A conceptual and animated study

1. DENTIN
BONDING
AGENTS
PRESENTED BY
ABIRAMI
VETRISELVAN

2.  INTRODUCTION
 HISTORY OF BONDING AGENTS
 COMPONENTS OF BONDING AGENT
 CHALLENGES IN ADHESION
 MECHANISM OF DENTIN ADHESION
 HYBRID LAYER
 IDEAL REQUIREMENTS OF DENTIN BONDING
AGENT
 CURRENT STRATEGIES IN ADHESION
 REQUISITES FOR PROPER ADHESION
 CLINICAL FACTORS IN DENTIN ADHESION
 INDICATIONS OF DENTIN BONDING AGENTS
 FAILURES IN ADHESION

3.  Dentin Bonding Agents are resinous materials used
to make a dental composite adhere to the dentin by
forming a hybrid layer.
 The introduction of adhesives have reduced the need
for extensive tooth preparation for restoration.

5.  CONDITIONER / ETCHANT
 PRIMER
 ADHESIVE

6. CONDITIONER PRIMER ADHESIVE
ORGANIC ACIDS-
Maleic acid, EDTA,
citric acid
NPG-GMA, HYDROPHOBIC
MONOMERS-
BIS-GMA,
UDMA
INORGANIC
ACID-
Phosphoric acid,
Nitric acid
HEMA,
Phenyl-P
DILUENT-
TEGDMA
POLYMERIC ACID
–
Polyacrylic acid
PENTA,
Bis-GMA
WETTING
AGENT-
HEMA
NPG-GMA- N-phenylglycine glycidylmethacrylate ; HEMA- Hydroxyethyl
methacrylate;

7. 1. Dentin is a dynamic tissue.
2. Dentinal fluid shows constant pulpal pressure.

8. 3. Presence of 25% water and 25% organic content
causes hydrolysis of adhesives.
4. It is close to pulp hence the adhesive should be non
irritant.
5. Presence of smear layer and smear plug after
cavity preparation.

9. 1. Bonding to the structure of dentin

10. (a) Denatured
collagen after
etching
(b) Opened
dentinal
tubules after
etching

11. HYDROPHILLIC NATURE OF
PRIMER

12. 2.Smear Layer
 Whenever a tooth surface is prepared with a bur or hand
instrument, residual organic and inorganic
components form a layer of debris on the surface of the
substrate called the Smear Layer.

13.  Thickness of smear layer – 0.5 - 2µm
 Thickness of smear plug – 1-10µm
 COMPOSITION :
a) SOLID PHASE- Hydroxyapatite crystals and altered
collagen.
b) LIQUID PHASE- Tortuous Fluid
c) BACTERIA
 CLINICAL SIGNIFICANCE:
i. Prevents the formation of hybrid layer between adhesive
and dentin.
ii. Decreases the surface energy of adhesive.
iii. Some amount of residual smear plug after mild etching
prevents post operative sensitivity.

15. 3. Wetting Of Tooth Surface
 Wetting is the property of a fluid to flow over a surface
uniformly.
 For ideal wetting to happen :
 The surface energy of the adherend should be high
 The surface tension of the adhesive must be less.

16. 4. Configuration factor
 C-factor refers to the ratio of number of bonded surfaces
of a restoration to the number of unbounded surfaces.
 Eg: For class 1 restoration
No. of bonded surface = 5
No. of unbounded surface = 1
C-factor = 5:1
 SIGNIFICANCE : Stress relief can occur through one
surface only.
 During light-induced polymerization of resin composite,
the shrinkage forces in high C-factor cavities cannot be
relieved by resin flow, resulting in the debonding of one
or more walls.

18. 5. Coefficient of Thermal Expansion
 An ideal restorative material must have a CTE similar
to that of tooth.
 Whereas composite has a CTE that is four times that
of tooth.
 This leads to micro-leakage.

19. 6. Occlusal loading
 Loading and unloading of restored teeth can result in
transitional or permanent interfacial gaps.
 Additionally the tooth substrate itself might be
weakened on cyclic loading. This reduces the bond
strength.

20.  The interface or zone where the adhesive resins of the
Dentin bonding agent micromechanically interlocks with
the intertubular dentin and collagen fibres.

