periodontal ligament

3. Contents:
Introduction
Definition
Extent and shape
Average width
Development of PDL
Orientation of PDL fibers
Structure
Cellular elements
Biochemical composition
Ground substance

4. Collagen
Sharpeys fibers
Periodontal fibers
Functions of PDL
Blood supply
Venous drainage
Lymphatics
Nerve supply
Age changes & clinical considerations
Conclusion
References

5. INTRODUCTION

6. DEFENITION
✢The periodontal ligament is composed of complex
vascular and highly cellular connective tissue the
surrounds the tooth root and connects its to the inner
wall of the alveolar bone.(CarranzaFerrari 12th edition)
✢It is that soft, specialized CT situated between the
cementum covering the root of the tooth and bone
forming the socket wall.(A.R.Tencate )

7. ✢Soft ,richly vascular and cellular connective tissue
which surrounds the roots of the teeth and joints
the root cementum with the socket wall.
(jan lindle 5th edition)
✢The periodontal ligament occupies the periodontal
space, which is located between the cementum and
the periodontal surface of alveolar bone and extends
coronally to the most apical part of the lamina
propria of the gingiva. (orban’s 13th edition)

8. SYNONYMS
 DESMODONT
 GOMPHOSIS
 PERICEMENTUM
 DENTAL –PERIOSTEUM
 ALVEOLODENTAL LIGAMENT
 PERIODONTAL MEMBRANE.

9. Radiographic Appearance
In radiograph it appears as a radiolucent line betweeen the root and
alveolar bone.

10. Extent and shape
✢In coronal direction it extends to the most apical part of the
lamina propria of gingiva.
✢At apical foramen it continuous with dental pulp.
✢PDL has the shape of a hour glass

11. Width of PDL
✢PDLwidth rangesfrom 0.15-0.38mm.
✢Thenarrowest areais atthemid-root ( Fulcrum).Theregion atthe alveolar
crestisthewidest areafollowed bytheapicalregion
.
✢Thewidth generallyreducedin:
Non-functional teeth.
Un-eruptedteeth.
✢While increased in:
Teethsubjectedto anocclusal stresswithin the
physiological limits .
Deciduousteeth
Bone
Dentin

12. Average width
✢DEPENDINGONAGE
✢11-16yrs- 0.21mm
✢32-52yrs- 0.18mm
✢51-67yrs- 0.15mm
✢ACCORDINGTOFUNCTIONALSTATE OF
THE TISSUES
✢Timeoferuption - 0.1-0.5mm
✢At thefurcation - 0.2-0.35mm
✢Hypofunction - 0.1-0.15mm

13. Conditions Associated With Widening Of PDL
Widening of periodontal ligament around the right mandibular second
molar is evident with loss of neighboring teeth, subjecting it to heavy
occlusal trauma

14. Panoramic radiograph demonstrates generalized periodontal ligament
widening due to trauma from orthodontic forces

15. Periapical radiographs show periodontal ligament widening around maxillary
and mandibular incisors due to periodontitis.

16. Periodontal ligament widening as a result of pulpo-periapical lesion is seen
in the left mandibular second molar.

17. Panoramic reconstructed cone-beam computed radiographic image shows
chronic sclerosing osteomyelitis with periodontal ligament widening
around right mandibular canine as well as mental fistula.

18. Development Of PDL
✢ Begins with root formation & prior to tooth eruption.
✢ Continuous proliferation of internal and external enamel epithelium
forms the cervical loop of the tooth bud.
✢This sheath of epithelial cells grows apically, in the form of Hertwigs
epithelial root sheath, between dental papilla and dental follicle.
✢The sheath forms forms circumferential structure encompassing dental
papilla separating it externally from dental follicle cells.
✢ The dental follicle cells located between alveolar bone and epithelial
root sheath are composed of two sub populations
1. mesenchyme cells of the dental follicle proper
2. perifollicular mesenchyme.

