Dentin bonding agent

prsentation includes different generations of dentin bonding agents along with their uses, advantages and disadvantages.

1. PRESENTED BY
DR MEENAL ATHARKAR
MDS
DEPT OF ENDODONTICS AND CONSERVATIVE
DENTISTRY

2. Content
Introduction
Definition of adhesive
Type of adhesion
Application of adhesive restoration
Adhesion in dentistry
Advantage of adhesion
Wetting of adhesive
Factor affecting adhesion
Composition of enamel & dentin
Changes in dentine
Smear layer

3. Internal & external dentine wetting
Classification of dentin bonding agent
Components of bonding agent
Hybridization
Glass ionomer adhesive
Adhesive amalgam restoration
Ceramic bonding
Microleakage
Biocompatibility
Summary
Conclusion
Reference

4. The concept of large preparations and extension for
prevention, proposed by BLACK in 1917 has gradually been
replaced by concepts of smaller preparations and more
conservative technique ,by concept of ADHESION in 1955,
given by BUONOCORE.
INTRODUCTION
JAMES B. SUMMITT- SECOND EDITION

5. ØThe adhesive or adherent or on dental terminology the
BONDING AGENT or ADHESIVE SYSTEM, may then be
defined as the material that ,when applied to the surface of
substance can join them together ,resist separation and
transmit load across the bond.
DEFINITION OF ADHESION
Adhesion –latin - to stick to
JAMES B. SUMMITT- SECOND EDITION

6. ØBond strength is the measure of load bearing capability of
the adhesives .
ØThe time period during which the bond remain effective is
referred to as durability.

7. 4 Different types of adhesion-
1.MECHANICAL ADHESION-
Interlocking of the adhesive with irregularities in the
surface of the substrate or adherend.
2.ADSORPTION ADHESION-
Chemical bonding between the adhesive and the
adherend,the forces involved may be primary (ionic,
covalent)or secondary (hydrogen bonds, dipole
interaction).
TYPES OF ADHESION
STURDEVANT’S- FIFTH EDITION

8. 3.DIFFUSION ADHESION-
Interlocking between mobile molecules, such as the
adhesion of two polymers through diffusion of polymer
chain ends across an interface.
4.ELECTROSTATIC ADHESION-
An electrical double layer at the interface of a metal with a
polymer that is part of the total bonding mechanism.

9. In dentistry, bond to tooth structure is by different
possible mechanisms:
1.Mechanical –penetration of resin and formation of
resin tags within the tooth surface.
2.Adsorption –Chemical bonding to the inorganic
component or organic component of tooth surface.
3.Diffusion-precipitation of substances on the tooth
surface to which resin monomer can bond
mechanically/chemically.
STURDEVANT’S- FIFTH EDITION

10. APPLICATION OF ADHESIVE RESTORATION
1. Restore Class I,II,III,IV,V and VI carious or
traumatic
defect.
2. Change the shape and color of anterior teeth.
3. Bond all ceramic restorations.
4. Seal pit and fissures.
5. Bond orthodontic brackets.
6. Bond periodontal splints and conservative tooth
replacement prosthesis.
7. Bond indirect resin –based restoration.

11. 8. Provides foundation for crowns.
9. Desensitizes exposed root surface.
10. Seals beneath/bond amalgam restoration to
tooth structure.
11.Impregnate dentine that has been exposed to
oral fluids, making it less susceptible to caries.
12.Bonds fractured fragment of ant. teeth.
13.Bonds prefabricated cast & posts.
14.Seal apical restorations placed during
endodontic surgery.
STURDEVANT’S- FIFTH EDITION

12. ØTraditionally, retention and stabilization of restoration often
resulted in removal of sound tooth structure, this is not
necessary in adhesive system.
ØAdhesion reduces microleakage at resin tooth interface.
(Post operative sensitivity, marginal staining, recurrent caries)
ADVANTAGE OF ADHESION

13. ØBetter transmission and distribution of functional stresses
across the bond interface to the tooth.
ØAdhesive techniques allow deteriorating restorations to be
repaired and debonded restorations to be replaced with
minimal or no loss of additional sound tooth structure.

