ACID BASE RESISTANT ZONE

DEEPA JINAN
BAPUJI DENTAL
COLLEGE &
HOSPITAL

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• Introduction
• Significance
• Mechanism of
formation
• Super dentin
• Super enamel
• Influencing factors
• Conclusion
• References

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Concept - Minimal cavity preparation widely
accepted
Placement of direct composite restorations using
adhesive systems
Dentin bonding systems simplified & improved
Mount GJ, Ngo H. Minimal intervention: a new concept foroperative dentistry. Quintessence Int 2000;31:527—33.
Mjo¨r IA. Clinical diagnosis of recurrent caries. J Am Dent Assoc 2005;136:1426—33.
Recurrent caries
major reasons for failure of resin composite
restorations

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Tsuchiya S1, Nikaido T, Sonoda H, Foxton RM, Tagami J. Ultrastructure of the dentin-adhesive interface after acid-base challenge. J Adhes
Dent. 2004 Autumn;6(3):183-90
SECONDARY CARIES
5
Tooth restored with composite
Bacteria
Low ph
Activate
enzymes
Expose
collagen
Secondary
caries
Demineralizati
on of dentin
Microgaps

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6Mount GJ, Ngo H. Minimal intervention: a new concept foroperative dentistry. Quintessence Int 2000;31:527—33.
Mjo¨r IA. Clinical diagnosis of recurrent caries. J Am Dent Assoc 2005;136:1426—33.
Physical properties of
restorative materials
Oral hygiene
Marginal intergrity
Durable adhesion & bonding
SECONDARY CARIES - PREVENTION

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Dent. 2004 Autumn;6(3):183-90
DENTIN BONDING SYSTEMS
7
Self-etching primer systemAcid etching systems
Acidic monomers
condition and prime dentin
surface
Roles of self-etching
primer & adhesive
combined to 1 application
step
Recognized by an
initial etching step
30—40% H3PO4 removes smear layer,
aggressive in demineralization

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Manufacturers have modified dentin
adhesive formulations
Dent. 2004 Autumn;6(3):183-90
Formulation of adhesives -
inhibitory effects on caries &
subsequent enzymatic degradation
Reports - using a single-bottle self-
etching adhesive, lower bond
strengths have resulted
Reducing technique sensitivity by
diminishing number of procedural
steps
Increasing resistance to acidic bacterial byproducts
at tooth–resin interface may effectively impede
progression of secondary caries
Creation of a zone that is acid-base resistant - ABRZ
Super Dentin Super Enamel

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To obtain good bonding to dentin - Monomer penetration into dentin and
its polymerization in situ - hybrid layer
COMPOSITE
ADHESIVE
HYBRID LAYER
SEM of the dentin hybridization formed upon
application of Adhesive
Theoretically
hybrid layer can
• Provide marginal
sealing of the
cavity
• Resist against
acid challenge to
prevent
secondary caries
Reported - none of adhesives
currently available
completely eliminate
nanoleakage along dentin-
restorative
interface
Dent. 2004 Autumn;6(3):183-90

Dent. 2004 Autumn;6(3):183-90
HYBRID LAYER
10
Key to all adhesively bonded
restorations is the formation of a hybrid
layer
Created after modification and/
or removal of the smear layer
Penetration of adhesive
monomers
Different for different types of bonding
agents

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Dent. 2004 Autumn;6(3):183-90
FORMATION
11
Acid
etching
systems
Created by penetration & polymerization of adhesive
monomers, after removal of smear layer & superficial
demineralization of dentin

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Dent. 2004 Autumn;6(3):183-90
FORMATION
12
Self etching
systems
monomers, after removal of smear layer & superficial

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Dent. 2004 Autumn;6(3):183-90
FORMATION
13
Self etching
systems
monomers, after modification of smear layer & superficial
Extremely thin (300 nm or less) these
adhesive systems categorized as
‘‘Nanointeraction Zone’’ type

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Dent. 2004 Autumn;6(3):183-90
VISUALISATION
14
Chemical approach
Hybrid layer subjected to Alternating application of an acid
and a base material - acid-base challenge
Hybrid layer visualized under SEM using
Acidic solution demineralizes
inorganic component, removes
HA, leaving
organic dentin components
Sodium hypochlorite remove
demineralized collagen- a clear
visualization of the hybrid layer
Chemical modifications
of interface
Mechanical modifications
of interface
1 2