19. Montage phase contrast photomicrograph of
the first molar tooth germ of a one-day-old
mouse showing the dental follicle. Notice the
inner layer of the follicle which is continuous
with the dental papilla (arrowed) around the
cervical loop, dp., dental papilla; do., dental
organ; il., inner layer; b. bone. Magnification
X450
bone
Dental epithelium
Dental follicle
Dental papilla
Perifollicular
mesenchyme

20. Development Of PDL….
As the root formation continues, cells in the peri
follicular mesenchyme gain their polarity, cellular
volume &become widely separated
Actively synthesize & deposit collagen fibrils in
developing PDL
(Grant’s 1989; Ten Cate’s 1971)
Type I collagen is secreted
Assembles as collagen bundles on the bone and
cementum surface
Establish continuity across the ligament space
-

21. Development Of Principal fibers

22. Orientation of principal fibers

23. StructureCells:
SYNTHETIC CELLS
Fibroblasts
Osteoblasts
Cementoblasts
RESORPTIVE CELLS
Osteoclasts
Fibroblasts
Cementoclasts
PROGENITOR CELLS
EPITHELIAL CELL RESTS OF MALASSEZ
DEFENSE CELLS
Mast cells
Macrophages
Eosinophils
Extra cellular substance:
FIBERS
Collagen
Elastic
Reticular
Secondry
Indifferent fiber plexus
GROUND SUBSTANCE
Glycosaminoglycan's
Proteoglycans
Glycoproteins

24. Synthetic Cells
Basic properties
✢Increased transcription of RNA and production of ribosomes which
is reflected by a large open faced or vesicular nucleus containing
prominent nucleoli.
✢Development of large quantities of RER covered by ribosomes.
✢Large amounts of golgi saccules and vesicles (seen as clear unstained
areas in light microscope).
✢Large numbers of mitochondria.
✢Abundant cytoplasm.

25. Fibroblast
Predominant cell
ORIGIN
✢Partly from ecto mesenchyme of the investing layer of dental
papilla and dental follicle.
✢Fibroblasts near cementum from ecto mesenchymal cells of
investing layer of dental papilla.
✢Fibroblast near alveolar bone from perivascular mesenchyme.
LIGHT MICROSCOPY
✢ACTIVE FIBROBLASTS- Large cells, extensive cytoplasm,abuntant
organelles,nucleus occupies large volume of cell with prominent
nucleoli.
✢ACTIVE FIBROBLASTS- Large cells with extensive network of
RER,well developed golgi apparatus.

26. Electron micrograph of
periodontal ligament of
rodent molar showing
fibroblasts oriented parallel
to the collagen fibers.
Cementum (C); socket wall
(B); nucleus
cementum
bone
nucleus

27. Fibroblasts…..
FUNCTIONS:
Secrete
Collagenandelastin(structuralconnective tissueproteins).
Proteoglycans,Glycoproteins,glycosaminogliycans(groundsubstance)
Matrixmetalloproteinases(MMPs)-enzymes.
Formationandremolding ofthePDLfibers
MaintainthewidthofthePDLfibersandthicknessofPDL
Producegrowthfactorsandcytokines(IGF-1,BMPs,PDGF,andIL-1)

28. Osteoblasts
Linesbone surface
ORIGIN
Primitive mesenchymal stem cell
LIGHT MICROSCOPY
Cuboidal inshape,with aprominentround nucleus atthe basal end ofthecell
ELECTRON MICROSCOPY
 ACTIVE CELL- abundant RER,Golgi apparatus.
FUNCTIONS
Formation ofnewbone
Regulation ofboneremolding
Mineralistion of osteoid
Secretion ofproteins(typev
collagen,osteonectin,osteopontin,RANKL,osteoprotegrin,proteoglycan
s,latentproteases,growth factors).

30. Cementoblasts
LINES SURFACE OF CEMENTUM
ORIGIN
HERS dental follicle
LIGHT MICROSCOPY
Cuboidalin shape,with abundantcytoplasmandalarge
vesicular nucleuswith oneor morenucleoli.
ELECTRONIC MICROSCOPY:
ACTIVECELLS-Allthe organelles requiredforprotein
synthesispresent.
Cellsdepositing cellular cementum-abundantcytoplasmic
processes.
Abundant mitochondria andlessamountof RERcomparedto
PDLfibroblasts.

31. Functions
 Lays down cementum which helps in attachment of the
tooth to the alveolar bone via the collagen fibers of the PDL.

