2. CONTENTS
INTRODUCTION
BASIC CONCEPTS OF ADHESION
MECHANISMS OF DENTAL ADHESION
INDICATIONS FOR ADHESIVE DENTISTRY
ENAMEL ADHESION
DENTIN ADHESION
DENTIN BONDING AGENTS AND THEIR
INDICATIONS
GENERATIONS OF DENTIN BONDING AGENTS
CLINICAL FACTORS IN DENTIN ADHESION
CONCLUSION
REFERENCES
3. INTRODUCTION
• The fundamental objective of all restorations since
centuries has been to create adhesion between two
dissimilar surfaces: mineralized tooth structure and the
restorative materials.
• The invention of dentin bonding agent is like a - dream
come true for dentistry, which led to the beginning of
new era of adhesive dentistry.
• The concept of dentistry with the introduction of
adhesives has changed from - Extension for Prevention
to PREVENTION OF EXTENSION !!!
4. The traditional “drill
and fill” approach is
fading now because of
numerous
advancements taking
place in restorative
dentistry.
5. ADHESIVE DENTISTRY
• Branch of dentistry which deals with adhesion or
bonding with natural sub stance of tooth,the
enamel and dentin
• The dentin bonding agents are based on the
mechanism of adhesion.
• The word adhesion comes ffrom the latin word
adhaerere(“To stick to”)
• Adhesion is defined as a state in which two
surfaces are held together by interfacial
forces,which may consist of valence forces,or
interlocking forces or both.(The American Soceity
for testing materials[Specification D 907].
6. INDICATIONS
Adhesive restorative techniques are currently used to
accomplish the following:
1. Restore Class I, II, III, IV, V, and VI carious or traumatic
defects
2. Change the shape and the color of anterior teeth
3. Improve retention for metallic crowns or for porcelain-
fused-to-metal crowns
4. Bond all-ceramic restorations
5. Bond indirect resin-based restorations
7. 6. Seal pits and fissures
7. Bond orthodontic brackets
8. Bond periodontal splints and conservative tooth
replacement prostheses
9. Repair existing restorations (composite, amalgam,
ceramic, or ceramometal)
10. Provide foundations for crowns
11. Desensitize exposed root surfaces
8. 12. Seal beneath or bond amalgam restorations to
tooth structure
13. Impregnate dentin that has been exposed to the
oral fluids, making it less susceptible to caries
14. Bond fractured fragments of anterior teeth
15. Bond prefabricated and cast posts
16. Reinforce fragile endo treated roots internally
17. Seal apical restorations placed during endodontic
surgery
10. PRINCIPLES OF ADHESION
• Adherend: The surface or substrate that is adhered
• Adhesive/adherent: A material that can join substances
together, resist separation and transmit loads across the bond
• Adhesive failure: The bond that fails at the interface between
the two substrates.
• Cohesive failure: The bond fails within one of the substrates,
but not at the interface.
11. MECHANISM OF DENTAL ADHESION
1. Mechanical adhesion: Interlocking of
adhesive with irregularities in the surface of
the substrate,or adherend. This would
incvolve the penetration of resin and
formation of resin tags.
12. 2.Adsorption: chemical bonding to organic
and inorganic components of tooth structure.
Chemical bonding may be vander waals
forces, dipole,H-bond,ionic and covalent.
13. 3.Diffusion: Interlocking between the mobile
molecules,such as adhesion of 2 polymers
through diffusion across an interface.
4.combination: Based on above three
mechanisms.
15. • WETTING is the ability of the liquid to flow easily over the entire
surface and adhere to the solid.
• If the adhesive does not wet the surface of the adherend,
adhesion between the adhesive and adherend will be negligible or
nonexistent.
16. Wetting is principally influenced by:
–Cleanliness of the adherend : Cleaner surface, greater
adhesion.
–Surface energy of the adherend: More surface energy, greater
adhesion
–CONTACT ANGLE
The extent to which an adhesive wets the surface of the
adherend may be determined by measuring the contact angle,
which is the angle, formed by the adhesive with the adherend at
their interface.
The stronger the attraction of the adhesive for the adherend, the
smaller will be the contact angle.
17. • The zero contact angle is the best to obtain wetting
Surface Energy
• The surface tension of the liquid & surface energy of the adherend ,
determine the degree of wetting.
• the harder the surface , the higher the surface energy , which means
that adhesive properties of the material is higher.
• A clean microroughened tooth surface has more surface energy than
a unprepared tooth surface
The acid etch technique generate high energy tooth surface and enhnce
adhesion
18. • SURFACE CONTAMİNATİON
• The substrate surface should be clean as
contamination prevents the adhesion.
