Periodontal Ligament.ppt

periodontal ligament - development, structure and composition, cells and fibers of PDL, ground substance, nerve and blood supply of PDL

1. Periodontal Ligament
Synonyms:
Periodontal Membrane
Desmodont
Gomphosis
Pericementum
Dental Periosteum
AlveolodentalLigament

2. Periodontium
The word Periodontiumrefers to the
attachment apparatus of teeth and consists :
–Cementum
–Alveolar bone lining tooth socket
–Periodontal ligament
–Part of Gingivafacing the tooth

3. Periodontal Ligament
The space occupied
by PDL is called
Periodontal Space
Coronally :-
Continuous with
Gingiva
Apically :-
Continuous with
Pulp
Is the connective tissue which surrounds the roots of
the teeth and Attaches tooth root to the bony alveolus

4. ThewidthofPDLrangesfrom0.15
–0.38mm
Thinnestaroundmiddle1/3
rd
of
rootandhas“Hour-Glass”
appearance
Reducedinnonfunctionaland
uneruptedteeth.
Increasedinteethsubjectedto
heavyfunctionalstresses.
Thickerindeciduousteeththan
permanentteeth.
Theprincipalfibersrunawavy
course fromCementumto
alveolarbone

5. Periodontal Ligament consists of:
–Cells
–Extracellular substance:
Fibers
Ground substance
Structure and Composition

6. Cells
of
Periodontal Ligament

7. Cells in Periodontal Ligament
A –Alveolar Bone B -Cementum

8. The cells of Periodontal Ligament:
1. Synthetic cells:
Osteoblasts
Fibroblasts
Cementoblasts
2. Resorptive cells:
Osteoclasts
Fibroblasts
Cementoclasts
3. Progenitor cells
4. Epithelial Cell rests of Malassez
5. Defense cells:
Mast cells
Macrophages
Eosinophils

9. Synthetic cells
UniquecharacteristicsofSynthesizingcells:
Vesicularnucleuscontainingprominentnuclei
AbundantcytoplasmcontainingnumerousRER
andIncreasedGolgibodies
LargenumbersofMitochondria
CellswithabovedescriptionpresentonAlveolar
surfaceofPDL Osteoblasts
Suchcellslyinginbodyofsoftconnectivetissueof
PDL Fibroblasts
Cellsfoundoncementalsurface Cementoblasts

10. Osteoblasts
Boneformingcellsliningthealveolarboneoftooth
socketcloselyresemblingcementoblasts
Cuboidinshapewithprominentsphericalandlarge
nucleusplacedatbasalendofcell
LargeamountsofRERgivesthecytoplasmofactive
osteoblastsaslightlybasophilichue
Activeosteoblastproducesanenormousquantityof
collagentype-I
Alkalinephosphataseispresentandismostlyfound
ontheapicalcellmembrane

12. Fibroblasts
A –Alveolar Bone
B –Fibroblasts
C –Cementum
D –Dentin

13. Fibroblasts
PredominantcellsinPDL
CapableofBothSecretionandDegradationof
Collagen
Fibroblastsnearcementumarederivedfrom
investinglayerofdentalpapillaandfibroblastsnear
AlveolarbonearederivedfromPerivascular
MesenchymeofDentalFollicleandshowabundant
Alkalinephosphataseactivity
Fibroblastsarelargecellswithextensivecytoplasm
andcharacteristicsofsynthesizingcellsareseen
prominently

14. Fibroblastsareofvariousshapes:
–Fusiform
–Tripolar
–Stellate
FibroblastsofPDLhaveCiliaandtheCiliais
associatedwithControlofCellcycleorInhibitionof
CentriolarActivity
Thesecellsproducegrowthfactorsandcytokines
suchasIGF-1,BMP’s,PDGF,IL-1,etc
TGF-βstimulatessynthesisofcollagenandInhibitsthe
synthesisofcollagenase

16. Functions of Fibroblasts
Toproducestructuralconnectivetissueproteins:
Collagen
Elastin
Proteoglycans
Glycoproteins
Glycosaminoglycans
Collagenolyticenzymes:
MatrixMetalloproteinases(MMP’s)
Fibroblastsareresponsibleforformationand
remodellingofPDL
Theyhaveasignalingsystemtomaintainwidthof
PDLbypreventingencroachmentofboneorcementum
intothePDLspace

