Transcript Slide 1

Dr. Raghuwar D Singh
Associate Professor
Prosthodontic Department
King George’s Medical University UP, Lucknow
ADHESION
1.
2.
3.
Sound tooth structure must be conserved.
Optimal retention must be achieved.
Microleakage must be prevented.
MECHANISM OF ADHESION
Factors in achieving adhesive bonds –
 Wetting
 Interpenetration
(formation of a hybrid
zone)
 Micromechanical Interlocking
 Chemical bonding
ACID ETCHING TECHNIQUE –
 Most
effective ways of improving the marginal seal &
mechanical bonding b/w Resin and Enamel .
Mode Of Action ::

It creates micro-porosities by etching of the enamel .
Etching increase the surface area .
 Etched enamel has a high surface energy and allows a
resin to wet the surface & penetrate into microporosities.
 Resin
Tags are approx 6microm in diameter and 1020micro m in length.
Acid Used ::

37 % Phosphoric acid is most commonly used acid .

Supplied in gel form .

Brush or Syringe is used for application on the
enamel .
Procedure ::

Dry the enamel surface completely .

Length of application = 60 sec.
but may be 15 sec.

After etching , dried enamel shows white , frosted
appearance .

If enamel surface is contaminated, re-etching for 10 sec .
BONDING AGENTS:
 Enamel
 Dentin
bond agents
bond agents
ENAMEL BOND AGENTS:
 Hydrophobic
 Unfilled
 Bis
resin
GMA
 TEGDMA
DENTIN BOND AGENTS:
Dentin
PROBLEMS IN BONDING TO DENTIN:
Dentin is a dynamic tissue that shows changes due to
ageing, caries or restorative procedures.
Dentinal tubules are filled with dentinal fluid which
constantly flow outward from the pulp.
Dentin has considerable amount of organic material &
water.
Dentin is close to pulp, so different chemical used for
bonding and etching may irritate the pulp.
ROLE OF SMEAR LAYER : Whenever
tooth surface is cut with hand or rotary
instruments, it causes small particles of the cut tooth
surface to the tooth producing the smear layer.
 Smear
layer is defined as any debris, calcific in nature
produced by reduction or instrumentation of enamel of
dentin or cementum.
Retention of smear layer:1) lowers dentin permeability
 2) prevent decrease in bond strength
 3) lowers effect of pulpal pressure on bond strength

** Recent generations adhesives involves modification
of smear layer to facilitate bonding.
It has two phases  Solid phase- made up of cutting debris, primarily
denaturated collagen and mineral.
 Liquid
phase- made up of tortuous fluid filled channels
around the cutting debris.
 Bacteria
entrapped in smear layer can survive and
multiply beneath the restoration.
CONDITIONING OF DENTIN:
 It
is defined as an alteration of dentin surface including
the smear layer with the objective of producing a
substrate capable of micromechanical and possibly
chemical bonding to dentin adhesive.
 Acid conditioners:
1. Phosphoric acid,
2. Citric acid,
3. Nitric acid,
4. Oxalic acid, and
5. Hydrochloric acid.
ChelatorsRemove the smear layer without decalcification or significant
physical changes on underlying dentin substrate.

Best known chelator conditioner is EDTA.
Thermal conditioningRecent trend is to use lasers in conditioning of teeth.
 Studies have conformed increased bond strengths with lased
dentin compared to those with unlased dentin.
The molecule designed for dentin bonding were
represented by an M-R-X molecule.



M- methacrylate group for bonding to resin matrix of
composite resin
R- spacer such as hydrocarbon chain
X- functional group for bonding to organic or inorganic
component of dentin.
ETCHENTS / CONDITIONERS
 ORGANIC ACID:-
Maleic acid, EDTA, Citric acid,
Tartaric acid.
 POLYMERIC ACID:-
Poly acrylic acid.
 INORGANIC ACID:-
Phosphoric acid, Nitric acid.

Hydrophilic
Primers/ Conditioners
Bonding liquid
PRIMERS

NTG-GMA

PMDM

BPDM

PENTA

HEMA
ADHESIVE RESINS
Hydrophobic monomers  BIS-GMA
 UDMA
Diluent  TEGDMA
Wetting agent  HEMA
DENTIN BONDING AGENTS:





First generation
Second generation
Third generation
Forth generation
Fifth generation
MCQS:

Most effective way of improving the marginal seal
and bonding between restorative resin and Enamel
is:
1. Using adhesive
2. Acid etching
3. Using both adhesive and acid etching
4. None of the above

Most commonly used acid for acid etching
technique:
1. 35% Phosphoric acid
2. 37% Phosporic acid
3. 37% Hydrochoric acid
4. 35% Citric acid

Chelators most commonly used to remove the smear
layer:
1. EDTA
2. BIS GMA
3. HEMA
4. Oxalic acid

The nature of enamel bonding agents should be:
1. Hydrophilic
2. Hydrophobic
3. Depending on the condition of enamel
4. Neutral

The length of application of acid in acid etching
technique should be:
1. 10 Second
2. 60 Second
3. 90 Second
4. 120 Second