DENTIN BONDING AGENTS

CONTENTS
 INTRODUCTION
 HISTORY
 DEFINITIONS
 BONDING MECHANISM
 WETTABILITY AND CONTACT ANGLE
 IDEAL REQUIREMENTS OF BONDING AGENT
 MICROSTRUCTURE OF DENTIN
 DIFFICULTIES IN DENTIN BONDING
 SMEAR LAYER
 ETCHING OF ENAMEL AND DENTIN

HYBRIDIZATION
REVERSE HYBRID LAYER
GHOST HYBRID LAYER
ELASTIC BONDING CONCEPT
WET Vs DRY BONDING
CHEMISTRY OF BONDING AGENT
COMPONENTS OF DENTIN BONDING AGENT
CLASSIFICATIONS OF DENTIN BONDING AGENTS
WATER TREES
AMALGAM BONDING
CERAMIC BONDING
CEMENTUM BONDING
RECENT ADVANCES
CONCLUSION

INTRODUCTION
 Today we are in the age of adhesive dentistry. The
traditional mechanical methods of retaining restorative
materials have been replaced by tooth conserving
adhesive methods.
 The development of adhesive approach to restorative
dentistry has brought many advantages such as better
esthetics, conservation of tooth structure, reduction in
micro-leakage.
 Adhesive technique has expanded the range of possibility
for esthetic dentistry. This is important as today’s patients
pay more attention to cosmetics than ever before.

HISTORY
 1951 - Oscar Hagger , a swiss chemist devoloped an acidic GPADMA
that permitted resin adhesion to dentin.
 The foundation for adhesives was made in 1955 where Buonocore
proposed that acids could be used to alter the surface of enamel to
make it more receptive to adhesion. This hypothesis was based on
industrial use of 85% phosphoric acid for 30 seconds.
 1957 - Bowen worked on bisphenol A-glycidyl methacrylate resin
and subsequently formed first composite material.
 1960-1970’s – 1st and 2nd Generation bonding agents
 1963 - Boyde and steward first described smear layer.
 1970 - Eick et al described the composition of smear layer and its
role in Bonding.

•1975 - Gwinnett and Silver stone described 3 patterns of etching in
enamel
• 1979 - Total etch concept of was proposed by Fusayama
•1980’s - 3rd Generation Bonding agents
•1982- Nakabayashi proposed the concept of hybrid layer
•Early 1990’s – 4th Generation Dentin bonding system
•1992 - Kanca et al has put forward the wet bonding technique
•1999 - Prati and Pashley described the formation of Reverse Hybrid
layer.
• Mid 1990s - 5th Generation Dentin Bonding Systems
• Early 2000’s - 6th Generation Dentin Bonding Systems
• 2003 - 7th Generation Dentin Bonding Systems

DEFINITIONS
Adhesion
• The forces or energies between atoms or
molecules at an interface that hold two phases
together.
Adherend
• The surface or substrate that is adhered.
Adhesive
• A material that can join substances together, resist
separation, and transmit loads across the bond.

WETTING
• The ability of a liquid to come into intimate contact
with solid substrate, facilitating the bonding.
ETCHING
• Dissolution of the substrate, removed by rinsing to
enhance intimate contact of adhesives with collagen.
PRIMING
• The process of cleaning, structural alteration and
increasing the adhesiveness of the substrate.

BONDING MECHANISM
Mechanical adhesion
Microscopic
Penetration
Stresse
s
Diffusion
Chemical adhesion
Primary valence forces
Secondary valence
forces
Ionic Bonds
Covalent bonds
Metallic bonds
Van der Waals
Hydrogen bonding

WETTABILITY AND CONTACT ANGLE
•An Important requirement for the occurrence of any of these
interfacial phenomena is that the two materials being joined must
be sufficiently wetted with close and intimate relation.
•Besides an intimate contact, sufficient wetting of the adhesive will
occur only if the surface tension is less than the surface energy of
the adherend.
•Wetting of a surface by a liquid is characterized by the contact
angle of a droplet placed on the surface

 The angle between adhesive &
adherend.
 Smaller the angle, better the
wettability.
 1800: Not accepted since all
liquids wet all solids to some extent.
 0-1800: Poor or incomplete wetting.
 00: Spontaneous wetting of liquid takes
place.

Ideal requirements of dentin bonding
agents:
1961 Phillips and Ryge:
High bond strength to dentin .
Provide bond strength to dentin similar to that of enamel.
Biocompatibility to dental tissue including the pulp.
Minimize microleakage at the margins of the restorations.
Prevent recurrent caries and marginal staining.
Easy to use and minimally technique sensitive.
Good shelf life.
Be compatible with a wide range of resins.
Non toxic and non sensitizing to the operators or patients.
Bonding agents should seal the tooth surfaces from oral fluids.

