Transcript
Eruption & Establishment Eruption & Establishment of the Dentitionof the Dentition
Oral HistologyOral Histology
Dent 206Dent 206
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
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
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
Tooth eruptionTooth eruption
Pre-eruptive PhasePre-eruptive Phase Pre-functional Eruptive PhasePre-functional Eruptive Phase Functional Eruptive PhaseFunctional Eruptive Phase
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
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
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
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
First permanent Molar First permanent Molar Developing in TuberosityDeveloping in Tuberosity
Permanent Molars Developing at Permanent Molars Developing at Angle of MandibleAngle of Mandible
Movement of teethMovement of teeth
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
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
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
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
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
Pre-functional Eruptive PhasePre-functional Eruptive Phase
Changes in tissuesChanges in tissues
Overlying erupting teethOverlying erupting teeth Surrounding erupting teethSurrounding erupting teeth Underling erupting teethUnderling erupting teeth
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
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
Permanent incisors
Gubernacualr canals
Crypts of second Permanent molars
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
Resorption of primary teethResorption of primary teeth
Resorbtion at apex
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
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
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
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)
Osteoclast Activity in Alveolar BoneOsteoclast Activity in Alveolar Bone
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
Fusion of Reduced Enamel Fusion of Reduced Enamel Epithelium & Oral EpitheliumEpithelium & Oral Epithelium
PenetrationPenetration
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
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
Development of dentogingival Development of dentogingival junctionjunction
Infant mandible 18 months
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
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
Eruption of permanent MolarEruption of permanent Molar
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
Periodontal LigamentPeriodontal Ligament
Development of Periodontal LigamentDevelopment of Periodontal Ligament
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
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
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
Development of Bony CryptDevelopment of Bony Crypt
Bony CryptsBony Crypts
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
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
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
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
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
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
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
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
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
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
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
Root elongationRoot elongation
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
Periodontal ligament fibersPeriodontal ligament fibers
Attachment release and re-attachment of the PDL Attachment release and re-attachment of the PDL fibrous bundlesfibrous bundles
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
Stages inStages inDevelopmentDevelopment
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