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Amelogenesis Imperfecta
Shilpa.M
Otherwise known as…..
•AI
• Hereditary Enamel Dysplasia
• Hereditary Brown Enamel
• Hereditary Brown Opalescent Teeth
What is Amelogenesis Imperfecta ?
Amelogenesis Imperfecta represents a
group of hereditary defects of enamel
unassociated with any other generalized
defects. It is entirely an ectodermal
disturbance , since the mesodermal
components of the teeth are basically
normal.
The term amelogenesis imperfecta is reserved
for hereditary defects of enamel that are not
associated with defects in other parts of the
body or other health problems. The enamel
defects are highly variable and include
abnormalities that are classified as hypo plastic
,hypo maturation, and hypo calcified. The
enamel in both the hypo maturation and hypo
calcified AI types is not mineralized to the level
of normal enamel and can be described as hypo
mineralized. AI can be inherited as an x-linked,
autosomal recessive (AR), or autosomal
dominant (AD) condition.
Prevalence
• 1 in 700 to 1 in 15,000
Etiology
• Dental enamel is a highly mineralized tissue with over
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95% of its volume occupied by unusually large, highly
organized, hydroxyapatite crystals. The formation of this
highly organized and unusual structure is thought to be
rigorously controlled in ameloblasts through the
interaction of a number of organic matrix molecules that
include
enamelin
amelogenin
ameloblastin
tuftelin
amelotin
dentine sialophosphoprotein (DSPP;)
enzymes such as kallikrein and
matrix metalloproteinase 20 (MMP20)
Any mutations in these proteins can cause AI.
AI&DI
Development of enamel..
• 3 stages..
formative stage
deposition of organic matrix.
Calcification stage
matrix mineralization
Maturation stage
crystallites enlarge and mature
AI
• 3 Types..
Hypoplastic
Hypocalcified
Hypomaturation
A 4th type of A I is a combination of
hypoplastic & hypomaturation types.
Classification of A I
• Based on clinical,histological,&genetic criteria-Witkop & Sauk
 Hypoplastic
Pitted, AD
Local, AD
Smooth, AD
Rough, AD
Rough, AR
Smooth, X-linked dominant
 Hypocalcified
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Diffuse AD
Diffuse AR
Hypomaturation
Diffuse , X-Linked recessive
Diffuse Pigmented, AR
Snow-capped teeth, X-linked
Combination Type
Hypomaturation-hypoplastic with taurodontism,AD
Hypoplastic-hypomaturation with taurodontism,AD
Clinical features..
• Hypoplastic Type.
The enamel is not formed to full normal
thickness
Hypocalcified Type.
• The enamel is so soft that it can be
removed by a prophylaxis instrument.
• Yellow brown or orange on eruption,
stained brown to black with time.
• Exhibits rapid calculus apposition.
• Coronal enamel lost with function, except
for the cervical portion which is
mineralized better.
• Autosomal recessive—more severe.
Hypomaturation Type.
• The enamel can be pierced by an explorer
point under firm pressure
• can be lost by chipping away from the
underlying normal appearing dentin.
• Teeth are normal in shape, but exhibit a
mottled , opaque white brown yellow
discoloration.
• Snow capped pattern- exhibit a zone of
white opaque enamel on the incisal or
Occlusal third of the crown.
Other features…
• Both dentitions are affected
• In Some cases teeth may appear normal, in
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others may be extremely unsightly.
Color of the crown can vary from yellow to dark
brown.
Enamel might have numerous parallel vertical
wrinkles or grooves.
Open contact points
Occlusal surfaces and incisal edges are
frequently abraded
Radiographic Features
• The enamel may appear totally absent
• When present may appear as a thin layer ,
chiefly over the tips of the cusps & on the
interproximal surfaces.
• In some cases calcification is so much
affected that enamel & dentin seem to
have the same radio density, making
differentiation between the two difficult.
Histological Features
• Hypoplastic type—disturbance in the
differentiation or viability of ameloblasts.
• Hypocalcification type– defects of matrix
structure and of mineral deposition.
• Hypomaturation type– alteration in
enamel rod & rod sheath structures.
Management
• Treatment depends on the specific AI type
and the character of the affected enamel.
• Treatments range from preventive care
using sealants and bonding for esthetics
to extensive removable and fixed
prosthetic reconstruction.
Treatment of hypoplastic type
• Therapy for the hypoplastic AI types typically
involves the use of bonding procedures to
protect the malformed teeth from caries and
improve esthetics.
• Hypoplastic teeth usually have reasonably well
mineralized enamel, albeit thin and/or pitted,
making them suitable for restorative therapies
involving bonding to the enamel .
• Composite resin or porcelain veneers can be
bonded to the anterior teeth when the incisor
shape, size and/or color requires modification.
Continued…..
• Orthodontic therapy may be used to partially
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close the interdental spaces prior to restoration
in those individuals having small square shaped
incisors and interdental spacing that is too
excessive to close with restorative therapy
alone.
Individuals with hypoplastic AI often can retain
intracoronal restorations such as amalgams and
composite resins.
• if the enamel is extremely thin and malformed
the teeth can require full dental coverage with
crowns.
Porcelain veneers
Treatment of hypocalcified &
hypomaturation types
• The hypomaturation and hypocalcified AI types
can be restored with conventional approaches if
the enamel is not severely involved.
• if enamel is severely hypomineralized and of
insufficient strength to retain bonded or
intracoronal restorations, full coverage
restorations should be placed.
• In cases of severely hypomineralized enamel,
stainless steel crowns are indicated in the
primary and early permanent dentitions.
Continued…
• stainless steel crowns with composite inserts or
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composite crowns that are retained both by
mechanical undercuts and bonding can greatly
reduce tooth sensitivity and provide reasonable
esthetics.
The dentist should not rely on retention from
bonding alone in those cases with very weak
and poorly mineralized enamel.
Continued….
• Resin crowns can be placed on permanent incisors soon
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after they begin to erupt during the mixed dentition
(about age 7 – 10 years). As the gingival margin
becomes exposed during continued tooth erupt the
resins are easily modified by adding resin to the gingival
margin of the tooth.
Ultimately, porcelain fused to metal or other custom
fabricated crowns can be placed on the dentition. This
may be delayed until late adolescence or early adulthood
when all the teeth are present, the teeth are fully
erupted, and the gingival height around the teeth has
stabilized.
While costly, these types of restorations can allow even
severely affected dentitions to be treated and achieve
excellent function and esthetics.
• The severely affected individual shown in Figure had AR
Hypomaturation AI and was treated over several years
with stainless steel crowns, orthodontics, orthognathic
surgery and eventually porcelain fused to metal crowns
to achieve this excellent result.