7 adhesion to dental tooth tissue 3 Lecture number 6 Operative dentistry Egypt Cairo University Palestine Gaza Al Azhar University Dr. Inas Alim Uploaded by Dr. Lama El Banna

1. ALPINE SKI HOUSE
Dr. Inas Ayoub Elalem
inas.alalem@gmail.com
00970599448344
1
Operative Dentistry V

2. Adhesion to dental
tooth tissue -2-

3. Fundamental principle of adhesion to tooth
structure:
Exchange Process
Involves two phases:
A) Removal of calcium phosphate contents to expose micro-
porosities in both enamel and dentin surfaces
B) Hybridization phase: infiltration and subsequent in situ
polymerization of resin within the created surface micro-
porosities.

4. Hybrid
Layer
Resin
Tags
Dentin Hybrid Layer
Hybrid
Layer
Resin
Tags
Enamel Hybrid Layer
This result in micromechanical interlocking that is
primarily based upon mechanism of diffusion

5. Resin/Enamel interface:
Adhesive resin absorbed by capillary
attraction within the created etched
enamel surface enveloping individually
exposed hydroxyapatite crystals
followed by in situ polymerization of
resin to create two types of resin tags:
Macrotages
Microtages ( major contributors to
retention of enamel)

6. Capillary action, capillary attraction: a manifestation of surface
tension by which the portion of the surface of a liquid coming
in contact with a solid is elevated or depressed, depending on
the adhesive or cohesive properties of the liquid.

7. Objectives of conditioning of enamel
1. Removal of organic pellicle and prismless enamel
2. Removal of the smear layer
3. Creation of enamel micro-porosities
4. Increase enamel surface energy

8. Methods:
Chemical Conditioners
Physical Conditioners ( LASER)
Mechanical Conditioners ( Air
Abrasion)

9. Physical Conditioners ( laser):
Laser energy enables localized melting and
ablation of the enamel surface; it affects
etching through a process of continuous
vaporization and micro-explosions, which
occur due to the vaporization of the water
trapped within the hydroxyapatite matrix.
Irrigation of the enamel by laser energy may
be beneficial since it inhibits enamel
demineralization and, thereby, caries
formation.
Laser leads also to a desensitized detnin due
to occlusion of dentinal tubules.

10. Patterns of Etching:
Three enamel etching patterns have been described:
Type I ( removal of enamel prism cores)
Type II ( removal of prism peripheries)
Type III ( not related to prism morphology)
Or simply enamel etching patterns could be in the form if inter-
prismatic ( 10-20 micrometers) and intraprismatic pattern ( 2-5
micrometers) of etching.

11. Clinical Features:
The etched surface appears white frosted ( chalky white).
Inter-
prismatic
etching
Intra-
prismatic
etching
Before etching After etching

12. Dentin bonding and hybridization
The primary factors critical in
determining an adequate adhesive
dentin bond are:
1. Wetting of the dentin substrate by
components of the adhesive system
2. Micromechanical interlocking via
resin penetration and entanglement
of exposed collagen fibrils in the
demineralized matrix.

13. The compositions of exposed
substrate differs radically from
mineralized dentin.
A collapsed collagen network
reduces the porosity and inhibits
resin penetration through
demineralized layer.
It forms a barrier between the
demineralized layer and the
underlying intact or untreated
dentin surface.
A collapsed collagen network
severely compromises the a/d
bond.

14. Formation of Dentin Hybrid Layer:
The ideal hybrid layer would be characterized as a 3-
dimernional polymer/collagen network that provides both a
continuous and stable link between the bulk adhesive and
dentin substrate.
The hybrid layer has been called the weakest link in the
Adhesive/dentin bond.

15. Wet versus Dry Bonding:
Water based primers
Alcohol based primers
Therefore, the wet-bond technique is considered a successful
method.

16. Disadvantages of wet bonding technique:
• 1. Overwet condition (
phase separation of
hydrophobic and
hydrophilic monomer
components resulting in
blisters and globule
formation at resin
dentin interface.

17. Disadvantages of wet
bonding technique:
2. Acetone quickly evaporates from the
primer bottle so that after the primer
solution is dispensed in dappen dish, the
primer bottle should immediately be
closed and the primer solution should
immediately be applied to the etched
surface.
3. Not allow white frosted appearance of
properly etched enamel to be detected.

18. Bond durability is critical for the longevity
of restoratives,
Because degerdation can
weaken adhesion and lead to
gaps beween teeth and
restortives.
The average replacement time
of these restorations is only 5-7
years, also replacing defective
dental fillings cost about five
billions dollars per year in the
US alone.

