Eruption Establishment of Dentition

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Eruption & Eruption & Establishment of Establishment of the Dentition the Dentition Oral Oral Histology Histology Dent 206 Dent 206

Transcript of Eruption Establishment of Dentition

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Eruption & Establishment Eruption & Establishment of the Dentitionof the Dentition

Oral HistologyOral Histology

Dent 206Dent 206

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Tooth EruptionTooth Eruption A process whereby a tooth moves from its A process whereby a tooth moves from its

developmental position in the jaw into its functional developmental position in the jaw into its functional position in the mouthposition in the mouth

The process by which developing teeth emerge The process by which developing teeth emerge through the overlying bone, soft tissues & oral through the overlying bone, soft tissues & oral mucosamucosa

No evidence that eruption ceases after occlusal No evidence that eruption ceases after occlusal contactcontact Over-eruption upon removal of antagonist toothOver-eruption upon removal of antagonist tooth

A continuous process ending only with the loss of the A continuous process ending only with the loss of the toothtooth

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Purpose of tooth eruptionPurpose of tooth eruption

Entering the oral cavityEntering the oral cavity Contacting teeth of the opposing archContacting teeth of the opposing arch Functioning in occlusion & masticationFunctioning in occlusion & mastication

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Phases of eruptionPhases of eruption

Pre-eruptive phasePre-eruptive phase Initiation of tooth development –Initiation of tooth development – Crown completionCrown completion

Pre-functional eruptive phasePre-functional eruptive phase Initiation of root development –Initiation of root development – Establishment of occlusal contactEstablishment of occlusal contact

Post-eruptive functional phase – protracted phasePost-eruptive functional phase – protracted phase Once occlusal contact is established – onwardsOnce occlusal contact is established – onwards Concerned with development & maintenance of occlusionConcerned with development & maintenance of occlusion

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Tooth eruptionTooth eruption

Pre-eruptive PhasePre-eruptive Phase Pre-functional Eruptive PhasePre-functional Eruptive Phase Functional Eruptive PhaseFunctional Eruptive Phase

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Pre-eruptive Phase Pre-eruptive Phase Movements in response to positional changes of Movements in response to positional changes of

adjacent developing crownsadjacent developing crowns Movements in response to changes in the maxilla Movements in response to changes in the maxilla

and the mandible as the face grows downwards and and the mandible as the face grows downwards and forwards forwards

Teeth make mesial and distal movements during Teeth make mesial and distal movements during lengthening of the jawslengthening of the jaws

Movement of successor teeth in relation to their Movement of successor teeth in relation to their predecessors when they adjust to the roots of the predecessors when they adjust to the roots of the primary dentitionprimary dentition

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Movement of successors Movement of successors

Movement ofMovement of Permanent anteriorPermanent anterior PremolarsPremolars

Change in relative Change in relative position is due to position is due to Eruption of the Eruption of the

predecessor toothpredecessor tooth Increase in heightIncrease in height

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Movement of anterior successorsMovement of anterior successors

Begin development Begin development lingual to the incisal lingual to the incisal tip of the primary tip of the primary teethteeth

As primary teeth As primary teeth erupt they are erupt they are lingual to the apical lingual to the apical third of the rootsthird of the roots

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Movement of permanent molarsMovement of permanent molars

Maxillary molarsMaxillary molars Develop within the tuberositiesDevelop within the tuberosities Occlusal surfaces slanting distallyOcclusal surfaces slanting distally

Mandibular molarsMandibular molars Develop in the ramiDevelop in the rami Occlusal surfaces slanting mesiallyOcclusal surfaces slanting mesially

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First permanent Molar First permanent Molar Developing in TuberosityDeveloping in Tuberosity

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Permanent Molars Developing at Permanent Molars Developing at Angle of MandibleAngle of Mandible

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Movement of teethMovement of teeth

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Rates of eruptionRates of eruption

TOOTHTOOTH ERUPTION RATEERUPTION RATEUpper central incisorsUpper central incisors 1 mm / month1 mm / month

Lower 2Lower 2ndnd premolars premolars 4.5 mm / 14 weeks4.5 mm / 14 weeks

33rdrd molars molars 1 mm / 3months1 mm / 3months

Crowded dentitionCrowded dentition < 1 mm in 6 months< 1 mm in 6 months

A balance between eruptive & resistive forceA balance between eruptive & resistive force Resistance (factors affecting eruption rate)Resistance (factors affecting eruption rate)

Overlying soft tissues & alveolar boneOverlying soft tissues & alveolar bone Viscosity of surrounding PDLViscosity of surrounding PDL Occlusal forcesOcclusal forces