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Dent. 2004 Autumn;6(3):183-90
VISUALISATION
15
Mechanical approach, argon-ion beam used to clearly
reveal the hybrid layer at the resin-dentin interface
Roughening of hybrid layer
through
Ar-ion beam etching caused by
selective removal of impregnated
resin component in demineralized
dentin
As a result of the edge effect of the
etched surface, this layer was
clearly distinct in the secondary
electron image of the interface

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Dent. 2004 Autumn;6(3):183-90
VISUALISATION
16
Acid-etching systems –
Clearly identify the hybrid layer by such chemical
or mechanical modification techniques
Self-etching primer adhesive systems
SEM observation of the hybrid layer using
sencountered limitations, since the hybrid
layerobserved was very thin
With development of simplified dentin bonding observation
method shifted from SEM to TEM, which provides images with
more interfacial details
SEM TEM

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Dent. 2004 Autumn;6(3):183-90
CLINICAL SIGNIFICANCE
17
Reinforced and modified dentin - superior resistance
against Acid challenge
Preventing formation of
secondary caries at
restorative margin
Several methods have been developed for laboratory
evaluation of secondary caries
Assessing demineralized lesions and
inhibition zones of dentin after acid challengePolarized light microscopy
Microhardness
Confocal laser-scanning
microscopy
Xray
analytical microscope
Scanning electron microscopy
Transmission electron
microscopy
Secondary caries arises from acid
production by microorganisms
Sealing of restoration
margins
Promotion of
restoration durability

Using an SEM, Tsuchiya et al. foremost observed artificial
secondary caries inhibition around restorations bonded to
bovine root dentin
Dent. 2004 Autumn;6(3):183-90
ACID BASE RESISTANT ZONE
‘‘Acid—base resistant zone’’ (ABRZ) found beneath the hybrid layer
18
Different from inhibition zone
formed due to release of fluoride
from materials - GIC
ABRZ was formed in spite of the
adhesive being fluoride-free

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To observe the ultrastructure of the dentin-adhesive interface after in vitro
sequential challenge by acidic and basic chemicals around adhesive
restorations
Dent. 2004 Autumn;6(3):183-90
PIONEER STUDY
19
Reactmer
Bond and
Reactmer
Paste BOX SHAPED CAVITIES IN
ROOT DENTIN
Clearfil SE
Bond &
Clearfil AP-X
Clearfil ABF
(experimental)
Clearfil AP-X
Single Bond
and
Clearfil AP-X
F-releasing restoration, RB/RP
thick acid-resistant zone
observed adjacent to restoration;
bonding resin, partially degraded
by AB challenge
For SE/APX, ABF/APX and
SB/APX, the bonding resins were
resistant to the acid-base
challenge
BOX SHAPED CAVITY
PREPARATION
NAIL VARNISH
DEMINERALISING
SOLUTION, PH 4.5
20MIN
1 Week in
water at 37
C
NaOCl 20 mins
SECTIONING
TRIMMING,
POLISHING, ARGON
ION ETCHING
SEM OBSERVATION

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Nikaido T, Weerasinghe DD, Waidyasekera K, Inoue G, Foxton RM, Tagami J. Assessment of the nanostructure of acid-base resistant zone by
the application of all-in-one adhesive systems: Super dentin formation. Biomed Mater Eng 2009; 19: 163-171.
INFLUENCE OF SELF ETCH PRIMER SYSTEMS
20
SB- Adhesive layer not damaged,
thick hybrid layer partially degraded
– nanometer sized pores within the
hybrid layer
RB – Degradation of adhesive –
solubilize of glass fibres
ABRZ – F release
SE & ABF – Adhesive not damaged
ABRZ Beneath thin hybrid layer

