 Structure I. Prisms or rods. II. Rod sheath. III. Inter-prismatic substance. IV. Striations. V.

Direction
of rods. VI. Hunter-Schreger bands. VII. Incremental lines. VIII. Surface structures. IX. Enamel
lamellae. X. Enamel tufts. XI. Dentino-enamel junction. XII. Odontoblastic processes and enamel
spindles.

Enamel Rods or Prisms

Characteristics
 Number: 5 – 12 millions.
 Direction: Run in oblique direction and wavy course.
 Length: greater than the thickness of E.
 Diameter average: 4 µm.
 Appearance: Have a clear crystalline appearance.
 Cross-section: hexagonal, round, oval, or fish scales.
Submicroscopic Structure Of Enamel Rods
 Keyhole or paddle-shaped.
 Separated by interrod substance.
 About 5 µm in breadth and 9 µm in length.
 The bodies are near the occlusal or incisal surface.
 The tails point cervically.
 The crystals; parallel to the long axis of the prism heads.
 Deviate about 65° from the tails.
Keyhole shaped E. rods Hexagonal ameloblasts Note crystal orientation Enamel Rod’s Shape
Crystals in rod and inter-rod enamel are similar in structure but diverge in orientation
Enamel Crystal
 Crystals length: 0.05 – 1 µm.
 Thickness: about 300 A°.
 Average width: about 900 A°.
 Cross sections: somewhat irregular.
Enamel Crystal Longitudinal Section Transverse Section
The Rod Sheath
A thin peripheral layer.
Darker than the rod.
Relatively acid-resistant.
Less calcified and contains more organic matter than the rod itself.
Electron Microscope : often incomplete.
Striations
•E. rod is built-up of segments (dark lines).
•Best seen in insufficient calcified E.
•Represent rhythmic manner of E. matrix formation.
•Segment length: about 4 µm.
Cross-striations
Direction of Rods
•Usually at right angles to the D. surface.
•Follow a wavy course in clockwise and anticlockwise deviation.
•At the cusps or incisal edges: gnarled enamel.
•At pits and fissures: rods converge in their outward course.
Hunter-Schreger Bands
•Alternating dark and light strips.
•Have varying width.
•Seen in large ground section (oblique reflected light).
•Originate from the DEJ.
Hunter-Schreger Bands This is Due to:
1. Change in the direction of E. rods.
2. Variation in calcification of the E.
3. Alternate zones having different permeability and organic material.
4. Optical phenomenon.
A. Incremental Lines of Retzius B. Neonatal Line Incremental Lines
Incremental Lines of Retzius:
 Brownish bands in ground sections.
 Reflect variation in structure and mineralization.
 Broadening of these lines occur in metabolic disturbances.
 Etiology
1. Periodic bending of E. rods.
2. Variation in organic structure.
3. Physiologic calcification rhythm.
Neonatal Line
 The E. of the deciduous teeth and the 1st permanent molar develop partly before birth and partly
after birth, the boundary between both is marked by neonatal line or ring.
 Etioloyg  Due to sudden change in the environment and nutrition.  The antenatal E. is better
calcified than the postnatal E.
SURFACE STRUCTURES
Surface Structures
a. Structureless layer
 About 30 µm thick.  In 70% permanent teeth and all deciduous teeth.  Found least
often over the cusp tips.  Found commonly in the cervical areas.  No E. prisms.  All the
apatite crystals area parallel to one another and perpendicular to the striae of Retzius.  More
mineralized than the bulk of E. beneath it.
b. Perikymata
 Transverse wave like grooves.  Thought to be the external manifestation of the striae of
Retzius.  Lie parallel to each other and to CEJ.  Number:  About 30 perik./mm at the
CEJ.  About 10 perik./mm near the incisal edge.  Their course is regular, but in the cervical
region, it may be quite irregular.  Powdered graphite demonstrates them.  It is absent in
the occlusal part of deciduous teeth but present in postnatal cervical part (due to undisturbed
and even development of E. before birth)
c. Rod ends
 Are concave and vary in depth and shape.  Are shallow in the cervical regions.  Deep
near the incisal or occlusal edges.
d. Cracks
 Narrow fissure like structure.  Seen on almost all surfaces.  They are the outer edges of
lamellae.  Extend for varying distance along the surface.  At right angles to CEJ.  Long
cracks are thicker than the short one.  May reach the occlusal or incisal edge.
e. Enamel cuticle
- Primary E. cuticle (Nasmyth’s membrane)
 Covers the entire crown of newly erupted tooth.  Thickness: 0.2 µm.  Removed by
mastication (remains intact in protective areas).  Secreted by postamloblasts.  EM: similar
to basal lamina..
- Secondary E. cutile (afibrilar cementum)
 Covered the cervical area of the enamel.  Thickness: up to 10 µm.  Continuous with
the cementum.  Probably of mesodermal origin or may be elaborated by the attachment
epithelium.  Secreted after E.O. retracted from the cervical region during tooth
development..
- Pellicle (a precipitate of salivary proteins.
 Re-form within hours after mechanical cleaning .  May be colonized by microorganisms
to form a bacterial plaque.  Plaque may be calcified forming calculus.
ENAMEL LAMELLAE
 Are thin, leaf like structures,
 Develop in planes of tension.
 Extends from E. surface towards the DEJ.
 Confused with cracks caused by grinding (decalcification).
 Extend in longitudinal and radial direction.
 Represent site of weakness in the tooth and three types; A, B, and C.
ENAMEL TUFTS
 Arise from DEJ.  Reach to 1/5 – 1/3 the thickness of E.  In ground section: resemble tufts of
grass.  Do not spring from a single small area.  The inner end arises at the dentin.  Consist of
hypocalcified E. rods and interprismatic substance.  The extend in the direction of the long axis of the
crown (best seen in horizontal sections).
DENTINO-ENAMEL JUNCTION
 Scalloped junction – the convexities towards D.  At this junction, the pitted D. surface fit rounded
projections of the enamel.  The outline of the junction is performed by the arrangement of the
ameloblasts and the B. M.
ODONTOBLASTIC PROCESSES AND ENAMEL SPINDLES
 The odontoblasts processes may cross DEJ (before the hard substance is formed) to the E. and ends
as E. spindles.  They are filled with organic matter.  The processes and spindles are at right angle to
the surface of the dentin.  The direction of spindles and rods is divergent.  Spindles appear dark in
ground sections under transmitted light.