33. Osteoclast
ORIGIN:
Hemopoietic stem cell ofmonocyte-macrophagelineage.
LIGHT MICROSCOPY:
Large andmultinucleated orsmall and mononuclear.
Appears tooccupy bays inbone(Howships lacunae)
ELECTRON MICROSCOPY
Numerous mitochondria and lysosomes, abundant Golgi
saccules andfreeribosomes but little RER.
FUNCTIONS
Plays an important roleinboneresorption.
Responsible forremolding.
Light micrograph of an osteoclast displaying
typical distinguishing characteristics: a large
cell with multiple nuclei and a foamy cytosol

35. Progenitor cells
. Periodontal ligament and the marrow spaces of
the alveolar bone contain stem and progenitor cells
that is continually renewing under physiologic
conditions which function as precursors cells
(Aukhil,1991;Berkovitz et al., 1995).
Morphology: Progenitor cell tend to have a small
closed faced nucleus.
Site and distribution: progenitor cells appear to be
in highest concentration in locations adjacent to
blood vessels.

36. Epithelial rests of malassez
First described by Malassez in 1884.
At the time of cementum
formation, the continous layer of
epithelium that covers the surface of
newly formed dentin breaks into lace
like strands.
The epithelial rests persists as a
network, strands, islands, or tubule
like structures, parallel to the surface
of root.

37. Fig. shows the presence of clusters of epithelial cells (ER) in the periodontal
ligament. These cells, called the epithelial cell rests of Mallassez, represent
remnants of the Hertwig's epithelial root sheath. The epithelial cell rests
are situated in the periodontal ligament at a distance of 25 μm from the
cementum (C) on the root surface. A group of such epithelial cell rests is
seen in a higher magnification.

39. Mast cells
These cells are associated with blood vessels.
ORIGIN
Hematopoietic stem cells
LIGHT MICROSCOPY
SHAPE: Round/oval
DIAMETER: 12-15 micron meters,
Numerous cytoplasmic granules-dense membrane bound vesicles 0.5-1
micron meters in diameter containing heparin,histamin and stain with
metahromatic dyes.
ELECTRON MICROSCOPIC
Cytoplasm- free ribosomes, short profiles of granular ER, few round
mitochondria and a prominent golgi apparatus
FUNCTIONS
The release of histamines into the extracellular environment-
proliferation of endothelial and mesenchymal cells.

40. Macrophages
Located adjacent to blood vessels
ORIGIN:
 Hematopoietic stem cell
LIGHT MICROSCOPY:
 Nucleus: Horse shoe or kidney shape with dense and
uneven layer of peripheral chromatin
 Nucleoli are rarely seen
ELECTRON MICROSCOPY:
 Resting macrophages- distinguished from fibroblasts by the presence of numerous microvilli,
lysosomes and membrane bound vesicles and paucity of RER and golgi complex
FUNCTIONS:
 Dual role: phagocytose dead cells secrete growth factors that regulate the proliferation of
adjacent fibroblasts
 Also synthesize- interferon, prostaglandins and factors that enhance the growth of fibroblasts
and endothelial cells.

41. Eosinophils
Occasionally seen
ORIGIN:
 Hematopoietic stem cell
LIGHT MICROSCOPY:
 8 micro meter in diameter, nuclei are bi-
lobed, granules with 1 or more crystalloid
structures, with bright red staining properties
with acidic dyes such as eosin.
FUNCTIONS:
Phagocytosis.

42. Cementicles
Calcified masses, adherent to or detached
from the root surfaces
(O.J. Mikola, Wm.H. Bauer,1949)
Represent dystrophic calcification
(example of regressive or degenerative
change)
Develop from: calcified epithelial rests,
calcified Sharpey’s fibers, Calcified,
thrombosed vessels within the PDL, around
small spicules of cementum or alveolar
bone traumatically displaced into the PDL

43. Small spicules of cementum torn from the root
surface or fragments of detached from the alveolar
bone. (Bosshardt DD, Selvig KA 1977)
If lying free in the PDL may resemble
cementicles, particularly after they have
undergone some remodeling through resorption &
subsequent repair.
Cemental tears

