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tooth developmentenamel

dentinroot formationcementumperiodontal ligamenttooth eruption



Vestibule

Developing teeth

Successional lamina (permanent teeth primordia)

(Lateral lamina)

Vestibular lamina

Primary lamina* Oral epithelium

Extensional lamina

( primary lamina)

(dental arch)

*

future ameloblasts

future odontoblasts(neural crest)

inner enamel epithelium

*apoptosis to form vestibule

ENAMEL

ORGAN

* lamina = epithelial ingrowth

molars4 mo (f) 4 yrs 5 yrs



1) Oral epithelium:-ameloblasts (enamel)

Oral mesenchyme*

2) dental papilla:-odontoblasts (dentin)-pulp cells

3) dental follicle:-cementoblasts (cementum)-fibroblasts

(periodondal ligament)-osteoblasts(alveolar bone)

1

3

2

Bud Stage:

* collagenous regionsweek 6

Oral epithelium Primary

dentallamina



What is the tissuebetwen the arrows?

Primary dental lamina



What is the cell layerat the arrow?

ENamel organ cap stage.

Inner enamel epithelium



Not ameloblast; really just an

inner enamel epithelium



Is this a primary tooth?



DF = Dental follicle:-cementum (cementoblasts) -periodontal ligament

(fibroblasts) -alveolar bone (osteoblasts)

epithelial pearls(of Serres)

DP = Dental papilla:-crown dentin-root dentin

DF DP

Gubernacular cord

Successional lamina



Bell Stage:

successionallamina

membranapreformativa

undifferentiatedenamel organ

vestibular

laminaprimarydentallamina

tongue

*

stellatereticulum



odontoblasts

ameloblasts

enamel

dentin

*

**

*

Tomes’ processTomes’ fiber

**Enamel deposition will occur ONLY on a dentin substrate**

Deposition of mineralized tissues:

Aprismatic

Dentin causes

differentiationof ameloblasts



*

Green asteriskis labeling:

a) enamel matrixb) enamelc) neither

Enamel itself will only appear when crown is

completely formed.

This is just an artifact.

You don't see enamel matrix because you only see

dentin in this view



What stage of toothdevelopment isdepicted?

(matrix)Check for deposition of mineralized tissue: this will mean

appositional stage



odontoblasts

outer enamelepithelium

stratumintermedium

stellate reticulum

enamelmatrix

inner enamel

epithelium(ameloblasts)

dentin

predentin

dentalpapilla

differentiatedameloblast

Thickest region will be on top.

Thickest dentin and enamel

Undifferentiated ameloblast vs

differentiated ameloblast.

Morphology changes

Apical end of cell makes enamel.

Polarity and nuclei shifts.



pre-ameloblasts

ameloblasts

membrana

preformativa

ameloblasts & stratum

intermedium cells are

perpendicular to each

other



enamel rod(prism)

DEJ

Tomes’process enamel crystals

+water, proteins(“enamel matrix”)

Amelogenesis

. .... ..dentin

aprismaticenamel

temporal progression

maturationstages



matrix

The arrows are pointing toward whatstructures? Tome's processes ?



Tomes’ processes

enamel crystals

enamel matrix

matrix



Enamel crystals

Enamel crystals growin length

(during enameldeposition phase)

amelogeninassembly

small nanospheres(hydrophilic)

removal ofhydrophilic tails

(enamelysin)

large nanospheres(hydrophobic)

Ca2+

Enamel crystals growin width

(during maturation phase)

enamelinnucleation?

enamel serineprotease

enamelin

enamelin

Tome’sprocess

Once crystal formation happens,

blue crystals get coated by

amelogenins.

Amelogenin is removed during

maturation



Enamel rods (prisms):

hydroxyapatitecrystals

AA

T

enamel proteins,protein fragments(between crystalites)

TB

GJ

secretory vesicles(protein secretion)

stratumintermedium

(tail)enamel crystalites



aprismatic enamel(20-100µ m) Prismatic enamel:

-results from loss ofTomes' process

-all crystalites ⊥ to surface

-highly mineralized-must be removed tocreate "tags" forbonding procedures

prismatic enamel

prismatic enamelDEJ

oralcavity

Prismatic vs. aprismatic enamel:



Enamel spindles:

DEJ

-extensions of odontoblast

processes (dentin tubules)-most abundant at cusp~5-50 µm

D

E



DEJ



The structures at thearrows are?