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Rate of eruptionRate of eruption

Slow eruption until the tooth reaches the oral mucosaSlow eruption until the tooth reaches the oral mucosa 2 – 4 years for permanent teeth2 – 4 years for permanent teeth

Rapid eruption as the tooth enters the oral cavityRapid eruption as the tooth enters the oral cavity 2/3s of root length has formed2/3s of root length has formed Maximum rate is 1 mm / monthMaximum rate is 1 mm / month

Eruption slows as the tooth approaches the occlusal Eruption slows as the tooth approaches the occlusal plane/contactplane/contact

No sex differenceNo sex differenceRacial differences may existRacial differences may exist

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Active eruption vs. passive eruptionActive eruption vs. passive eruption

ActiveActive Axial movement of the toothAxial movement of the tooth

PassivePassive Retraction of adjacent soft tissuesRetraction of adjacent soft tissues

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Pre-functional Eruptive PhasePre-functional Eruptive Phase Starts with the initiation of root formationStarts with the initiation of root formation Ends when reaching occlusal contactEnds when reaching occlusal contact

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Pre-functional Eruptive PhasePre-functional Eruptive Phase Root formationRoot formation

Proliferation of Epithelial Root SheathProliferation of Epithelial Root Sheath Initiation of dentinogenesis in the rootInitiation of dentinogenesis in the root Formation of the pulp tissuesFormation of the pulp tissues An increase in follicular fibrous tissueAn increase in follicular fibrous tissue

MovementMovement Elongating roots need a spaceElongating roots need a space Reduced enamel Epithelium fuses with the oral epitheliumReduced enamel Epithelium fuses with the oral epithelium

PenetrationPenetration Entrance into the oral cavityEntrance into the oral cavity Enamel cuticle covers enamelEnamel cuticle covers enamel No bleedingNo bleeding

Intra-oral occlusal/incisal movementIntra-oral occlusal/incisal movement Until contact with opposing crown occursUntil contact with opposing crown occurs Clinical crown vs. Anatomical crownClinical crown vs. Anatomical crown

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Pre-functional Eruptive PhasePre-functional Eruptive Phase

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Changes in tissuesChanges in tissues

Overlying erupting teethOverlying erupting teeth Surrounding erupting teethSurrounding erupting teeth Underling erupting teethUnderling erupting teeth

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Overlying erupting teethOverlying erupting teeth Eruption pathway Eruption pathway (Inverted (Inverted

triangular area)triangular area) Zone of degenerationZone of degeneration

Blood vessel decrease in numberBlood vessel decrease in number Nerves break down and degenerateNerves break down and degenerate

Gubernacular cord at the Gubernacular cord at the periphery of the degenerative periphery of the degenerative zonezone

Follicular fibers directed toward Follicular fibers directed toward the mucosathe mucosa

Gubernacular canal contains the Gubernacular canal contains the gubernacular cordgubernacular cord

The cord is composed of a central The cord is composed of a central strand of epithelium surrounded by strand of epithelium surrounded by connective tissueconnective tissue

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Overlying erupting teethOverlying erupting teeth OsteoclastsOsteoclasts

Resorption of overlying boneResorption of overlying bone (In successor teeth) resorption of the root of the (In successor teeth) resorption of the root of the

predecessorpredecessor OsteoblastsOsteoblasts

Build up of resorbed areas after tooth movementBuild up of resorbed areas after tooth movement

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Permanent incisors

Gubernacualr canals

Crypts of second Permanent molars

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Resorption of primary teethResorption of primary teeth

Begins within 1 year of Begins within 1 year of root completionroot completion

Similar to bone resorptionSimilar to bone resorption Dentine and cementum are Dentine and cementum are

resorbed resorbed but not enamelbut not enamel By osteoclastsBy osteoclasts

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Resorption of primary teethResorption of primary teeth

Resorbtion at apex

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Root resorptionRoot resorption

May be inherentMay be inherent May be related to pressure from permanent May be related to pressure from permanent

successor against overlying bone or toothsuccessor against overlying bone or tooth Non-supporting evidencesNon-supporting evidences

Surgical removal of permanent tooth germSurgical removal of permanent tooth germ Resorption of predecessor root still occurredResorption of predecessor root still occurred Resorption is delayedResorption is delayed

Clinical evidenceClinical evidence Successor is absent/abnormally positioned – shedding Successor is absent/abnormally positioned – shedding

still occurs but can be retardedstill occurs but can be retarded

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Factors affecting rate of root Factors affecting rate of root resorptionresorption

