Enamel / dental implant courses

ENAMELENAMEL
 INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
 Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

 There are two things in life that aThere are two things in life that a
sage must preserve at everysage must preserve at every
sacrifice, the coats of his stomach &sacrifice, the coats of his stomach &
the enamel of his teeth. Some evilsthe enamel of his teeth. Some evils
admit of consolations, but there areadmit of consolations, but there are
no comforters for dyspepsia & theno comforters for dyspepsia & the
toothache -----Henry Lytton Bulwertoothache -----Henry Lytton Bulwer

 Why should we know about enamel ?Why should we know about enamel ?

CONTENTSCONTENTS
1. Introduction1. Introduction
2. Physical characteristics2. Physical characteristics
3. Chemical Composition3. Chemical Composition
4. Amelogenesis4. Amelogenesis
5. Enamel Proteins5. Enamel Proteins
6. Disturbances in Enamel formation6. Disturbances in Enamel formation
7. Structures associated with enamel & DEJ7. Structures associated with enamel & DEJ
8. Structures associated with appositional growth of enamel8. Structures associated with appositional growth of enamel
9. Structures associated with changes in enamel rod orientation9. Structures associated with changes in enamel rod orientation
10. Structures associated with surface of tooth10. Structures associated with surface of tooth
11. Non Carious defects of enamel11. Non Carious defects of enamel
12. Age Changes in Enamel12. Age Changes in Enamel
13. Mechanism of action of Fluorides13. Mechanism of action of Fluorides
14. Clinical characteristics of normal & altered enamel14. Clinical characteristics of normal & altered enamel
15. Conclusion15. Conclusion

INTRODUCTIONINTRODUCTION
 Enamel is a hard, mineralised tissueEnamel is a hard, mineralised tissue
that covers the anatomical crowns ofthat covers the anatomical crowns of
teethteeth
 Enamel has evovled as an epithelialEnamel has evovled as an epithelial
derived protective covering of thederived protective covering of the
teethteeth
 The cellsresponsible for theThe cellsresponsible for the
formation of enamel,the ameloblasts,formation of enamel,the ameloblasts,
are lost as the tooth erupts into theare lost as the tooth erupts into the
oral cavityoral cavity www.indiandentalacademy.comwww.indiandentalacademy.com

PHYSICALPHYSICAL
CHARACTERISTICSCHARACTERISTICS 1. Thickness1. Thickness
 2. Hardness2. Hardness
 3. Permeability3. Permeability
 4. Color4. Color
1. Thickness:1. Thickness:
 Varies from tooth to tooth and in different areas of the same toothVaries from tooth to tooth and in different areas of the same tooth
 Thickest over the cusps - about 2.5mm to knife edge at cervicalThickest over the cusps - about 2.5mm to knife edge at cervical
 2. Hardness:2. Hardness:
 Hardest calcified tissue in the human bodyHardest calcified tissue in the human body
 Withstand masticatory forces & protect underlying dentin & pulpWithstand masticatory forces & protect underlying dentin & pulp
 Brittle in natureBrittle in nature
 3. Permeability:3. Permeability:
 Acts like a semipermeable membraneActs like a semipermeable membrane
 Clinical consideration: Exchange of ionsClinical consideration: Exchange of ions
 4. Color:4. Color:
 Varies from yellowish white to grayis h whiteVaries from yellowish white to grayis h white
 The color of enamel depends on degree of calcification & the color of theThe color of enamel depends on degree of calcification & the color of the
underlying dentinunderlying dentin
 Clinical considerations:Clinical considerations:

CHEMICAL COMPOSITIONCHEMICAL COMPOSITION
Enamel is composed of inorganic , organic substances and waterEnamel is composed of inorganic , organic substances and water
CompositionComposition
By weight By volumeBy weight By volume
Inorganic -96% Inorganic-89%Inorganic -96% Inorganic-89%
material materialmaterial material
Organic-1% Organic – 2%Organic-1% Organic – 2%
Water-3% Water-9%Water-3% Water-9%
Inorganic : Calcium phosphate (Hydroxyapatite)Inorganic : Calcium phosphate (Hydroxyapatite)
Calcium carbonateCalcium carbonate
MagnesiumMagnesium
PotassiumPotassium
SodiumSodium
FluorideFluoride
Organic: 2 groups of proteinsOrganic: 2 groups of proteins
1. Amelogenins -90%1. Amelogenins -90%
2. Non-amelogenins-10%2. Non-amelogenins-10%


AMELOGENESISAMELOGENESIS
 Amelogenesis or enamel formation is a two stepAmelogenesis or enamel formation is a two step
process, organic matrix formation andprocess, organic matrix formation and
mineralizationmineralization
 Ameloblasts secrete matrix proteins & areAmeloblasts secrete matrix proteins & are
responsible for creating & maintaining anresponsible for creating & maintaining an
extracellular environment favourable tomineralextracellular environment favourable tomineral
depositiondeposition
 Amelogenesis has been described in 6 phasesAmelogenesis has been described in 6 phases
but generally subdivided into 3 main functionalbut generally subdivided into 3 main functional
stagesstages
 1. Presecretory stage1. Presecretory stage
 2. Secretory stage2. Secretory stage
 3. Maturation stage3. Maturation stage