45. Principal Fibers
The most important elements of the periodontal ligament are the principal
fibers, which are collagenous in nature and arranged in bundles and follow
wavy course when viewed in longitudinal section.
 They are associated with abundant non collagenous proteins typically found
in bone and cementum like osteopontin and bone sialoprotein.
 They are thought to contribute to the regulation of mineralization and to
tissue cohesion at sites of increased biomechanical strain

46. Principal fibers of the periodontal
ligament follow a wavy course
when sectioned longitudinally. Collagen fibers embedded in
the cementum and bone.
cementum
Bundle
bone

47. Light micrograph of periodontal
ligament of human premolar. Note that
collagen fiber bundles (blue) are cut
transversely and segregated by
cytoplasmic processes of connective
tissue cells (red). Azan stain, x 500

48. High-power electron micrograph of
collagen fibrils in human periodontal
ligament inserting into acellular
extrinsic fiber cementum (x 25,000)

49. Collagen
 Collagen is a protein composed of different amino acids, the most
important of which are glycine, proline, hydroxylysine and
hydroxyproline.
 The amount of collagen can be determined by its hydroxyproline content.
 There are at least 19 recognized collagen species encoded by at least 25
separate genes, dispersed among 12 chromosomes.

50. Structure
 Collagen is composed of 3 polypeptide strands held together in helical
configuration by hydrogen bonds to form the typical triple helix
configuration
 High-resolution crystal structure of a
collagen triple helix

51. Natural type I collagen has D = 67 nm

52.  Collagen is synthesized by fibroblasts, chondroblasts, osteoblasts, odontoblasts, and other cells.
 Collagen biosynthesis occurs inside the fibroblasts to form tropocollagen molecules.
MICROFIBRILS FIBRILS FIBERS BUNDLE
Collagen fibrils have a
transverse striation with
a characteristic
periodicity of 64nm.

53. The several types of collagen are distinguished by their chemical composition,
distribution, function, and morphology.
o Type I Bone, Periodontal Ligament
o Type II Cartilage
o Type III Reticular fibers
o Type IV Basement membrane.
o Type V Bone
o Type VI Ligaments, skin, bone.
o Type VII Anchoring fibrils of basement membrane
o Type VIII Dermis
o Type IX Cartilage
o Type X, XI Cartilage, Bone
o Type XII Alignment and organization of periodontal fibers
o Type XIII Epidermis Cartilage

54. Collagen……
 Collagen is responsible for maintenance of the framework .
 Tone of tissues.
 Tensile strength is greater than steel.
 Collagen imparts a unique combination of flexibility and strength to
the tissues.

55. The terminal portionsoftheprincipal fibersthat
areinserted intothe cementum andboneare
termed sharpey’s fibers.
Onceembedded inthewall ofthealveolus orinthe
tooth,sharpey's fiberscalcify toasignificant
degree.
Sharpye’s fibers

56. Sharpye’s fibers……
•Light micrograph of human
periodontal ligament
showing the collagenous fiber
meshwork interposed between
the root cementum (C) and the
socket wall (B).
Note the presence of Sharpey’s
fibers in the bone (arrows).
Azan stain, x250

57. Principal fibers of PDL
✢Transseptal
✢Alveolar crest group
✢Horizontal
✢Oblique
✢Apical
✢Inter-radicular

58. Transseptal Group
✢Extendinterproximally over thealveolarbone crest andareembeddedin
thecementumof adjacenttooth.
✢Theyarereconstructedevenafterthedestruction ofthealveolarbone in
periodontal disease.
Function:
Resistmesialanddistaltooth movement.
Dentin
Bone
Dentin

59. Alveolar Crest Group
✢Extendobliquely fromthecementumjustbeneaththe junctional
epitheliumto thealveolar crest.
✢Fibersalsorunfrom the cementumover thealveolar crestandto the
fibrouslayeroftheperiodontium covering thealveolarbone.
FUNCTIONS:
1. Preventsextrution oftooth.
2. Resistlateralmovementsofthe tooth.
CLINICAL SIGNIFICANCE:
✢ Incision of thesefibersduringperiodontalsurgerydoesnot increase
tooth mobility unlesssignificant attachmentloss hasoccurred.
Bone Dentin

