Dentine Bonding Agents

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Dentine bonding agents

Dr Syed Sohaib Daud


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Adhesion

The state in which two surfaces are held together by interfacialforces which may consist of valence forces or interlocking orboth.

(American society for testing and materials)

An adhesive is a material that join two surfaces together and is

able to transfer load from one surface to other.


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Mechanism of resin bonding

Mechanical

Adsorption

Diffusion Combination of three


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Adsorption


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Acid washing /

rinsing

Removes smear layer

Dissolves HA

Drying shrinks remaining

Collagen polymer

molecules Rehydration /

primingSwells colla en

Mechanism of dentine bonding


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Monomer

penetration

Mechanism of dentine bonding

Monomer polymerisation

And collagen

entanglement


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Challenges in dentine bonding

Dentine contains substantial amount of water and organicmaterial as compared to enamel.

It contains dens network of tubules.

Smear layer prevents the penetration of adhesive into tubule by fo
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Development

First generation It consisted of co monomer NPG-GMA (N-phenylglycine

glycidyl methacrylate).

Low in-vitro dentine bond strength.

In-vivo results were also discouraging.

Carbon-13 nuclear magnetic resonance analysis showed that noionic bonding develops between NPG-GMA and hydroxyaptite.


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1st generation:

Smearlayer

Adhesive resin

Composite

1950-1970s


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Second generation Clearfill bond was the first product of second generation of

dentine adhesives.

It was a phosphate ester(phenyl-p andhydroxyethylmethacrylate[HEMA] in ethanol).

Its mechanism of action was based on the polar interactionbetween negatively charged phosphate groups in the resin andpositively charged calcium ions in hydroxyapatite.

They had low dentine bond strength of only 1 to 1.5 Mpa.

Presence of loosely attached smear layer and absence ofhydrophilic groups posed major problems.

Resistance to water was low.


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Third generation The concept ofacid etchingwas first introduced in 1979 by

Fusayama.

Clearfill new bond was introduced in 1984 and contained HEMAand 10-carbon molecule known as 10-MDP(10-methacryloxyethyl decyl dihydrogenphosphate).

Some materials were designed to modify smear layer andallow penetration of acidic monomer.

Another treatment of smear layer with acidic primer was

proposed using aqueous solution of 2.5% maleic acid, 55%HEMA, and a trace of methacrylic acid(scotchbond 2).


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3rdgeneration:

1st step:-Total etchingLeaving freeminerals on surface-Rinse surface-Total drying ofsurface

2nd step :

adding primer

3rd step:Adding adhesiveresin,Then adding

Composite

Smear layerResidual

waterPrimerAdhesive

3rdgeneration

Composite


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Fourth generation/Three step total etch adhesive

Fourth generation of dentine adhesives was introduced for useon acid etched dentine.

This technique is also known as total etch or etch and rinsetechnique.

Application of acid results in partial or total removal of smearlayer and demineralization of underlying dentine up to depth of7.5 microns.


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Fourth generation dentine adhesive include three components

1. A phosphoric acid gel that is rinsed off.

2. A primer containing reactive hydrophilic monomers in ethanol,acetone, or water.

3. An unfilled or filled resin bonding agents containinghydrophobic monomer (Bis-GMA) combined with hydrophilicmolecules (HEMA).


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Acid etching also alter the free surface energy of dentine whichis undesirable.

Primer in three step technique is designed to increase criticalsurface energy of dentine.

When primer and bonding agents are applied they results information of a hybrid layer and resin tags.

This generation was proved successful both in vivo and in vitrowith dentine resin bond strength of 13-80 Mpa.


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4thgeneration:

1st step:-Totaletching(removal ofsmear layer)Leaving free mineralson surface-Rinse surface-Without drying ofsurface (residual

2nd step :

adding primer

3rd step:Adding adhesiveresin & then

composite

4thgeneration

Composite

Smear layerResidual water

PrimerAdhesive resin


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Fifth generation/one bottle, Total etch This system combine the primer and bonding agents into a single

solution.

Separate etching is still required.


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Pri

m

e

Ad

h

e

5th generation:5thgeneration

Prim

ermixed

with

adh

esive


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Sixth generation/self-etching primer system These self etching primers, first introduced in Japan, include a

phosphonated resin molecule that performs function of primingand etching simultaneously.

They do not require rinsing off.

The bonding mechanism is based on the simultaneous etching ofenamel and dentine, forming a continuum in the substrate andincorporating smear plugs into the resin tags.

It simplifies the bonding technique.

Elimination of rinsing and drying reduce the possibility of overwetting or over drying.

SEPs are less technique sensitive.


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Less discrepancy between the depth of demineralization anddepth of resin infiltration.

Less postoperative sensitivity.

One disadvantage is that they do not etch enamel as well asphosphoric acid.


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Self-etching primer adhesive

system


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Seventh generation/self etching adhesives(all in one) This generation include the materials that incorporates the

classic steps of etching, priming, and bonding into one solution.

All in one adhesive contain uncured ionic monomer that contactthe composite material directly.

Presence of this un reacted acidic monomer is responsible fortheir incompatibility with self cured resin.

These adhesives act as semi permeable membrane and henceresult in degradation of dentine resin interface.

These resin monomer might be too hydrophilic which makethem susceptible to water degradation.


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Comparison of the Classification and Components ofDental Adhesive Systems

STEP 4TH GEERATION 5THGENERATION 6THGENERATION 6TH GEN(MIXINGREQUIRED)

7TH GEN

SELF ETCHINGADHESIVE

SELF ETCHINGADHESIVE

Etching of enamel

dentine

Etchant Etchant Self etching primerSelf-etching, self-

primingresin/sealer

Self-etching, self-

primingresin/sealerdesensitizer,disinfectant

Priming of dentin Primer Self-primingresin/sealer

Self etchingprimer

Self-etching, self-primingresin/sealer

Self-etching, self-primingresin/sealerdesensitizerdisinfectant

Sealing of enameland dentine

Resin/sealer Self-primingresin/sealer

Resin/sealer Self etching, self primingresin/sealer

Self-etching, self-primingresin/sealerdesensitizerdisinfectant


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Comparison of the Number of System Components and Clinical PlacementSteps of Dental Adhesive Systems

Generation steps Description Components1st 2 Etch enamel,

apply adhesive2

2nd 2 Etch enamel,

apply adhesive

2

3rd 3 Etch enamel,apply primer

2-3

4th 3 Total etch, apply

primer

3-5

5th 2 Total etch, apply adhesive.

2

6th 1 Apply self etch

adhesive

2


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Thank you

Documents

Dentine Bonding Agents