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Self etch adhesive
systems
Dent. 2004 Autumn;6(3):183-90
MECHANISM OF FORMATION
Residual HA
left around the collagen
fibrils, hybrid layer
21
Morphology of ABRZ was
dependent
on the composition of the
adhesive material
Receptor for
chemical interactions
with functional
monomersA Strong interaction
b/w HA & monomer -
enhance adhesive-
dentin interface stability
against acid attack
Demineralize dentin
partially
Water solubility of resulting
salts varied among different
acid functional monomers

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Caries free & Caries affected
dentin
Dent. 2004 Autumn;6(3):183-90
SUPER DENTIN
Self etch systems
22
Thicker ABRZ In presence of
fluoride ions
Functional monomers
influence formation
Duration of acid base
challenge
ABRZ: acid-base resistant zone, B:
bonding, CR:composite resin, D:
dentin, HL: hybrid layer, OL: outer
legion

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Formation of an enamel ABRZ - Li et al
Li N, Nikaido T, Takagaki T, et al. The role of functional monomers in bonding to enamel: acid-base resistant zone and bonding performance.
J Dent. 2010;38(9):722-730.
SUPER ENAMEL
23
ABRZ in enamel similar to that in dentin
ABRZ not below bonding surface – at interface
Parts not dissolved after acid base challenge
High mineral content – matrix structure different from dentin collagen network
HAP Crystals distributed all over demineralized layer

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Ultrastructure of ABRZ at the interface of human dentin specimens
when
THREE DIFFERENT BONDING SYSTEMS WERE USED
Total etch –
Single Bond
Single step self etch
primer – Aqua Bond
PLUS
Two step self etch
primer – clearfil
SE
ABRZ clearly observed when self-etching primer systems
were used, but not Total etch
Phosphoric acid etched too strongly, which resulted in the disappearance
of ABRZ
Self-etching primer systems etched the dentin surface mildly -remaining
mineral phase of dentin

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Ultrastructures around the adhesive-
dentin interface for single Bond.
dentin interface for Clearfil SE Bond.
dentin interface for AQ Bond Plus - A
thin ABRZ, Erosion around the
bottom of ABRZ
Good mechanical properties of the
adhesive rendered multi-functional
methacrylates
Nanospaces might be present
beneath ABRZ - incomplete
monomer penetration into the
demineralized dentin

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Miho Tsujimoto, Toru Nikaido, Go Inoue1, Alireza SADR2 and Junji TAGAMI1,2. Ultrastructural observation of the acid-base resistant zone of
all-in-one adhesives using three different acid-base challenges. Dental Materials Journal 2010; 29(6): 655–660.
INFLUENCE OF FLUORIDE
26
Ultrastructure of dentin-adhesive interface analysed
FLUORIDE RELEASING SYSTEM & FLUORIDE FREE SYSTEM
Clearfil SE
bond
FL-Bond II(FL
II)
FL-Bond (FL)
Thicker ABRZ observed in fluoride releasing system
Formation of thick ABRZ related to fluoride release in
adhesive resin
Decrease the rate of apatite dissolution

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Delta shaped region of ABRZ was formed from the upper
slope to the end of outer lesion
Amount of fluoride release from the adhesive systems
affected the level of dentin acid resistance at the interface
interface created at the dentin-adhesive interface by a fluoride-
releasing adhesive was more stable than that of a similar
fluoride-free adhesive

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To investigate the effect of fluoride concentration in adhesives on
morphology of acid-base resistant zone (ABRZ)
SEVEN EXPERIMENTAL 2 STEP ADHESIVES WITH DIFFERENT
CONCENTRATIONS OF NAF
F 0
SEM images catogarized into three types
Concentration of NaF in the adhesive resin influenced the
amount of dentin structure remaining after acid-challenge
F 50F 10 F 20 F 75 F 90 F 100

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Butt joint with no slope
formation
Slight slope formation of the
joint
Clear, round slope formation at
the junction
Sloped ABRZ formation was predominately
observed only in F90and F100

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Dent. 2004 Autumn;6(3):183-90
CARIES FREE & CARIES AFFECTED DENTIN
30
Ultrastructure of ABRZ Using two step self etching primer (Clearfil Bond
SE)
IN CARIES FREE & CARIES AFFECTED DENTIN
Intact dentin -1 μm thick
Caries-affected dentin - 1.5 μm
thick