1. PRESECRETORY STAGE1. PRESECRETORY STAGE
 Has 2 phases : 1. Morphogenetic phaseHas 2 phases : 1. Morphogenetic phase
 2. Differentiation phase2. Differentiation phase
 1. Morphogenetic phase:1. Morphogenetic phase:
 Occurs during the bell stageOccurs during the bell stage
 Shape of the crown is determinedShape of the crown is determined
 cells still can undergo mitotic divisioncells still can undergo mitotic division
 basal or proximal portion towards SIbasal or proximal portion towards SI
 distal portion towards enamel formationdistal portion towards enamel formation
sideside
 low columnarlow columnar
 nucleus-centre, golgo-proximal,nucleus-centre, golgo-proximal,
mitochondria-scatteredmitochondria-scattered
 11stst
junctional complex- proximaljunctional complex- proximal

Functional stages in the life
cycle of the cells of the inner
dental epithelium
•morphogenic stage
•histodifferentiation
•initial secretory stage
•secretory stage
•ruffled-ended ameloblast of
the maturative stage
•smooth-ended of the
maturative stage
•protective stage

PRESECRETORYPRESECRETORY
 Morphodifferentiation:Morphodifferentiation:
 Occurs during the bell stageOccurs during the bell stage
 Shape of the crown is determinedShape of the crown is determined
 Histodifferentiation:Histodifferentiation:
 Differentiation of ameloblastsDifferentiation of ameloblasts
 Resorption of the basal lamina of theResorption of the basal lamina of the
internal enamel epitheliuminternal enamel epithelium
 Epithelial-mesenchymal interactionsEpithelial-mesenchymal interactions

SECRETORYSECRETORY
 Initial layer of aprismatic enamel formedInitial layer of aprismatic enamel formed
 Ameloblasts develop Tomes’ processesAmeloblasts develop Tomes’ processes
 Matrix secretion to final thicknessMatrix secretion to final thickness
 Initiation and continuation ofInitiation and continuation of
mineralisation to 30% by weightmineralisation to 30% by weight
 Crystal elongationCrystal elongation
 Matrix degradationMatrix degradation
 Development of prismatic structureDevelopment of prismatic structure

MATURATION PHASEMATURATION PHASE
 Transition phase:Transition phase:
 Ameloblasts shorten, 50% dieAmeloblasts shorten, 50% die
 Vascularisation of the enamel organVascularisation of the enamel organ
 Re-formation of ameloblast basalRe-formation of ameloblast basal
laminalamina
 Cessation of matrix secretionCessation of matrix secretion
 Continued matrix degradationContinued matrix degradation
 Selective matrix withdrawalSelective matrix withdrawal

 Maturation proper:Maturation proper:
 Cycling of ruffled and smoothCycling of ruffled and smooth
ameloblastsameloblasts
 Final degradation and withdrawal ofFinal degradation and withdrawal of
matrixmatrix
 Crystal growth continues of toCrystal growth continues of to
completioncompletion
 Final third of mineralisation afterFinal third of mineralisation after
protein removal completeprotein removal complete

PROTECTION PHASEPROTECTION PHASE
 Enamel organ degeneratesEnamel organ degenerates
 Enamel coverings establishedEnamel coverings established
 EruptionEruption

 2. Differentiation phase:2. Differentiation phase:
 differentiation of ameloblastsdifferentiation of ameloblasts
 reversed polarityreversed polarity
 tall columnar, RER increasestall columnar, RER increases
 fragmetation of basal lamina byfragmetation of basal lamina by
cytoplasmic projectionscytoplasmic projections
 22ndnd
junctional complex-distal –imp. Rolejunctional complex-distal –imp. Role
in amelogenesisby tightlyholding togetherin amelogenesisby tightlyholding together
ameloblasts & determining at differentameloblasts & determining at different
times what may/may not pass b/n them totimes what may/may not pass b/n them to
enter or leave the enamelenter or leave the enamel

2. SECRETORY STAGE2. SECRETORY STAGE
 Ameloblasts reflects their intenseAmeloblasts reflects their intense
synthetic & secretory activitysynthetic & secretory activity
 Ameloblasts develop Tomes processAmeloblasts develop Tomes process
 mRNA for enamel proteins –mRNA for enamel proteins –
ribosomes on RER – proteins –ribosomes on RER – proteins –
cisternae – golgi –packaged intocisternae – golgi –packaged into
mbsg – distal extremity – tomesmbsg – distal extremity – tomes
process-initial layerof aprismaticprocess-initial layerof aprismatic
enamel formed.enamel formed.