Increased masticatory loadsIncreased masticatory loads Less resorption when deciduous teeth are splinted after Less resorption when deciduous teeth are splinted after

removal of successor germsremoval of successor germs Rest periodsRest periods

Resorption is not a continuous processResorption is not a continuous process Reparative tissue may be formedReparative tissue may be formed Reattachment of PDLReattachment of PDL Reparative tissue is cemental-likeReparative tissue is cemental-like Repair > resorption leads to loss of PDL & ankylosis to Repair > resorption leads to loss of PDL & ankylosis to

surrounding bonesurrounding bone

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Ankylosed primary teethAnkylosed primary teeth

Failure of continuing eruptionFailure of continuing eruption Position remains constant in the Position remains constant in the

jawjaw Height of alveolar bone Height of alveolar bone

increasesincreases Tooth sinks gradually below Tooth sinks gradually below

the levels of adjacent teeththe levels of adjacent teeth Called submerged teethCalled submerged teeth Submerging may continue to an Submerging may continue to an

extent where teeth become extent where teeth become completely buried within bonecompletely buried within bone

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Hard tissue resorption Hard tissue resorption Osteoclasts resorb the Osteoclasts resorb the

minerals at the ruffled minerals at the ruffled border in 2 phasesborder in 2 phases Extra-cellular phaseExtra-cellular phase

Mineral is separated from Mineral is separated from collagen and broken into small collagen and broken into small fragmentsfragments

Intra-cellular phaseIntra-cellular phase Osteoclasts ingest mineral Osteoclasts ingest mineral

fragmentsfragments

Organic material resorption Organic material resorption occurs by Special fibroblast occurs by Special fibroblast (fibroblast-fibroclast cell)(fibroblast-fibroclast cell)

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Osteoclast Activity in Alveolar BoneOsteoclast Activity in Alveolar Bone

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Shedding of primary teethShedding of primary teeth

Primary dentition from about 2 to 7 yearsPrimary dentition from about 2 to 7 years Mixed dentition from 7 to 13 yearsMixed dentition from 7 to 13 years During mixed dentition period nearly 50 teeth During mixed dentition period nearly 50 teeth

are accommodated in the jaware accommodated in the jaw

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Fusion of Reduced Enamel Fusion of Reduced Enamel Epithelium & Oral EpitheliumEpithelium & Oral Epithelium

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PenetrationPenetration

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Development of dentogingival junctionDevelopment of dentogingival junction

Tooth approaches oral epitheliumTooth approaches oral epithelium Proliferation and union betweenProliferation and union between

Outer layer of REEOuter layer of REE Basal layer of oral epitheliumBasal layer of oral epithelium

Degeneration of epithelium covering the incisal edges/cusp tipsDegeneration of epithelium covering the incisal edges/cusp tips Crown emerges through an epithelial-lined pathwayCrown emerges through an epithelial-lined pathway Passive separation of oral epithelium from the crownPassive separation of oral epithelium from the crown Emergence without bleedingEmergence without bleeding

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Development of dentogingival junctionDevelopment of dentogingival junction

REE is retained as the junctional epitheliumREE is retained as the junctional epithelium Junctional epithelium acts as an epithelial sealJunctional epithelium acts as an epithelial seal Attached to the unerupted part of the crownAttached to the unerupted part of the crown

Reduced enamel component is believed to be Reduced enamel component is believed to be replaced eventually by oral epitheliumreplaced eventually by oral epithelium

Gingival crevice forms when more of the crown is Gingival crevice forms when more of the crown is exposedexposed

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Development of dentogingival Development of dentogingival junctionjunction

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Infant mandible 18 months

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Eruption vs. root completionEruption vs. root completion

Eruption is complete Eruption is complete before root formation is before root formation is completecomplete

Root is completedRoot is completed Primary teethPrimary teeth

1-1.5 yrs post-eruption 1-1.5 yrs post-eruption Permanent teethPermanent teeth

2-3 yrs post-eruption2-3 yrs post-eruption

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Eruption of permanent molarsEruption of permanent molars

Permanent molars do not have primary precursorsPermanent molars do not have primary precursors Permanent molars erupt through alveolar bonePermanent molars erupt through alveolar bone Bone loss occurs before approaching the oral epitheliumBone loss occurs before approaching the oral epithelium Tooth organ epithelium makes contact with oral mucosaTooth organ epithelium makes contact with oral mucosa Causes stretching and thinning of the oral mucosaCauses stretching and thinning of the oral mucosa Rupture of oral epitheliumRupture of oral epithelium Tooth emerges until clinical contact with the opposing Tooth emerges until clinical contact with the opposing

tooth is madetooth is made

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Eruption of permanent MolarEruption of permanent Molar