19. Mechanism of dentin-adhesive interface
degradation:
1) Degradation of the hybrid layer:
In the period following adhesive application.
Dentin is acid etched----Disruption of the tooth structure by drilling
stimulates propylitic enzymes----can degrade the exposed collagen
component of the hybrid layer----hydrolysis and consequent extraction
of the adhesive resins that have infiltrated the demineralized dentin
matrix----facilitated by the ingress of water into loosely cross-linked or
hydrophilic domains of the adhesive----limited monomerpolymer
conversion because of adhesive phase separation and lack of
compatibility between photoinitiator and hydrophilic phase----The
poorly polymerized hydrophilic phase degrade rapidly in the aqueous
environment----nanoleakage channels----water movement along hybrid
layer

20. Mechanism of dentin-adhesive interface
degradation:
2) Degradation of methacrylate adhesive
Prolonged exposure to oral fluids, water begins to penetrate the
resin----water initially enters the matrix by diffusion into
loosely cross-linked or hydrophilic domains or may trapped
within the matrix during photo-polymerization in the moist
environment----water presence promote the chemical
hydrolysis of ester bonds in methacrylate materials----fastens
in low ph caused by foods or cariogenic bacteria—breaking
down a carboxylate and alcohol degradation products of ester
hydrolysis----enhancing the local ingress of water.

21. Factors affecting the interface durability:
• Miscellaneous• Water
• Saliva• Stress
Interface Durability
AdhesiveDentin

22. Factors affecting the interface durability:
1. Dentin related factors:
Smear layer
Deep layer ( resin tags) versus superficial dentin ( hybrid layer)
Bonding to gingival marginal dentin ( less mineralized, less
adhesive infiltration, higher water content, lower
monomer/polyermer conversion)
Bonding to altered dentin ; Caries affected ( thicker hybrid layer,
aready partially demineralized, reduction in monomerpolyermor
conversion, zones of disorganized collagen converted to gel
“phase transition” which inhibit adhesive infilitration.

23. Factors affecting the interface durability:
Adhesive system related factors:
Etch and rinse adhesive.
Self-etch adhesives; ( incomplete resin infiltration, incomplete
resin polymerization )
All-in-one adhesive ( water sorption and water uptake due to
incorporation of water in resin monomers, more hydrophilicity)

24. the high concentrations of water have raised questions about
potentially harmful effects on polymerization, given that
incomplete water removal can cause water trees.
This also applies for the high concentrations of solvent that
may cause incomplete resin polymerization in case of
incomplete evaporation.

25. Factors affecting the interface durability:
3. Micro-mechanics of adhesive interface: (a/d interface
subjected to chemical and mechanical stresses, inducing the
proliferation of surface and subsurface flaws.
4. Extrinsic and intrinsic water sorption: leads to plasticization
of the adhesive and loss of interfacial a/d bond strength as a
result of water attack----intrinsic sorption inhibited the light
polymerization of HEMA.
5. Role of saliva in bond degradation: saliva contains a variety
of enzymes which may participate in the degradation of the
adhesive as well as the composite.

26. Factors affecting the interface durability:
6. Miscellaneous factors:
Clinical related factors: cavity size, cavity type, and the
number of restored surfaces.
Operator related factors
Patient related factors
Material related factors

27. Potential prevention solution for bond
degradation.
• 1. Material dependent attempts:
a) Modifying the methacrylate side chain: as (4-MET, 10 MDP,
phenyle-P) Chemical bond, mild acid minimize nanoleakage,
leave substantial amount of hydroxyapatite around the collagen
fibrils to mask the cleavage site and keep the enzymes fossilized.
b) Photo-initiator incorporation
c) Crystallization by resin adhesive, glass ionomer cement or
bioglass
d) Addition of protease inhibitors as 2% CHX to protect dentin
degradation

28. Potential prevention solution for bond
degradation.
• E) collagen cross-linking agents; enhance mechanical
proprieties of dentin matrix, reduce biodegradation rates of
collegen ( Proanthocyanidins natural cross-linker that
stimulate collagen biosynthesis.
• F) Biomimetic remineralization of resin-dentin bonds:
utilized nanotechnology to mimic what occurs in
biomineralization----replace rein sparse regions of the hybrid
layer with appetite crystallites small enough to occupy the
extrafibrillar and intrafibrillar compartment of collagen
matrix.

29. Potential prevention solution for bond
degradation.
2. Technique dependent attempts:
A) Dentinal occlusion ( oxalate occlusion ) to decrease the
outward dentinal flow from acid etched dentin during bonding.
Total etch using it after acid etching before adhesive, self etch
resulted in the formation of calcium oxalate crystals which
occlude the patent tubules and interfere with hybridization.
B) Ethanol-wet bonding: to eliminate water from the bonded
interface to decrease water sorption, resin plasticization and
eliminate enzyme-catalyzed hydrolytic collagen degradation

30. Potential prevention solution for bond
degradation.
2. Technique dependent attempts:
C) Rubber dam isolation to limit the impact of water or saliva
contamination.
D) Extended adhesive application time with rubbing action,
allowing proper resin penetration and solvent evaporation
E) Warm air dryness to accelerate solvent evaporation.

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