14. Ø The two materials must be in sufficient close and intimate
relation ,this is one of the important requirement of interfacial
phenomenon.
ØThe surface tension of adhesive is less than surface energy of
the adherend.
Ø0 degree contact angle means complete wetting of adherend
by adhesive.
WETTING OF ADHESIVE

15. Ø Physico-chemical properties of adherend/adhesive.
Formation of surface contaminants during cavity preparation.
Ø Development of external stresses that counteract the process
of bonding.
Ø Oral environment ,which is subject to moisture , physical
stresses , change in temperature & ph.
FACTORS AFFECTING ADHESION TO THE
TOOTH STRUCTURE

16. ENAMEL DENITN
Ø95% is the inorganic
content-hydroxyapatite
crystals.
ØEnamel is smooth,
homogenous in structure
and composition,
irrespective of its depth
and location making it
more susceptible to
bonding.
ØWith higher percentage of
water, inorganic content such
as type 1 collagen.
These constituents are unevenly
distributed in
intertubular ,peritubular dentin
making dentin heterogeneous.
ØDentin is also an intrinsically
wet tissue thereby adhesion
becomes difficult.
COMPOSITION & STRUCTURAL ASPECTS

18. oDR. OSKAR HAGGER developed monomer based on
glycerophosphoric acid dimethacrylate that was
chemically cured wih sulphinic acid.
oDevelopment of SEVITRON early commercial
adhesive.

19. oBUONOCORE –industrial use of 85% phosphoric
acid- facilitates adhesion of paints & resin to metallic
surface.
Acid etching transforms smooth enamel into
irregular surface & increases its surface free energy.
When fluid resin based material is applied it
penetrates into surface & forms resin microtags.

20. Etchants Used –
1. Phosphoric acid – as liquid or gel
Conc more than 50 % - monocalcium phosphate
monohydrate( prevent further
dissolution ).
 Conc more than 40 %- dissolve less calcium & etch pattern
with poorer definition.
Conc less than 27% - dicalcium phosphate monohydrate
precipitate.(cannot be easily removed )
Conc 30 – 40 % - for 15 sec thought to be ideal.
[Silverstone et al]
Higher conc-deeper tagsbreak away leaving 5- 10 microns

21. SIMONSEN RJ reported that there was no diffrence
in retention rate of pit & fissure sealents when
enamel surface were etched for120 sec v/s 60 sec.
HOSOYA & GOTO reported-no difference between
appearance of prism structure by etchin for either
60 /30 sec.
But with further reduction in etching time, absence
of prism structure was reported after phosphoric
acid etching.
DENTAL HARD TISSUES & BONDING

22. Enamel etching
3 different micro morphologic pattern :
TYPE I : dissolution of prism core without dissolution
of prism periphery.
TYPE II : periphery enamel is dissolved , core is left
intact.
TYPE III : less distinct , whose topography is not
related to enamel prism morphology.

23. Physiologic Pathologic
Changes in dentine

24. Because of aging,caries,abrasion and erosion there occurs
production of sclerotic changes
Sclerotic dentin if having any patent canals will have low
permeability and tend to be insensitive to external stimuli.
Heavily sclerosed dentin has areas of complete hypermineral
isation .These changes result in dentinal substrate that is less
receptive to adhesive treatment than normal dentin
SCLEROTIC DENTIN

25. SCLEROTIC DENTIN
Obstruction- dentinal tubule
Apposition – peritubular dentine
Precipitation- mineral crystal

26. SMEAR LAYER
Composition- hydroxyapatite and altered denatured collagen.

27. v Occlusal dentin is more permeable over the pulp horn
than at the centre of the occlusal surface,proximal
dentin being more permeable than occlusal dentin and
coronal dentin being more permeable than root
dentin.
v High dentin permeability makes dentin more difficult
substrate for bonding than enamel.
INTERNAL &EXTERNAL DENTIN WETNESS

28. vEarly dentin adhesive failed primarily because of their
Hydrophobic nature.
vExternal dentinal wetness or environmental humidity has
been demonstrated to negatively affect the bond strength .