17. Differences between
PDL Fibroblasts
Ectomesenchymalorigin
ExpressionofAlkaline
phosphataseandcyclic
AMPisMORE
MotileandContractile
andhencecangeneratea
forcefortootheruption
Gingival Fibroblasts
Mesodermalorigin
ExpressionofAlkaline
phosphataseandcyclic
AMPisLESS
Non-contractileandno
roletoplayintooth
eruption

18. Cementoblasts

19. Cementoblasts
Cuboidalcellswithlargevesicularnucleus
Activeincementumformationfoundadjacenttothe
surfaceofcementumandshowalltheprominent
featuresofsynthesizingcells
Cellsdepositingcellularcementumshowabundant
basophiliccytoplasmandcytoplasmicprocessesand
nucleiarefoldedandirregularlyshaped
Cellsdepositing-acellularcementum–DONOT
SHOWprominentcytoplasmicprocesses

20. Cementoblsts

21. Resorptive Cells
Osteoclasts & Cementoclasts:
Found in areas of resorption.
Multinucleated
Originate from undifferentiated mesenchymal
cells in periodontal ligament.

22. Osteoclasts in
Howship’s
Lacunae
Osteoclasts
Howship’s Lacunae

23. Cytoplasmofthecellsproducea
substancewhichdissolvestheorganic
componentsofboneandachelating
agentcapableofbringingcalciumsalts
intosolution.
Whereevertheircytoplasmcomes
intocontactwithbone-hollowsor
groovescalled'Howship'sLacunae'are
formed.
Whenboneresorptionceases-they
disappear.

24. Progenitor cells
These cells have the capacity to undergo
mitotic division.
They give rise to all of the specialized
synthetic cells.
Epithelial cell rests of Malassez:
Remanents of Hertwig’s Epithelial Root
Sheath.
Epithelial double strands and islands limited
by basement membrane of reticulin.

25. Cell
Rests of
Malassez

26. Mast cells
Thesearesmallroundorovalcells.
12-15μm.
Characterized by numerous
cytoplasmicgranules.
Thesegranulescontainheparinand
histamine.
Histamineplaysandimportantrolein
inflammatoryreactionsandalsoin
antigenantibodyreaction.

28. Macrophages
Thesecanbevisualizedbythepresence
ofphagocytosedmaterialintheircytoplasm.
Theyarederivedfrombloodmonocytes.

30. Extracellular Substance
Comprises of:
–Fibers:
Collagen
Oxytalan.
–Ground substance:
Proteoglycans
Glycoproteins.

31. Fibers
of
Periodontal
Ligament

32. Fibers
Made up of collagen and Oxytalan.
Elastic fibers are restricted to the walls of blood
vessels.
The majority of fibers are collagen.
Mostly made up of type I collagen and some
amount of type III collagen.
The collagen fibers are gathered in bundles
having a clear orientation relative to the
periodontal space -“Principal fibers”.

33. Principal Fibers
Root
Alveolar Bone
Principal fibers

34. Principal Fibers
Arranged in five groups:
1. Alveolar crest group.
2. Horizontal group.
3. Oblique group.
4. Apical group.
5. Inter-radicular group.

35. Principal Fibers
1.Alveolar crest
2.Horizontal
3.Oblique
4.Apical
5.Interradicular

36. Principal Fibers
Alveolar Crest group:
Theyradiatefromthecrestofthe
alveolarprocessandattachthemselvesto
thecervicalpartoftheCementum.
Thesefibersresisttilting,intrusive,
extrusiveandrotationalforces.
MostoftenconfusedwithDentoperiosteal
fibers

38. Horizontalgroup:
Theyrunatrightanglestolongaxisof
toothfromCementumtoBone.
Roughlyparalleltotheocclusalplaneofthe
arch
Theyarefoundimmediatelyapicaltothe
alveolarcrestfibergroup.Theyarelimited
mostlytothecoronalone-fourthofthe
periodontalligamentspace.
Thesefibersresisthorizontalandtipping
forces.

