Enamel is the hardest tissue in the human
body. Its mineral portion is approximately 96%
of its weight,the rest is organic components
The mineral elements include hydroxyapatite
crystals, approximately 0.03μm to 0.2 μm,
surrounded by a thin film of firmly bound
Poorly mineralized enamel –more white
More mineralized –more translucent.
DIRECTION OF RODS
• The rods are oriented at right angles to the dentin
• In the cervical & central parts of the crown of a
permanent teeth, they are approximately horizontal.
• Near the incisal edge or tip of cusps they change
gradually to an increasingly oblique direction until they
are almost vertical in the region of the edge or tip of the
• CLINICAL SIGNIFICANCE:-
• Follow the direction of enamel RODS during cavity
preparation so that enamel margins are supported.
• If the discs are cut in an oblique plane, the bundles of
rods seem to interwine more irregularly.
• Its optical appearance of enamel is called gnarled
• CLINICAL SIGNIFICANCE:-
• This enamel is not subject to cleavage as regular
• This enamel does not yield readily to pressure of hand
These projections arise in Dentine and extend into
enamel in the direction of long axis of crown,
hence may play a role in spread of caries.
Contains mostly organic material which is WEAK
AREA, therefore predisposes tooth to entry of
bacteria ,hence dental caries..
Transverse wave like grooves appear to be theTransverse wave like grooves appear to be the
external manifestations ofexternal manifestations of striae of retziusstriae of retzius..
Continuous around the tooth and parallel to eachContinuous around the tooth and parallel to each
other and to the CEJ.other and to the CEJ.
Seen in freshly erupted teeth or in tooth which isSeen in freshly erupted teeth or in tooth which is
not subjected to abrasive forces.not subjected to abrasive forces.
Average ofAverage of 30 perikymata/mm30 perikymata/mm in cervical regionin cervical region
andand 10/mm10/mm in occlusal region.in occlusal region.
These may contribute to adherance of
plaque material which results in caries.
Covers newly erupted tooth.
Membrane replaced by pellicle.
Microbes invade pellicle to form
Occasionally found on root surface
towards cervical margin.
Importance: Predisposed to plaque
accumulation following gingival
They – act as
bacterial/ food traps
thickness of enamel
predispose tooth to
dental caries is defined as a multifactorial ,
transmissible ,infectious oral disease caused
primarily by the complex interaction of cariogenic
oral flora with fermentable dietary carbohydrates
on the tooth surface over time.
White opaque chalky spots observed when the
tooth surface is desiccated are termed as
incipient caries Sturdevant 4th
Radiographically seen as faint radiolucency
Chalky white spot
Caries which becomes static or stationary and doesn't
show any tendency for further progression
Clinically intact ,discolored ( black or brown spots )
Body of the lesion
For an ideal enamel wall , following are
the Noy’s structural requirements-
1) The enamel wall must rest on sound dentine
and all carious dentine must be removed
2)Enamel which forms cavosurface angle must have
their inner ends resting on sound dentin
3) The rods which form cavosurface angle must be
supported on sound dentine and their outer ends
must be covered by restorative material (possibly by
giving a bevel)
4) Cavosurface angle must be beveled so that the
margins will not be exposed to injury in condensing
restorative material against it.
o Defective matrix formation.
o Enamel has not formed to full normal thickness
o Enamel is so soft that it can be removed by a
o Defective mineralization of formed matrix
o Immature Enamel crystals
o Defective enamel can be pierced by an explorer
point under firm pressure
1) Small teeth with short root
2) Open contact
General features of Amelogenesis
3) Discoloration ranging from
yellow to dark brown.
5)Enamel could look wrinkled
6)Delay in eruption
7)Occlusal surfaces and incisal edges severely
1. Enamel may be totally absent
2. Appear as thin layer, chiefly over the tips of the
cusps and the interproximal surfaces.
3. Same radiodensity as dentin , it become
difficult to differentiate between two
2)Selective odontotomy esthetically reshaping the
Incomplete or defective formation of the organic
4.Ingestion of fluoride
1) Hutchinsons incisors
(screw driver shaped central incisors)
2) Mulberry molars
(small globular masses of enamel on occlusal surface)
Hypoplasia due to syphilis
•Selective odontotomy and esthetic reshaping of the
Generalized type of intrinsic stain
When the tetracycline is administered during
the time of enamel formation it forms a
complex chelating compound with the organic
and inorganic components of the enamel. The
created compound is very stable.
Discoloration depends upon:
Length of time over which administration occurred
Form of tetracycline
According to Moffitt:
Critical period for tetracycline induced
discoloration in deciduous dentition
• 4 months in utero to 3 months postpartum
(maxillary and mandibular incisors)
• 5 months in utero to 9 months postpartum
(maxillary and mandibular canines)