29. Classification of Dentin bonding agents
1)According to generation
§ First Generation
§ Second
§ Third
§ Fourth
§ Fifth
§ SEP
§ All in one
§ Eight
2)According to adhesion strategy (number of clinical applications)
§ Total etch
§ Self etch
§ Resin modified glass ionomer
3)According to chemical composition

30. 4) According to treatment of smear layer
§Removed
§Modified
§Preserved
5) According to mode of curing
§Chemical
§Light
§Dual
6) According to Ph
§Mild
§Intermediate
§Strong

31. I.ACCORDING TO GENERATIONS

32. FIRST GENERATION-
M= methacrylate group
X= reactive group
R= spacer
FIRST GENERATION
oDR. OSKAR HAGGER developed monomer based on
glycerophosphoric acid dimethacrylate that was
chemically cured with hydrochloric acid & later with
sulphinic acid.
oDevelopment of SEVITRON early commercial adhesive.
M= metacrylate group
R= spacer
X= reaction

33. Cervident was the first generation bonding
system.(1965)
NPG-GMA (N-phenylglycine glycidyl methacrylate)
being the surface active co-monomer that chelates
with the calcium on the tooth surface to generate
water resistant chemical bonds of resin to dentinal
calcium.
Disadvantage- In vitro dentin bonding strength-2-3
MPa
 No ionic bond developed between NPG-GMA and
hydroxyapatite. Therefore leading to poor clinical
results.

34. The first product of 2
nd
generation is CLEARFIL BOND
SYSTEM F introduced in Japan.(1978)
Composition- Phosphate-ester of methacrylate derivatives
{HEMA in ethanol}
Mechanism of action- Based on POLAR interaction
between negatively charged phosphate group in the
resin and positively charged calcium ions in the smear
layer.
SECOND GENERATION

35. Scotch bond, bondlite were other 2
nd
generation phosphate
ester dentin bonding systems.
Disadvantage:
◘ They had in vitro bond strength of only 1-5 MPa which
was considered below the 10Mpa value as a threshold
value.
◘ Secondly these resins were devoid of hydrophilic groups
and had large contact angles on the intrinsically moist
surface.

36. Basis was laid by the JAPENESE philosophy of etching
dentin to remove smear layer. But because of concerns that
acid etching led to pulpal inflammation was discouraged
before 1980.
CLEARFIL bond was introduced in 1984 containing
HEMA,10 MDP (methacryloyloxy decyl dihydrogen
phosphate) having long hydrophobic and short hydrophilic
components.
Drawbacks-It led to reduced availability of calcium for
interaction with chelating surface active comonomer
THIRD GENERATION

37. In 1984 BOWEN et al supplemented the calcium ions by
application of 6.8% ferric oxalate as an acid conditioners
leading to formation of insoluble precipitate of ferric
oxalate,ferric phosphate.
Ferric oxalate because of its BLACK interfacial staining
was replaced by aluminium oxalate.
DRAWBACKS-Micro retention created by etching
contributes more to bonding than does any precipitate .
Bond strength: 3-13 MPa

38. In 1982 Nakabayashi et al- dentin etched with
aqueous solution of 10% citric acid & 3% ferric
chloride, followed by aqueous solution of 35 %
HEMA in self adhesive resin of 4-META.
Based on this- C&B Metabond, amalgam bond
plus,super bond D liner were available.
Removal of smear layer with chelating agent like
EDTA was introduced with GLUMA.
SCOTCH BOND2 was the first product to receive
provisional acceptance from ADA.

39. Mechanism of action- Removal of smear layer by an
aqueous solution of 2.5% MALEIC acid ,55% HEMA by
the application of unfilled bis-GMA adhesive resin.
ADVANTAGES-
Simultaneous etching and impregnation of dentinal
surfaces with this acidic hydrophilic monomers solution
enabled more consistent and durable result.
Other products: colten ART bond,superlux, universal
bond.
DISADVANTAGE -
Mixed results of good and poor performance.
Significant improvements in bond strength of materials of
this generation had been reported & ranged from 9 to
grater than 18 MPa.

40. Bond Strength of Several Adhesive

41. James.R.Dunn

43. In early 1990s, introduction of MULTI STEP dentin adhesive
system led to significant advances.
Mechanism of action-
Pretreatment of dentin being done with
conditioners/primers to make the heterogeneous and
hydrophilic dentin substrate more receptive to bonding.
FOURTH GENERATION

44. Then there is application of low viscosity adhesive resin that
copolymerizes with the primed dentinal surface layer and
simultaneously offering bonding receptors for hydrophobic
composite resin.
With this multi step application procedure ,the term adhesive
was replaced by BONDING AGENT.
Primer Adhesive
Etchant

45. THREE STEP,TOTAL ETCH ADHESIVE-(4
TH
GEN)
This is also called as ETCH AND RESIN
This system includes-
1.Phosphoric acid gel that is rinsed off.
2. Primer containing reactive hydrophilic monomers in
ethanol/acetone
3.Application of unfilled/filled resin bonding agent
CURRENT OPTIONS

46. THREE STEP, TOTAL ETCH ADHESIVE

47. This system has a bond strength of 17-30MPa that is
comparable to enamel bonding.
Clinical retention rates of this system is close to100% as
compared to 20% of 2
nd
generation adhesive system.
SCOTCH BOND 2 ,ALL BOND2,SCOTCH BOND MULTI
PURPOSE comes under this category.