21.  Steps in formation of hybrid layer
1. Acid etching- partial demineralization of
hydroxyapatite crystals.
2. Opening of dentinal tubules
3. Formation of resin microtags within the
intertubular dentin.

22.  Biocompatible
 Must form strong permanent bond to the tooth
 Coefficient of thermal expansion must be similar to that
of tooth
 Low film thickness and viscosity
 Good dimensional stability
 Low thermal conductivity
 Prevent microleakage
 Good shelf life

23. Etch
and
Rinse
Self
etch
MODERN
ADHESIVES

25. o Acid etching is the use of an acidic substance to
prepare the tooth's natural enamel for the application
of an adhesive.
o The acid roughens the surface microscopically,
increasing retention of resin sealant.
o Etching of dental enamel with acid removes the
smear layer and opens enamel tubules.

26.  Etch and rinse technique uses 37% Phosphoric acid
that is let to etch for 20 seconds followed by rinsing.
 This forms a frothy white appearance on the enamel
with microporosities.

29.  Self-etch systems have an acidic resin which etches
and primes without the need for etching or rinsing,
and then there will be a subsequent application of
bond.

30.  It contains methacrylated phosphoric acid ester
that etches and primes simultaneously.
 This prevents the complete removal of the smear
layer hence leading to decreased post operative
sensitivity.
 The hydroxyapatite crystals are left intact and the
collagen meshwork is prevented from complete
collapse.

32. TOTAL ETCH SELF ETCH
Contains three step and two
step techniques.
Contains two step technique
and all in one adhesion
system.
Greater Bond strength. Lesser bond strength.
Complete removal of smear
layer.
Some amount of smear layer
remains.
Higher chances of post
operative sensitivity.
Lesser chances of post
operative sensitivity.
Complete collapse of collagen
network.
Collagen is left intact.

33. Fig: Higher risks of hydrolysis of hydroxyapatite crystals in total
etch (Right) compare to self etch(Left)
Fig: Greater Post operative sensitivity in total etch (Right ) compared
to self etch (Left)

34.  Retention of small amount of Smear Layer.
 Water acts as a plasticizer to keep the collagen
from collapsing.
 Excess water causes decreased bonding.
 Proper isolation preventing saliva contamination.
 Hybrid layer = 1-5µm
 Resin tags = 10-20µm

35.  SCLEROTIC DENTIN – It is a type of dentin that is obliterated
with tricalcium phosphate crystals. It is hard to etch.
 Occurs in aged people
 Dentin beneath a carious lesion
 Dentin exposed to oral cavity in non-carious lesions
 SOLVENT – The solvent in the adhesive influences the clinical
behaviour.
 Acetone based adhesives show more sensitivity due to lower
retention rate than ethanol based adhesives.
o POLYMERISATION SHRINKAGE – It occurs at the surface
of the resin. It is reduced by the use of flowable composite . Minimum
shrinkage stress of 7MPa is present in any restoration.

36.  TYPE OF COMPOSITE- Type of composite plays an
important role in Class V restoration.
 Microfilled Composites have lower Young’s modulus hence
are flexible and relieve stresses near gingival area.
 Other types with higher Young’s modulus are used in
posterior restorations.
 NANOLEAKAGE – Small porosities in the hybrid layer or at
the transition between hybrid layer and dentin that allow the
penetration of silver nitrate dyes.
 Spotted pattern – in self etch adhesives.
 Reticular Pattern – In case of water contamination in
bonding area.
 MICROLEAKAGE- The passage of bacteria and its toxins at
the interface of restoration margins and tooth surface.
 Occurs at resin dentin interface. This does not show up
immediately.

38.  Failures of adhesion occur at three regions which are
generally combined when the actual failure occurs.
1. Cohesive failure in the substrate
2. Cohesive failure within the adhesive
3. Adhesive failure at the interface of substrate and
adhesive.
o Failure is mainly caused due to the polymerization
shrinkage .

39.  Class 1,2,3,4,5 & 6 type composite restorations.
 Used to adhere full and partial veneers.
 Seal pits and fissures.
 Desensitize exposed roots.
 Bond amalgam restorations to tooth.
 Luting of orthodontic appliances.
 Bond fractured segments of anterior teeth.
 Bond pre-fabricated metal or fibre posts.
 Seal root canals.