Adhesives

ADHESIVESADHESIVES

Dr. Fazal ur Rehman QaziBDS,FCPSAsst. Prof.Operative Dentistry DIKIOHS

FRQ

The Next Jungle...Adhesives

3

Principles of AdhesionPrinciples of Adhesion

Clean surfaces

Closely approximating surfaces

Maximum surface area of contact

Good surface wetting by the adhesive

Stable over long-term

Requirements for BondingRequirements for Bonding

+ >Mechanical Adhesion

ChemicalAdhesion

Stress over Bond Lifetime

•Enamel, Dentin•All areas of the bond •Stresses: residual (shrinkage) thermocycling occlusion mastication•Chem / Bio environment

• Surface area• Penetration of resin• Undercuts• Cured adhesive strength

•Ionic bonds•Metallic bonds•Covalent bonds•Dipole interactions•Van der Waals

Mechanical Adhesion

Etching Priming Bonding

Dentistry

VELCRO(Hook and Loop

Fastener)

6

Structure of DentinStructure of Dentin

Erosion

TranslucentDentine

Inner Occlusal Dentine

Outer Occlusal Dentine

PULP

Multizoned Carious Lesion

Reactive Dentine (erosion, abrasion)Physiologic Dentine (aging, wear) -many occluded tubules

4% vol

28% vol

Heymann & Bayne 1993

Cavity edge Axial wall

Cementum

Gingival floor

7

>50% Class V & IIcavity surfaces had oblique or parallel cut dentinetubule orientations

DIRECTION OF DENTINAL TUBULES

8

Direction of Tubules and Prisms

Potential for poor bonding to dentine at gingival floors

Dentine tubulesDentine tubules Hybrid layerHybrid layer MicroleakageMicroleakage

End on (90End on (90ºº)) 30-35 µm + tags30-35 µm + tags Signif. lowerSignif. lower

Parallel cutParallel cut 1-10 µm + few tags1-10 µm + few tags Signif. higherSignif. higher

9

Moisture on Exposed Dentine

Sources: Oral humidity Saliva Triple syringe Dentine tubules

10

The Smear Layer The Smear Layer

~1-5 µm

Bond strength to tooth

structure ~2-5 Mpa

Can be altered or removed

11

Hybrid Layer Formation in Dentine

ETCHANTPRIMER

ADHESIVE RESIN

IntertubularDentine

PeritubularDentine

Dentinal Tubules

HybridZone

Collagen

FRQ

1960 1970 1980 1990 2000 2010

1st / 2nd GenerationOnly bond to enamel, pH neutral

3rd Gen.pH < 7

3-step Etch&Rinse

2-stepEtch&Rinse

2-stepSelf-etch

1-stepSelf-etch

1989: Hybrid layer

Dental AdhesivesHistory

Enamel Etch Concept – Buonocore 1955

N-Phenyl-Glycin-Glycidyl-MethacrylateBowen 1965

1983 Scotchbond / 3M Bis-GMA-PO4-ester

1988 Scotchbond 2 / 3M Maleic acid/HEMA

1973 Concise Enamel Bond / 3M

1960 1970 1980 1990 2000 2010

1th / 2th GenerationNo etching, pH-neutral

3th Gen.pH < 7

3-step Etch&Rinse

2-stepEtch&Rinse

2-stepSelf-etch

1-stepSelf-etch

1989: Hybridlayer



1983 Scotchbond / 3M Bis-GMA-PO4-ester

1988 Scotchbond 2 / 3M Maleic acid/HEMA

1960 1970 1980 1990 2000 2010


3th Gen.pH < 7

4th Gen.Etch&Rinse

5th Gen.Etch&Rinse

6th Gen.Self-etch

7th Gen.Self-etch

1989: Hybridlayer



1960 1970 1980 1990 2000 2010


3th Gen.pH < 7

3-stepEtch&Rinse

5th Gen.Etch&Rinse

6th Gen.Self-etch

7th Gen.Self-etch

1989: Hybridlayer



1960 1970 1980 1990 2000 2010


3th Gen.pH < 7

3-stepEtch&Rinse

2-stepEtch&Rinse

6th Gen.Self-etch

7th Gen. Self-etch

1989: Hybridlayer



1960 1970 1980 1990 2000 2010


3th Gen.pH < 7

3-step Etch&Rinse

2-stepEtch&Rinse

2-stepSelf-etch

7th Gen.Self-etch

1989: Hybridlayer



1960 1970 1980 1990 2000 2010


3th Gen.pH < 7

3-step Etch&Rinse

2-stepEtch&Rinse

2-stepSelf-etch

1-stepSelf-etch

1989: Hybridlayer



1990 2000 2010

3-step Etch&Rinse

2-stepEtch&Rinse

2-stepSelf-etch

1-stepSelf-etch

1989: Hybridlayer

Dental AdhesivesGenerations

FRQ

FRQ

Tooth composition

Enamel (wt%) Dentin (wt%)

