periodontium (10) [edocfind.com]
TRANSCRIPT
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PERIODONTIUMPERIODONTIUM
Oral HistologyOral HistologyDent 206Dent 206
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PeriodontiumPeriodontium
Four tissue supporting the tooth in the jawFour tissue supporting the tooth in the jaw
CementumCementum
Periodontal ligamentPeriodontal ligament Alveolar boneAlveolar bone
GingivaeGingivae
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CementumCementum
Thin layer of calcified tissue covering the root inThin layer of calcified tissue covering the root inthethe humanhuman teethteeth
Present in the crowns of some mammalsPresent in the crowns of some mammals Adaptation to herbivorous dietAdaptation to herbivorous diet
One of four tissues supporting the toothOne of four tissues supporting the tooth(periodontium)(periodontium)
The least known ofThe least known of Periodontium tissuesPeriodontium tissues
All mineralized tissuesAll mineralized tissues
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CementumCementum
Varies in thicknessVaries in thickness
Thick @ apex (50Thick @ apex (50--200 m) & inter200 m) & inter--radicular regionsradicular regions
Thin cervically (10Thin cervically (10--15 m)15 m)
Contiguous with PDLContiguous with PDL
Firmly adherent with root dentineFirmly adherent with root dentine
Highly responsive mineralized tissueHighly responsive mineralized tissue Maintenance of root integrityMaintenance of root integrity
Maintenance of functional position ofMaintenance of functional position oftoothtooth
Tooth repair & regenerationTooth repair & regeneration
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CementumCementum
SlowlySlowly--formed throughout lifeformed throughout life
Allowing continual reattachment of PDL fibersAllowing continual reattachment of PDL fibers
Cementum can be regarded as a mineralizedCementum can be regarded as a mineralizedcomponent of PDLcomponent of PDL
PrecementumPrecementum -- a thin mineralized layer on thea thin mineralized layer on thesurface of the cellular cementumsurface of the cellular cementum
Similar to bone, howeverSimilar to bone, however -- Avascular & not innervatedAvascular & not innervated
Less rapidly resorbedLess rapidly resorbed orthodonticsorthodontics
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CementCement--enamelenamel
junctionjunction
Pattern IPattern I
Cementum overlaps enamel for a short distanceCementum overlaps enamel for a short distance Most predominantMost predominant 60% of sections60% of sections
Pattern IIPattern II Enamel meet cementum at butt jointEnamel meet cementum at butt joint
Occurs in 30% of sectionsOccurs in 30% of sections Pattern IIIPattern III
Enamel fails to meet cementumEnamel fails to meet cementum
Dentine between them is exposedDentine between them is exposed
10% of sections10% of sections
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Physical propertiesPhysical properties
Pale yellowPale yellow
Softer than dentineSofter than dentine
PermeabilityPermeabilityVaries with age and type of cementumVaries with age and type of cementum Decreases with ageDecreases with age
Cellular is more permeableCellular is more permeable
More permeable than dentineMore permeable than dentine
Readily removed by abrasion after gingivalReadily removed by abrasion after gingivalrecessionrecession
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Chemical propertiesChemical properties
InorganicInorganic OrganicOrganic WaterWater
By weightBy weight 65%65% 23%23% 12%12%
By volumeBy volume 45%45% 33%33% 22%22%
Hydroxyapatite crystals similar to those in boneHydroxyapatite crystals similar to those in bone
More concentration of trace elements (F) at surfaceMore concentration of trace elements (F) at surface
F levels higher in acellularF levels higher in acellular
Collagenous organic matrix, primarily type ICollagenous organic matrix, primarily type I
Molecules involved in PDL fiber reattachment &/orMolecules involved in PDL fiber reattachment &/ormineralizationmineralization Bone sialoprotein, osteopontin & cementumBone sialoprotein, osteopontin & cementum--specific elementsspecific elements
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Classification of cementumClassification of cementum
Presence or absence of cellsPresence or absence of cells
Cellular cementumCellular cementum
Acellular cementumAcellular cementum Nature & origin of organic matrixNature & origin of organic matrix
Extrinsic fiber cementumExtrinsic fiber cementum
Intrinsic fiber cementumIntrinsic fiber cementum
Mixed fiber cementumMixed fiber cementum
CombinationsCombinations
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Acellular cementumAcellular cementum
Most common patternMost common pattern-- adjacent to dentineadjacent to dentine
StructurelessStructureless
Afibrillar cementumAfibrillar cementum Exists betweenExists between
Acellular cementumAcellular cementum
Hyaline layer (of HopewellHyaline layer (of Hopewell--Smith)Smith)
Mineralized GSMineralized GS Covers cervical enamelCovers cervical enamel
Results following loss ofREEResults following loss ofREE
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Acellular cementumAcellular cementum
Root dentine
Fibres of
PeriodontalLigament
CementumEpithelial
Rests
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Cellular cementumCellular cementum
Most common patternMost common pattern Apical areaApical area
InterInter--radicular areasradicular areas
Overlying acellular dentineOverlying acellular dentine
CementocytesCementocytes InactiveInactive
In lacunaeIn lacunae appear dark in GSappear dark in GS Processes present in canaliculiProcesses present in canaliculi
Processes connected via gap junctionsProcesses connected via gap junctions
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Cellular cementumCellular cementum
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Cementocytes vs.Cementocytes vs.
