Develpoment of enamel / dental implant courses

DEVELOPMENT OF
ENAMEL
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education

 INTRODUCTION
 FUNCTIONS
 PROPERTIES
 COMPONENTS
 DEVELOPMENT:
EPITHELIAL ORGAN
LIFE CYCLE OF AMELOBLAST
AMELOGENESIS
 BIOLOGICAL CONSIDERATION
 AGE CHANGES
 CONCLUSION
 REFERENCESwww.indiandentalacademy.com

Amelogenesis
 Enamel formation.
 It is slow developmental process
 Can take as long as 5 yrs
Ref:Ten Cate:Oral histology development ,structure&functionwww.indiandentalacademy.com

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 Two step process
 1st
step: Produces partially mineralized
enamel(30%)
 2nd
step: Influx of additional mineral coincident
with removal of organic material and water

component Secretory
stage
mid
maturation
Late
maturation
Water 5 3 1
Mineral 29 93 95
Protein 66 4 4

 Ameloblasts secrete matrix proteins and are
responsible for creating & maintaining an extra
cellular environment favorable to mineral
deposition

 Pre Secretory stage
 Secretory stage
 Maturation stage

Pre Secretory stage
 Differentiating ameloblasts acquire their pheno
type
 Change polarity
 Develop an extensive protein synthetic apparatus
 Prepare to secrete the organic matrix of enamel

Secretory stage
 Ameloblasts elaborate and organize entire
enamel thickness

Maturation stage
 Ameloblasts modulate and transport specific ions
required for concurrent accretion of mineral.

Presecretory stage:
 Morphogenetic phase
 Differentiation phase

Secretory stage

 Fine structure of
Secretory stage
ameloblasts
reflect their
intense synthetic
and Secretory
activity

 Secretion by ameloblasts is continuous and
Secretory granules are not stored for prolonged
period.
 Secretory granules are released against the newly
formed mantle dentine along the surface of
process.
 This forms initial layer of enamel

 As initial layer is
formed,ameloblasts
migrate away from
dentine surface and
develop distal
portion of tomes
process as an out
growth of proximal
portion

 The rod and inter
rod configuration
of enamel
crystals is a
property of
ameloblasts and
their tomes
process

 Formation of inter rod enamel is always a step
ahead
 rod and inter rod enamel is of identical
composition,differ only in orientation of their
crystals

 Eventually ameloblasts becomes shorter and
loses its distal portion of tomes process.
 Hence cell now has same overall appearance as
when it was forming initial enamel.

 Enamel layer is
thus composed
of rod
containing layer
sandwiched
between thin
rod less initial
and final layers

Maturation stage
 2/3rd
of formation
time is occupied
by maturation
stage.
 Crystal growth
during maturation
stage occurs at
expense of matrix
proteins and
enamel fluid.

 Transitional phase
 Maturation proper

Transitional phase
 After full thickness of
immature enamel has
formed.
 Ameloblasts undergo
significant morphologic
changes in preparation
for their next functional
role,that of maturing
enamel

Maturation proper
 Next ameloblasts become involved in the
removal of water and organic material from
enamel& additional inorganic material is
introduced.

 MODULATION:cyclic
creation,loss,and
recreation of highly
invaginated ruffle ended
apical surface or smooth
border.

 Significance of modulation is uncertain,but they
seem related to calcium transport and alteration
in permeability of enamel organ

Age changes
 Attrition
 Discoloration
 Reduced permeability
 Modifications in surface layer

At 12 yrs
age

At 25 yrs age

At 52 yrs age

Attrition:
 Wear facets increasingly pronounced in older
people.
 Evidenced by loss of vertical dimension of the
crown and by flattening of proximal contour.
Ref:orban’s oral histology&embryologywww.indiandentalacademy.com

Discoloration
 Teeth darken with age
 Why….? Controversial
 Addition of organic material or deepening of
dentine color

Permeability
 Becomes less permeable
 With age the pores diminish as the crystal
acquire more ions.

Modification in surface
layer:
 Surface of unerupted and recently erupted teeth
covered with pronounced rod ends and
Perikyamata.
 Generalized loss of rod ends, slower flattening of
Perikyamata later disappear completely

 Total amount of organic matrix with age is
controversial
 Localized increase in elements like fluorine.

Clinical considerations
 Dental caries
 Fluoridation
 Acid etching techniques
 Bleaching

 Enamel rods: susceptibility of crystallites to acid
correlated to their orientation.
 Gnarled enamel:does not yield readily to
pressure of bladed,hand cutting instruments
during tooth prep
Ref:sturdevant:art & science of operative dentistry:4th
edwww.indiandentalacademy.com

 Orientation of the enamel rod head and tail and
gnarling of enamel rods provide strength by
resisting,distributing and dissipating impact
forces.
 Enamel tufts:role in spread of dental caries

 Enamel lamellae: mostly organic material hence
weak area predisposing a tooth to the entry of
bacteria.
 Enamel spindles: serve as pain receptors

 Rod ends: concavities vary in depth and
shape,they contribute to adherence of plaque
material with resultant caries attack.

Dental caries
 Striae of retzius
 Movement of ions through carious enamel can
result in acid dissolution of underlying dentine
before actual cavitations of enamel

 Caries preferentially attack cores of rods and
more permeable Striae of retzius,which promote
lateral spreading and undermining adjacent
enamel.

Fluoridation
 Incorporation of fl ions makes Hydroxyapatite
crystals more resistant to acid
dissolution,decreasing rate of demineralization
and increasing rate of remineralization

Acid etching
 Removes plaque,debris & thin layer of enamel
 By dissolving minerals in enamel, etchants
remove the outer 10 micrometers on the enamel
surface and makes a porous layer 5–50
micrometers deep
 It increases porosity through dissolution of
crystals

Etching patterns
 Type 1: preferential removal of rods

 Type 2: preferential removal of interrod enamel
& rod remains intact

 Type 3: less regularly,irregular & indiscriminate

Bleaching
 Decrease in micro hardness
 Increase in surface roughness
Ref:Braz. oral res. vol.18 no.4 São Paulo Oct./Dec. 2004

Ref:Braz. oral res. vol.18 no.4 São Paulo Oct./Dec. 2004

References:
Ref (1): Inderber Singh: Human Embryology :1991: 5th
edition
Ref (2): B.K.B.Berkovitz, G.R.Holland, B.J.Moxham : Oral
Anatomy, Histology & Embryology:2002: 3rd edition
Ref (3): S.N.Bhaskar: Orban’s oral Histology &
Embryology: CBS Publishers: 1990: 10th edition
Ref (4): Dr.A.N.Radhakrishnan: Oral histology Dental
anatomy & Oral Physiology:1996:1st edition

Ref (5): DR.S.I Balaji :Dental Anatomy,
Histology & Embryology: 1998: 1st
edition
Ref (6): A.R Ten cate: Oral Histology, Development,
structure & Function:1994:4th edition
Ref (7): James K.Avery:Essentials of oral histology and
embryology:clinical approach:1st
edition
Ref (8): Sturdevant:art & science of operative dentistry:4th
edition

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Develpoment of enamel / dental implant courses

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