Enamel

tuftsDEJ

hypomineralized,rich in the acidprotein ‘tuftelin’

DEJ

ES



The arrow is pointing to what structure? Howcould you test your answer?



X

= ameloblast

Enamel lamellae-hypomineralized (mineralization failure)

-resemble enamel matrix -protein-rich-prone to develop cracks



The lines that have the same orientation as thearrows represent what structures?

Rods are running in direction

of arrows



ameloblast

Tomes’ process

Enamel crossstriations

(short period,diurnal increments)

2.5 –6 um

Daily incremental growth line



Striae of Retzius

(long period)

1

234567

Weekly growth intervals



Striae of Retzius (long period)

-weekly reduced rate of secretion-unequal termination of growth cycle

(delayed interrod termination)-crystal orientation is disrupted

interrod

rod Striae

Striae

Striae

321



Neonatal lines

Did this tooth begin mineralization inthe 1st, 2nd or 3rd trimester?



The arrows represents what structures?



Perikymata“imbrication lines of Pickerill”

7-10 days



The arrows depict ___ - __ __?



parazones(light bands)

diazones(dark bands)

50 µm



Hunter-Schreger lines

enamelsurface

parazone

diazone

parazone

pulpcavity DEJ

dentin



Gnarled enamel



Which successional tooth is older?



Which successional tooth is older?Does enamel maturation HAVE to

occur prior to eruption?



Enamel crystals

Enamel crystals growin length

(during enameldeposition phase)

amelogeninassembly

small nanospheres

(hydrophilic)

removal ofhydrophilic tails

(enamelysin)

large nanospheres(hydrophobic)

Ca2+

Enamel crystals growin width

(during maturation phase)

enamelinnucleation?

enamel serineprotease

enamelin

enamelin

Tome’sprocess



ameloblasts

reduced enamel

epithelium

“basal lamina” orprimary cuticle

-increase in crystal thickness (& consequent reduction in intercrystalline space)

(1.5 nm 25nm)-secretion of calcium & phosphate ions-removal of water and protein (mostly amelogenin, squeezed to surface by

expanding crystals)-final protein content:

enamel pitsamelogenin (90%)enamelintuftelinameloblastin

(sheathlin)

(10%) 1-2% ofenamel

H2O, protein minerals

DEJ .. .... ..

aprismaticenamel

synthesis maturation

secretory & ruffledborder stages

aprismaticenamel

Enamelmaturation:

enamel rod(30% mineralized)



Dentin Enamel

Formed throughout life Formed prior to eruptionContains nerves No nerves

Contains cell processes AcellularContains collagens Contains enamel proteinsSmall crystals Large crystalsOne step mineralization Two step mineralization



odontoblasts

dentin

predentin

Dentin deposition:

dentinal tubules(Tomes’ fibers)



nerveaxons

microtubules

intertubular

intra(peri)tubular



Intertubular dentin

Peritubular dentin(intratubular,

sheath of Neuman)

hypermineralized(no collagen)

ns



A What type of dentin isdepicted at "A"?



Demarcation linePrimary dentin(circumpulpal)

CP

3o

2o

Pulpcavity

mantle dentin

enamel

(a.k.a. reactionary, restorative,reparative, response)

tubules if present, very irregular

Dentin typesa) branchingb) less mineralized

c) collagen⊥

to DEJ

TGL

1o

CP 1o

2o

CP

Mantle:

Secondarydentin

(formedafterroot

completion)



circumpulpaldentin

mantledentin

enamel

Polarized light

mantle

dentin20-150 uMthick

enamel

circumpulpaldentinmantle dentin found only

in crown



Demarcation linePrimary dentin(circumpulpal)

Secondarydentin

(formedafterroot

completion)

CP

3o

2o

mantle dentin

enamel

(a.k.a. reactionary, restorative,reparative, response)

tubules if present, very irregular

Dentin typesa) branchingb) less mineralized

c) collagen⊥

to DEJ

TGL

1o

CP 1o

2o

CP

Mantle:

Pulpcavity



What type of dentin isdepicted at the arrow?