39. Obliquegroup:
Mostnumerousandoccupy
nearly2/3rdoftheligament.
Theyareattachedto
cementumapicallyfromtheir
attachmenttothebone
therebyresultingintheir
obliqueorientationwithinthe
periodontalspace
Thesefibersconstitutethe
mainattachment.
Thesefibersresistvertical
andintrusiveforces.

40. Apicalgroup:
Theyradiatefromthe
cementumattheroottipto
becomeanchoredintothe
fundusofthebonysocket.
Theapicalfibersresistthe
forcesofluxation,may
preventtoothtippingand
protectdelicatebloodand
lymphvesselsandnerves
traversingthePDLspaceat
therootapex.
Thesefibersarenotseenon
incompletelyformedroots.

41. InterradicularGroup:
From thecrestof
interradicularseptum,bundles
extendtofurcationof
multirootedteeth.
Thesefibersresisttooth
tipping,torquingandluxation.
Thesefibersarelost,ifage-
relatedgingivalrecession
proceedstotheextent,that
thefurcationareaisexposed.
Totallossofthesefibers
occurs in chronic
inflammatory periodontal
disease.

42. Oblique set

43. Inter-radicular

44. Elastic Fibers
Therearethreetypesofelasticfibers,whichare
histochemicallyandultrastructurallydifferent.
Theyare,thematureelasticfibers,(elastin)
fibers,theelauninfibers,andtheoxytalanfibers.
Elauninandoxytalanfibershavebeendescribed
asimmatureelasticfibers.
Matureelasticfibersconsistofamicrofibrillar
componentsurroundinganamorphouscoreof
elastinprotein.

45. ElauninFibers
Elauninfibersareseenasbundlesofmicrofibrils
embeddedinarelativelysmallamountof
amorphouselastin.
Thesefibersmaybefoundwithinthefibersofthe
gingivalligament.

46. Oxytalan Fibers
These are immature elastic fibers.
Found in the periodontal ligament.
Largely restricted to the walls of blood vessels.
The orientation of these fibers is quite different.
They tend to run axially -one end being
embedded into cementum or possibly in bone
and the other -into the wall of a blood vessel.
In the vicinity of apex they form a complex
network.

47. Reticular Fibers
Thesearefineimmaturecollagenfiberswith
argyrophilicstainingpropertiesandarerelatedto
basementmembraneofbloodvesselsand
epithelialcellswhichliewithintheperiodontal
ligament.
ThesefibersarecomposedoftypeIIIcollagen.

49. Ground Substance
in
Periodontal Ligament

50. Ground Substance
Glycosaminoglycans:
–Hyaluronic acid
–Dermatan sulfate
–Chondroitin sulfate.
Carbohydrates, proteins, lipids and Glycoproteins.
Other Structures Present in connectinve tissue:
–Blood vessels
–Lymphatics
–Nerves and Cementicles.

51. Functions
1.Formative
2.Supportive
3.Sensory
4.Nutritive
5.Occlusion
6.Reparative
7.Protective

52. Branching Principal Fibers

53. Sharpey’s Fibers
A –Alveolar Bone B -Cementum

54. Sharpey'sFibers:Thecollagenfibersare
embeddedintothecementumononesideof
theperiodontalspaceandintoalveolarbone
ontheother.
IntermediatePlexus:
Whenexaminedunderlightmicroscope
thefibersappeartobejoinedinthemid
regionoftheperiodontalspacegivingrise
toazoneofdistinctappearance,socalled
"IntermediatePlexus"–believedtobesitefor
rapidremodelingoffibers.

55. Intermediate Plexus

56. Blood Supply
&
Lymphatic Drainage

57. Blood Supply:
From three sources -
1. From the apical vessels supplying the
dental pulp.
2. Branches from intra-alveolar vessels.
3. Branches form gingival vessels.
Lymphatics:
Net work of lymphatic vessels following
the path of blood vessels.

58. Nerve Supply

59. Nerves are usually associated with blood vessels
Pass through foramina in the alveolar bone to
enter the periodontal ligament.
Myelinated or non myelinated.
Either large or small in diameter:
-larger diameter -concerned with touch.
-smaller diameter -concerned with pain.
Cementicles:
Calcified bodies.
Origin is probably from degenerated epithelial
cells –forming a nidus for calcification.

60. Nerve Bundles
A –Alveolar bone
B -Dentin