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Dent. 2004 Autumn;6(3):183-90
CARIES FREE & CARIES AFFECTED DENTIN
31
• Caries affected dentin - intertubular dentin is already partially demineralized
and more porous – more permeable to the primer than in normal dentin.
Intact dentin -1 μm thick
Caries-affected dentin - 1.5
μmthick
• Smear layer more porous than normal dentin - resin monomer penetrate
deeper resulting in a thicker hybrid layer

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Waidyasekera K, Nikaido T, Weerasinghe DS, Ichinose S, Tagami J. Reinforcement of dentin in self-etch adhesive technology: a new concept. J
Dent 2009; 37: 604-609
TEM EVALUATION
32
TEM was performed at the adhesive-dentin interface and selected area
electron diffraction (SAED) was performed to
Dentin reinforcement and secondary caries inhibition potential
Identify the type of crystallites present in ABRZ
Fluoride free self
etching adhesive
system
ABRZ formed With Clearfil SE & Clearfil protect.
Single bond devoid of ABRZ
ABRZ formed was a dentin-like structure but which was more
acid-resistant than normal dentin
Fluoride releasing
self etching
adhesive system
Acid etch system

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Dent 2009; 37: 604-609
TEM EVALUATION
33
TEM was performed at the adhesive-dentin interface and selected area
electron diffraction (SAED) was performed to
Identify the type of crystallites present in ABRZ
SAED confirmed the crystallites in ABRZ as apatite
ABRZ formed was not purely dentin, but rather a combination
of dentin and the adjacent hybrid layer

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Dent 2009; 37: 604-609
TEM EVALUATION
34
Clearfil SE Bond. ABRZ is
pointed with arrows
Clearfil Protect Bond-ABRZ
SingleBond- Hybrid layer is
pointed with arrows

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INFLUENCE BY ACIDIC SOLUTION
35
Ultrastructure of dentin-adhesive interface analysed using two all-in-one
adhesive systems (Clearfil Tri-S Bond, TB; Bond Force, BF)
AFTER DIFFERENT ACID-BASE CHALLENGES
Demineralizin
g solution
H3PO4HCl
Thickness of ABRZ created in PA and HCl was thinner than in
DS for both adhesive systems
Probably due to the higher degree of acidity of these solutions
ABRZ observed for both all-in-one adhesive systems
morphological features influenced by ingredients of both
adhesive material and acidic solution

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36
Ultrastructure of adhesive-dentin
interface in DS. Thickness of ABRZ
0.6μm
interface in PA. ABRZ was thinner
than in DS
interface in HCl. Thickness of ABRZ
0.2 μm
Morphological characteristics and demineralization kinetics of ABRZ different
from normal dentin.

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37
interface in DS. Thickness of ABRZ
0.6μm
Morphological characteristics and demineralization kinetics of ABRZ different
from normal dentin.
Thickness of ABRZ 0.6
μm, with a sloping border and a
broadening bottom effect o f Fl
Clearfil Tri-S
Bond
Bond Force

A
B
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J Dent. 2010;38(9):722-730.
INFLUENCE0F FUNCTIONAL MONOMERS
38
MDP monomer interacted chemically with hydroxyapatite forming strong and
stable ionic bonds with calcium
10-MDP > 4META > Phenyl P
MDP HA
Ca
This reaction produced a MDP-calcium salt that had a lower solubility
Yoshida et al- Chemical bonding potential different among functional
monomers
The length and flexibility of alkyl spacer chain – effect on polymerization
reactivity of functional monomers
MDP – Long linear alkyl chain and a phosphoric acid ester group that
increases polymerization efficacy

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INFLUENCE OF FUNCTIONAL MONOMERS
39
Ultrastructure of Enamel-adhesive interface analysed influence of
interchanging functional monomers has not been investigatedfor two-step
self-etching adhesive systems
CONTAINING DIFFERENT FUNCTIONAL MONOMERS
MDP
Primer & Bonding
Phenyl P –
Primer
MDP - Bonding
MDP – Primer
Phenyl P -
Bonding
ABRZ found in all adhesive systems containing MDP either in
primer or bond
P-M Group had thickest ABRZ
P-P Group
Lower curing efficacy
Limited chemical bonding capacity
Resulting Ca Salts susceptible to dissolution
Phenyl P
Primer &
Bonding