CLINICAL USES OF DENTIN BONDING
SYSTEMS:
1. Bonding of directly placed resin based restorative materials.
2. Bonding of indirectly placed restorative materials.
3. Bonding of ceramic restorations.
4. Bonding of amalgam restorations.
5. Bonding of prefabricated and cast posts.
6. Bonding orthodontic brackets.
7. Bonding periodontal splints
8. Repair existing restorations.
9. Sealing of pits and fissures of posterior teeth.
10. Treatment of cervical sensitive dentine.
11. Reattachment of fractured tooth fragments.
12. Pulp capping.
13. Reinforce fragile roots internally.
14. Seal apical restorations placed during endodontic surgery

MICRO-STRUCTURE OF
DENTIN
50%
HA
30%
Collagen
20%
Fluid

Dentinal tubules Pulp DEJ
• Diameter (microns) 2.5 0.8
• Number 45,000 20,000
• Tubular surface area 25% 3%
•Human dentin is a heterogenous material composed of a
solid (circumpulpal) phase surrounding a network of
tubules.
•These tubules, measuring about 1 to 3 micrometer in
diameter, contain elongated cell bodies that radiate from
the the dental pulp organ throughout the entire dentin.

•Dentin is composed of different volume fractions of
inorganic; calcium hydroxyapatite, protein (mostly
collagen) and water. These three phases create the basic
building block of bone and teeth.
•Collagen, a triple helical protein, self-organizes into
bundles called fibrils. These fibrils are well organized and
contain regularly spaced regions of high and low protein
density called the overlap and gap zones respectively.
•The HAP crystals are believed to then grow within these
gap zones reinforcing the weak collagen structure.

These tubules span the thickness of dentin, from the
pulpal cavity to the surface of the dentin and are
surrounded by a highly mineralized ring of Hydroxyapatite
called Peritubular dentin (PTD).
The mineralized collagen fibrils are then organized
tangentially to the surface of the PTD creating the
Intertubular dentin (IDT). This complex structure allows
dentin to be tough and strong, thus maintaining the
structural integrity of teeth.

Difficulties In Dentin Bonding
Complex histologic structure and variable
composition.
Contain vital processes of the pulp odontoblasts.
Hence, vital dentin is a sensitive structure.
High water content provides competition with any
adhesive biomaterial for bonding to dentine.
Dentin is subjected to physiologic & pathologic change in
composition & microstructure due to ageing, irritation.
 Plasma like fluid in the dentinal tubules is under a slight
but constant outward pressure from the pulp 25- 30 mm

Regional variation in the permeability characteristics
of dentin

SMEAR LAYER
•While instrumenting , in addition to superficial debris,
it
has been shown, using the scanning electron
microscope,
that a layer of sludge material was always formed
over
the surface of dentinal walls. This layer of debris has
been called the smear layer.(Boyde et al in 1963)
•The inorganic material in the smear layer is made-up
of tooth structure and some nonspecific inorganic
contaminants
•The organic components may consist of heated
coagulated proteins (gelatin formed by the
deterioration of collagen heated by cutting
temperature), necrotic or viable pulp tissue and

 Factors affecting formation of smear layer :
 Speed
(High speed instrumentation, the smear layer is tightly
attached to the prepared surface}.
 Type of Instruments
Coarse diamond burs produces thicker smear layer than
carbide fissure burs .
Coolant of water spray does not prevent smearing but
appears to significantly reduce the amount and
distribution of it

REMOVE OR RETAIN ??
REMOVE
 The exposed collagen
network provides reactive
groups that can chemically
interact with primers.
 Exposed collagen promotes
micromechanical bonding to
resin
 Tubules are open for good
retention
RETAIN
 Use of bonding agents that
can penetrate the smear layer
and incorporate into bonding
layer
 Protective barrier.
 Lowers dentinal permeability.
 Lowers pulpal pressure

ETCHING:
The objectives of enamel etching are to :
Clean the enamel
Remove enamel smear layer
Creates micropores(20-25u) by removal of prismatic and
interprismatic mineral crystals
Increase surface energy of enamel(2000times) to produce
monomer infiltration to seal enamel surfaces with resins
All these contribute to retention of resin composite
restoration.

Two types of resin tags interlock within the etch-pits. “
 Macrotags space surrounding the enamel prisms
 Microtags result from resin infiltration/polymerization within
the tiny etch-pits at the cores of the etched enamel prisms.
latter are especially thought to contribute with regard to
retention to enamel.

Ends of enamel rods (A) are more effectively etched,
producing deeper micro-undercuts than when only
the sides of enamel rods are etched(B)

50 % phosphoric acid for 60 seconds
monocalcium phosphate monohydrate precipitate
Concentrations below 25%
dicalcium phosphate dihydrate precipitate
Concentrations above 40%
Dissolve less calcium and etch patterns with poorer
definitions
37% for 15 sec is considered appropriate.
Citric acid ‐10% , Polyacrylic acid‐40% ,Maleic acid.