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Surrounding erupting teethSurrounding erupting teeth

Formation begins with root formationFormation begins with root formation From delicate fibers parallel to the surface of the tooth into From delicate fibers parallel to the surface of the tooth into

well-organized fibrous bundleswell-organized fibrous bundles Blood vessels become more dominantBlood vessels become more dominant As root elongates more fibrous bundles appearAs root elongates more fibrous bundles appear Fibres increase in density and number as the tooth eruptsFibres increase in density and number as the tooth erupts Fibers attach and release and re-attach rapidly as the root Fibers attach and release and re-attach rapidly as the root

elongateselongates Alveolar bone increases in height accordinglyAlveolar bone increases in height accordingly After functional occlusion fibers gain their mature orientationAfter functional occlusion fibers gain their mature orientation

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Periodontal LigamentPeriodontal Ligament

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Development of Periodontal LigamentDevelopment of Periodontal Ligament

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Alveolar ProcessAlveolar Process

The alveolar process develops during the The 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 No distinct boundary exists between the body

of the maxilla or mandible and the alveolar of the maxilla or mandible and the alveolar processprocess

If teeth are lost the alveolar bone disappearsIf teeth are lost the alveolar bone disappears

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Alveolar Bone Alveolar Bone

Crypt increases in Crypt increases in height to height to accommodate the accommodate the root formationroot formation

Alveolar bone Alveolar bone deposited deposited appositionally around appositionally around emerging crownemerging crown

Increase in heightIncrease in height

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Development of Bony CryptDevelopment of Bony Crypt

AA Deciduous tooth & Deciduous tooth &

permanent successor permanent successor initially share cryptinitially share crypt

BB Bone subsequently forms Bone subsequently forms

to encase the permanent to encase the permanent toothtooth

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Development of Bony CryptDevelopment of Bony Crypt

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Bony CryptsBony Crypts

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Underlying erupting teethUnderlying erupting teeth

Occlusal movement provides an Occlusal movement provides an underlying space (fundic region)underlying space (fundic region)

Highly fibroblasticHighly fibroblastic Fine strands of fibers that calcify Fine strands of fibers that calcify

into bone trabeculae (ladder-like into bone trabeculae (ladder-like arrangement)arrangement)

As the tooth moves up, bone As the tooth moves up, bone trabeculae become denser and trabeculae become denser and the spaces are filled with bonethe spaces are filled with bone

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Mechanisms of tooth eruptionMechanisms of tooth eruption

Theories of tooth eruptionTheories of tooth eruption Tooth is pushed out as a result of forces generated beneath Tooth is pushed out as a result of forces generated beneath

& around it& around it Alveolar bone growthAlveolar bone growth Root growthRoot growth Blood pressure/tissue fluid pressuresBlood pressure/tissue fluid pressures Cell proliferationCell proliferation

Tooth is pulled out as a result of tension within the PDLTooth is pulled out as a result of tension within the PDL

No theory is yet supported by sufficient experimental No theory is yet supported by sufficient experimental evidenceevidence

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Eruptive mechanismEruptive mechanism

A property of the PDLA property of the PDL Does not require a tractional force pulling the Does not require a tractional force pulling the

tooth outwardstooth outwards MultifactorialMultifactorial A combination of A combination of

Fibroblast activityFibroblast activity Vascular and/or tissue hydrostatic pressuresVascular and/or tissue hydrostatic pressures

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Role of PDL in eruptionRole of PDL in eruption

Root resectionRoot resection Surgical removal of proliferative tissue at the base of a Surgical removal of proliferative tissue at the base of a

continuously growing incisorcontinuously growing incisor Root transectionRoot transection

Cutting the incisor into proximal & distal portionsCutting the incisor into proximal & distal portions

Resected & transected incisors continue to erupt Resected & transected incisors continue to erupt because their PDL is still intactbecause their PDL is still intact

Tractional pulling forces are unlikely to have a roleTractional pulling forces are unlikely to have a role

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Role of PDL in eruptionRole of PDL in eruption

Eruptive potential is also inherent in the Eruptive potential is also inherent in the precursor of the PDL – dental follicleprecursor of the PDL – dental follicle Unerupted premolar removed from its follicle & Unerupted premolar removed from its follicle &

replaced with a metal replica – relica erupts replaced with a metal replica – relica erupts because the dental follicle was retainedbecause the dental follicle was retained

