early tooth development

8/3/2019 Early Tooth Development

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Development of thetooth & its supporting

structures

Oral HistologyOral Histology

Dent 206Dent 206


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Early tooth developmentEarly tooth development

Three overlapping phasesThree overlapping phases

InitiationInitiation

Sites of future teeth establishedSites of future teeth established

Dental laminaDental lamina Appearance of tooth germsAppearance of tooth germs

MorphogenesisMorphogenesis

Shape is determined by cell proliferation and cell movementShape is determined by cell proliferation and cell movement

HistogenesisHistogenesis Differentiation of cellsDifferentiation of cells

Formation of dental tissuesFormation of dental tissues


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Early signsEarly signs

Condensation of ectomesenchymal tissue and capillaryCondensation of ectomesenchymal tissue and capillarynetworks beneath oral epithelium at specific sitesnetworks beneath oral epithelium at specific sites

Primary epithelial band (PEB)Primary epithelial band (PEB) Oral epithelium thickens & invaginates into condensedOral epithelium thickens & invaginates into condensed

ectomesenchymeectomesenc

hyme

PEB dividesPEB divides Vestibular laminaVestibular lamina

Buccally to form the oral vestibuleBuccally to form the oral vestibule

Degeneration of central cells to produce the buccal sulcusDegeneration of central cells to produce the buccal sulcus

Oral vestibuleOral vestibule

Dental laminaDental lamina Lingually to form the teethLingually to form the teeth

ArchArch--shaped band of tissueshaped band of tissue

A series of swellings at the deep surfaceA series of swellings at the deep surface

Enamel organsEnamel organs


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DentalDental

lamina &lamina &vestibularvestibular

laminalamina


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Tooth germTooth germ

Bud stageBud stage

Cap stageCap stage

Bell stageBell stage


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Bud stageBud stage

Enamel organEnamel organ

Epithelial condensationEpithelial condensation

Spherical/ovoidSpherical/ovoid

Poorly morphoPoorly morpho-- and histodifferentiatedand histodifferentiated

Successive development of tooth germ involves aSuccessive development of tooth germ involves a

complex interaction between the epithelial and thecomplex interaction between the epithelial and the

mesenchymal componentsmesenchymal components

No development when separated and cultured individuallyNo development when separated and cultured individually

Basement membraneBasement membrane


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http://www.usc.edu/hsc/dental/ohisto


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Cap stageCap stage

Early cap stageEarly cap stage Deeper surface invaginates to form a capDeeper surface invaginates to form a cap--shaped structureshaped structure

Still poorly differentiated cellsStill poorly differentiated cells

Distinction betweenDistinction between Central portionCentral portion

Rounded cellsRounded cells Peripheral cellsPeripheral cells

Internal enamel epithelium IEEInternal enamel epithelium IEE

External enamel epithelium EEEExternal enamel epithelium EEE

Late cap stageLate cap stage Stellate reticulum SRStellate reticulum SR

Central cells become separated with intercellular spacesCentral cells become separated with intercellular spaces

EEE cells remain cuboidalEEE cells remain cuboidal IEE cells become more columnarIEE cells become more columnar

Mesenchymal cells continue to surround the enamel organMesenchymal cells continue to surround the enamel organ Dental papillaDental papilla

Dental follicleDental follicle


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Early bell stageEarly bell stage

Differential cell division along IEEDifferential cell division along IEE

Mapping out the occlusal pattern of the crownMapping out the occlusal pattern of the crown

Cessation of cell divisionCessation of cell division

At future cups & incisal edgesAt future cups & incisal edges Active cell divisionActive cell division

At fissure sites & marginsAt fissure sites & margins

Dental lamina breaks downDental lamina breaks down Losing connection with oral epitheliumLosing connection with oral epithelium

Dental lamina between tooth germs is lostDental lamina between tooth germs is lost

Remnants of dental lamina may remain as Epithlial RestsRemnants of dental lamina may remain as Epithlial Restsof Serres that may be involved in the aetiology of cystsof Serres that may be involved in the aetiology of cysts


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Histodifferentiation leads to appearance of 4Histodifferentiation leads to appearance of 4distinct layersdistinct layers

EEEEEE

Cuboidal cellsCuboidal cells

FunctionsFunctions Maintenance of the shape of the enamel organMaintenance of the shape of the enamel organ

Exchange of substances between enamel organ and dentalExchange of substances between enamel organ and dentalfolliclefollicle

Cervical loopCervical loop Increased cell divisionIncreased cell division

At junction EEE and IEEAt junction EEE and IEE


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Stellate reticulumStellate reticulum

Fully developed at this stageFully developed at this stage

Star shaped cells with many branching processesStar shaped cells with many branching processes

FunctionsFunctions

Protection of underlying tissue against physical disturbanceProtection of underlying tissue against physical disturbance

Maintenance of tooth shapeMaintenance of tooth shape

Its hydrostatic pressure is in equilibrium with that of the dentalIts hydrostatic pressure is in equilibrium with that of the dental

papilla allowing the proliferation of IEE to determine crownpapilla allowing the proliferation of IEE to determine crown

morphogenesismorphogenesis


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Stratum intermedium SIStratum intermedium SI 22--3 layers of flattened cells over IEE3 layers of flattened cells over IEE

May be concerned with protein synthesis, transport of materials toMay be concerned with protein synthesis, transport of materials toand from IEE cells and concentration of cellsand from IEE cells and concentration of cells

IEEIEE Columner cells that become elongated starting from the cusp tipsColumner cells that become elongated starting from the cusp tips

and incisal edgesand incisal edges

Desmosomes connect cells together and with stratum intermediumDesmosomes connect cells together and with stratum intermediumcellscells