ETCHING PATTERNS.
Enamel etching results in three different micro morphologic pattern
as described by Silverstone et al in 1975 .
 Type I involves the dissolution of prism cores without dissolution of
prism peripheries
HONEY COMB

The Type II etching pattern --the peripheral
enamel is dissolved, but the cores are left
intact .
COBBLESTONE
Type III etching pattern is a
mixture of Type I and Type II
configurations.

Type IV - pattern has a pitted enamel surface
•It displayed only a random distribution of depressions
with no preferential destruction of either cores or
peripheries.
•These pitted areas occasionally occurred in little
patches over the enamel surface.

Type V
•Has a flat, smooth surface after etching
•Similar to Type IV patterns, Type V etching shows
no evidence of prism outlines.
•Type V are extremely flat and smooth, and they lack
microirregularities for penetration and retention of
resins

ETCHING TIME
15-30sec
45-60sec
60-90sec

CHANGES IN DENTIN STRUCTURE AFTER
ETCHING
Changes in intertubular dentin :
•Exposes longitudinally/obliquely oriented collagen fibres
Interfibrillar spaces : 15-20nm
Changes in peritubular dentin :
•Opens tubule orifices in typical funnel shape configuration
•Exposes circularly oriented collagen fibril arrangement
•Decrease surface energy
•Increase surface roughness

HYBRIDIZATION-Nakabayashi,1982
The structure formed in dental hard tissues by demineralization of
the surface and subsurface, followed by infiltration of monomers
and subsequent polymerization.

ZONES OF HYBRID LAYER
i) Top layer : Amorphous electron dense phase consisting
of denatured collagen.
ii) Middle layer : Cross sectioned & Longitudinally sectioned
collagen fibrils seperated by electrolucent spaces of 10-
20 nm
iii) Bottom layer : Gradual transition to underlying unaltered
dentin, with partially demineralized zone containing HA
crystals enveloped by resin/abrupt transition.

Tubule wall hybridization:
Extension of the hybrid layer into tubule wall area.
Hermetically sealing the pulp dentinal complex against microleakage.
Especially protective when bond fails at top or bottom of the hybrid
layer
The resin tags keep tubules sealed as they break off at the level of
hybrid layer. This is attributed to tubule wall hybridization which
ensures a leakage free seal of tubules.
Lateral tubule Hybridization :
Formation of tiny hybrid layer into the walls of lateral tubule branches.
This microversion of hybrid layer typically surrounds a central core of
resin called microresin tag.

NANOLEAKAGE
•The susceptibility of this demineralized collagenous zone
was proved by Sano et al who showed the penetration of
silver ions beneath the resin impregnated layer between
resin and decalcified tooth structure even in the absence of
any gap formation.
•Presence of sub micron spaces within the hybrid layer in
the absence of gap formation between resin composite
and the hybrid layer.
•They also stated that this might allow dentinal or oral fluids
to slowly permeate through the hybrid layer into the non
hybridized collagen zone causing its hydrolytic degradation
even in the absence of microleakage.

REVERSE HYBRID LAYER
 Prati et al reported the formation of a "reverse" hybrid layer
by application of NaOCI after acid etching.
 This procedure not only removes the exposed collagen but
also solubilizes the fibrils down into the underlying
mineralized matrix to create sub micron porosities within
the mineral phase. Cylindrical channels previously
occupied by collagen fibrils are now available for resin
infiltration within the mineralized matrix.
 Such dentin surfaces have been proposed as mineralized,
hydrophilic alternatives to collagen rich, hydrophobic acid-
demineralized dentin, possessing increased stiffness and

GHOST HYBRID LAYER
Aluminum oxide air abrasion (white arrows) resulted in partial removal of
the original hybrid layer (HL), followed by the formation of a new ghost-like
hybrid layer (HL2). The adhesive layer interface (ALi) was also modified,
allowing for the incorporation of aluminum oxide powder even after
cleaning.

ELASTIC BONDING CONCEPT
•The final Stiffness or rigidity of a resin
Composite may play a compensating role in
coping with polymerization stress.
• Viscous Adhesive---Thick resin layer
Stretching of this layer provide sufficient elasticity
to relieve stress of resin composite.
• Bonding layer thickness of 125um
Distribute
stress
induced
Thermal
changes,wat
er absorption
occlusion
Limited inhibition
of polymerization
by Oxygen
Reduce
shrinkage
stress

WET Vs DRY Bonding
 Wet bonding was introduced by Kanca and by Gwinnett
et al, in the 1990s
 When acetone/ alcohol based primers are applied to moist
demineralized dentine, the water diffuses from the wet
dentine into the acetone, while the acetone diffuses into the
demineralized dentine matrix.
 This chemical dehydration of the collagen network caused
by substitution of water by acetone also increases the
modulus of elasticity of collagen.

 The water is gradually lost as the solvents and resin
monomers occupy the spaces around the collagen
fibrils. Therefore, there is much less shrinkage.
Disadvantages
 Acetone quickly evaporates -should be quickly
applied -ratio of monomer &acetone changes
 Another disadvantage of keeping the cavity walls wet
after conditioning is that one cannot observe the
white frosted appearance of enamel that indicates
that it has been properly etched.