48. Also known as 5
th
Generation Adhesives .
They combine the primer and bonding agent into a single
Solution with separate etching still required.
This has the advantage of –
•Reducing the number of steps
•Reducing corresponding application time
Thereby making more user friendly adhesive system.
ONE STEP PLUS,PRIME AND BOND NT,OPTIBOND SOLO
PLUS,BOND 1 come under this category.
ONE BOTTLE TOTAL ETCH ADHESIVE

49. ETCHANT
PRIMER + BONDING
AGENT
ONE BOTTLE, TOTAL ETCH ADHESIVE/ FIFTH
GENERATION
Bond Strength- upto 75 MPa
ONE STEP PLUS,PRIME AND BOND NT,OPTIBOND SOLO
PLUS,BOND 1 come under this category.

50. In this system, acidic primers include phosphonated resin
molecule that performs 2 functions-
Etching and priming of enamel and dentin simultaneously.
(2.5%NITRIC , 10%CITRIC,10%MALEIC)
Advantages-
1. It simplifies the bonding technique.

2. Elimination of rinsing and drying
3. Thereby reducing the possibility of overwetting /
overdrying.
SELF ETCHING PRIMERS

51. DISADVANTAGE-
1.They do not etch enamel, as good as with phosphoric acid.
2.Seal of enamel margin might be compromised.
3.Enamel bonds are more likely to undergo
deterioration when stressed than the total etch system

53. They are classified as –
1. MILD- Excellent dentin bond strength and poorer
enamel bond strength.e.g Clearfil E bond.
2. AGGRESSIVE-They are reverse of mild.
3.MODERATE-Combination of both of the above
CLASSIFICATION OF SELF ETCHING PRIMERS

54. SEP are accurately called non rinsing conditioner .
These do not provide higher bond strength or better clinical
performance than phosphoric acid etchants.
They do not etch enamel to the same depth as phosphoric
acid. e.g NRC,Tyrian SPE.
The low enamel bond strength with NCR/PRIME might be
Because of low cohesive strength of adhesive resin layer than
etching potential of non rinsing conditioner.
Bond Strength- 75 MPa
NON RINSING CONDITIONERS

55. SELF ETCHING PRIMER-

56. Self etching adhesive/ all in one
Trend towards simplification, no rinse, self
etching.
These contain uncured ionic monomer that
contact composite.
These tend to behave as semi-permeable
membrane resulting in hydrolytic degradation
of resin dentin interface.
Acidic- demineralize enamel & penetrate
smear layer, hydrophilicity of resin monomer
is high.(organophosphate,carboxylate.
All in one
adhesive

57. Adper prompt L- pop, brush & bond,iBond.
Application of 4 consecutive coats for XENO III & 5
coat for iBond, increases bond strength & decreases
nanoleakage.
 Bond Strength – 60 MPa

58. Advantage:
Simultaneous deminerlization & resin infiltration.
No postconnditioning rinsing
Not sensivitive to diverse dentin-wetness conditions
Time saving application procedure
Possibility for single-dose packing.
 Effective dentin desensitizer.
Disadvantage
Some need refrigeration
Decreased shelf life due to acidic formulation

59. IS THIS THE FIRST 8TH-GENERATION BOND ?
Futura Bond DC Dual-Cured
It is dual-cured and works with all light-, self-
or dual-cured resins.
It works in a self-cured mode without any
light: Great for postcementation
It takes only 35 seconds from start to finish
 It needs only one coat
 It comes in unit dose providing the freshest
chemistry each time.
SURBHI ET AL 2012

60. It does not need to be refrigerated or shaken before
use
 No sensitivity
 Over 30 MPa bond strength to dentin and enamel.