60. Horizontal group
✢Extendatright anglesto thelong axisofthetooth from
cementumto the alveolarbone.
Function:
✢Resisthorizontal andtipping forces.
Oblique group
✢Largest group offibers.
✢Thefiberbundlesrunobliquely.
✢Theirattachmentin theboneissomewhat coronal
(higher) thantheattachmentinthecementum.
Function:
✢Resistvertical masticatory forcesandtransform them
into tension on alveolarbone.
Bone
Dentin
bone
dentin

61. Apical group:
✢The bundles radiate from the apical region of the root
to the surrounding bone
Function:
resists vertical force.
Inter radicular group:
The bundles radiate from the inter radicular septum to
the furcation of the multirooted tooth.
Function:
resists vertical and lateral forces.
dentin
bone
dentin
bone

62. Elastin Fibers
Elastin fibers of micro fibrillar component
surrounding an amorphous core of elastin
protein.
Seen on walls of afferent blood vessels..

63. Elaunin fibers
✢Seen as bundles of micro fibrils embedded in
relatively small amount of amorphous elastin.
✢Found with in fibers of gingival ligament.

64. Oxytalyn fibers
✢Immature fibers.
✢Consists of micro fibrillar component.
✢0.5-2.5 microns in diameter.
✢Fibers run in axial direction one end being embedded
in cementum or possibly bone and the other often in the
wall of a blood vessel.
FUNCTIONS:
✢ Supporting blood vessels of periodontal ligament.
✢ Play a role in tooth support.

65. Oxytalan fibers (stained dark
purple) running in
the apico-occlusal direction. Note
that their course does not
correspond with that of the collagen
fibers in the periodontal ligament.
Cementum (C), x 500.

66. Indifferent fiber plexus
✢Small collagen fibers associated with the large
principal collagen fibers .
✢Fibers run in all directions, forming a plexus
called Indifferent fiber plexus.

67. GROUND SUBSTANCE
 Gellike matrix
 Presentinevery nookand cranny,interstices
between fibersand between fibrils.
FUNCTIONS:
 Properfunctioningofthe cell.
 Fiber orientation.
 Control of collagenfibrillogensis.
 Ion,water bindingandexchangecapacity.
 Bindingof growth factors.

68. Itconsistsof
 Glycosaminoglycan's
 Proteoglycans
 Glycoproteins
 70%ofwater
Glycosaminoglycan's
• Maintype– Hyaluronan occupieslarge
volume ofPDL
• Dermatin
• Chondratin
• Heparin sulphate

69. Proteoglycans
 Compoundscontaining glycosaminoglycan's attachedtoa proteincore.
MAINTYPES:
 Dermatansulfate
 Proteoglycan containing chondratin sulphate
 Dermatansulfatehybrids
OTHERS:
 Fibromodulin
 Perlecan
 CD44
 Syndecan 1andsyndecan 2

70. Proteoglycans…..
FUCTIONS:
 Assistsincollagenfibrillogenesisandincreasethe
strengthofcollagenfibrils.
 Controls hydration of extracellular matrix of CT.

71. Glycoproteins
Predominant glycoprotein FIBRONECTIN
promotes attachmentofcells tothecollagen fibrils
Involves in cellmigration andorientation
TENASCIN
Found adjacent to alveolar bone and cementum
Transfers the forces of mastication and stress
VITRONECTIN
present adjacent to elastin fibers.
OTHERS: osteonectin, laminin,undulin.

72. Functions of PDL
1. Physical
2. Formative andRemodeling
3. Nutritive
4. Sensory
5. Regulation of periodontal ligamentwidth
6. Eruptive
7. Homeostatic

73. Physical
1. Transmission of occlusal forces to the bone
2. Attachment of teeth to bone.
3. Maintenance of gingival tissues in their proper
relationship to the teeth.
4. Provision for a soft tissue ‘CASING’ to protect
the vessels and nerves from injury by
mechanical forces .
5. Resistance to impact of occlusal forces
✢SHOCK ABSORPTION : Tensional theory &
Viscoelastic theory

74. Tensional Theory
✢Ascribestheprincipal fibersofPDL themajorresponsibilityinsupporting
thetoothandtransmittingtheforcestothebone.
Forceisappliedtothetooth
Principal fibersfirstunfoldandstraighten
Transmitforcetothe alveolarbone causingelasticdeformationofthesocket.
Whenalveolarbonehasreacheditslimit,theforceistransferredto
underlyingbasalbone
✢Manyinvestigatorsfindthistheoryinsufficienttoexplain available
experimental evidence.

