This document provides information on the different generations of dentin bonding agents. It discusses the definitions and requirements of ideal bonding agents. It describes the mechanisms and challenges of bonding to enamel versus dentin. The development and limitations of first through seventh generation bonding agents are outlined, focusing on how newer generations aimed to simplify procedures and improve bond strength to dentin over time. The key aspects of enamel bonding, dentin bonding, and the role of the smear layer are summarized.

1. DENTIN BONDING
AGENTS
KIRANPREET KAUR GREWAL
FINAL YEAR
GURU NANAK DEV DENTAL COLLEGE AND RESEARCH
INSTIUTE, SUNAM.

2. DEFINATIONS
 Adhesion: It is the force or intermolecular attraction
that exists between molecules of two unlike
substances when placed in intimate contact with
each other.
 Adhesive: the substance added to produce the
adhesion.
 Adherend: the material to which adhesive is
applied .

3.  Etchant: Chemicals such as phosphoric acid
etc. are used for improving the reactivity of
the substrate and to remove smear layer or
demineralization of the superficial enamel and
dentin.
 Primer: These are the monomer dissolved in
solvent such as water , acetone or alcohol.
These agents are applied over the etched
surface facilitating the easy flow of resin.
 Bonding agent: It is an unfilled resin that
consist of both hydrophilic monomer and
hydrophobic monomer.

4. REQUIREMENTS OF IDEAL BONDING
AGENT
 Should be biocompatible.
 Should bond effectively to both enamel and dentin.
 Should be resistant to degradation in oral
environment.
 Should be Non toxic.
 Should be Non irritant.
 Should have Good dimensional stability.
 Should be easy to use.

5. ENAMEL BONDING
 Enamel is the hardest tissue of human body
consists of 95% mineralized inorganic substance
i.e. hydroxyapatite crystals.
 Due to high mineral content the bonding in enamel
is good as compared to dentin.
 Enamel is etched using 37% phosphoric acid
applied for 15-30 seconds.
 Etching creates 5-50 microns deep microporous
layer into which adhesive resin flow.
 This results in long lasting enamel bond achieved
via micromechanical interlocking between resin and
enamel.
 Bond strength: 15-25 Mpa.

7. DENTIN BONDING
 Bonding to dentin presents a greater challenge as
compared to enamel bonding.
 In dentin inorganic part is only 50%.
 Hydroxyapatite crystals are arranged randomly in organic
matrix.
 Dentin contains dentinal tubules which contains processes
of the pulp. These makes the dentin sensitive.
 Fluid present in the dentinal tubules constantly flows
outwards which reduces the adhesion of composite resin
to dentin.
 Relative area offered by dentin tubules decreases with
increasing distance from pulp. Since the tubules are more
numerous and wider near the pulp, there is more fluid and
less dentin, this makes dentin bonding less effective in
deeper dentin than superficial dentin.

8.  The presence of smear layer makes the wetting of
dentin by adhesive more difficult.
ROLE OF SMEAR LAYER IN DENTIN BONDING
 Smear layer: Residues of dentin which adheres tightly
to dentin & fills the tubules after cavity cutting.
 The smear layer fills the orifices if the dentinal tubules
by forming smear plugs & decreases the permeability of
dentin up to 86%.
 Smear layer is composed basically of hydroxyapatite
and altered denatured collagen.
 The removal of smear layer and smear plugs with
acidic solution may result in increase of the fluid flow
onto exposed dentin surfaces.

11. MECHANISM OF DENTIN BONDING
 Composite resins do not show microscopic contact
with dentin when placed directly into the cavity.
 In order to overcome this, an intermediate layer of
fluid is used which combines with composite resins
and components of dentin.
 Dentin adhesives should be both hydrophobic as
well as hydrophilic.
 It is required to be hydrophilic so as to be able to
displace dentinal fluids and thereby permitting
penetration into porosities in dentin.
 Hydrophobic properties are needed to allow
bonding to composite resin.

13. DEVELOPMENT OF DENTIN BONDING SYSTEMS
FIRST GENERATION DENTIN ADHESIVE:
 Given by S.S White.
 There is development of surface active copolymer
NPG-GMA (N-phenylglycine glycidyl methacrylate)
 This copolymer could bond on the tooth surface to
generate water resistant chemical bonds of resin to
dentinal tubules.
 It bonds to the calcium component of dentin.
 Since they could bond with calcium ions in tooth
structure, they form stronger bonds with enamel then
dentin.