61. II. Depending on the ph ( Van Meerbeck et al 2001)
Ø Mild ( ph ≥ 2 )
Ø Intermediary strong ( ph of 1.5 )
Ø Strong ( ph ≤ 1 )
Mild : cause hybridization and intermolecular bonding.
Ex - Clearfil SE
Panavia ED primer
Hybridisation: Hybrid layer is of submicron size and resin tag formation is
less
Intermolecular bonding: Hydroxyapatite acts as a receptor for additional
molecular interactions with specific carboxyl or phosphate groups of
monomers like 4 META

62. Intermediary adhesives :
 Are more acidic than “ mild” adhesives, so
achieve greater micromechanical interlocking at
the enamel surface, although the hybrid layer
produced at the dentin surface is thin, at around 1
micron.
Ex - Xeno III
AdheSE primer
Optibond Solo Plus SE primer
I Bond

63. Strong adhesives :
The mechanism of bonding is similar to total etch,
with the formation of hybrid layer and no chemical
reaction may take place, since the hydroxyapatite is
entirely removed.
Ex - NRC
Adper Prompt

64. III. Classification based on the number
of clinical application steps
1.Total etch adhesives:
 3 step
 2 step
2.Self etch adhesives:
 2 step
 1 step
3.Resin modified glass ionomer adhesives

65. IV.According to chemical composition
( Craig)
Ø Polyurethanes(1-6 Mpa)
Ø Polyacrylic acids(2-4 Mpa)
Ø Organic phosphonates
Ø 4 META (3-7 Mpa)
Ø HEMA+bis GMA(11-17 MPa)
Ø Ferric oxalate+ NPG GMA( 4-12.5 Mpa)

66. V. On the basis of treatment of smear layer:
1. Removed:
 Tenure
 Mirage bond
 Clearfil liner bond system
2. Modified:
 All bond
 Scotch bond 2
 XR Bond
3. Preserved:
 Scotch bond dual cure
 Prima universal bond

68. VII.According to their mode of curing:
1.Chemical cure:
Amalgabond plus
2.Light cure:
One bond
Gluma comfort bond
3.Dual cure:
Clearfil liner bond 2V
Prime and Bond NT dual cure.

69. COMPONENTS OF DENTIN BONDING
AGENT :
It consists of 3 essential parts
1. Conditioners
2. Primers
3. Adhesives

70. These serve as the actual adhesion promoting agents,
containing the hydrophilic monomers dissolved in
organic solvents such as acetone/ethanol.
Because of their volatile characteristics, these solvents
can displace water from the dentinal surface and
moist collagen network ,promoting the infilteration of
monomers through nanospaces.
PRIMERS

71. Conditioning of the dentin
Defined as- Alteration done after the creation of
dentin cutting debris, termed the smear layer, to
create a surface, capable of micromechanical and
chemical bonding to dentin bonding agent.
Changes after conditioning:
 Removal or modification of smear layer
 Opening of dentinal tubule orifices.
 Modifications in organic matter
 Decalcification of inorganic portion.

72. Can be done by -
1.Chemicals
 Acids
 Calcium chelators
2.Thermal
Lasers

3.Mechanical
Abrasion

73. 1. Phosphoric acid : First dentin conditioner
37% H
3PO
4 should be used.
2. Nitric acid :
a.Stronger than H
3PO
4
b.Concentration of 2.5% causes funneling of the
orifice.
3. Citric acid :
a. 10% citric acid is recommended.
b. 10% citric acid + 3% ferric chloride was
recommended by Nakabayashi.
c. Lately, Kurray proposed a combination of 10%
citric acid and 20% CaCl
2 to stabilize collagen
during etching.

74. 4. Pyruvic acid:
Pyruvic acid buffered with glycine is used to facilitate
polymerization reactions and adjust the pH.
5. Maleic acid: 10%
a.Removes only smear layer, not plugs.
6.Polyacrylic acid:
a.40% solution is used.
b.Recent product.
c. A 10 second application opens up the dentinal tubules
but does not effect pulp as the particle size is greater
than diameter of dentinal tubules.

75. 7.Hydrochloric acid : Causes violent surface
reactions as carbonate is converted to CO
2 and
Ca.
Calcium chelators:
 Chelators are used to remove the smear layer
without decalcification or significant physical
changes to the underlying substrate as opposed to
strong acid etchants.