Dry Bonding:
Refers to the bonding in which the acid etched dentin is dry
and uses the adhesive systems that provide water based
primers.
 Too much water would rapidly re-expand the collagen
network but would also dilute the monomer concentration.
 35-50% HEMA in water provided the maximum bond
strength,water in these primers probably plasticized the
stiffened, collapsed collagen network so that it re-
expanded and increased its permeability to primer resins.

Over Dryness
There will be collapse of collagen fibres and demineralised dentin.
Inaffective penetration due to the collapsed collagen has been obse
ultramorphologically as the formation of “HYBRIDOID ZONE”.

“OVER WET” PHENOMENA
•In the total-etch, wet bonding technique, there is
the danger that some regions in complex
cavity preparations (such as proximal boxes)
may be too wet.
•When single bottle primer/adhesives are applied,
the solvent may diffuse into the water, instead of
vice versa, forcing adhesive monomers to undergo
phase changes, forming blisters, resin globules.

CHEMISTRY
M R X
Where,
M -- is the double bond of methacrylate which
copolymerizes with composite resin.
R -- is the spacer which makes the molecule large.
X -- is a functional group for bonding which bonds to
inorganic or organic portion of dentin

 Bonding to the organic part of dentin
 Interaction with
 Amino (–NH),
 Hydroxyl (–OH),
 Carboxylate (–COOH),
 Amide (–CONH) groups
 Dentin bonding agents have
 isocyanates,
 aldehydes,
 carboxylic acid
 anhydrides and
 carboxylic acid chlorides
present in dentinal
collagen.
which extract hydrogen from the
above mentioned groups and
bond chemically.

Components of dentin bonding
agents
Etchants
Primers
Adhesives
Initiators and accelerators
Fillers
Other ingredients.

ETCHANTS
 Alteration of dentin surface including smear layer with
the objective of producing a substrate capable of
micromechanical and possibly chemical bonding to
dental adhesives

The various acid etchants used are:
Organic Polymeric
Polyacrylic acid
Maliec acid
Tartaric acid
Citric acid
EDTA
Acidic monomers
Mineral acids
Hydrochloric acid
Nitric acid
Hydrofluoric acid

Calcium chelators:
Remove smear layer without decalcification or significant
physical changes in the underlying dentin substrate.
No funnel shaped changes are seen.
EDTA
pH of 7.4
Tublicid : 0.1% EDTA
0.15% Benzalkonium chloride
Scrubbed on the surface for a few seconds,
Smear layer removal, smear plug intact

Lasers:
Nd: YAG lasers used at 10-30 pulses per second.
The surface is desensitized by occlusion of open and
permeable dentinal tubules.
Air abrasion:
Aluminium oxide particles are used for air abrasion of a
particle size of 0.5 microns.

Primers are defined as chemicals capable of improving
the wettability of adherents or capable of being
incorporated into the surface of the substrate to form
chemical bonds across the interface (Causton, 1982).
•Adhesion promoting agents
•Hydrophilic
•Role of solvents-ethanol ,acetone
•Objective- hydrophilic hydrophobic& spongy
HEMA-the main component

Commonly used primers are
 2-5% NTG-GMA(N-Tolyglycine- glycidyl methacrylate)
 16% BPDM (Biphenyl dimethacrylate)
 30-55% HEMA (Hydroxy ethyl methacrylate)
 6% PENTA( dipentaerythritol penta acrylate
monophosphate)
 10% PMDM (Pyromellitic acid diethyl methacrylate)

Adhesives
Form resin tags to seal open dentinal tubules initiates and
advance the polymerization reaction and co polymerizes with the
primer molecules
-Stabilizes the formed hybrid layer and resin tags
-Provide sufficient methacrylate double bonds for
copolymerisation with the successively applied restorative resin.
Commonly used are:
Bis GMA, UDMA, TEGDMA, Methacrylated phosphates,
PENTA.
Act as a stress relaxation buffer to relieve polymerization
contraction stresses.
May contain fillers.( Optibond solo, Prime and bond NT)

Initiators and Accelerators:
Light cured: camphoroquinone and an organic amine.
Dual cured bonding agents :catalyst to promote self
curing.
Fillers:
Mostly unfilled
Inorganic fillers 0. 5% to 40% by wt.
Microfillers, or nanofillers

Functions of nanofillers:
1. Prevents nanoleakage.
2. Causes uniform thickness of adhesive layer
3. Better flexibility to adhesives
4. Better dissipation of forces
5. Scatter of light is prevented

1st generation dentin adhesives
 These contained N-phenylglycine and glycidyl
methacrylate (NPG-GMA).
 NPG-GMA is a bifunctional molecule
 This means that one end of this molecule bonds to
dentin while the other bonds (polymerizes) to
composite resin.
 Bond strength - 1 to 3 MPa.
 First commercially available was CERVIDENT.
Chelation with calcium on the tooth surface to generate
water resistant chemical bonds of resin to dentinal

Agents used in this generation:
NPG-GMA.
Glycerophosphoric acid dimethacrylate.( GPA-
DMA).
Cyanoacrylates
Polyurethanes.
DISADVANTAGES
Low bond strengths of only 2-3 MPa.
Hydrolysis of GPA-DMA in oral environment.
Difficulty in bulk polymerization of cyanoacrylates.
Instability of NPG-GMA in solution.