 ROLE OF TOMES PROCESS:ROLE OF TOMES PROCESS:
 Initial enamellayerInitial enamellayer
formed,ameloblasts migrate awayformed,ameloblasts migrate away
from the dentin surface & developfrom the dentin surface & develop
the distal portion of tomes processasthe distal portion of tomes processas
an outgrowth of the proximal portionan outgrowth of the proximal portion
 The rod and interrod configuration ofThe rod and interrod configuration of
enamel crystals is a property of theenamel crystals is a property of the
ameloblasts & their tomes processameloblasts & their tomes process

 Secretion ofenamel proteins occursSecretion ofenamel proteins occurs
from 2 sitesfrom 2 sites
 1.secretionfromthefirst site on the ppTP1.secretionfromthefirst site on the ppTP
close to JC around cel l resulsts in theclose to JC around cel l resulsts in the
formation of enamel partitions thatformation of enamel partitions that
delimit a pitdelimit a pit
 2. secretion from the 22. secretion from the 2ndnd
site (along onesite (along one
face of dpTP) later fills this pit withface of dpTP) later fills this pit with
matrix that regulates formation of rodmatrix that regulates formation of rod
enamelenamel
 At both sites enamel is identicalAt both sites enamel is identical
composition,and rod and interrodcomposition,and rod and interrodwww.indiandentalacademy.comwww.indiandentalacademy.com

Scanning electron micrograph of the
surface of a developing human tooth from
which ameloblasts have been removed.
The surface consists of a series of pits
previously filled by tomes’ processes the
walls of which are formed by interred
enamel.
In cross section the distal portion of
tomes’ process (dpTp) appear as
ovoid profiles surrounded by interred
enamel. They decrease in size as
towards dentinoenamel junction as
the rod(R) grows in diameter.RGS
rods growth sites.

Ameloblasts and its secretary sites: proximal end and distal end of
tomes’ process forming rod and inter rod enamel.

 Crystal elongationCrystal elongation
 when outer portion of enamel layerwhen outer portion of enamel layer
is formed, Ameloblasts becomesis formed, Ameloblasts becomes
shorter& loses its dpTP- final fewshorter& loses its dpTP- final few
increments contain no rodsincrements contain no rods
 Full thickness of immature enamelFull thickness of immature enamel
formedformed

3. MATURATION STAGE3. MATURATION STAGE
 Has 2 phases: 1. Transitional phaseHas 2 phases: 1. Transitional phase
 2. Maturation proper2. Maturation proper
 1. Transitional phase:1. Transitional phase:
 ameloblasts shorten, 50% dieameloblasts shorten, 50% die
 vascularisation of the enamel organvascularisation of the enamel organ
 re-formation of ameloblast basalre-formation of ameloblast basal
laminalamina
 cessation of matrix secretioncessation of matrix secretion
 continuation of matrix degradationcontinuation of matrix degradation
 selectivematrix withdrawalselectivematrix withdrawal

 2. Maturation proper2. Maturation proper
 principal activity of A –bulk removal ofprincipal activity of A –bulk removal of
water & organicmaterial from E to allowwater & organicmaterial from E to allow
introduction of additional inorganicintroduction of additional inorganic
 Modulation – cyclic creation, loss &Modulation – cyclic creation, loss &
recreation of a highly invaginated ruffle-recreation of a highly invaginated ruffle-
ended apical surfaceor a smoothendedended apical surfaceor a smoothended
apical surface.apical surface.
 Significance M uncertain- seem to beSignificance M uncertain- seem to be
related to maintaining an environment thatrelated to maintaining an environment that
allows accretion of mineral content & lossallows accretion of mineral content & loss
oforganic matrix , in part thru alterationsoforganic matrix , in part thru alterations
inpermeability of the enamel organinpermeability of the enamel organwww.indiandentalacademy.comwww.indiandentalacademy.com

 Ruffle-ended A Smooth-ended ARuffle-ended A Smooth-ended A
 1.proximal j-leaky 1. distal j – leaky1.proximal j-leaky 1. distal j – leaky
 2.show considerable 2.leak small proteins2.show considerable 2.leak small proteins
 endocytotic act. &other moleculesendocytotic act. &other molecules
 contain lysosomes little endocyt., act.,contain lysosomes little endocyt., act.,
 Ca binding proteins no Ca-ATPase act.,Ca binding proteins no Ca-ATPase act.,
 membrane associatedmembrane associated
 Ca-ATPases that promCa-ATPases that prom
 otes pumping of Caotes pumping of Ca
 ions into maturing Eions into maturing E
 3.active incorporation 3.permits exit of3.active incorporation 3.permits exit of
proteinfragmentsproteinfragments
 of mineral ions into & waterof mineral ions into & water
 crystalscrystals