osteocytesosteocytes CementocytesCementocytes
More widely dispersedMore widely dispersed
R
andomly arrangedR
andomly arranged Canaliculi oriented towardsCanaliculi oriented towards
PDLPDL nutritionnutrition
OsteocytesOsteocytes
OsteonOsteon Haversian systemHaversian system
Organized cellsOrganized cells
Circumferential lamellaeCircumferential lamellae
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Relationship between acellular &Relationship between acellular &
cellular cementumcellular cementum More common patternMore common pattern
AcellularAcellular cervicallycervically
Acellular closer to dentineAcellular closer to dentine CellularCellular apicallyapically
Cellular covers acellularCellular covers acellular
Less common patternsLess common patterns
AlternatingAlternating
Acellular overlies cellularAcellular overlies cellular
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Extrinsic & intrinsic fiber cementumExtrinsic & intrinsic fiber cementum
Extrinsic fiber cementumExtrinsic fiber cementum
Fibers derived from insertingSharpys fibers of PDLFibers derived from insertingSharpys fibers of PDL
Intrinsic fiber cementumIntrinsic fiber cementumRun parallel to root surface at right angles toRun parallel to root surface at right angles to
extrinsic fibersextrinsic fibers
Fibers derived from cementoblastsFibers derived from cementoblasts
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Acellular extrinsic fiber cementumAcellular extrinsic fiber cementum
AEFCAEFC
Over cervical halfOver cervical half 2/3s of the root2/3s of the root
Bulk of cementum in premolarsBulk of cementum in premolars First formed cementumFirst formed cementum -- acellularacellular
Thickness of 15 mThickness of 15 m
All collagen are from Sharpys fibersAll collagen are from Sharpys fibers
Though GS from cementoblastsThough GS from cementoblasts
Fibers wellFibers well--mineralizedmineralized
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Cellular intrinsic fiber cementumCellular intrinsic fiber cementum
CIFCCIFC
Fibers deposited by cementoblastsFibers deposited by cementoblasts
F
ibers run parallel to root surfaceF
ibers run parallel to root surface No role of tooth attachmentNo role of tooth attachment
In apical 1/3 & interIn apical 1/3 & inter--radicular areasradicular areas
May beMay beTemporaryTemporary extrinsic fibers gain reattachmentextrinsic fibers gain reattachment
PermanentPermanent without attaching fiberswithout attaching fibers
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Acellular intrinsic fiber cemetumAcellular intrinsic fiber cemetum
If cementum forms slowly in CIFCIf cementum forms slowly in CIFC
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Cellular mixed stratified cementumCellular mixed stratified cementum
Alternating AEFC with CIFCAlternating AEFC with CIFC
Root apexRoot apex
Furcation areasFurcation areas
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MixedMixed--fiber cementumfiber cementum
Collagen fibers derived fromCollagen fibers derived from Extrinsic fibersExtrinsic fibers
Intrinsic fibersIntrinsic fibers
Intrinsic fibers run between the extrinsic fibersIntrinsic fibers run between the extrinsic fibers
Two typesTwo types rate of formationrate of formation Acellular mixedAcellular mixed--fiber cementumfiber cementum
Well mineralized fibersWell mineralized fibers Cellular mixedCellular mixed--fiber cementumfiber cementum
Less well mineralized fibersLess well mineralized fibers
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Cemental incremental linesCemental incremental lines
Irregular rhythm of depositionIrregular rhythm of deposition
Not related to activity & quiescenceNot related to activity & quiescence
R
elated toR
elated to Difference in the degree of mineralizationDifference in the degree of mineralization Composition of organic matrixComposition of organic matrix
Imprecise periodicityImprecise periodicity
AcellularAcellular closer, thinner & regular linescloser, thinner & regular lines
CellularCellular -- farther apart, thicker & irregular linesfarther apart, thicker & irregular lines
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Incremental linesIncremental lines
Cementum is formed rhythmically and can beCementum is formed rhythmically and can be
seen as being composed of layersseen as being composed of layers
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Resorption & repair of cementumResorption & repair of cementum
Less susceptibility to resorption than boneLess susceptibility to resorption than bone
Localized resorption areas occurLocalized resorption areas occur