1o & 2o - formed by odontoblasts

3o - formed by newly recruited

mesenchyme (PULP responds to insult)

Potential fate of 1o & 2o dentin:Dead tracts - empty, sealed tubulesSclerotic - fully mineralized tubules

(excess peritubular dentin)

dead tracts

scleroticdentin

3o



Translucent dentin

Physiological-increases linearly with age (use in forensics)-begins to form at root apex-physically similar to sclerotic dentine



Incremental growth lines (diurnal) of Von Ebner(short period lines)

tubules



Lines of Owen(pronounced Andresen line)

Linesof

Owen

Incremental growth lines (weekly) ofAndresen (long period lines)

~weekly deposition-duration equivalent to striae

of Retzius in enamel*-cause unknown

~1 wk

secondarycurvature *implies similar cause, but unknown



The arrows represent......?



Interglobular dentin

enamel

Tubule direction isunaffected - but they

lack peri (intra)tubular dentin(hypomineralized)



24 hourspredentin

dentin



Globular mineralization

collagen +dentinphosphoprotein

(DPP)

calcospherite“globularmineralization”



Globular mineralization



interglobular dentin(hypomineralized)



These holesrepresent whatstructures?



The region between thearrows is called_______?



hyaline layer(mantle equivalent)

Tomes' granularlayer

Root dentin



Tomes' granular layer

highly branchedodontoblast tubules

“granules”



Development of root& supporting structures

-root proper-cementum-periodontal ligament-pulp cavity

apical foramen

-root growth commencesonly after crown completion

-root growth initiation

coincides with axialeruption phase

-root maturation may takeup to 3 years



Identify the structures labeled “A”(hint: they are cytokeratin positive)

C t /d ti



mesenchymalcells from follicle

(presumptive cementoblasts)

Dentin

Enamel

Intermediate

cementum

rootdentin

intermediatecementum

cellularcementum

CEFC)

cementocyte

**Cementum deposition willoccur ONLY on a dentin substrate**

Hertwig’s root sheath

Cementum/dentinformation:

CEFC=cellular extrinsic

fiber cementum



Hertwig’sRootSheath




root dentin – pulp mesenchyme



Hertwig’sRootSheathintermediate cementum – epithelial product





pre-cementoblasts

intermediate cementum – epithelial productroot dentin – pulp mesenchyme




pre-cementoblasts





pre-cementoblasts

intermediate cementum – epithelial productcementum – follicular mesenchyme





pre-cementoblasts


cementum – follicular mesenchyme




pre-cementoblasts





Identify the tissueat the arrow

(be specific)



canaliculi

cementocyte(lacuna)

PL

incrementallines ofSalter

cementoblasts

appositionalgrowth

Cellular & acellularcementum

-avascular-canaliculi not interconnected-forms anchoring substrate for PL



Repaired cementum(cellular intrinsicfiber cementum)

Cementum formation



epithelial restsof Malassez

HRS

Cementum

Dentin

cementicle(attached)

Cementum formationaberrations:

Hertwig’s root



root sheath discontinuity

Cementum

Exposed

rootdentin

Enamel

(alternatively, mayform enamel pearl)

*

*

enamelpearl

Hertwig s rootsheath anomalies:

root sheath adhesion



NC

Hertwig’sRootsheath

X



NC


X



NC


X

root canal

accessory root canal



What tissue waspresent at the

* in life?

*



loss of lamina duradue to osteosarcoma



Identify the tissuebetween the arrows

(Is it demineralizedor ground?)

Periodontal ligament:



r n g m n-attachment (usu. bone cementum)-cushioning-tooth positioning:

eruptiondrift

-source of repair cells-mechanoreceptors

pulp

cells: fibroblastscementoblastscementoclastsosteoblastsosteoclasts

epithelial cellsdefenseneural

DF

Alveolar bone(L. alveus: hollow sac, cavity)



interstitial

“spaces”

0.2 - 0.4 mm

1) PL collagen - high turnover rate

2) PL fibroblasts- intercellular connections- cilia (microtubules = 9+0)

3) contains cells for synthesis, repair,defense etc.