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INFLUENCE0F FUNCTIONAL MONOMERS
40
Ultrastructure of enamel-adhesive
interface after acid–base challenge
in M–M group. Thickness of ABRZ
0.5μm
in M–P group. Thickness of ABRZ
0.2μm

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INFLUENCEOF FUNCTIONAL MONOMERS
41
in P–M group. Thickness of ABRZ
1μm –
Etching with Phenyl-P produced a
deeper and porous etchingpattern
in P–P group. ABRZ Absent

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INFLUENCE OF FUNCTIONAL MONOMERS
42
Effect of functional monomers in all-in-one adhesive systems on
formation of acid-base resistant zone (ABRZ) in enamel and dentin was
analysed
Experimental adhesive systems containing three functional monomers
MDP 4-META3D-SR
Formation of enamel/dentin ABRZ was confirmed in all adhesives, but the
morphology was influenced by the functional monomers
Enamel ABRZ was thinner than dentin ABRZ in all adhesives
Differences in chemical interaction between HA and the functional
monomers of the adhesives - ultrastructural differences of the adhesive-
dentin interface
MDP 3D-SR

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INFLUENCE OF FUNCTIONAL MONOMERS IN ALL-IN-ONE ADHESIVE SYSTEMS
43
MDP-dentin, PH 1.9
Stable ionic bond with Ca
3D-SR-dentin, PH-2
Several phosphate groups capable
of interacting with Ca at multiple
sites
4-META-dentin, PH 2.2,
• Nanospaces caused by incomplete
monomer penetration
• Limited bonding capacity with ca
PH -
POTENTIAL TO
DISSOLVE HAP
MOLECULAR
WEIGHT
DISSOLUTION
RATE OF SALT
FORMED

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INFLUENCE OF FUNCTIONAL MONOMERS IN ALL-IN-ONE ADHESIVE SYSTEMS
44
4-META-enamel, PH 2.2,
• Nanospaces caused by incomplete
monomer penetration
• Limited bonding capacity with ca
MDP-enamel, PH 1.9
Stable ionic bond with Ca
3D-SR-enamel, PH-2
Several phosphate groups capable
of interacting with Ca at multiple
sites

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S
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Potential to create ‘Super tooth structures’
J Dent. 2010;38(9):722-730.
45
Reinforced Dentin & Enamel – SUPER DENTIN/ENAMEL
Bear ability to prevent primary & secondary caries
Development of new materials -
Mechanical, Chemical & Biological protection of the dental
structures

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S 46
• Mount GJ, Ngo H. Minimal intervention: a new concept foroperative
dentistry. Quintessence Int 2000;31:527—33
• Mjor IA. Clinical diagnosis of recurrent caries. J Am Dent
Assoc2005;136:1426—33.33.
• Tsuchiya S1, Nikaido T, Sonoda H, Foxton RM, Tagami J. Ultrastructure of
the dentin-adhesive interface after acid-base challenge. J Adhes Dent. 2004
Autumn;6(3):183-90.
• Li N, Nikaido T, Takagaki T, et al. The role of functional monomers in
bonding to enamel: acid-base resistant zone and bonding performance. J
Dent. 2010;38(9):722-730.
• Miho Tsujimoto, Toru Nikaido, Go Inoue, Alireza Sadr and Junji TagamI.
Ultrastructural observation of the acid-base resistant zone of all-in-one
adhesives using three different acid-base challenges. Dental Materials
Journal 2010; 29(6): 655–660.
• Nikaido T, Weerasinghe DD, Waidyasekera K, Inoue G, Foxton RM, Tagami
J. Assessment of the nanostructure of acid-base resistant zone by the
application of all-in-one adhesive systems: Super dentin formation. Biomed

R
E
F
E
R
E
N
C
E
S 47
• Waidyasekera K, Nikaido T, Weerasinghe DS, Ichinose S, Tagami J.
Reinforcement of dentin in self-etch adhesive technology: a new concept. J
Dent 2009; 37: 604-609.

ACID BASE RESISTANT ZONE

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