14.  Smear layer is ignored.
 Example: Cervident.
LIMITATIONS OF FIRST GENERATION
BONDING AGENT:
 Low bond strength: 2-3Mpa.
 Loss of bond strength over time.
 Lack of stability of individual component
during storage.

15. SECOND GENERATION DENTIN ADHESIVE:
 Clearfil Bond system F was the first product of second
generation bonding agent which was introduced in
Japan in year 1978.
 It was a phosphate ester material.
 Its mechanism of action was based on the popular
interaction between the negatively charged phosphate
group of resin & positively charged calcium in smear
layer.
LIMITATIONS:
 Smear layer was the weakest link in the system
because of relatively loose attachment to dentin
surface.
 Bond Strength was low : 1-5MPa.

16. THIRD GENERATION DENTIN ADHESIVE:
 Introduced in 1979.
 These were designed not to remove the entire smear
layer, but rather to modify it and to allow penetration of
acidic monomers.
 Involves the concept of phosphoric acid etching before
application of phosphate ester type of bonding agent.
LIMITATIONS:
 But because bonding agent have hydrophobic nature,
acid etching did not produce the significant improvement
in dentin bond strength inspite of flow of resin into open
dentinal tubules.
 Pulpal inflammatory responses were thought to be
triggered due to application of acid.

17. FOURTH GENERATION DENTIN ADHESIVE:
 These are introduced for the use on acid –etched dentin.
 Multiple bottle adhesive system.
 Smear layer is considered as an obstacle that must be
removed so that resin can be bonded to the underlying dentin
substrate.
 Fourth generation adhesives are basically composed of:
I. An acid etching gel that is rinsed off.
II. A solution of primers that are relatively hydrophilic monomers
in ethanol, acetone and/or water.
III. Fluid bonding agent.
 Acid open up the dentinal tubules, thus creating microporosity
of intertubular dentin.
 When primer and bonding resins are applied to etched dentin,
they penetrate the intertubular dentin, forming resin dentin
interdiffusion zone or “hybrid layer”.

18.  Examples:
1. All Bond-2
2. Scotch Bond Multipurpose
3. Optioned FL
4. Clearfil Liner Bond 2

19. Hybrid layer:
 Also known as resin-dentin interpenetration/
interdiffusion zone.
 This is the zone where the adhesive resin of the
dentin bonding agent micromechanically
interlocks within the intertubular dentin and
surrounding collagen fibers.

20. FIFTH GENERATION DENTIN ADHESIVES:
 Commercially available adhesive proves to be
satisfactory but it contain several time consuming steps
to be applied.
 So “one bottle” adhesive system was introduced.
 In this there is combination of primer and bonding agent
steps, but a separate etching step.
Total etch adhesive system:
 Simultaneous application of an acid to enamel and
dentin, known as the total etch technique.
 It was initiated in Japan .
 In this phosphoric acid etching of dentin is done before
applying phosphate ester type of bonding agent.
 Bond strength: 17-30MPa.

21.  Examples:
1. Prime and bond
2. Optibond solo
3. Single Bond

23. SIXTH GENERATION DENTIN ADHESIVES:
 Introduced in 2000.
 These are single bottle adhesives combine
etching, priming & bonding in a single solution &
as single step.
 It consists of self etching primers which are used
in place of separate etchant
 Less effective bond with enamel as compared to
dentin due to high acidic content.
 These are further of 2 types:
 Self-etching primer & adhesive.
 Self-etching adhesive.

24.  Self-etching primer & adhesive:
 Two bottles: Liquid 1(acidic primer)
Liquid 2(adhesive)
 Acidic primer applied to the tooth followed by adhesive.
 Light cure formulations.
 Solvent is water.
 Self-etching adhesive:
 Two bottles consisting of acid primer and adhesive.
 A drop of each liquid is mixed and applied to the tooth.
 Light cure formulations.
 Examples:
 Xeno III

26. SEVENTH GENERATION DENTIN ADHESIVE:
 The self etching primers was introduced in Japan.
 These acidic primers include a phosphonated resin
molecules that performs two functions simultaneously-
Etching & Priming of dentin and enamel.
 Unlike conventional etchants, self etching primers are
not rinsed off.
 In addition to simplifying the bonding technique, the
elimination of rinsing and drying steps reduces the
possibility of overwetting or overdrying.
 They also have properties of disinfection &
desensitization.
 Bond strength: 20-28MPa.
 Example: I bond
G bond

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