Basement membraneBasement membrane Dental papillaDental papilla

Less differentiated than enamel organLess differentiated than enamel organ


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Late bell stageLate bell stage

Appositional stageAppositional stage

Hard tissue formationHard tissue formation

Dentine formation precedes enamel formationDentine formation precedes enamel formation

Appearance of a lingual downgrowth of EEEAppearance of a lingual downgrowth of EEE In deciduous tooth germsIn deciduous tooth germs

Successor laminaSuccessor lamina

Gives rise to tooth germs of permanent successor teethGives rise to tooth germs of permanent successor teeth

In permanent tooth germsIn permanent tooth germs Is a transient structure that disappears eventuallyIs a transient structure that disappears eventually

Behind second deciduous molars dental lamina growsBehind second deciduous molars dental lamina growsbackwards to bud off permanent molars successivelybackwards to bud off permanent molars successively


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Late bell stageLate bell stage

Reciprocal interactionReciprocal interaction

Dentine & enamel formation commences atDentine & enamel formation commences at

Cusp tipsCusp tips

Incisal edgesIncisal edges

Developing ameloblasts (Preameloblasts/matureDeveloping ameloblasts (Preameloblasts/mature

IEE cells) induce adjacent mesenchymal cells toIEE cells) induce adjacent mesenchymal cells to

become columnar and differentiate intobecome columnar and differentiate intoodontoblasts and secrete predentine & dentineodontoblasts and secrete predentine & dentine

Dentine induces ameloblasts to secrete enamelDentine induces ameloblasts to secrete enamel


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Transient structuresTransient structures

Enamel knotEnamel knot A localized mass of cells in the center of IEEA localized mass of cells in the center of IEE

A bulge into dental papillaA bulge into dental papilla

NonNon--proliferative cellsproliferative cells

Produce signaling moleculesProduce signaling molecules

Disappears & contribute cells to enamel cordDisappears & contribute cells to enamel cord Enamel cordEnamel cord

A strand of cells extending from SI into SRA strand of cells extending from SI into SR

May be involved in mechanical transformation of cap stage into bell stageMay be involved in mechanical transformation of cap stage into bell stage

Termed enamel septum when reaching EEETermed enamel septum when reaching EEE

Enamel navelEnamel navel

A small invagination at junction with EEEA small invagination at junction with EEE Enamel nicheEnamel niche

Area enclosed by the double attachment of enamel organ to dental laminaArea enclosed by the double attachment of enamel organ to dental lamina


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Nerve & blood supplyNerve & blood supply

Nerve supplyNerve supply

Nerves supply starts as a plexus under dentalNerves supply starts as a plexus under dentalpapilla during cap stagepapilla during cap stage

Nerves spread & penetrate dental papilla withNerves spread & penetrate dental papilla withonset of dentinogenesisonset of dentinogenesis

Blood supplyBlood supply

Blood vessels invade dental papilla at early bellBlood vessels invade dental papilla at early bellstagestage

Blood vessels are evident in dental follicle in closeBlood vessels are evident in dental follicle in closeassociation with EEE which they never penetrateassociation with EEE which they never penetrate


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DentinogenesisDentinogenesis

DP cells induce IEEDP cells induce IEEcells to differentiatecells to differentiate

Differentiated IEEDifferentiated IEEcells then induce DPcells then induce DPcellscells--odontoblastsodontoblasts--dentinedentine

DentineDentine--amelogenesisamelogenesis

PredentinePredentine


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AmelogenesisAmelogenesis

2 processes2 processes

Organic matrixOrganic matrix

AmelogeninAmelogenin

MineralisationMineralisation


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Reduced Enamel epitheliumReduced Enamel epithelium


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Root developmentRoot development


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Multiple rootsMultiple roots


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Epithelial rests ofMalassezEpithelial rests ofMalassez


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DentalDental

folliclefollicle Undiff. Mes. CellsUndiff. Mes. Cells

CementoblastsCementoblasts

FibroblastsFibroblasts OsteoblastsOsteoblasts


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CementogenesisCementogenesis


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Tooth eruptionTooth eruption

PrePre--eruptive phaseeruptive phase

Related to tooth germ movement beginning duringRelated to tooth germ movement beginning during

crown formationcrown formation PrePre--functional eruptive phasefunctional eruptive phase

Eruption until occlusal contact is madeEruption until occlusal contact is made

Functional eruptive phaseFunctional eruptive phase Compensation for jaw growth and occusal wear of theCompensation for jaw growth and occusal wear of the

enamelenamel


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PrePre--eruptive stageeruptive stage

Teeth adjust relative to the forming boneTeeth adjust relative to the forming bone In response to positional changes of neighboringIn response to positional changes of neighboring

crownscrowns

Growth of the jawsGrowth of the jaws


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PrePre--functional eruptive stagefunctional eruptive stage

Root formationRoot formation

MovementMovement

PenetrationPenetration IntraoralIntraoral

Clinical crownClinical crown

Anatomic crownAnatomic crown


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MovementMovement

Eruption pathway

Gubernacular cord

Resorption


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PDL fibersPDL fibers


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Tooth emergenceTooth emergenceDentogingival JunctionDentogingival Junction


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Emergence through mucosaEmergence through mucosa


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Eruption theoriesEruption theories

Root growthRoot growth

Pulpal pressurePulpal pressure

Increased pressure to decreased pressureIncreased pressure to decreased pressure

Modification of PDLModification of PDL

Other theoriesOther theories

Increased vascularityIncreased vascularity

Increased bone formationIncreased bone formation EndocrineEndocrine

Enzymatic degradationEnzymatic degradation

early tooth development

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