Could be caused by microtraumaCould be caused by microtrauma May continue to root dentineMay continue to root dentine
By multinucleated odontoclastsBy multinucleated odontoclasts
Resorption filled by mineralized tissueResorption filled by mineralized tissue(resembles cellular cementum)(resembles cellular cementum)
Reversal lineReversal line
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Reparative cementum vs. cementumReparative cementum vs. cementum
Wider uncalcified zoneWider uncalcified zone
Less mineralizedLess mineralized
Smaller crystalsSmaller crystals Calcific globules are presentCalcific globules are present
Differences are related to different speed of formationDifferences are related to different speed of formation
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Clinical considerationsClinical considerations
Cemental callusCemental callus
Root fractureRoot fracture
N
o remodeling to original dimensions of the rootN
o remodeling to original dimensions of the root CementiclesCementicles
Free or attached pieces in PDLFree or attached pieces in PDL
MicrotraumaMicrotrauma
Apical & middle 1/3s of rootApical & middle 1/3s of root
Root furcationRoot furcation
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Clinical considerationsClinical considerations
SupraSupra--eruption of teetheruption of teeth
Tooth wearTooth wear
Local hypercementosisLocal hypercementosis
Reaction to PA inflammationReaction to PA inflammation
Difficulty in extractionDifficulty in extraction
Pagets diseasePagets disease multiple teeth withmultiple teeth withhypercementosishypercementosis
Cementum narrowing root canal andCementum narrowing root canal andshifting the junction between dentalshifting the junction between dentalpulp & PDL cervicallypulp & PDL cervically
Pulp removal in RCT up to that pointPulp removal in RCT up to that point
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Periodontal ligament PDLPeriodontal ligament PDL
Dense fibrous connective tissueDense fibrous connective tissue
Occupies the area between the root of the toothOccupies the area between the root of the tooth
and the walls of the alveolar socketand the walls of the alveolar socket Derived from the dental follicleDerived from the dental follicle
Continuous withContinuous with
the connective tissue of the gingiva above thethe connective tissue of the gingiva above thealveolar crestalveolar crest
The dental pulp at the apical foramenThe dental pulp at the apical foramen
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Periodontal ligament spacePeriodontal ligament space
Variable in width, average 0.2Variable in width, average 0.2mmmm
looks hourglass in shapelooks hourglass in shape
Reduced in unerupted & nonReduced in unerupted & non--functional teethfunctional teeth
Increased in teeth subjectedIncreased in teeth subjected
to heavy occlusal stressto heavy occlusal stress Narrows slightly with ageNarrows slightly with age
Narrower in permanent teethNarrower in permanent teeth
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Functions of PDLFunctions of PDL
AttachmentAttachment
Has a role in tooth eruption andHas a role in tooth eruption and
supportsupport
Its cells repair the alveolar bone &Its cells repair the alveolar bone &
cementumcementum Neurological control of masticationNeurological control of mastication
through its mechanoreceptorsthrough its mechanoreceptors
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Components of PDLComponents of PDL
FibersFibers
Ground substanceGround substance
CellsCells
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Fibers of PDLFibers of PDL
CollagenCollagen
Type I (70% of fibers)Type I (70% of fibers)
Type III (20% of fibers)Type III (20% of fibers)
Found in the periphery ofSharpys fibers attachment into alveolar boneFound in the periphery ofSharpys fibers attachment into alveolar bone
Small amounts of type V, VI as well as basement membrane collagen IVSmall amounts of type V, VI as well as basement membrane collagen IV& VII associated with the epithelial rests& VII associated with the epithelial rests
Highest turnover of collagen is in PDLHighest turnover of collagen is in PDL
Higher near apexHigher near apex
Even across the width of PDLEven across the width of PDL
Rate could be related to the amount of occlusal stressRate could be related to the amount of occlusal stress Oxytalan (in humans) or elastinOxytalan (in humans) or elastin
Attached into cementumAttached into cementum
May have a role in tooth supportMay have a role in tooth support
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Principal fibers of PDLPrincipal fibers of PDL
