Periodontal ligament, fibers, functions, blood supply

This seminar describes the PDL, its fibers, functions, blood supply, lymphatic drainage, nerve supply.

1. PERIODONTAL LIGAMENT
STRUCTURES AND FUNCTIONS

2. Purpose statement
Thestudentsshouldunderstandthestructuresand
functionsofPeriodontalligament.

3. Learning objectives
Sr
no
LO Domain Level
1 Explain the Periodontalligament fibers Psychomoto
r
Must know
2 Explanationof thecellular elements CognitiveMust know
3 To explain the ground substance of Periodontal
ligament.
CognitiveMust know
4 To write the Functions of Periodontal ligament.CognitiveMust know
5 Explain the innervations and radiological
characteristics of Periodontal ligament.
CognitiveNice to
know

4. INTRODUCTION
Theperiodontiumisadynamicstructurethatisservedthroughout
lifebyauniquevasculararrangement,alymphaticsystemanda
highlyspecializednetworkofnervouselements.
Unlikereptilesandlowerspeciesteetharenotattachedrigidlyto
boneinhumansandothermammals.Ratherthereisa0.15to0.4
mmspaceinterveningbetweenthecementumcoveringtherootand
theboneofalveolarprocess.Thisspaceisoccupiedbyasoft
connectivetissuecomplexthatsupportsandmaintainseachtooth
withinanosseouscrypt.Thisstructurereferredtoas‘periodontal
ligament’completelyfillsthecircumferentiallyinterveningspace.

5. DEFINITION
Periodontal ligament is defined as the connective tissue that
surrounds the root of the tooth and connects it with bone
Other names
Desmodont
Gomphosis
Pericementum
Dental periosteum
Alveolodentalligament
Periodontal membrane

6. Principal fibres of PDL
Collagenous
Bundles
Wavy
Sharpey’sfibres
Terminal portions of principal fibres that insert in
cementum& bone

7. Transseptal group
Extend interproximally over the
alveolar crest
Embedded in the cementum of
adjacent teeth
Reconstructed even after destruction
of alveolar bone.

8. Alveolar crest group
Extendobliquelyfromthe
cementumjustbeneaththe
junctionalepitheliumtothe
alveolarcrest.
Preventextrusionofteeth
Resistlateralmovements

9. Horizontal group
Fibresrunatrightanglestothe
toothfromthecementumtothe
bone
Functionissameasalveolargroup

10. •LargestgroupinPDL
•Extendfromcementuminacoronal
directionobliquelytobone
•Bearthebruntofmasticatorystresses
&transformthemintotensiononthe
alveolarbone
Oblique group

11. Apical group
Radiatefromthecementumtothe
boneatthefundusofthesocket
Donotoccurinincompletely
formedroots

12. Interadiculargroup
Fan out from cementum to the
tooth in furcation areas of
multirooted tooth

13. Oxytalan fibres-Run parallel to root surface and attach in
cementum
Eluanin fibres-Elastic meshwork

14. Fibres appear to course parallel to the root surface forming a
loose intersecting network
EvidentintheapicalhalfofthePDL
Indifferent fibre plexus

15. CONTENTS
Cells Extracellular
Cementoblasts
Epithelial cell
rests
Defense cells
Mast cells
Macrophages
Ground substance
Glycosoaminoglycans
Glycoproteins
OsteoblastsFibroblasts Fibres

16. Resorptive cells Defense cells Other cells
Osteoclasts NeutrophilsProgenitor cells
Cementoclasts Macrophage Epithelial cell rests of Mallassez
• Mast cells
Eosinophils

17. Fibres Ground substance
Components
Collagen fibres Proteoglycans
Oxytalinfibres Glycoproteins
Eluaninfibres High water content (70%)
Elastin fibres
Periodontal ligament shows Type I, III,V and Type XII
collagen.

18. Noncollagenous proteins
Mediators of cell adhesion
Term coined by Tamkunet al
Mediate binding of cells to extracellular proteins and to one
another
αand βsubunits
Important for
Diapedesisof white cells
Clot formation
INTEGRINS

19. FUNCTIONS
1.Physicalfunctions
Provisionofasofttissuecasing
Transmissionofocclusalforcestobone
Attachmentoftheteethtothebone
Maintenanceofgingivaltissueintheirproperrelationshipto
theteeth
Resistancetotheimpactofocclusalforces
2.Formativeandremodellingfunctions
3.Nutritionalandsensoryfunctions

20. 1. Physical Functions
Shock absorption
Two theories
Tensional theory
Principal fibresof the PDL –support the tooth
Force application –unfold and straighten
Load from alveolar bone –basal bone
Viscoelastic theory
Fliudmovement
From PDL marrow spaces of bone
Fibresabsorb the slack and tighten
Blood vessel stenosis, arterial back pressure causing ballooning of
vessels, blood filtrates into tissues
Replenshing

21. Transmission of occlusal forces to bone
Principal fibres
Axial force-oblique fibres alters wavy untensed course, assume full
length and sustain
Horizontal force-two phases
Within the confines of the PDL
Displacement of the facial and lingual plates
Areas of tension-taut
Areas of pressure-compressed

22. 2. Formative and Remodelling
Formation of cementum and bone
Repair process
Remodelling
Old cells and fibres are broken down and replaced by new
ones
High turnover of collagen in PDL

23. 3. Nutritional and Sensory
Supplies nutrients to cementum, bone and gingiva by the eay of blood
vessels and provide lymphatic drainage
Sensory nerve fibres-Tactile, pressure & pain sensations by trigeminal
pathways
Nerve bundles-Free endings
• Ruffini like corpuscles
• Spindle like endings

24. INNERVATION
Touch,pressure,painaswellasproprioceptivefunction
Ismediatedbythedentalbranchesofalveolarnervesthroughapical
perforationsofthetoothsocket.
Byersetal–studyonperiodontalinnervation
HealthyPDLisrichlyinnervatedbymechanoreceptors.
Receptorsareactivatedbytouch,pressureandmovementofthe
toothduringmastication.
SensoryreceptorsaremorenumerousintheapicalthirdofthePDL
Terminateinbranched“Ruffinilikeendings”

25. SUMMARY
Theperiodontiumconsistsofboth
fibrousandmineralizedtissueswhose
homoestasisdiffersdramaticallydue
toproteincomposition,cellularelements,
mineralization,metabolismandfunction.
Inhealththeprimarycomponentoftheperiodontal
ligamentisasystematicarrangement.Diseaseof
periodontalligamentandothercomponentsof
periodontiumaccountsforagreatdealoftotallossinthe
adultpopulation.

26. APPLIED ANATOMY
Theperiodontalligamenthasashockabsorbingquality,aswellas
hydraulic-liketendencytorespondtoaxialloadingwithanincreased
pressurethatcounteractstheapicallydirectedtoothmovement.
Whenthetoothissubjectedtoincreasedocclusalload,itwillbe
slightlydepressed,andwhenunloaded,itwillhavereboundeffect.
BeingawareofthesepropertiesofPeriodontalligamentcanallow
clinicianstomodifytheirclinicalprocedures.

27. Expected Questions
•Explain the Functions of Periodontal ligament.(2marks)
•Write in short about Periodontal ligament fibres.
(2 marks)
•Write in brief about innervations and Radiographic
characteristic of Periodontal ligament. (10 marks)

28. REFERENCES
Carranza’sclinicalperiodontology-11
th
edition
ClinicalperiodontologyandImplantDentistry-JanLindhe5
th
edition
Theperioodntiuminhealthanddisease-Berkovitz

29. Thank You