76. EDTA:
Commercially available as “Tublicid”. It contains
0.1% EDTA and 0.15% Benzalkonium chloride.
Removes smear layer, not plugs.
It is scrubbed on the surface of the smear layer for a
few seconds, then left passively for another 60
seconds followed by additional scrubbing.
Disadvantage:
Removes small amount of Ca, thus causing fall in
the bond strength.

77. Shag carpet appearance
 Appears when dentin surface after being
acid etched is actively scrubbed with an acidic
primer solution.
 The combined mechanical and chemical
action of rubbing the acid etched dentin with
an acidic primer dissolves additional mineral
salts while fluffing and separating the
entangled collagen at the surface.

78. Thermal conditioners:
Lasers: Nd:YAG laser used at 10 to 30 pulses per
second.
 The mechanism of action is through
microscopic explosions caused by thermal
transients, incresasing bondable fraction of
inorganic dentin & micromechanical retention.
Laser causes
Desensitization of dentin.
Decrease microorganisms
 Creates micromechanical retention.

79. Mechanical conditioners:
Abrasion:Al
2O
3 is used for micro abrasion.
0.5 μ particles are used.
It is based on removal of demineralized &
discolored tooth tissue & results in formation
of smear layer.

80. Primers
Primers are the agents that promote wetting of the
dentin with the bonding agent and increase the
penetration of the bonding agent into the dentin.
They have surface tension less than the surface free
energy of the acid etched dentin.
Amphiphilic bifunctional molecules.
The primer monomer should be amphiphilic or
hydrophilic because they must compete with water
and diffuse through water in the depths of
demineralized zone.
 Monomers used are : HEMA, NPG-GMA, PMDM,
BPDM, PENTA

81. Mechanism of action of bonding agents :
Hydrophilic part: Displaces water & wets the surface. Permits penetration into
porosities of dentin. Reacts with organic and inorganic portions ( phosphate
esters Or carboxylic acid groups ) Capable of bonding to dentin.
Hydrophobic part: Reacts with the restorative resin which is hydrophobic.
Usually made of Methacrylate group.
 R- Spacer :Is responsible for making the molecule large enough to keep
methacrylate groups spatially located for optimal chemical reaction with the
composites.

M R X

82. The solvents used in primers
1.Acetone based primers –
Advantages :
Excellent water chaser,
Dries quickly
Disadvantages :
Evaporates quickly after being dispensed.
Can evaporate from the container & change the composition.
Sensitive to wetness of dentin ( risk of over drying. )
Multiple coats may be required.
Offensive odour.
Volatile, bond strength may be significantly reduced.
Ex - One step
Prime and Bond NT
Gluma one bond.

83. 2. Ethanol based primers –
Advantages :
Evaporates less quickly
Less sensitive to wetness of dentin.
Good surface energy and good penetration.
Disadvantages :
Extra drying time.
Ex - Excite
Optibond solo plus

84. 3. Water based primers –
Advantages :
Slow evaporation
Not sensitive to wetness of dentin.
Have capacity to raise collapsed fibers.(9%-50%)
Disadvantages :
Long drying time.
Water can interfere with adhesive if not removed
Ex -Amalgabond plus
 Prompt l pop
 Scotch bond multipurpose

85. Combination of the solvents that can be used in
primers
Acetone & H
2O
Eg: Tenure- quick
Acetone & ethanol
Eg: All bond 2 ( Bisco)
Ethanol & water
Eg: Gluma comfort bond
Scotchbond

86. Adhesive resin
Major role of adhesive is to stabilize the hybrid layer
& to form resin extension into the dentinal tubule ,
called resin tags.
Adhesive can be light cured.
In this way adhesive is not displaced & adequate
light intensity is available to sufficiently cure &
stabilize the resin tooth bond to resist stress

87. After acid etching ,there occurs an initial demineralisation
of dentinal surface ,causing exposure of collagen fibres
with interfibrillar micro porosities.
These micro porosities subsequently diffused with low
viscosity monomer.
Zone in which resin of adhesive system micromechanically
interlocks with dental collagen is known as HYBRID LAYER.
HYBRIDISATION

88. 3 Different Zones of Hybrid Layer:
TOP LAYER -collagen fibres are more loosely arranged individual
collagen fibrils are directed towards adhesive resin.
MIDDLE LAYER -it contains cross sectioned and longitudinally
sectioned collagen fibres separated by electronlucent spaces.
BASE -there is partially demineralised zone of dentin containing
hydroxyapatite enveloped by resin.