 Bulk-degrading enzymes degradeBulk-degrading enzymes degrade
organic matrix into fragments whichorganic matrix into fragments which
pass b/n leaky distal junctions ofpass b/n leaky distal junctions of
smooth-ended cellssmooth-ended cells
 Crystal growth continues toCrystal growth continues to
completioncompletion

POST-MATURATIONPOST-MATURATION
 Enamel organ degeneratesEnamel organ degenerates
 Enamel coverings establishedEnamel coverings established
 eruptioneruption

ROLE OF ENAMEL PROTEINS INROLE OF ENAMEL PROTEINS IN
ENAMEL DEVELOPMENTENAMEL DEVELOPMENT
 1. Amelogenins:1. Amelogenins:
 aggregate-enamel nanospheres-adhere toaggregate-enamel nanospheres-adhere to
developing enamel crystals-crystal growthdeveloping enamel crystals-crystal growth
occurs along c-axis of crystaloccurs along c-axis of crystal
 2. Non-amelogenins:2. Non-amelogenins:
1. Tuftelin: restricted near the DEJ1. Tuftelin: restricted near the DEJ
induction, initiation of mineralization orinduction, initiation of mineralization or
linkingb/n E & Dlinkingb/n E & D
2. Ameloblastin: assists ameloblasts in2. Ameloblastin: assists ameloblasts in
adhering to the forming enamel surfaceadhering to the forming enamel surface
3.Enamelin:largest& restricted to rod area3.Enamelin:largest& restricted to rod area
present only at growing enamel surfacepresent only at growing enamel surface
Promotes crystal elongationPromotes crystal elongation

ROLE OF PROTEOLYTICROLE OF PROTEOLYTIC
ENZYMES IN ENAMELENZYMES IN ENAMEL
DEVELOPMENTDEVELOPMENT 1. Enamelysin:1. Enamelysin:
 secreted during secretory stagesecreted during secretory stage
 responsible for limited proteolysisresponsible for limited proteolysis
 production of E decreases duringproduction of E decreases during
postsecretory transitionpostsecretory transition
 2. Serine protease (KLK4):2. Serine protease (KLK4):
 production begins in transition stageproduction begins in transition stage
 continues through out maturationcontinues through out maturation
stagestage
 remove amelogenins from theremove amelogenins from the
intercrystal areas allowing growth inintercrystal areas allowing growth in
crystalwidth & thicknesscrystalwidth & thicknesswww.indiandentalacademy.comwww.indiandentalacademy.com

DISTURBANCES IN ENAMELDISTURBANCES IN ENAMEL
FORMATIONFORMATION
 1. Defect in matrix formation:1. Defect in matrix formation:
 Hypoplasia: defect of enamel foundHypoplasia: defect of enamel found
 Causes:Causes:
 1. systemic 2. local 3. hereditary1. systemic 2. local 3. hereditary
| | || | |
c. hypoplasia trauma A.I.c. hypoplasia trauma A.I.
Exanthemat- infectionExanthemat- infection
ous infectionsous infections
RicketsRickets

 2. Defect in Maturation:2. Defect in Maturation:
 Hypocalcification:deficiency in theHypocalcification:deficiency in the
mineral content of the enamelmineral content of the enamel
 causes:causes:
 1. systemic 2. local 3.1. systemic 2. local 3.
hereditaryhereditary
| | || | |
febrile trauma A.Ifebrile trauma A.I
mottled enamel infectionmottled enamel infection
tetracycline stainstetracycline stainswww.indiandentalacademy.comwww.indiandentalacademy.com

STRUCTURES ASSOCIATEDSTRUCTURES ASSOCIATED
WITH INITIAL ENAMELWITH INITIAL ENAMEL
FORMATION & DEJFORMATION & DEJ
 1. Enamel Rod1. Enamel Rod
 2. DEJ2. DEJ
 3. Enamel tufts3. Enamel tufts
 4. Enamel spindles4. Enamel spindles
 5. Enamel lamellae5. Enamel lamellae

 long , slender mineralised structureslong , slender mineralised structures
whichextend from the DEJ to thewhichextend from the DEJ to the
surface of enamel in tortuous coursesurface of enamel in tortuous course
 Dia 4 micr – DEJ 8 micr-surface ofDia 4 micr – DEJ 8 micr-surface of
enamelenamel
 The rods are composed of millions ofThe rods are composed of millions of
small, elongated hydroxapatite crystalssmall, elongated hydroxapatite crystals
arranged in characteristic patternarranged in characteristic pattern
within the rods.within the rods.
 Each crystal in turn is composed ofEach crystal in turn is composed of
thousands of subunits called unit cells,thousands of subunits called unit cells,
which are stacked like building blocks.which are stacked like building blocks.
Enamel Rod

 Apatite crystalsApatite crystals
are arrangedare arranged
approximatelyapproximately
parallel to theparallel to the
long axis of thelong axis of the
prisms...prisms...
 Crystals flareCrystals flare
laterally to anlaterally to an
increasingincreasing
degree as theydegree as they
approach the rodapproach the rod
periphery.periphery.