Rootless erupt because they are surrounded by Rootless erupt because they are surrounded by dental follicledental follicle

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Role of PDL in eruptionRole of PDL in eruption

Lathyrogens are drugs that inhibit cross-liking of Lathyrogens are drugs that inhibit cross-liking of collagencollagen

Eruption rates of lathyritic incisors are unaffectedEruption rates of lathyritic incisors are unaffected No tractional elements in pulling the tooth outwardsNo tractional elements in pulling the tooth outwards Teeth erupt in the absence of well-developed PDLTeeth erupt in the absence of well-developed PDL Disproving the theory of contraction of PDL collagenDisproving the theory of contraction of PDL collagen

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Role of PDL in eruptionRole of PDL in eruption

ConclusionConclusion Connective tissue surrounding the tooth contains Connective tissue surrounding the tooth contains

the eruptive elements - 2 viewsthe eruptive elements - 2 views Force is produced by activity of fibroblasts contractility Force is produced by activity of fibroblasts contractility

& motility& motility Vascular/hydrostatic pressure in & around the tooth is Vascular/hydrostatic pressure in & around the tooth is

responsible for eruptionresponsible for eruption

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Role of PDL fibroblast Role of PDL fibroblast motility/contractilitymotility/contractility

Cells exert tractional forces via Cells exert tractional forces via contractility/motility through contractility/motility through Collage networkCollage network Cell-to-cell contactsCell-to-cell contacts

Colchicine is a drug that disturbs intracellular Colchicine is a drug that disturbs intracellular microtubulesmicrotubules

Colchicine retards eruptionColchicine retards eruption

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Role of PDL vascular/hydrostatic Role of PDL vascular/hydrostatic pressurepressure

Vascular pressure can change the position of a Vascular pressure can change the position of a tooth in its sockettooth in its socket

Tooth moves in synchrony of arterial pulseTooth moves in synchrony of arterial pulse At death, blood pressure is zero – eruption At death, blood pressure is zero – eruption

ceasesceases Changes is eruptive behavior uponChanges is eruptive behavior upon

Administration of vasoactive drugsAdministration of vasoactive drugs Interference with sympathetic vasomotor nervesInterference with sympathetic vasomotor nerves

Stimulation of cervical sympathetic nervesStimulation of cervical sympathetic nerves

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Role of PDL vascular/hydrostatic Role of PDL vascular/hydrostatic pressurepressure

There should be a pressure differentials along the There should be a pressure differentials along the PDLPDL

Proteoglycan is increased during active eruptionProteoglycan is increased during active eruption Increased number of fenestrations on the capillaries Increased number of fenestrations on the capillaries

during active eruptionduring active eruption Fenestrations are higher near the base & low near the Fenestrations are higher near the base & low near the

alveolar crestalveolar crest Differential vascular activity across the length of the PDLDifferential vascular activity across the length of the PDL

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Other theories of tooth eruptionOther theories of tooth eruption

Growth of the rootGrowth of the root Pulpal pressurePulpal pressure Detachment & reattachment of PDL fibersDetachment & reattachment of PDL fibers Cell proliferationCell proliferation Increased bone formation around the teethIncreased bone formation around the teeth EndocrineEndocrine Vascular changesVascular changes Enzymatic degradationEnzymatic degradation

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Root elongationRoot elongation

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Pulpal PressurePulpal Pressure Many blood vessels in Many blood vessels in

apical region cause tissue apical region cause tissue fluid to build upfluid to build up

Increased vascularity Increased vascularity pressure potential between pressure potential between the highly vascular the highly vascular diaphragmatic proliferation diaphragmatic proliferation zone and the degenerative zone and the degenerative eruption pathway eruption pathway

PPT T -Tissue pressure-Tissue pressurePPII - Intrapulpal pressure - Intrapulpal pressure

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Periodontal ligament fibersPeriodontal ligament fibers

Attachment release and re-attachment of the PDL Attachment release and re-attachment of the PDL fibrous bundlesfibrous bundles

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Functional Eruptive PhaseFunctional Eruptive Phase Continues as long as teeth Continues as long as teeth

area presentarea present Compensation toCompensation to

Increase in alveolar process Increase in alveolar process heightheight

Attrition/abrasion of Attrition/abrasion of incisal/occlusal surfacesincisal/occlusal surfaces

Loss of opposing tooth (over Loss of opposing tooth (over eruption)eruption)

Cementum deposited atCementum deposited at Root apexRoot apex Furcation areasFurcation areas

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Stages inStages inDevelopmentDevelopment