4) contains “anti-calcification” properties-hyaluronidase treatment leads to

mineralization

D

C

B



cortical bonespongy bone

alveolar bone proper(lamina durabundle bone)

Principalfibers

5 µ mprincipal fiber

supporting bone:

1) apical2) oblique3) horizontal4) alveolar crest5) transseptal 6) gingival



bone

rootdentin

sharpey’sfibers

PL fibers

Oxytalan fibers



Oxytalan fibers(microfibril component of elastic fibers)

Pulp



Pulp

cell-rich zone

(progenitorodontoblasts)

nerve axon(unmyelinated)

odontoblastprocess

cell-free zone-artifact?-reduced in root

odontogenic zone:

*

*columnar in crown;cuboidal in root pulp



generalsensory

autonomic(sympathetic)

-fibroblasts (col I and III)-nerve cell axons-schwann cells-endothelial cells-inflammatory cells-macrophages-mesenchymal progenitor cells

lymphatic

vein &

artery

unmyelinatedhere

Pulp denticles



Pulp dent clesPulp stones (false denticles)

false pulp stone(concentric)

true pulp stone(denticle)

Eruption &



Eruption &Shedding

1) tooth movements

2) resorption

3) eruption

Tooth movements:



1) Preeruptive:

-up to crown completion(prior to initiation of root formation)-movement due to permanent tooth growth, jaw growth-associated with alveolar bone remodeling (as are prefunctional

& functional stages)

a) Tooth body movementresorption synthesis

b) Relative movement (relative positioning)

c) Eccentric movement

2) Eruptive:



2) Eruptive:-begins during initiation of root formation-secretory phase of amelogenesis

has ended (A)-fusion of reduced enamel

epithelium and oral epithelium (B,C)-tooth emergence (E)-intraoral movement until clinical

contact with opposing crown (F,G)

3) Functional:



)-root completion (apical foramen narrows, tooth reaches occlusion) (A)

1-1.5 yrs for primary teeth2-3 yrs for permanent teeth

-final organization of PL fibers is achieved-movement to compensate for enamel wear (B)-movement to compensate for tooth wear/loss (C, D)

attrition ofincisive enamel

compensatorythickeningof cementum

A B

mesiallabial

trans-septal



mesial

mesial

distal

distal

buccal

lingual (palatal)

lingual

(palatal)

vertical(super-eruption)

mesial drift

C

D

pfibers

Forces driving tooth eruption:



Forces driving tooth eruption:

1) Pulpal pressure andpulpal growth

2) Traction by periodontalfibers and fibroblasts

3) Root elongation

4) alveolar boneremodeling

Factors affecting eruption



local:

-overcrowding (supernumary teeth)-tooth impaction-ankylosis

systemic:

-osteopetrosis (osteoclast disruption)-Ca2+ disruption (Rickets, parathyroidproblems etc.)

environmental:

mesiodens

impacted molar

ankylosed tooth

g p



The cavities depicted at "A" are madeby________? (be specific) What are theycalled?

A

Resorption/shedding of primary tooth:



p g f p m y

D

D

odontoclasts inHowship’s lacunae

Dentin

Primary tooth shedding:-loss of root (“mineraloclast” resorption)

-concomitant loss of PL fibers -loss of bone-mastication forces

Resorptive cells (mineraloclasts):



odontoclast (dentin resorption)

ameloclast (enamel resorption)cementoclast (cementum resorption)osteoclast (bone resorption)

sorpt c s (m n ra oc asts)

multinucleate cellsderived from fusionof monocyte-macrophagecells

enamel: 96% mineralizeddentin: 70% mineralizedbone: 65% mineralizedcementum: 60% mineralized

Howship’s lacunae

Soft tissues (periodontal



Soft tissues (periodontalligament) also becomes

remodelled in resorptionzone

What structure occupies these foramina



What structure occupies these foraminain life? Is the dentition present primary

or secondary?

Gubernacular



Gubernacularcord in canal

Gubernacular corddoes not "pull" toothinto oral cavity

(surgical removal leads to

ossification ofgubernacular canalbut the tooth eruptsnonetheless)

Gubernacular cord:(L rudder)



(L. rudder)

-remnant of dental lamina

-acquires ECM coating-prevents bone formation



The cellular tissue

between the arrowsis called the ______?



Formation of junctional epithelium & 1o

cuticle



enamel

reduced enamelepithelium

dentin

Formation of junctional epithelium & 1o

cuticle



enamel

reduced enamelepithelium

primarycuticle

dentindentin

outer enamel



developmental(primary)

cuticle

reduced enamel

epithelium

Nasmyth’s

membrane

enamel

mepithelium

inner enamelepithelium



e n a m e l s p a c e

gingivalepithelium

REE



e n a m e l s p a c e

gingivalepithelium

REE

Attachment epithelium: mature tooth



dentinenamel space

gingival sulcus

gingiva

epthelialattachment(junctionalepithelium)

enamel surfacei d lli l



plaque

enamel surfaceabove & belowgingival sulcus

acquired pellicle

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