89. -
As we go deeper into the dentin ,there is increased
number of dentinal tubules leading to increased
dentinal fluid and along with it less demineralised
dentin available to for bonding.
With new adhesive system it is not a problem.
Tubule wall hybridization provides firm attachment
of resin tag necks to the dentinal tubule wall also
providing hermetic seal of the dentinal tubules.
TUBULE WALL HYBRIDISATION

90. Problems in bonding
1)Presence of 30% organic material and 20% fluid
in dentin (resins are hydrobhobic)
2)Random arrangement of hydroxyapatite crystals
in the organic matrix.
3)Tubular nature of dentin that permits fluid flow,
adversely affects bonding.
4)Sclerosed dentin is difficult to penetrate as
peritubular dentin becomes wider.

91. 5)Presence of smear layer complicates bonding
6)Permeability of dentin differs at various sites.
7)Variation in arrangement of tubules & their shape.

92. C factor
 The ratio between the number of bonded surfaces
and the number of unbonded surfaces .
 Lesser the C factor, better is the bonding and less
chances of failure of the restoration.
 Occlusal class I preparation: C factor of 5.
 Proximoocclusal Class II preparation: C factor of 4.
 Mesioocclusodistal Class II preparation: C factor of 3.

93. vThe passage of bacteria & their toxins between restoration margin &
tooth preparation walls.
vBest preparation with no microleakage is preparation in enamel with
cavosurface margin.
vGenerally fluid is present in the marginal gap of composite
restoration under which micro-organisms survive.
v Bond strength decreases with time & resin-dentin interface under go
ultrastructural changes that jeopardize adhesion.
MICROLEAKAGE

94. Specimens are immersed in disclosing solution eg:
silver nitrate, methylene blue, basic fuchsin.
Dye penetrates resin-dentin intreface where ever
gaps occurred.
After sectioning the teeth, depth of dye penetration is
measured & averaged for sample size.

95. Small porosities in hybrid layer or at transition
between hybrid layer & mineralized dentin .
Based on the silver ammonium nitrate penetration
1.SPOTTED PATTERN-
It is seen in hybrid layer due to incomplete resin
Infilteration.
2. RETICULAR PATTERN-
It is seen in adhesive layer because water was not
removed from bonding sites.
NANOLEAKAGE

96. WATER TREES-
Associated with porosities in polymerized
adhesive layer.
This area of increased permeability at
polymerized adhesive resin is because incomplete
removal of water which prevents complete
polymerization.

97. These are also known as BONDING AGENTS consisting
of Hydrophobic monomers (bis-GMA,UDMA) and
hydrophilic Monomers(TEG-DMA) and HEMA as
wetting agents.
Ideally the dental adhesives should be HYDROPHOBIC
and HYDROPHILIC.(according to PHILIPS 10
TH
EDITION).
Nowadays AUTOCURING as well as PHOTOCURING
resin are used.
ADHESIVE RESINS

98. APPLICATION OF
BONDING AGENT
CURING OF THE
BONDING GENT

99. ACID ETCHING ,PRIMING,HYBRIDISATION-

100. DRY VERSUS MOIST DENTIN SURFACE-
Vital dentin is inherently wet, so complete drying is
difficult to achieve clinically.
Water becomes an obstacle for attaining an effective
adhesion of resin to the dentin.
In WET state-Wide gaps separate the collagen by the
presence which give space to resin infilteration.
In DRY state or air drying-Hydrogen bonds replace
water, leaving no interfibrillar space for resin
infilteration.

102. By air drying, the alteration(collapse) of collagen fibres
occurs thereby preventing the monomer to penetrate
the nanochannels that are formed by the dissolution of
hydroxyapatite crystals between collagen fibres.
This technique has enhanced the bond strength by
preserving the porosity of collagen network available
for monomer diffusion.
WET BONDING TECHNIQUE

103. It is resin diluted version of resin modified glass ionomer
restorative material.
There mechanism of adhesion is based on
MICRO MECHANICAL and CHEMICAL interaction.
Pretreatment of the tooth surface done with polyalkenoid
acid that removes the smear layer and exposes the
collagen leading the formation of RESIN TAGS
(mechanical bonding).
TYPES OF ADHESIVES:
GLASS IONOMER ADHESIVE

104. CHEMICAL BONDING by ionic interaction of carboxyl
group of polyalkenoic acid with calcium of hydroxyapatite
crystals that remain attatch to collagen fibres.