75. Visco elastic theory
✢According tothis,thedisplacement oftoothislargelycontrolledbyfluidmovement, with
fibers havingonly secondaryrole (Bien SM, 1966 and Birn H, 1966)
appliedon tooth
Extra-cellular fluid from PDL escapes to marrow spaces
Depletion of fluid, Fibers absorb slack and tighten
Blood vessels stenosis
Arterial back pressure created
Ballooning of vessels
Passage of blood
Lost fluid replenished

76. Transmission of occlusal forces to bone
✢Arrangementislikesuspensionbridge or hammock.
✢The oblique fibers alter their wavypattern andsustain
the major part oftheaxial force.
AXIS OF ROTATION
✢Singlerooted tooth at junction ofmiddle andapical 3rd
of theroot.
✢Multirooted tooth inthe bone between the roots below
furcation.

77. Distribution of faciolingual forces (arrow) around the axis of rotation (black circle on root) in a
mandibular premolar. The periodontal ligament fibers are compressed in areas of pressure
Distribution of faciolingual forces (arrow) around the axis of rotation (black
circle on root) in a mandibular premolar. The periodontal ligament fibers are
compressed in areas of pressure

78. • The apical portion of the root moves in a
direction opposite to the coronal portion.
• Areas of tension→ Principal fiber bundles are
taut rather than wavy.
• Areas of pressure→ fibers are compressed, the
tooth is displaced & a corresponding distortion
of bone exists in a direction of root movement

79. Formative and remolding
✢Cells have the capacity to resorb & synthesize
the extracellular substance of the CT ligament,
alveolar bone & cementum.
✢Participate in physiologic tooth movement & in
repair of injuries.
✢PDL is constantly undergoing remodeling old
cells and fibers are broken down and replaced by
new ones

80. Radio autographic studies with radio active
thymidine, proline, and glycine indicate a high turn
over rate of collagen in PDL.
 A rapid turnover of sulfated GAGs in the cells and
amorphous ground substances also occur
 Sodek ,1977 found collagen synthesis in PDL of adult
rat to be
- two fold greater than that of gingiva,
- four fold greater than that of skin, &
- six fold greater than that of bone

81. NUTRITIVE
✢Blood vessels provide anabolites and other substance
required by the cells of ligament-by cementocytes and
osteocytes.
✢The blood vessels are also concerned with the removal of
catabolites

82. Sensory
Periodontal ligamentis abundtly suppliedby sensorynerve
fibers.
✢Capable oftransmittingtactile, pressure,andpainsensation
by trigeminalpathways.
✢4 typesof neuralterminations areseen
1. Freenerveendings - pain
2. Ruffini likemechanoreceptors (apical area)
3. Meissner’s corpuscles - mechanoreceptors (middle 3rd)
4. Spindle likepressureand vibration endings(apex)

83. Homeostatic
PDL resorb and synthesis ECS of CT of
ligament, alveolar bone, cementum. takes place
continuously with varying intensity throughout the life.
✢Collagen of PDL has fastest turned over rate of all CT in
the body.
✢Important homeostatic measure maintaing width of
pdl throughout the life ( cellular signaling system).
✢FAILURE: Ankylosis and or root resorption
Quality of tissues will be changed.

84. ✢In all areas of PDL this is apparently a
continual slow death of cells, which are replaced
by new cells that are provided by cell division of
progenitor cells in the ligament.