• Adhesive should be able to fill their regularities
making the surface smooth allowing proper or
intimate contact
• INTERPENETRATION
Means formation of hybrid layer (resin –dentin
interdiffusion zone)
the ability to form a good interface with dentin is also a
factor
19. MICROMECHANICAL BONDING
To achieve strong bonding through micromechanical
bonding , wetting monomers must adapt to enamel and
fill enamel surface irregularities and or infiltrate into
demineralised collagen network in dentin.
CHEMICAL BONDING
Some acid monomers have additional capability of forming
chemical bonds with calcium in the residual tooth tissue
Eg. Acids with phosphate or caboxyl group
20.
21. *
*To bond to enamel, it is very important to focus on the
mineral component (hydroxyapatite) of enamel.
* ACID CONCENTRATIONS
Buonocore, 1955
*was the first to reveal the adhesion of acrylic resin to
acid etched enamel.
*used 85 percent phosphoric acid for etching
*Silverstone revealed that the optimum concentration
of phosphoric acid should range between 30 to 40
percent to get a satisfactory adhesion to the enamel.
22. *Etching time
currently 15 secs recommended. An etching time of 60
sec originally recommended for permanent enamel using
30-40%
Form of acid
* Liquid or gel
*Liquid easily flows and cannot be confined so gel is more
used.
Placement of acid
* syringe or brush
*Syringe more common
23. Mechanism of etching:
Acid etching coverts smooth enamel to very
irregular surface
3 types of etch patterns have been
described
Type I: (Preferential prism center etching)
Dissolution of prism cores without
dissolution of prism peripheries
honey comb appearance. The average
diameter of the hollowed prism core is
measured as about 3µm. This is the most
commonest type of etching pattern.
Type II: Dissolution of peripheral enamel
without dissolution of prism core.
cobblestone appearance
24. Type III : Mixed pattern.
Etching pattern is less distinct
and includes areas resembling
type I and type II patterns as well
as regions in which the etching
pattern appears unrelated to
prism morphology.
associated with the presence of
prism less enamel and appears as
a generalized surface roughening.
RINSING
rinsed with water spray for 5 sec
to completely wash off acid
25. DRYING
Proper drying cause “FROSTY “ appearance.
Prevent contamination by saliva or blood
ENAMEL BONDING AGENTS
Consisted of BISGMA or UDMA diluted with
TEGDMA to lower viscosity
They flow easily to microporosities
26. RESIN MICROTAG FORMATION MECHANISM
Enamel acid etching – removes 10 micron of enamel
Creates microporous layer 5 to50 microns deep
Smooth surface – irregular surface with high surface energy 72dynes/cm
Unfilled liquid acrylic resin (enamel bonding agent)
Wets the surface
Enters into microporosities by capillary action
Two types of resin tags are formed
Macrotags microtags
(form between enamel prisms peripheries ) (form at the core of enamel prisms )
29. Adhesion of restorative materials to enamel has
become a routine and reliable aspect of modern
restorative dentistry,
But adhesion to dentin has proved to be more difficult
and less predictable.
Much of the difficulty in bonding to dentin is the result
of the complex microstructure and variable
composition of dentin in different areas of the tooth.
30.
The composition of dentinis much different than enamel, and
behave differently when etched with acid.
The presence of water and organic components lower the
surface energy of dentin and make bonding with hydrophobic
resins essentially impossible.
31. Dentin is an intrinsically hydrated tissue, penetrated by a maze
of 1- to 0.25-μm-diameter fluid-filled dentin tubules.
Movement of fluid from the pulp to the DEJ is a result of a slight
but constant pulpal pressure
Pulpal pressure has a magnitude of 25 to 30 mm Hg or 34 to 40
cm H2O. So there is constant flow of fluid.
Dentinal tubules enclose cellular extensions from the
odontoblasts and are in direct communication with the pulp .
Inside the tubule lumen, other fibrous organic structures are
present, such as the lamina limitans, which substantially
decreases the functional radius of the tubule.
32. Distribution of tubules in
dentin
Dentin close to the pulp shows
a
higher tubule density than in
dentin remote from the pulp.
The higher the tubule density,
the lower the bond strength
values of the dentin adhesives
33. whenever tooth structure is prepared with a bur
or other instrument, residual organic and
inorganic components form a layer of debris on
the surface of the substrate which is termed as
substrate.
Smear layer fills the orifices of dentin tubules and
form smear plugs and decreases dentin
permeability by nearly 90%
34. Thickness of smear layer : 0.5-2 µm
Thickness of smear plug : 1-10µm
COMPOSITION
Iatrogenically produced smear layer is
predominantly made of hydroxiapatite and altered
denatured collagen.