105. Mineral content of dentin as in case of sclerotic
dentininfluence the success of an adhesive restoration .
Bruxism /eccentric movement may generate lateral forces
that cause concentration of stresses around cervical areas
which may cause failure of bonding at resin dentin
interface.
Type of composite also play an important role.
CLINICAL FACTORS IN DENTIN
ADHESION

106. Desensitisation- Dentinal hypersensitivity occurs
because of dentinal fluid movement.
Dentin adhesives treat hypersensitivity by formation of
resin tags and a hybrid layer .
The precipitation of fluids in tubules also may account for
the efficacy of desensitising solutions.
EXPANDED CLINICAL INDICATIONS FOR
DENTIN ADHESION

107. In case of amalgam ,there is delayed interfacial marginal
leakage occuring at the amalgam-tooth interface.
Corrosion products seal the interface after a few months
leading to microleakage.
To overcome this problem adhesive systems have been
proposed.
The attatchment mechanism is not fully understood,but it
may be micromechanical entanglement of uncured
adhesive material with setting amalgam during
condensation of amalgam.
ADHESIVE AMALGAM RESTORATION

108. Advantages-
It reduces microleakage
Improves marginal integrity of amalgam
Reduces recurrent caries
It causes reinforcement of the residual tooth structure.
Limitations-
Shows poor results in repair/strengthening of old
amalgam restoration.
It shows no reinforcing effect for wide tooth preparations.
Primary retention features are still required .

109. ADHESIVE AMALGAM RESTORATION-

110. ◘ Bonding resin to ceramic surface is based on the
combined effects of micro mechanical interlocking and
chemical bonding
◘ Procedure done-
Ceramic surfaces are etched with hydrofluoric acid
Ammonium fluoride for increasing the surface area
and create microporosities leading to mechanical
interlocking.
CERAMIC BONDING

111. Chemical bonding to ceramic is achieved by sialanisation with
coupling agent.
A silane group at one end chemically binds to hydrolysed silicon
dioxide at the ceramic surface and methacrylate group at other
end copolymerising with adhesive resin.

112. Despite past apprehension about potential acid penetration
into dentinal tubules and pulp space ,the interactions of
etchants with dentin is limited to superficial 1.9-5.8 micro
meter.
Effect of etchants are limited to buffering effect of
hydroxyapatite and collagen which may act as a barrier
reducing the rate of demineralization.
Current etchants used are hypertonic which draw fluid from
dentin toward the surface osmotically thereby altering the
exposed collagen.

BIOCOMPATIBILITY

113. Adverse pulpal reactions after a restorative proceduremay not
be caused by the material used in that procedure but by
bacteria remaining in, or penetrating the preparation.
1. Bacterial invasion of the pulp, either from the tooth
preparation or from an existing carious lesion
2. Bacterial penetration into the pulp caused by a faulty
restoration
3. Pressure gradient caused by excessive desiccation or
by excessive pressure during cementation32,47
4. Traumatic injuries
5. latrogenic tooth preparation-excessive pressure, heat, or
friction .32
6. Stress derived from polymerization contraction of composites
and adhesives.

114. An important note on the biocompatibility issue is the
importance of tooth preparations with enamel peripheries.
When all margins are in enamel, polymerization shrinkage
stresses at the interface are counteracted by strong
enamel adhesion. Thus, marginal gaps are less likely to
form, and the restoration is sealed against bacteria.

115. CONCLUSION
The clinical performance of present day adhesives
has significantly improved, allowing adhesive
restorations to be placed with a high predictable
level of clinical success.
Most of new products are improvements over
there predecessor therefore it is indispensible for
the professionals to know about them in order to
select and use them correctly.

116. REFERENCES
Fundamentals of operative dentistry-2
nd
edition
–JAMES B.SUMMITT ,J WILLIAM ROBBINS
Sturdevant –Art and science of operative dentistry -
5
th
edition THEODORE M .ROBERSON, HERALD
O.HEYMANN
Philips –Science of dental materials-10
th
edition
Dental hard tissue & bonding
G.Eliades,D.C.Watts,T.Eliades
Craig- dental material eleventh edition