85. Eruptive
 The cells vascular elements and extra cellular
matrix proteins of PDL enables
 PDL provides Space
Acts a medium for cellular remodeling and hence continued
eruption and a proximal shift occurs.
Enables mammalian teeth of
limited eruption to adjust their
position while remaining firmly
attached to the bone socket

86. Blood supply
✢Abundant vascular supply
ARTERIAL SUPPLY:
The blood supply is derived from inferior and superior
alveolar arteries to mandible and maxillae ,reach the PDL from
three sources:
1. Branches in the PDL
2. Brancnhes from intra-alveolar vessels
3. Branches from gingival vessels
VENOUS DRAINAGE:
✢ Venous channel accompany the arterial counter parts.
✢ Channels are larger and receive blood from capillary net
work

87. • Branches of the
intraseptal vessels –
perforate the lamina dura
& enter the ligament.
• After entering the PDL,
perforating rami
anastomose & form a
polyhedral network
which surrounds the root
like a stocking

88. Nerve supply
✢ The nerve follow almost the same course
as the blood vessels.
✢ Nerve bundle divide → myelinated
fibers → lose their myelin sheath →
end in one of the 4 types of neural
termination

89. 1.Free nerve endings
- terminal arborization of thick/fine myelinated fibers
- 0.2-1 um in diameter
- fine, non myelinated fibers only type of ending in tooth
pulp → classic model of pure nociception.
2. Ruffini - like→ apical area
3. Meissner's corpuscles → mid-root, for tactile perception
4. Spindle shaped (Krause type end bulbs) → temperature receptor,
present at apex of the tooth

90. Lymphatic
✢A network of lymphatic vessels, following the path of
the blood vessels, provide the lymph drainage of the
PDL.
✢The lymph from pdl drains lymph nodes of head
and neck.
✢The sub mental nodes drains labial and lingual
gingiva of the mandibular incisors.
✢The sub mandibular lymph nodes drains the
lingual gingiva of the mandibular premolar and molar.
✢The third molar drains directly to jugulo
digastric lymph nodes

91. The maxillary palatal gingiva is drained into the deep
cervical lymph nodes.
The buccal gingiva of the maxilla drains into the
submandibular lymph nodes.
course apically - pass through the fundus of the socket or
they may pass through the cribriform plate to empty into
larger channels pursuing intraosseous paths

92. Age changes in PDL
✢CTinyoungerindividuals Regular andwell organized
✢With aging Irregular
in celldensityand fibrous component.
in mitotic activity .
chemotaxy andmotility
in production oforganicmatrix
Lossof mucoploysacchrides withaging
Innoof epithelial cellrest of malassez
Inwidth ofPDL space

93. In no : of elastic fibers
One of the prominent age change s is seen in the calcified
tissues of periodontium, the bone and the cementum, is
scalloping and the periodontal ligament fibers are
attached to the peaks of these scallops than over the entire
surface as seen in younger periodontium.

94. Unique features of PDL
✢ Ithascellsthat form and resorb cementum, bone, and
collagenfibersina specificorientation connectingthe
two mineralized tissuesmakesit unique.
✢ Hightissue HYDROSTATIC PRESSURE
✢ Extremely cellular, fibroblasts showingmanyinter
cellular contacts, well innervatedwith many mechano
receptors, highlyvascular unlikein anyother CT
inadult
✢ Presenceof pre-elastinfibers like oxytalyn

95. ✢Recently ithasbeen shownthatthePDLbearsaresemblance to
immature, fetal like CT .
✢Thefeaturesbeing highcellularity,veryhighratesof turnover
andwithsignificantamountoftype IIICollagen.
Thecollagen fibersarealsoshowreduciblecrosslinkin collagen
dehydrodihydroxy lisinonorleucine.
ThegroundsubstanceofPDL occupieslargevolumewithhighcontent
ofgluconate richproteoglycansandglycoproteinstenascin and
fibronectin.
 ThusPDL hasstructural,ultrastructural,and biochemicalfeatures
likefetal tissue.Thishashelped usto understandperiodontal
inflammatorydiseasesand forevolving newertreatment.