Altered collagen acquire gelatinised consistency
due to friction and heat
CLINICAL CONSIDERATIONS
the presence of intact smear layer is detrimental
for bonding
OPTIMAL DENTIN BONDING can take place by:
a) Complete removal of smear layer prior to the
bonding procedure by using etch and rinse
adhesive
b) Incorporation of smear layer into bonding layer
by using self etch adhesives.
35. c. Complete removal of smear layer increases the
permeability of dentinal tubules by more than 90%.
ADVANTAGES AND DISADVATAGES
Reduction of dentin permeability to toxins and oral
fluids;
Reduction of diffusion (usually inwards) and
convection of fluids (outwards by hydrostatic pressure
or inwards, for example, while restorations are
cemented),
Reduction of wetness of cut dentin surfaces, and
Prevention of bacterial penetration of dentinal tubules.
36. Wetness and the harboring of bacteria or their products,
It reduces the surface energy which compromises surface
wetting,
Prevents the intimate surface contact between the adhesive
and dentin substrate, and
Prevents resin penetration into dentinal tubules
It acts like a separating agent since it is an intrinsically weak
structure that bond weakly to the underlying dentin (Tao and
Pashley)
Further, the mineral component of the smear layer may
dissolve slowly under a leaking restoration or may be removed
by acid produced by bacteria to leave a gap which in turn
increases marginal leakage and possibly secondary caries.
37. DENTIN BONDING AGENTS
Bonding agents can be defined as material of low viscosity, when
applied on the tooth surface and forms thin film after setting.
This thin film strongly bonded to tooth surface, on which the viscous
composite restorative resin is applied. This sets forming an integrated
resin restoration
38. IDEAL REQUIREMENTS
Biocompatible
Non toxic, Non irritant, Non poisonous
Low film thickness, Low viscosity
Form strong permanent bond
Good dimensional stability
Similar C.O.T.E as tooth
Low thermal conductivity
Good shelf life
Prevent micro leakage
40. ETCHANTS
ORGANIC ACID:- Maleic acid ,EDTA ,citric acid, tartaric acid.
POLYMERIC ACID:- poly acrylic acid
INORGANIC ACID:- phosphoric acid, nitric acid.
Main Actions:
• Heavily alters or removes the smear layer
• Demineralizes peritubular and intertubular surface dentin and, thereby, exposes
collagen fibrils.
• Demineralizes up to a depth of 7.5 microns
• Depth of demineralization depends on type of acid, its concentration, and etching
time
• More mineralized peritubular dentin is etched more deeply than the intertubular dentin
• Increases dentin permeability by 4 to 9 times.
41. PRIMER
Primer is usually a bi functional monomer in a
volatile solvent such as acetone or alcohol; a
bi functional monomer has a hydrophilic end
and a hydrophobic end
Examples of bifunctional monomers include
HEMA (hydroxyethyl methacrylate),
NMSA (N-methacryloyl-5- aminosalicylic
acid),
NPG (N-phenylglycine),
PMDM (pyromellitic diethylmethacrylate), and
4-META (4- methacryloxyethyl trimellitate
anhydride).
42. ADHESIVE RESIN
Adhesive is an unfilled or partially filled resin; may
contain some component of the primer (e.g. HEMA) to
promote increased bond strength.
Main Actions:
Combines with the primer’s monomers to form a resin-
reinforced hybrid layer (resin-dentin interdiffusion zone)
from 1 to 5 microns thick.
Forms resin tags to seal the dentin tubules provides
methacrylate groups to bond with the subsequently
placed resin composite
45. *
FIRST GENERATIONS
*Development of NPG-GMA, a surface active co-monomer was the basis of
first commercially available dentin bonding agent.
*ADHESION TO SMEAR LAYER
*Theoretically NPG-GMA was supposed to chelate with calcium in dentin to
form water resistant chemical bond to dentin
*In this M -un saturated methyl methacrylate group
*X -acidic phosphate group to react with calcium of dentin
*But bond strength produced by this agent very low (2-3 mpa).
*Clinically this agent did not successfully bond composite resin to dentin.
46. SECOND GENERATION
Introduced in 1970s and attempted to bond chemically to
either inorganic or organic components of dentin
But they produced only limited bond strength (5-6 mpa).
Amino acid groups,carboxylic acid grups to effect bonding to
dentin
Materials tried were:- halogen phosphoric acid esters of Bis-
GMA, NPG-GMA, PHENYL-P
Based on polar interaction btwn neg charged phosphate group
in resin and positively charged ca ions in smear layer
Examples:-
Clear fill bonds system F
scotch bond
bond lite.