2nd generation adhesives
 Phosphate ester dentin bonding agents were introduced
containing phenyl-P & HEMA in ethanol.
 Its mechanism of action was based on polar interactions
between negatively charged phosphate groups in resin
and positively charged Ca ion in the smear layer.
 Bond strength: 1- 5 Mpa

Examples:
Clearfil bond system F.
Bondlite ( Kerr).
Prisma Universal Bond( Johnson and
Johnson).
DISADVANTAGES
Low bond strength of 1-10 Mpa
Hydrolysis of the bonds between phosphonate esters
and dentin
Poor clinical performance:
Bond achieved limited by cohesive failure in
smear layer or break at the smear layer dentin
surface.
Resins were devoid of hydrophilic groups, large
contact angles on intrinsically moist surfaces, did
not wet the dentin well.

3rd Generation
 Three step systems.
 PHOSPHATE BASED (HEMA+10 MDP)
 Required either removal, modification or dissolution of the
smear layer.
Dentin etching (Introduced by Fusuyama)
Primer application
Application of an unfilled resin.
 Bond strength: 3-8 mpa
 Eg: Scotch bond 2

4th Generation- Early 1990s
•Total etch concept/Moist Bonding
•Hybrid layer Nakabayashi 1982
Impregnation of resin into partially decalcified
dentin followed by polymerization created a resin
reinforced

Advantages:
Good Bond strength: 17-25 Mpa.
No reduction in bond strength when applied to moist surface.
Can bond to mineralized tissue as well as metal, amalgam,
composite and porcelain
Disadvantages:
Multiple steps: Technique sensitive.
Unless the primer and adhesive are applied consecutively, the
overlying composite resin will not bond to the surface.
Agents used in this generation
All bond 2( Bisco Dental)
Amalgam- bond( Parkell)
Clearfil Liner Bond( Kuraray)
Imperva Bond( Shofu Dental)
Optibond( Kerr)
Scotch bond multipurpose( 3M Dental)

5th Generation- Mid 1990s
Totally removes smear layer
Based on Total etch concept
2 step system
• Etching
• Priming + Bonding
Moist bonding technique

Advantages:
Good bond strength.
Time saving and relatively simpler to use.
Some agents have incorporated fluoride and
elastomeric components to improve marginal integrity.
Disadvantages:
•They lack many of the components to perform
multisubstrate bonding.
Post operative sensitivity
(most common in situations that magnify effects of
composite polymerization shrinkage.)

6th Generation- Early 2000s
Primer and etchant are combined in one step.( Self etching
primers)
•Contains phosphate derivatives of hydrophilic
monomer such as phenyl-P.
•It also contains 50% HEMA or other hydrophilic
monomer, so they both etch and primer the dentin
Type I Two step/ Non rinsing conditioner/ Self etch primer
systems
Type II One step/ Self etching adhesives/ All in one
systems(Requires mixing)
Examples: Clearfil® SF Bond (Kurarray)
Simplicity™ (Apex),

ADVANTAGES:
No need to acid etch with phosphoric acid.
No post conditioning rinsing required.
Reduced post operative sensitivity
Simultaneous demineralization and resin infiltration.
Less sensitive to degree of wetness and dryness.
Low technique sensitivity
DISADVANTAGES
Less effective bonding of enamel
Initial bond might deteriorate with aging, which could lead to premature
failures.
Bonding to Sclerotic and caries affected dentin might be problematic
May inhibit set of self cure or dual cure resin materials.

7th Generation- 2003
The system is quite similar to the 6th generation but a desensitizing agent
was added to overcome the problem of hypersensitivity .
•It is a, single-component, no-mix, one-step application dental adhesive
with an etchant, adhesive, desensitizer, and photo-initiator
•They combine conditioning, priming & application of adhesive resin but
unlike 6th gen don’t require mixing.
Contains both hydrophilic &hydrophobic components.

Disadvantages
• complex nature of mixed solutions - more prone to phase
separation & formation of droplets within adhesive layer.
•Lack of Polymerization-thin film
Examples:
•iBond™ (Heraeus)
•Xeno® IV (Dentsply)
•G-Bond™ (GC)
•Complete (Cosmedent)
•OptiBond® All-In-One (Kerr)

ADPER PROMPT L POP:
It has 3 compartments
Compartment 1: Containing methacrylated phosphoric
acid, esters photoinitiators, stabilizers.
Compartment 2: Contains water, complex fluoride and
stabilizers.
Compartment 3: Has a microbrush.