96. External forces in pdl
Within physiologic limits, thePDL canaccommodate
increasedfunctionwith
- anincreaseinwidth,
- athickeningofits fiber bundles, and
- anincreaseindiameter &numberof Sharpey’sfibers
✢Forces that exceed the adaptive capacity ofthe
periodontium produce injurycalled trauma from occlusion.
✢Slight excessivepressure:resorption ofbone, wideningof
PDLspace
✢Slightexcessivetension:elongation ofPDL fibers&
apposition of bone

97. Clinical considerations
✢ Initial tooth movement following the
application of the force in the direction indicated
by the arrow. In the direction of the force, the
periodontal ligament (PDL) becomes initially
narrow and according to the distribution of the
stresses, direct or indirect resorption occurs. This
area has always been termed as the pressure area.
On the opposite side, widening of the PDL is
observed and cellular activity is characterized by
bone apposition. This area has traditionally been
termed as the tension side

98. • Application of large forces results in necrosis of PDL and
alveolar bone on the pressure side and movement of the tooth
will occur after the necrotic bone has been resorbed by
osteoclasts located on its endosteal surface.
• Inflammatory diseases of the pulp progress to the apical
periodontal ligament and replace its fiber bundles with
granulation tissue .
• This lesion is called a periapical granuloma may contain
epithelial cells that undergo proliferation and produce a cyst

99. Replantation and transplantation
The length of time before a tooth is re implanted (within
half an hour) and how it is transported to the dentist (in
saline) are critical in successfully saving and re-implanting
the tooth.
 The periodontal ligament will regenerate and revascularize
 A tooth that is replaced within half an hour has a 90% chance
of successful re-implantation

100. Dentalimplantslack periodontal ligamentfibersand
theyhave arigid connectionto bone(Osseointegration).

101. Neoplasms arising from PDL
Cemento-ossifying fibroma –Middle age,mandible (midbody),
Women Predilection (slight)& Blacks, Well Circumscribed
Reactive fibro-cemento-osseous lesions of PDL origin:
1. Periapical cemento-osseous dysplasia (PCD)– young-middle
age,black female, apical area ofanterior mandibular teeth.
2. Focal cemento-osseous dysplasia – women predilection, poster
mandible.
3. Florid cemento-osseous dysplasia –Middle-elderly black
women

102. Effect of hyper & hypo glycaemia on PDL
Nishimura et al, 1998 -PDLcells - susceptible to hyper&hypoglycemia
&effects- mediated via the integrinsystem.
Hyperglycemia – increasedexpressionof fibronectinreceptor →
resultsin reduced cellular adhesion &motility → probable tissue
impairment.
Hypoglycemia –decreased expressionof fibronectinreceptor →
lowers theviability &ultimately results incelldeath & hencetissue
impairment

103. • Carranza’s Clinical Periodontology, 10th Edition
• Clinical Periodontology and Implantology by
Jan Lindhe, 5th edition
• Oral Histology and Embryology by Orban, 13th
edition
• Tencate oral histology, 5th edition
• Fundamentals of Periodontics, 2nd Edition, by
Thomas G. Wilson, Kennath S. Kornman
• Hassel TM. Tissues and cells of periodontium.
Periodontol 2000, Vol. 3, 1993, 9-38.
• The Periodontium - Hubert E Schroeder
References

104. • Bartold PM, Walsh LJ, Sampath Narayan A. Molecular
and cell biology of gingiva. Periodontol 2000, Vol. 24,
2000, 28–55.
• Cho MI, Garant PR. Development and general
structure of the periodontium, Periodontol 2000, Vol.
24, 2000, 9–27.
• Ertsenc W, Mcculloc HG , Sodek HJ. The periodontal
ligament: a unique, multifunctional connective
tissue. Periodontol 2000. Vol. 13, 1997, 20-40.
• Wright JM. Reactive, dysplastic and neoplastic
conditions of periodontal ligament origin.
Periodontol 2000, Vol. 21, 1999, 7-15.

105. • Xiong J, Gronthos S, Bartold PM. Role of the epithelial cell
rests of Malassez in the development, maintenance and
regeneration of periodontal ligament tissues. Periodontol
2000, Vol. 63, 2013, 217–233.
• Bosshardt DD, Selvig KA.Dental cementum: the dynamic
tissue covering of the root. Periodontol 2000 1997;13:41-75
• Hamed Mortazavi et al ,Common conditions associated
with periodontal ligament widening Imaging Science
in Dentistry 2016; 46: 229-37
• Fusanori Nishimura, Periodontal Disease as a
Complication of Diabetes Mellitus* Annals of
Periodontology Vol. 3, No. 1, July 1998..

106. Thank you….