 Deviations up to 40o have beenDeviations up to 40o have been
reported.reported.
 Many areas in human enamelMany areas in human enamel
seems to contain rods surroundedseems to contain rods surrounded
by rod sheath and separated byby rod sheath and separated by
interred substances, a moreinterred substances, a more
common pattern is a “keyhole” orcommon pattern is a “keyhole” or
paddle shaped prism.paddle shaped prism.
 In longitudinal section, it passesIn longitudinal section, it passes
through”through” headsheads” or “” or “bodies”bodies” ofof
one row of rods and the “one row of rods and the “tails”tails” ofof
the adjacent row.the adjacent row.
 In cross section, many rodsIn cross section, many rods
resemble fish scales.resemble fish scales.
 The rod sheath contains isThe rod sheath contains is
significant around three- fourth ofsignificant around three- fourth of
circumference of rod. The portioncircumference of rod. The portion
of interrod region locatedof interrod region located
directly cervical to particular rod isdirectly cervical to particular rod is
not separated by rod sheathnot separated by rod sheath
because the crystals there arebecause the crystals there are
confluent with those making upconfluent with those making up
the rod.the rod.

DIRECTION OF ENAMEL RODSDIRECTION OF ENAMEL RODS
 In general the enamel rods are arrangedIn general the enamel rods are arranged
right angle to the dentino-enamel junction.right angle to the dentino-enamel junction.
They run from dentinoenamel junction to theThey run from dentinoenamel junction to the
tooth surface. The directions of enamel rodstooth surface. The directions of enamel rods
are different in permanent and deciduousare different in permanent and deciduous
teeth.teeth.
Permanent toothPermanent tooth Deciduous toothDeciduous tooth
Incisal or occlusal thirdIncisal or occlusal third The rods run oblique from DEJ to surfaceThe rods run oblique from DEJ to surface
(+36(+3600
))
The rods run oblique to the long axis ofThe rods run oblique to the long axis of
the tooththe tooth
Middle thirdMiddle third The rods run horizontal to the long axisThe rods run horizontal to the long axis
of the toothof the tooth
The rods run horizontal to the long axisThe rods run horizontal to the long axis
Cervical thirdCervical third The rods run apical from the DEJ to theThe rods run apical from the DEJ to the
surface(-13surface(-1300
))
The rods run horizontal to the long axisThe rods run horizontal to the long axis

 Deciduous tooth:Deciduous tooth:
 No apical inclinationNo apical inclination
in cervical regionin cervical region
 Permanent tooth:Permanent tooth:
 Apical inclination ofApical inclination of
rods in cervicalrods in cervical
regionregion

DENTINOENAMEL JUNCTIONDENTINOENAMEL JUNCTION
 Junction b/nJunction b/n
enamel & dentinenamel & dentin
 Scalloped –Scalloped –
increases surfaceincreases surface
area –enable 2area –enable 2
matrices tomatrices to
interlockinterlock
 PreventsPrevents
shearing of theshearing of the
enamel duringenamel during
functionfunctionwww.indiandentalacademy.comwww.indiandentalacademy.com

ENAMEL TUFTSENAMEL TUFTS
 HypomineralisedHypomineralised
areas of enamelareas of enamel
near the DEJ &near the DEJ &
enter into theenter into the
enamel to about 1/5enamel to about 1/5
to1/3 of itsto1/3 of its
thickness; resemblethickness; resemble
tufts of grasstufts of grass
 c/c : areas ofc/c : areas of
enamel weaknessenamel weakness

ENAMEL SPINDLESENAMEL SPINDLES
 Odontoblastic processesOdontoblastic processes
sometimes cross the DEJsometimes cross the DEJ
into enamel; these areinto enamel; these are
termed as enameltermed as enamel
spindles. The enamelspindles. The enamel
spindles ends arespindles ends are
thickened. They maythickened. They may
serves as pain receptors,serves as pain receptors,
explaining the enamelexplaining the enamel
sensitivity experienced bysensitivity experienced by
some patients duringsome patients during
tooth preparation. Thetooth preparation. The
enamel rods are formedenamel rods are formed
at an angle to the axis ofat an angle to the axis of
the ameloblasts, thethe ameloblasts, the
direction of spindles anddirection of spindles and
rods is divergent. Inrods is divergent. In
ground section theyground section they
appear dark I transmittedappear dark I transmitted
light due to degenerationlight due to degeneration
of organic matter of theof organic matter of thewww.indiandentalacademy.comwww.indiandentalacademy.com