Bond Strength 17-25Mpa 20-25Mpa 18-25Mpa 20-30 Mpa

Etch and rinse Self-etch
Hybridization of
dentin
Difficult to
perform but stable
and durable over
time when done
properly
Easy to perform durable :primarily for mild
self etch adhesives
Bond to enamel
and marginal
integrity on
enamel
excellent Fairly good and clinically acceptable :can
be improved by additional phosphoric acid
etching
Postoperative
sensitivity
Good chance for
this ,especially
with overetching
or overdrying of
the dentin
Less chances of this, but not impossible
Comparison of the performance of current self-
etch adhesives with the etch and rinse approach

Etch and rinse Self-etch
Water solubility
of the adhesive
Withstands
hydrolysis fairly
well when nano-
leakage is
absent
Higher :some call them a
semipermeable membrane”
Color stability of
the adhesive
Good color
stability ,good
choice for high
–end esthetic
restoration
Not that good :owing to its
hydrophilicity,good chance of water
uptake(stains accompany the water )in
the adhesive
Ease of use If operator is
well trained and
potential errors
are recognized
,not difficult to
use
Easier to use but technique sensitive
too
Most difficult is the removal of the
water from the adhesive

Classification based on the number of clinical
application steps
•Etch & Rinse
Three‐Step - conditioner, primer, adhesive
Two‐Step - conditioner, (primer & adhesive)
• Self‐Etch
Two‐Step • (conditioner & primer), adhesive
One‐Step • (conditioner & primer & adhesive)

Depending on the pH
Van Meerbeck et al 2003

Classification of current adhesives based on type of
solvent of primer or combined primer/adhesive resin
Acetone
(ABC Enhanced,EG Bond)
Water
(ART Bond,Clearfil SE)
Ethanol
(Excite,PQI)
Acetone
Ethanol(All
-Bond 2)
Acetone
Water
(AQ Bond)
Ethanol
water(Gluma)

Classification of Bonding Agents based on their effect on
smear layer:
Smear layer removing dentin bonding agents
 Used after the smear layer is completely removed using
total-etch tech(Enamel & dentin are simultaneously
etched using 37% phosphoric acid)
 Bond to dentin micromechanically by formation of resin
tags & hybrid layer.
 Examples: - Single bond
-Gluma
-Optibond Solo

- Aim to modify the smear layer & incorporate it in bonding process.
- Based on the concept that smear layer is a natural barrier to the
pulp, preventing bacterial penetration & reduce outflow of dentinal fluid
that can affect bonding.
-Removal of Only superficial smear layer and resin intermingling
with deeper layers
Examples:
- Pro Bond
- Prime & Bond 2.1
- Compoglass
Smear layer modifying dentin bonding agents

Smear layer dissolving dentin bonding agents
 Demineralize the smear layer & superficial dentin
without removing the smear plugs.
 “self-etching primers” & “self-etching adhesives”.
 Both enamel & dentin are simultaneously etched and
primed by acidic primers.
 Examples: -self-etching primers : ADHESE
-self-etching adhesives : Prompt-L-Pop

CLASSIFICATION BASED ON FILLERS
Low filled:
-lower film thickness
-applicable in situations in which adhesive must be light cured
before seating an indirect restoration
High filled :
-greater film thickness
-stronger physical properties

Classification based on fluoride release
1.Fluoride releasing adhesives
2.Fluoride free adhesives
Slow release of fluoride increases local concentration of
fluor-apatite in mineralized dentin just beneath hybrid layer.
The less soluble mineral prevents release of hydrolytic
enzymes from mineralized matrix thus improving long
term stability.
(Nakajima,Okeda,Ogata,Tagami,Pashley,2003)

Classification of Bonding Agents based
on their shear bond strength
Three categories of dentinal adhesives are proposed:
•Category I - Includes adhesives with shear bond strength
values between 5 and 7 Mpa.
•Category II- includes dentinal adhesives with shear bond
strengths between 8 and 14 Mpa.
•Category III- includes adhesives with shear bond
strength values above 20 Mpa.

WATER TREES
•All-in-one adhesives--very acidic and very hydrophilic.
• They attract and absorb water, leading to leaching of
unpolymerized monomers or hydrolytic degradation
products through water-filled channels called water trees.
• These channels pass from the hybrid layers, through the
adhesives,
to the adhesive-composite interface.
•Lower bond strength
•Less durable.
•Does NOT occur in self-etching primer adhesive systems.

REVERSE WATER TREES
 In case of Reverse water trees, they appear to originate
from water trapped at the interface between the adhesive
and the overlying resin composite.
 During light curing some of the water that has reached
the top of the adhesive layer cant escape..The heat
generated by light curing reflect water back into less
polymerized subsurface
 They spread downward with their branches pointing
toward the dentin. Reverse water trees are frequently
affiliated with water blisters that are trapped along the
adhesive composite interface.