In permanent dentition
• 3-5 months postpartum to 7 yrs of age
Discoloration varies from yellow –orange to dark blue
Chlortetracycline –grayish stains
Minocycline –grayish discoloration
Oxytetracycline –yellow stains
Generalized intrinsic stain
Chronic ingestion of flouride ions interfers with
ameloblast function during formative stage of
tooth development and disturb their activity
1) Mild changes
• White flecking or spotting of
2)Moderate to severe changes
•Brown staining of surface
•Tendency of enamel to fracture
Can occur due to
1. Tobacco/tea stains
2. Poor oral hygiene
3. Food colors
4. Gingival bleeding
5. Existing restorations
6. Chromogenic bacteria
3. Tetracycline and other drugs.
4. Age changes.
5. Non vital teeth
6. Internal resorption.
7. Hereditary disorders.
Avoidance of the foods and beverages that cause stains
Using proper tooth brushing and flossing techniques
Professional tooth cleaning: Some extrinsic stains may
be removed with ultrasonic cleaning , enamel
microabrasion, enamel macroabrasion
Surface tooth structure loss resulting from
direct frictional forces between contacting teeth
. (Marzouk 1st
Types of Attrition
1.Occluding surface attrition
2.Proximal surface attrition
1. Tooth to tooth contact
2.Parafunctional mandibular movements
2. Flattening of incisal and occlusal surface
3. Flattening of inclined planes
4. Flattening of proximal contact areas
5. Facet formation
6. Reverse cusp
7. Loss of vertical dimension of teeth
8. Decay at occluding areas
9. Angular chelitis
11.Temporo mandibular problems
Flattening of incisal
1. Para functional activities should be controlled
with protecting occlusal splints.
2. Endodontic therapy for pulpally involved teeth
3. Occlusal equilibration, by selective grinding of
4. Restorative modalities(only metallic restoration)
Surface loss of tooth structure resulting from
direct friction forces between teeth and
external objects, or from frictional forces
between contacting teeth components in the
presence of an abrasive medium.
1. Improper use of tooth brush
2. Improper use of tooth pick and dental floss
3. Habitual opening of bobby pins with teeth.
4. Use of abrasive dentifrices
1. Linear in outline(following path of brush bristles)
2. Angular peripheries
3. Notching of central incisors
4. Wedge shaped ditch on proximal
exposed root surface
1. Diagnosing the cause
2. Removing the causative factor(habits)
3. Desensitizing exposed dentin(if tooth is
4. Restorative treatment
Loss of tooth structure resulting from chemico-
mechanical acts in the absence of specific
microorganisms Marzouk 1st
1. Ingested acid(lemon and citrus fruits)
2. Chronic vomiting
3. Frequent regurgitation
Rate of erosion is 1micron per day
1. Shallow, broad, smooth ,highly polished,
scooped out depression on the enamel surface
adjacent to cementoenameljunction
2. Confined to gingival third of labial surface
1. Complete analysis of diet, chronic vomiting,
environmental factors should be performed
2. Restorative treatment
(tooth colored material can be used with
minimal or no tooth preparation)
Strong eccentric occlusal force resulting in
microfractures at the cervical area of tooth causing
wedge shaped defects
Heavy force in eccentric occlusion
Wedge shape defect
Defect has smooth surface
Age changes & Clinical considerations
•Attrition is seen in aged people.
•Wear facets are common.
•Decrease in vertical dimension and flattening of
•Color changes with age.
•Caries incidence is less in aged people.
•Surface composition: more amount of fluoride and
localized increase in nitrogen.
It decreases the solubility of enamel
It acts in the following way:
I. Forms fluoroapatite which is less soluble than
II. Inhibits demineralization
IV.Inhibits bacterial metabolism
ACID ETCHING TECHNIQUE- Buonocore in 1955
Micromechanical bonding b/w enamel and resin
based restorative material.
Mode of action-
Increases the porosity of exposed surfaces by
dissolution of crystals - creates a micro porous
layer from 5 to 50 µm deep
Three etching patterns predominate:-
(Preferential removal of rods)
(Junction b/w type 1 n type 2)
(Preferential dissolution of prism
Enamel etching transforms the smooth enamel
surface into an irregular surface
Etched enamel has high surface energy
(72 dynescm) allow resin to wet the tooth surface
better when resin penetrates into micro porosities
and polymerized to forms resin tags
Resin tags interlocked with
the surface irregularities
created by etching which
form mechanical bond to
Originally recommended 60 secs using 37% phosphoric
Currently,etching time for most etching gel is 15 sec
Aprismatic enamel requires double the etching time
required by prismatic
Involves the surface dissolution of enamel by acid
along with the abrasiveness of the pumice to remove
superficial stains or defects
Commercially developed system for enamel
[PREMA (Premier enamel micro abrasion)
In 1984 Mc Closkey reported this technique
In1986 Croll and cavanaugh modified this technique
PREMA contains a reduced concentration of
hydrochloric acid (approx 11%)+ silicon carbide
particles in a water soluble gel paste.
Mode of action
1. Physical removal of stained outer enamel layer by
stripping action of acid and abrasive action of
2. The etching action removes interprismatic
substance and changes light refraction
3. There is oxidation of some pigments
Removal of localized superficial white spots and other
surface stains or defects is called macroabrasion
12 fluted composite finishing bur or fine grit finishing
diamond in a high speed handpiece is used
Enamel is an important structural entity of the tooth
hence its protection is utmost important.
Its function is to form a resistant covering of the
teeth, rendering them suitable for mastication.
Marzouk : Operative Dentistry, First Edition
Orban :Oral Histology and Embryology,Tenth
Oral pathology SHAFER’S
Sturdevant :Art and Science of Operative
Dentistry, Fifth and sixth Edition
Ten Cates: Oral Histology , Seventh Edition
Enamel microabrasion,theodore p croll