ENAMEL LAMELLAEENAMEL LAMELLAE
 Formed as the result of localfailure ofFormed as the result of localfailure of
maturation processmaturation process
 Thin,leaf like structures that extend from theThin,leaf like structures that extend from the
enamel surface toward the DEJ & sometimesenamel surface toward the DEJ & sometimes
extending& penetrating into dentin.extending& penetrating into dentin.
 HypomineralisedHypomineralised
 3 types of lamellae3 types of lamellae
 Type A lamellae composed of poorly calcifiedType A lamellae composed of poorly calcified
rod segmentsrod segments
 Type B – lamellae composed of degeneratedType B – lamellae composed of degenerated
cellscells
 Type C- lamellae filled wthorganic matter andType C- lamellae filled wthorganic matter and
debris from salivadebris from saliva
 Type A- enamel ; Type B & C may reach theType A- enamel ; Type B & C may reach the
dentindentin www.indiandentalacademy.comwww.indiandentalacademy.com

WITH APPOSITIONAL GROWTHWITH APPOSITIONAL GROWTH
OF ENAMELOF ENAMEL
 1. Cross-striations1. Cross-striations
 2. Incremental lines of Retzius or2. Incremental lines of Retzius or
Brown striaeBrown striae
 3. Neonatal line3. Neonatal line

CROSS-STRIATIONSCROSS-STRIATIONS
 Each enamelrod is built up ofEach enamelrod is built up of
segments separated by dark linessegments separated by dark lines
that give ita striated appearancethat give ita striated appearance
 These segments seem to be aThese segments seem to be a
uniform depth of about 4uniform depth of about 4
micrometersmicrometers
 More prominent in enamel that isMore prominent in enamel that is
more hypomineralisedmore hypomineralised

INCREMENTAL LINES OFINCREMENTAL LINES OF
RETZIUS OR BROWN STRIAERETZIUS OR BROWN STRIAE
Longitudinal section showing incremental
linesin coronal and cervical area

 Brownish bandsBrownish bands
 Illustrates the incremental patternof enamelIllustrates the incremental patternof enamel
 Reflects variations in structure &Reflects variations in structure &
mineralisation either hypo ormineralisation either hypo or
hypermineralisationhypermineralisation
 Attributed to periodic bending of rods or toAttributed to periodic bending of rods or to
a physiologic calcification rhythma physiologic calcification rhythm
 Cross striations indicate daily variationCross striations indicate daily variation
insecretory activity of ameloblasts.insecretory activity of ameloblasts.
Incrementallines represent weekly orlongerIncrementallines represent weekly orlonger
rhythmrhythm

NEONATAL LINESNEONATAL LINES
 enamel of deciduousenamel of deciduous
teeth develops partlyteeth develops partly
before and partly afterbefore and partly after
birth. The boundarybirth. The boundary
between the two portionsbetween the two portions
of enamel in theof enamel in the
deciduous teeth isdeciduous teeth is
marked by anmarked by an
accentuated incrementalaccentuated incremental
line of Retzius, theline of Retzius, the
neonatal line or neonatalneonatal line or neonatal
ring. It appears to be thering. It appears to be the
result of the abruptresult of the abrupt
change in thechange in the
environment andenvironment and
nutrition of the newbornnutrition of the newborn
infant.infant.
 The prenatal enamelThe prenatal enamel
usually is betterusually is better
developed than thedeveloped than the www.indiandentalacademy.comwww.indiandentalacademy.com

WITH CHANGESIN ENAMEL RODWITH CHANGESIN ENAMEL ROD
ORIENTATIONORIENTATION
 1. Gnarled Enamel1. Gnarled Enamel
 2. Hunter-Schreger bands2. Hunter-Schreger bands

GNARLED ENAMELGNARLED ENAMEL
 Groups of enamel rods mayGroups of enamel rods may
intertwine, twisted, and are moreintertwine, twisted, and are more
irregular. Such kind of appearance ofirregular. Such kind of appearance of
enamel is calledenamel is called Gnarled enamelGnarled enamel. It. It
appears if the tooth is cut in anappears if the tooth is cut in an
oblique direction near the dentinoblique direction near the dentin
region of the cuspal or incisal edge.region of the cuspal or incisal edge.
it is an optical appearance of theit is an optical appearance of the
enamelenamel
 it aids in resisting to the highit aids in resisting to the high
masticatory loads without fracture.masticatory loads without fracture.www.indiandentalacademy.comwww.indiandentalacademy.com

HUNTER-SCHREGER BANDSHUNTER-SCHREGER BANDS
 Alternating light & darkAlternating light & dark
bands seen in enamel inbands seen in enamel in
obliquely reflected lightobliquely reflected light
 Start at DEJ & extendStart at DEJ & extend
about3/5 to 4/5 ofabout3/5 to 4/5 of
enamel thicknessenamel thickness
 Due to a regular changeDue to a regular change
in the direction ofin the direction of
enamel rods whichis aenamel rods whichis a
functional adaptation tofunctional adaptation to
minimize the chanace ofminimize the chanace of
cleavage in the axialcleavage in the axial
direction underdirection under
masticatory forcesmasticatory forces
 Differences in theDifferences in the
pattern of sectioning ofpattern of sectioning of
enamel rodsenamel rodswww.indiandentalacademy.comwww.indiandentalacademy.com