Theories of Water trees
 Water Remnant theory: Left out water
 Water Flux Theory: Evaporative
Osmotic

AMALGAM BONDING
Must have Auto-polymerizing capability
First layer-light cure
Bond strength : 2-20 Mpa
ADVANTAGES
 Conservative preparation
 Increase fracture resistance of restored tooth
 Seal margins better
 Decrease post operative sensitivity
 Prevent permeation of corrosion product
Examples: ALL BOND 2
AMAGAM BOND PLUS
CLEARFIL LINER BOND

CERAMIC BONDING
CONVENTIONAL SILICA BASED
•Partly of mechanical interlocking & partly of chemical
union.
•Mechanical retention is obtained by etching fitting surface
of porcelain with dilute Hydrofluoric acid(6-10%) or
ammonium bifluoride to increase surface roughness &
allowing low viscosity resin to penetrate into pores by
capillary action.
Chemical union occurs by interaction of silicate ceramic
surface & silane coupling agent of composite-

Inert ceramics: Aluminium oxide and Zirconia
based
 Air Abrasion
 Tribochemical SURFACE treatment
 phosphate based adhesive (panavia).10 MDP

CEMENTUM BONDING
One of the most frequent clinical problems associated with
class-II and class-V cavities in adhesive resin restorations
is the weak link of restorative material to root dental
structures, when the cervical margin is located below the
cementoenamel junction.
 Ferrari et al. reported that cementum treated with dentin
bonding systems is infiltrated by the resin, but the
predictability of the bond is unclear.

•The shear bond strength of a resin composite to EDTA
conditioned sound cementum, after treatment with an
aqueous primer composed of 5% glutaraldehyde and 35%
hydroxyethyl methacrylate, was estimated as 6MPa.
•It seems that after demineralization the increased intrinsic
fibrial
content of intact cementum surface creates an organic
network that lacks the cohesive strength of demineralized
dentin collagen, and although it is reinforced by resin
infiltration, results in low bond strength.
•Modification of intact cementum surfaces to improve
adhesion may include a eproteination step, prior to any
adhesive treatment, in order to remove the high organic
content and expose the inorganic substrate, like conditioning
with aqueous solutions of sodium hypochlorite (NaOCl)

Futurabond DC- 8th Generation
•It is dual-cured and works with all light, self or dual-
cured resins .
•Nanosized cross linking agents with fused silica
particles
•It works in a self-cured mode without any light – great
for endo
• It takes only 35 sec. from start to finish.
• It needs only one coat.

Surpass: A Universal Eighth Generation
Bonding System
Has the best attributes of the fourth generation
and the ease of the sixth-generation bonding
systems
Consists of three bottles: an etchant/conditioner,
a primer, and a separate hydrophobic bonding
resin
Etchant/conditioner is not rinsed from the tooth.
Bond Strength: 50 Mpa

Fluoride releasing bonding agents
 Anti-cariogenic
 Increase dentin bond strength
 Increase the local concentration of fluoro-apatite in the mineralized
dentin just beneath the hybrid layer
 Prevent the release of hydrolytic enzymes from the matrix.
 Reduce the solubility of intrinsic calcium phosphate within the hybrid
layer.
Examples:
 CLEAR FIL SE BOND PLUS
 ONE UP BOND F
 G BOND

FL BOND II
FL-Bond is a self-etching fluoride releasing two-step adhesive system
which features an excellent bond to both enamel and dentin and
provides a secure marginal seal.
•The primer has new effective adhesive promoting monomer and new
photo initiator and is free of HEMA and acetone to considerably
minimize odour, post operative sensitivity
•The FL-BOND Bonding Agent incorporates fluoride containing S-PRG
filler (Surface Pre-Reacted Glass-ionomer) which continuously provide
fluoride to the tooth structure.

Matrix Metallo-Protineases
Host-derived matrix metalloproteinases (MMPs), found both in saliva
and
in etched dentin, have been shown to be involved in the degradation
of the
unprotected collagen fibrils within the hybrid layer.

Role Of MMP Inhibitors
 Dentin MMPs can be activated following the demineralization
of the dentin surface by acids, resulting in collagenolytic and
gelatinolytic activities.
 Effective synthetic MMP inhibitor must contain a functional
group (e.g., carboxylic acid, hydroxamic acid, sulfhydryl)
capable of chelating the active-site zinc ion in the MMP
molecule.
 resulting in improved micromechanical retention of the
adhesive within the collagen matrix, suggesting an auxiliary
bonding mechanism.
Examples:
 CHX(0.2-2%), quaternary ammonium methacrylate resin
Monomers, Batimastat,Galardin

Desensitization
 precipitation of proteins in the tubule
 Penetrates the tube as far as 200um.
 Forms series of bridges across the tubule.
 Impermeable to odontoblastic fluids.
Examples : GLUMA SYSTEM(5% GLUTARALDEHYDE+35%
HEMA)
ALL BOND 2

MULTIPURPOSE BONDING
 Scotchbond™ Universal Adhesive is a combined Total-Etch,
Self-Etch and Selective-Etch adhesive.
1. Etchant: 35% phosphoric acid
2. Primer: water (40%), HEMA (47%) and poly-alkenoic acid
copolymer (13%)
3. Adhesive: Bis-GMA (65%), HEMA (34%) and
4. Initiators/accelerators (1%)
 It offers one simple adhesive application technique for both
direct and indirect indications and bonds to all surfaces
including enamel, dentin, glass ceramic, zirconia, noble and
non-precious alloys, and composites - without additional
primer.