47. THIRD GENERATION
Third generation attempted to deal with smear layer and dentinal fluid
They employed two approaches:-
Modification of smear layer to improve its property
Or
Removal of smear layer without disturbing smear plugs that occlude the
dentinal tubules.
The idea was to avoid aggressive etching of dentin because it cause pulpitis
ACIDS USED
2% nitric acid
2.5% maleic acid with HEMA
10% citric acid with 3% ferric chloride
10% phosphoric acid
Eg:- Tenure, Scotch bond, Gluma C&B metabond
48.
49. Developed in 1990s,Multiple step
Total etch concept & moist bonding technique
Multiple bottles
-etch and rinse adhesives
-three step adhesives
-total etch adhesives
Etching with phosphoric acid required
Rinsing required
Light and dual cured formulations available.
ETCHANT:- Phosphoric acid, citric acid/ calcium
chloride, oxalic acid/ aluminum nitrate.
PRIMER:- NTG-GMA/BPDM,HEMA/GPDM,4META
ADHESIVES:- Bis-GMA,TEGMA
Eg:- all bond 2 ,panavia 21.
50.
51. The concept of “Hybrid Layer” propsed by
Nobo Nakabayashi in 1982
Layer formed by interdiffusion of low viscosity
monomers into exposed collagennetwork and
intertubular dentin to form resin-dentin
interdiffusion zone.
52. This are simplified version of fourth generation
In fifth generation bonding agents primer and
adhesives are in same bottle.
Etching and rinsing required
ETCHANT:- Phosphoric acid,
PRIMER:- PENTA, Methacrylated phosphonates
SOLVENT:- acetone, ethanol/water.
These agents are inferior to fourth generation
bonding agents in terms of bond strength.
Eg:- single bond3,Gluma comfort bond.
FIFTH GENERATION
53. SIXTH GENERATION
These includes self etching primers where the etchant
and primer are in one bottle and adhesive resin in
another bottle.
Manipulation is easy , show good bond strength to
dentin but not to enamel
Etching and rinsing not required
Primer applied first then adhesive.
ACIDIC PRIMER ADHESIVE:- Methacrylated
phosphates
SOLVENT:- Water
Eg:- clear fill SE bond,XENO
54.
55. 2 types :
Self etching primers
etchant and primer in one bottle
while adhesive is in separate
bottle. For this system,first the
etchant and primer are applied on
tooth surface eg: XENO,Clearfil SE
bond
Self etching adhesive
primer,adhesive and etchant all
in one but require mixing eg:
prompt L pop
56. ADVANTAGES
Comparable adhesion and bond strengths to enamel and
dentin
Reduces postoperative sensitivity because they etch and
prime simultaneously
They etch the dentin less aggressively than total etch
products
The demineralized dentin is infiltrated by resin during the
etching process
57. One bottle- no mixing required.
Etching and rinsing not required
Light cured formulation
Useful for direct applications with light cured
restorative material.
ACIDIC PRIMER ADHESIVE:- Methacrylated
phosphates
SOLVENT:-Water
58.
59. A new category of composite resin restorative materials, which
include what could be referred to as an “eighth-generation”
bonding system, has just become available for use.
This new technology features a bonding agent which is contained
within the composite resin restorative material.
A self-etching, self-adhering flowable composite technology
eliminates the need for a separate bonding application step with
composites for direct restorative procedures.
Utilizing previous adhesive technology (found in the OptiBond
system [Kerr]), this new self-etching, self-bonding flowable
composite resin system (Vertise Flow [Kerr]), simplifies the
placement of direct composite restorations.
60. • Since fifth-, sixth- and seventh-generation
systems are incompatible with self-cure
materials and dual-cure materials that
cannot be effectively light-cured
• Futura bond DC dual cured
• It is dual-cured and works with all light-,
self- or dual-cured resins
• It takes only 35 sec. from start to finish
• It needs only one coat .
• Futurabond DC cures without any light in
the self-cured mode. This is a big advantage
for root canal cementation.
• Futurabond DC eliminates the problem of
the “pooling effect” with moisture
61. CONCLUSION
• Adhesive restorative dentistry originated with the work of
Buonocore in 1955 who developed the concept of acid
etching.
• Since then adhesive materials and techniques have
developed at a rapid rate.
• Dentin bonding agents have advanced greatly over the
last two decades and can now provide predictable
bonding to enamel and dentin.
• The various advances in adhesive technology have
expanded the applications of DBA to include bonding of
composite ,ceramic and metallic restorations successfully
to tooth structure.