WITH SURFACE OF TOOTHWITH SURFACE OF TOOTH
 A structureless layer of enamel of about 30A structureless layer of enamel of about 30
micrometers thick is found in all deciduousmicrometers thick is found in all deciduous
teeth & in about 70% of permanent teethteeth & in about 70% of permanent teeth
 Rods are not seen. Heavily mineralisedRods are not seen. Heavily mineralised
thanthe enamel beneath itthanthe enamel beneath it
 Other structures found in the newly eruptedOther structures found in the newly erupted
teeth are:teeth are:
 1. Perikymata1. Perikymata
 2. Rod ends2. Rod ends
 3. Cracks (lamellae)3. Cracks (lamellae)
 4. Enamel cuticle4. Enamel cuticle
 5. Pellicle5. Pellicle

PerikymataPerikymata
These are transverse,These are transverse,
wave like grooves,wave like grooves,
believed to be thebelieved to be the
external manifestation ofexternal manifestation of
the striae of Retzius.the striae of Retzius.
These are continuousThese are continuous
around the tooth andaround the tooth and
parallel to each otherparallel to each other
and to theand to the
cementoenamelcementoenamel
junction. Atjunction. At
cementoenamel junctioncementoenamel junction
about 30 perikymataabout 30 perikymatawww.indiandentalacademy.comwww.indiandentalacademy.com

Enamel rodsEnamel rods
 These are concave and varyThese are concave and vary
in depth and shape. Shallow near thein depth and shape. Shallow near the
cervical and deepest at incisal orcervical and deepest at incisal or
occlusal area. In young patient theseocclusal area. In young patient these
area are more prone to caries attackarea are more prone to caries attack
due to easy adherence to plaque.due to easy adherence to plaque.

CracksCracks
 Originally the term crack was used toOriginally the term crack was used to
describe narrow, fissure likedescribe narrow, fissure like
structure it has been demonstratedstructure it has been demonstrated
that they are actually outer edges ofthat they are actually outer edges of
lamellae. They originate at rightlamellae. They originate at right
angle to the dentinoenamel junctionangle to the dentinoenamel junction
and extend to the varying distance.and extend to the varying distance.
They are evenly spaced but longerThey are evenly spaced but longer
lamellae are thicker than shorterlamellae are thicker than shorter
ones.ones. www.indiandentalacademy.comwww.indiandentalacademy.com

Enamel cuticleEnamel cuticle
 A delicate membrane calledA delicate membrane called
nasmyth’s membrane (primary enamelnasmyth’s membrane (primary enamel
cuticle) covers the entire crown of thecuticle) covers the entire crown of the
newly erupted tooth. It is removed bynewly erupted tooth. It is removed by
mastication. Electron microscopemastication. Electron microscope
studies showed, this membrane is astudies showed, this membrane is a
typical basal lamina found beneathtypical basal lamina found beneath
most epithelial. Its wavy course itsmost epithelial. Its wavy course its
visible under light microscope. Thisvisible under light microscope. This
cuticle is secreted after the epithelialcuticle is secreted after the epithelial
enamel organ retracts from the cervicalenamel organ retracts from the cervical
region during tooth development.region during tooth development.www.indiandentalacademy.comwww.indiandentalacademy.com

PelliclePellicle
 After tooth erupted in oral cavity,After tooth erupted in oral cavity,
salivary protein and glycoproteinssalivary protein and glycoproteins
has affinity to attach to enamelhas affinity to attach to enamel
surface. This layer forms on thesurface. This layer forms on the
enamel surface is called pellicle. It isenamel surface is called pellicle. It is
less then one micron thickness. Inless then one micron thickness. In
the beginning it is free of bacteriathe beginning it is free of bacteria
but it is a source for bacteriabut it is a source for bacteria
attachment later. This pellicle is darkattachment later. This pellicle is dark
and amorphous in nature. It isand amorphous in nature. It is
removed by brushing andremoved by brushing and
mastication but it forms withinmastication but it forms withinwww.indiandentalacademy.comwww.indiandentalacademy.com

CEMENTOENAMELCEMENTOENAMEL
JUNCTIONJUNCTION
 Exhibits 3 types of relationshipsExhibits 3 types of relationships
 1. 60% - cementum overlaps enamel1. 60% - cementum overlaps enamel
 2. 35% - enamel & cementum meet2. 35% - enamel & cementum meet
edge to edgeedge to edge
 3. 5% - they do not meet & dentin in3. 5% - they do not meet & dentin in
this areathis area
 is not covered by cementumis not covered by cementum

