june ; 59(1): 185–202.

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