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Presentation- yahia (1) adhesion in dentistry.pptx
1. Adhesion aspect in operative dentistry
mahmoud yahia aboalwafaa
mohamed zaid
mahmoud badran
This Photo by Unknown Author is licensed under CC BY
2. The force that binds two
different materials
together when they are
brought into intimate
contact
Adhesion
Introduction
3. •Principles of adhesion
• Two phases :
1. Removal of calcium phosphate
( microporosities in both E & D )
2. ’’ hybridization phase “ involves infiltration
and polymerization of resin
This Photo by Unknown
4. Mechanism of adhesion
1. Mechanical :
occurs when the solidified
adhesive interlocks
micromechanically with the
roughness
2. Chemical :
bonding of different materials by
the interaction of atoms or
molecules at an interface
3. Physical (electrostatic) :
it is weak bond between
electrical double layer forms at
the interface between smooth
and different surface
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5. Classification of dental
adhesives:
• 1- Chronological “Generational” Classification
• 2- Scientific Classification
• 3- Classification according to the clinical
application steps
• 4- Classification according to smear layer
handling mechanism
• Development of adhesives: Chronological
“Generational” classification:
• Only adhesives from fourth to eighth generation
are currently on the market. The First, second
and third Generation adhesives, showed many
disadvantages and low bond strength to the
tooth structure so they are not available in the
market any-more.
6. • Van Meerbeek et al, 2001;
have suggested a
scientifically based
classification with three
main groups of adhesives:
• • Etch and Rinse
Approach.
• • Self-Etch Approach.
7. I. Etch and Rinse
Approach
• A- Conditioning Enamel: Objectives:
• 1. Removal of organic pellicle and
prismless enamel
• 2. Removal of the smear layer
• 3. Creation of enamel microporosities (5-
50μm)
• 4. Increase Enamel surface energy from
32 to 72 dynes/cm2 Methods:
• 1. Chemical conditioners: .
• 2. Physical conditioners (LASER): - The
substrate surface is altered by microscopic
explosions caused by thermal transients
increasing the bondable fraction of
inorganic dentin. - This will lead to a
decrease in the organic fraction of the
substrate. - Laser leads also to a
8. • Factors affecting successful
enamel acid etching:
• 1- Type of acid: phosphoric
acid is the most commonly
used.
• 2- Acid concentration
• 3- Time of etching;
• 4- Form of etchant:
• 5- Rinsing time
• 6- Method of activation of
etching (rubbing, agitation,
and/or repeated application of
fresh acid)
• 7- Instrumented or non -
instrumented enamel
9. • B- Dentin Conditioning:
Objectives:
• 1. Total removal of the
smear layer and smear
plugs
• 2. Demineralize the
superficial dentin surface
• 3. Exposes a microporous
layer of organic collagen
fibers thus increasing the
microporosity of the
intertubular dentin (0.05-
0.1μm)
10. • Problems encountered
dentin after etching:
• 1. Decrease surface
free-energy (44.8
dynes/cm2) due to high
proteins (collagen)
exposed.
• 2. Increased
permeability and
wetness of dentin hinder
adhesion.
16. III Glass-
ionomer
approach
• Glass ionomers are the only materials that are self-
adhesive to tooth tissues
• - One step or direct application of the material
• - Two steps application involving pre-treatment with a weak
polyalkenoic acid conditioner. - The application of
Polyalkenoic-acid conditioner for 10-to-20 seconds
increases bonding efficiency due to:
• 1. Cleaning effect
• 2. Partial demineralization by which the surface area is
increased and micro porosities for micromechanical
interlocking are exposed.
• 3. Chemical interaction of polyalkenoic acid with residual
hydroxyapatite.
• • The auto-adhesion of glass ionomer has recently been
determined to be due to: 1. Micromechanical interlocking.
• 2. True chemical bonding occurs between the carboxyl
groups of the polyalkenoic acid and calcium of
hydroxyapatite.
17. • Factors affecting the
interface durability.
I. Dentin related factors
II. Adhesive system
related factors
III. Micro mechanics of
adhesive interface
IV. Extrinsic and intrinsic
water sorption
V. role of saliva in bond
degradation
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18. I. Dentin related factors
• Dentin smear layer:
• • A layer of 2-5μm of
calcific debris
• • Advantages of smear
layer:
• 1- It reduces dentin
permeability by about
86%
• 2- Minimizes post-
operative
hypersensitivity and
preventing the
19. • Disadvantages of
smear layer :
• It incorporates microorganism
and is loosely attached to the
• underlying dentin providing for
a weak joint between the tooth
• tissues and the restorative
material
21. are few dentinal tubules and
large amounts of intertubular
dentin are available.
2. Thus bonding the
mechanism is through hybrid
layer formation.
3. On the other hand, in deep
dentin, the dentinal tubules
are abundant with limited
amounts of intertubular
dentin, so the
resin tags bonding is
23. Bonding to
altered
dentin:
In most of the clinical situations clinicians
usually bond adhesives to
caries affected dentin or abraded sclerotic
dentin
- The hybrid layer formed on caries affected
dentin was thicker than
those formed on healthy dentin
caries affected dentin may be characterized
by zones of
disorganized collagen, acid etching could
promote phase transition of
this disorganized collagen to a gel. The gel
could inhibit adhesive
infiltration
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25. • Etch and rinse
adhesives
• The complete filling
of the exposed space
by subsequent
application of resin
• monomer is
unattainable within
the short time
available
• The exposed
collagen fibrils here
may be structurally
unstable
• due to hydrolysis,
reducing long term This Photo by Unknown Author is licensed under CC BY
26. • Self-etch
adhesives:
• To overcome the
shortcomings of the
formation of an exposed
collagen
• network within the
bonds of the total-
etching adhesives.
• Regions of incomplete
resin infiltration or
incomplete resin
• polymerization within
the hybrid layers or
bonding resin may
represent
• pathways for fluids, a
phenomenon termed
nanoleakage.
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27. • All in one adhesive
system
Water sorption of
adhesive resin is
proportional to its
hydrophilic
Characteristics
- The self-etching
ability of one bottle
adhesives is
commonly
achieved by
incorporation of water
in resin monomers
that enables
ionization of acidic
monomers
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28. Micro-mechanics of
the adhesive
interface:
• Under clinical function dentin adhesives
are subjected to both chemical and
mechanical stresses.
• The interplay between the two forms of
stress is expected to result in an
alteration of the properties of the
adhesive with time.
• The mechanical property change results
from a variety of mechanisms including
proliferation of surface and subsurface
• flaws due to combined effects of
mechanical loads and exposure to
salivary esterase and changes the
chemical nature of the polymer.
• Therefore, the change in the mechanical This Photo by Unknown Author is
29. Extrinsic and
intrinsic water
sorption.
• Adsorption of extrinsic water
leads to plasticization of the
adhesive and loss of
interfacial adhesive dentin
bond strength as a result of
water attack.
• This increases water
sorption after polymerization
and/ or extraction of water
soluble unreacted
monomers.
• Water uptake in the
adhesive layer increases the
This Photo by Unknown Author i
30. Role of saliva
in bond
degradation:
• Human saliva contains a
variety of enzymes which
may participate in the
degradation of the adhesive
as well as the composite.
• Human saliva samples have
been shown to contain
cholesterol esterase and
pseudo-cholinesterase
activity in sufficient quantity
to degrade composite resin.
31. MOPOS
MOPOS (Modified Polyacid System) is a
unique and patented molecule
responsible for both the self-adhesion and
the mechanical strength of
Surefil one™ restorative