ENAMEL PEARLSENAMEL PEARLS
 Occasionally the cells of the epi. RootOccasionally the cells of the epi. Root
sheath remain adherent to the dentinsheath remain adherent to the dentin
surface, they may differentiate intosurface, they may differentiate into
functioning ameloblasts & form smallfunctioning ameloblasts & form small
round islands of enamelround islands of enamel
 Such droplets of enamel is calledSuch droplets of enamel is called
enamel pearlenamel pearl
 Found near the bifurcation orFound near the bifurcation or
trifurcation of the multirooted teethtrifurcation of the multirooted teeth

NON CARIOUS DEFECTS OFNON CARIOUS DEFECTS OF
ENAMELENAMEL
 1. Attrition1. Attrition
 2. Abrasion2. Abrasion
 3. Erosion3. Erosion

AGE CHANGES IN ENAMELAGE CHANGES IN ENAMEL
 1. Enamel is a nonvital tissue that is1. Enamel is a nonvital tissue that is
incapableincapable
 of regenerationof regeneration
 2. with age, enamel becomes2. with age, enamel becomes
progressively wornprogressively worn
 3. teeth darken with age3. teeth darken with age
 4. becomes less permeable with age4. becomes less permeable with age

55.. with age the composition of the surfacewith age the composition of the surface
layer changes as ionic exchanges occurslayer changes as ionic exchanges occurs
with the oral environmentwith the oral environment
 6. the surface structures like6. the surface structures like
perikymata & rod ends disappearperikymata & rod ends disappear
with a ge, first at the points ofwith a ge, first at the points of
highest contour.highest contour.

MECHANISM OF ACTION OFMECHANISM OF ACTION OF
FLUORIDESFLUORIDES
 1. by rendering enamel more1. by rendering enamel more
resistant to aci d dissolutionresistant to aci d dissolution
 2. increases remineralization2. increases remineralization
 3. by inhibiting bacterial enzyme3. by inhibiting bacterial enzyme
system which converts sugars intosystem which converts sugars into
acids present in the plaqueacids present in the plaque

CLINICAL CHARACTERISTICS OFCLINICAL CHARACTERISTICS OF
NORMAL & ALTERED ENAMELNORMAL & ALTERED ENAMEL
HYDRATEDHYDRATED DESICCATEDDESICCATED
SURFACESURFACE
TEXTURETEXTURE
SURFACESURFACE
HARDNESSHARDNESS
NORMALNORMAL
ENAMELENAMEL
TranslucentTranslucent TranslucentTranslucent SmoothSmooth HardHard
HYPOCALCIFIHYPOCALCIFI
ED ENAMELED ENAMEL
OpaqueOpaque OpaqueOpaque SmoothSmooth HardHard
INCIPIENTINCIPIENT
CARIESCARIES
TranslucentTranslucent OpaqueOpaque SmoothSmooth SoftenedSoftened
ACTIVEACTIVE
CARIESCARIES
OpaqueOpaque OpaqueOpaque CavitatedCavitated VerySoftVerySoft
ARRESTEDARRESTED
CARIESCARIES
Opaque ,Opaque ,
darkdark
Opaque ,Opaque ,
darkdark
RoughenedRoughened HardHard

CONCLUSIONCONCLUSION
 Enamel is hardest mineralised tissue thatEnamel is hardest mineralised tissue that
covers the anatomical crowns of teethcovers the anatomical crowns of teeth
 It withstand the masticatory forces & givesIt withstand the masticatory forces & gives
protection to the underlying dentin & pulp.protection to the underlying dentin & pulp.
 Enamel cannot be regenerated since theEnamel cannot be regenerated since the
ameloblasts which forms this getsameloblasts which forms this gets
degenerated.degenerated.
 Therefore, it should be preservedTherefore, it should be preserved
whenever possible, because there is nowhenever possible, because there is no
material to exactly duplicate it till now.material to exactly duplicate it till now.

REFERENCESREFERENCES
 1. Tencate’s Oral Histology , development,1. Tencate’s Oral Histology , development,
structures & function 7structures & function 7thth
edition, 141-190edition, 141-190
 2. Orban’s Oral Histology & Embryology 112. Orban’s Oral Histology & Embryology 11thth
edition, 49-101edition, 49-101
 3.Oral development & Histology James K. Avery3.Oral development & Histology James K. Avery
33rdrd
edition 92-104 153-171edition 92-104 153-171
 4. Sturdevant’s Art & Science of Operative4. Sturdevant’s Art & Science of Operative
Dentistry 5Dentistry 5thth
edition 18-24edition 18-24
 5. Oral Anatomy, Histology & Embryology –5. Oral Anatomy, Histology & Embryology –
B.K.B. Berkovitz, G.R. Holland, B.J. Moxham 3B.K.B. Berkovitz, G.R. Holland, B.J. Moxham 3rdrd
edition 101-118edition 101-118
 6. A Text Book of Oral Pathology 46. A Text Book of Oral Pathology 4thth
edition,edition,
Shafer, Hine, Levey 4Shafer, Hine, Levey 4thth
edition 53-58.edition 53-58.

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