Fibers exist as bundles (principalFibers exist as bundles (principal
fibers) running in differentfibers) running in differentorientations in different regionsorientations in different regions Dentoalveolar crest fibersDentoalveolar crest fibers
Horizontal fibersHorizontal fibers
Oblique fibersOblique fibers Apical fibersApical fibers
Interradicular fibersInterradicular fibers From crest of interradicular septum toFrom crest of interradicular septum to
furcationfurcation
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Principal fibers of PDLPrincipal fibers of PDL
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Sharpys fibersSharpys fibers
Principal fibersPrincipal fibers
embedded intoembedded intocementum andcementum and
bonebone
More numerous butMore numerous but
smaller at cementalsmaller at cemental
endend
Mineralized andMineralized andunmineralized partsunmineralized parts
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Ground substance of PDLGround substance of PDL
60% of PDL by volume60% of PDL by volume
Main componentsMain components Hyaluronate GAGsHyaluronate GAGs
ProteoglycansProteoglycans
GlycoproteinsGlycoproteins
Functions of GSFunctions of GS
Ion and water binding & exchangeIon and water binding & exchange Control of collagen fibrillogenesis & fiberControl of collagen fibrillogenesis & fiber
orientationorientation
Tooth support & eruptionTooth support & eruption -- high tissue fluidhigh tissue fluid
pressurepressure
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Cells of PDLCells of PDL FibroblastsFibroblasts
Fusiform cells with manyFusiform cells with manyprocessesprocesses
FunctionsFunctions secretion andsecretion andturnover of fibersturnover of fibers Regeneration of tooth supportRegeneration of tooth support
apparatusapparatus Adaptive responses toAdaptive responses to
mechanical loadingmechanical loading CementoblastsCementoblasts
CementCement--forming cells liningforming cells liningcemental surfacecemental surface
Cuboidal cellsCuboidal cells
OsteoblastsOsteoblasts BoneBone--forming cells liningforming cells lining
tooth sockettooth socketResemble cementoblastsResemble cementoblasts
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Cells of PDLCells of PDL
Cementoclasts & osteoclastsCementoclasts & osteoclasts
Resorbing cellsResorbing cells
Howships lacunaeHowships lacunae
Epithelial rests cellsEpithelial rests cells Cuboidal cells that stain deeplyCuboidal cells that stain deeply
Close to cemental surfaceClose to cemental surface
Defence cellsDefence cells
MacrophagesMacrophages
Mast cellsMast cells
EosinophilsEosinophils
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Blood vessels of PDLBlood vessels of PDL
Separate from those entering pulpSeparate from those entering pulp
Some from alveolar bone through foraminaSome from alveolar bone through foramina
Some from pulp through accessory canalsSome from pulp through accessory canals
Major vessels lie between principal fiber bundle close toMajor vessels lie between principal fiber bundle close toalveolar bonealveolar bone
Capillary plexus around the toothCapillary plexus around the tooth
Crevicular plexus of capillary loopsCrevicular plexus of capillary loops Veins do not follow arteries but drain into intraalveolarVeins do not follow arteries but drain into intraalveolar
venous networksvenous networks
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Innervation of PDLInnervation of PDL
SensorySensory
NociceptionNociception
MechanoreceptionMechanoreception
Sensitivity to occlusal loadsSensitivity to occlusal loads
Guidance to intercuspationGuidance to intercuspation
AutonomicAutonomic
Associated with blood vesselsAssociated with blood vessels
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Alveolar processAlveolar process
The alveolar process develops during theThe alveolar process develops during the
eruption of teetheruption of teeth
Grows at a rapid rate at the free borderGrows at a rapid rate at the free border Proliferates at the alveolar crestProliferates at the alveolar crest
No distinct boundary exists between the body ofNo distinct boundary exists between the body of
the maxilla or mandible and the alveolar processthe maxilla or mandible and the alveolar process If teeth are lost the alveolar bone disappearsIf teeth are lost the alveolar bone disappears
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Development of bony cryptDevelopment of bony crypt
Deciduous tooth &Deciduous tooth &permanent successorpermanent successorinitially share cryptinitially share crypt
Bone subsequently formsBone subsequently formsto encase permanentto encase permanenttoothtooth