G-Bond
 4 MET monomer : Strong consistent bond to dentin
 Phosphoric acid ester monomer : Consistent bond to
enamel.
Nanointeraction technology:
Non-conventional interface with the dentin – a “Nano
Interaction Zone” (NIZ) with minimal decalcification and
almost no exposure to collagen fibers. Ionic bond with
hydroxyapatite of tooth structure.

Nano filled adhesives
 These fillers were mainly silica or glass of varying
sizes.
 Filled adhesives had greater film thickness, greater
ability flex and can help dissipate the stress of
composite polymerisation.
 Higher filled, larger particle filled adhesives yielded
stronger physical properties .
 These nano fillers are generally Amorphous silica
dioxide which are 100 times smaller than the fillers in
hybrid composites which results in optimal optical
properties.

Advantages
 Increased adhesive strength to both enamel and
dentin
 Increased marginal integrity
 Sufficient film thickness for one-coat, one cure
technique
 Deeper penetration into dentinal tubules
 The filled adhesives should be rubbed on the surface
to lift the filler particles so that small spaces between
collagen fibrils are not clogged, which could act as a
barrier to permeation
Examples: Prime and Bond NT (7nm)
Excite ( 12 nm)

Antibacterial Agents
Clearfil™ SE Protect, an antibacterial self-etching
adhesive.
SE Protect contains an antibacterial monomer, MDPB
(methacryloyloxyl-dodecyl pyridinium bromide) which
disinfects the tooth’s surface during its application

Go! One Component Self-Etching Light-Cure
Adhesive
 Go! is a super quick adhesive saves valuable chair
time
 HEMA free
 No post-operative sensitivity
 High fluoride release
Assists in strengthening the tooth &preventing
recurrent decay.
 Quick color change
Initially, Go! is a dark yellow color, but upon curing, it
changes to clear.

Frog Self-Etch Adhesive
 Self etcher
Frog self-etching primer infiltrates cut tooth surfaces, effectively
dissolving the smear layer formed during cavity preparation.
Does not require a separate etching step. Instead, the dentinal
tubules are simultaneously plugged as they are etched.
 Optimal pH
Frog’s optimal pH of 2.0 allows the unblocking of dentin tubules
without aggressively decalcifying the tooth surface.

 The gripper
- Frog deeply penetrates to form a very strong
bond enabling a perfect grip to the tooth surface.
- maintains the hydroxyapatite in the collagen
fibrils assisting in mechanically bonding the
adhesive to the tooth surface.
 Protecting the pulp
Post-operative sensitivity is prevented: no
separate etching, washing and / or drying
required, hence over drying cannot occur. Patient
comfort is maximized

 Nano
Frog’s specially treated nanofillers improve the
cohesive strength of the bond and ensure good
adaptation to tooth structure when applied to both
dentin and enamel. There will be complete
marginal sealing to protect the restoration margins
against the diffusion of oral fluids and
microorganisms.
 Low film thickness
Frog’s low film thickness of 12 microns ensures
invisible margins.

PULP CAPPING AGENTS?
Direct pulp capping with a dentin bonding system in
human teeth: a clinical and histological evaluation.
Silva GA, Oper Dent. 2006 May-Jun;31(3):297-307.
 This study evaluated the pulpal response in human dental pulp to
direct pulp capping with the Single Bond Adhesive System (SBAS)
after 10% or 37% phosphoric acid etching and after capping with
Calcium Hydroxide
 Conclusion: SBAS should be avoided for vital pulp therapy, while
CH remains the capping agent of choice for mechanically exposed
human dental pulp.

Adverse effects of human pulps after direct pulp
capping with the different components from a total-
etch, three-step adhesive system
Maria de Lourdes Rodrigues Accorinte, Dental Materials (2005) 21,
599–607
Group 1—acid+ primer+adhesive were used as
recommended; Group 2—only primer was applied; Group
3—only bonding resin (light-cured for 10 s); Group 4—only
composite resin (light-cured for 40 s); Group 5—calcium
hydroxide.
Conclusion:
Adhesive components (primer or adhesive) as well as a
composite should be avoided for pulp capping. Ca(OH)2
should be the first choice for pulp capping

CONCLUSION
 Advances in adhesive dental technology have radically
changed restorative dentistry.
 Numerous systems are available for strong bonding of
resin to dentin, however this system must be used
properly to optimize their clinical performance.
 The advent of new resin technologies like self etch
primers, simplified the procedure and is comparatively
less technique sensitive than the total etch technique.
 In future with the continued growth of new technology, it
will be up to the dentist to make the RIGHT CHOICE.

DENTIN BONDING AGENTS

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