STRUKTUR ENAMEL ANTARA LAIN :

ENAMEL PRISMATA/ENAMEL ROD

 berjalan ke permukaan gigi
 Hampir tegak lurus dengang arah bergelung (huruf S)
 Penampang melintang  hexagonal tak sempurna (seperti lubang kunci)
 Unit dasar dari enamel
 merupakan masa kristal A k r i s t a l h i d r o k s i a p a t i t
yang terkemas rapat dalam suatu pola
y a n g teroganisir.arah kristal hidroksiapatit yang menyusun
enamel rods akanm e m p e n g a r u h i b e b e r a p a s i f a t e n a m e l
seperti kekuatan, dan daya tahanterhadap asam. +ada
potongan melintang enamel rods tampak spertilubang
kunci yang terdiri dari bagian kepala dan eko r. Bagian
kepalamengarah ke mahkota gigi sedangkan pada bagian
e k o r m e n g a r a h k e ser0ikal. &rah prisma ke permukaan tidak lurus
melainkan bergelombang.+ada bagian kepala prisma terdapat prism
sheath yang didalamnya terdapatkristal hidroksiapatit. +rism sheath yang
merupakan pembatas atau sarunganatara kristal hidroksipapatit
dengan interrod enamel, pembungkus ini mengandung lebih banyak
protein enamel
 Secara struktural enamel terdiri atas jutaan enamel rod atau prisma yang
merupakan struktur komponen terluas.
 Struktur ini berubah-ubah jumlahnya dari kira-kira 5 juta pada insisivus
mandibula sampai sekitar 12 juta pada molar maksila.
 Prisma ini memanjang dari arah perbatasan enamel dan dentin ke
permukaan enamel, serta saling mengikat satu sama lain.
 Pada potongan melintang tampak seperti keyhole yang terdiri atas kepala
dan ekor.
  Pada bagian kepala prisma terdapat “prism sheath” yang di dalamnya
terdapat kristal hidroksiapatit. Sumbu kristal sejajar dengan arah prisma di
dasar prisma dan tampak memanjang di ujung prisma. Di antara kristal
terdapat celah berisi matriks yang sukar diamati sebab terdiri dari zat
berupa “gel” yang tidak berstuktur. Bentuk “gel” tersebut memungkinkan
matriks mengikat kristal. Di antara kristal juga terdapat “cross striations” dan
di bagian lebih luar terdapat “striae of retzius” yang arahnya dari perbatasan
enamel-dentin ke permukaan bersudut tajam.
BANDS OF HUNTER A SCHREGER -GARIS HUNTER A SCHREGER
 Merupakan fenomena optis akibat pergantian arah dari enamel rods.
Garis ini terlihat gelap terang.
GARIS RETZIUS
 garis pembentukan email
 garis dari dento enamel junction ke permukaan gigi
 dentino enamel junction  batas dentin dan enamel
ENAMEL CUTICULA
 membran yang menutupi permukaan enamel
 menghilang sesudah enamel (gigi) menjalankan fungsinya
ENAMEL LAMELLAE
 matriks dentin yang berkembang masuk ke dalam enamel, panjang lebih dari
½ tebal enamel
ENAMEL TUFT
 matriks dentin yang masuk ke dalam enamel dengan akhiran mengurai
ENAMEL SPINDLE
 matriks dentin yang masuk ke dalam enamel dengan akhiran menebal