Minerals 97 % 70 %

Organic 1 % 20 %

Water 1 % 10 %

FRQ

-Straight forward bonding-Strong acids etch very well-Surface can be dry-Resin flows in spaces-Polymerizes forming strong bond

Bonding to EnamelEtch enamel with 35% phosphoric acid

Enamel etch pattern

FRQ

Bonding Mechanism to Dentin

1st, 2nd generation: only bond to etched enamel, bond to dentin best achieved by sandwich technique with glass ionomer base

3rd generation: weakly acidic primers partially dissolve the smear layer and etch dentin – low bond strength due to inadequate resin systems

FRQ

Bond to Dentin – the Hybrid Layer

e.g. 4th Generation

Bonding

Primer

Resin tags

Composite

FRQ

The Hybrid LayerDemineralized, resin-impregnated dentin

Concept established by Nakabayashi (1980s)

TEM visualization techniques by Yoshida and van Meerbeek (1998)A – glass filled adhesive resin (Optibond FL)H – hybrid layerT – dentin tubuleR – resin tagI – nondemineralized intertubular dentin

B. van Meerbeek et al., J. Dent. Res. 1998 2 µm

FRQ

Etching enamel and dentin (total etch)

Hydrophilic primer wets and penetrates dentin very well

Hydrophobic bond

Introduced around 1993

First adhesives with high dentin bond strength

Gold standards (Optibond FL, Scotchbond Multipurpose)

4th Generation Adhesives

44thth Generation Generation

A B

Etch Prime Bond

FRQ

Etching enamel and dentin (total etch)

Hydrophilic primer and hydrophobic bond of 4th generation combined into one bottle

Introduced around 1997

Most popular adhesives in many parts of the world

Examples: Prime&Bond NT, Optibond Solo Plus, Singlebond 2

5th Generation Adhesives


Etch Prime+

Bond

FRQ

5th Generation AdhesivesAdvantages:

Less steps compared to 4th generation

Long clinical history of over 10 years

Disadvantages:

Highest incidence of post-operative sensitivities

Higher technique sensitivity

moisture of etched dentin

thickness of adhesive layer

phase separation

Loss of dentin bond strength over time

FRQ

Etched dentin

Bur Cut dentin with smear layer

-More complicated bonding-Acids demineralize and open tubules-Surface is hydrophilic and must be kept moist-Requires priming-Must be completely sealed to prevent sensitivity

Etched Dentin and Post-operative Sensitivity

FRQ

Smear Layer after Cavity PreparationCavity preparation produces smear layer

Smear plugs close orifices of dentin tubules

FRQ

Etching opens Dentin Tubules

Etching with phosphoric acid (and also strong self-etch adhesives with pH <2) remove smear plugs

Open tubules (etched bovine dentin): smear layer is removed

Adhesive needs to close open tubules completely!

Perfect Impregnation

No Sensitivity

Unperfected Impregnation

Nanoleakage

NoImpregnation

Sensitivity

Weak Hybridization

Microleakage

Resin Impregnation

FRQ

WET DRY

MOIST

Right Surface Moisture

An Issue with Total Etch Adhesives…

FRQ

Dull dentin appearance indicates dehydration

What happens if the tooth surface is overdried?What happens if the tooth surface is overdried?

The collapsed collagen decreases porosity and reduces adhesive absorption : Increases chance for sensitivity

FRQ

The tooth surface needs to be moist!The tooth surface needs to be moist!

Expanded collagen is porous and will absorb adhesive: minimizes post-op sensitivity.

FRQ

„Phantom“ Hybrid LayerPerdigao, 1995

Overetched, overdried dentin

Adhesive resin

Uninfiltrated, collapsed collagen (removed by NaOCl)

Resin tags in non-demineralized dentin

FRQ

Consequences of Over-DryingCollapse of collagen network

Incomplete infiltration and seal of the etched dentin

Fluid movement within collagen leads to post-operative sensitivities

Lower bond strength

No protection of the exposed collagen against degradation

Endogenic enzymes (matrix metalloproteinases / MMPs) are liberated and activated during etching step

MMPs are active in incompletely infiltrated dentin and lead to significant loss of dentin bond strength over a few months

FRQ

How to Minimize POS with 5th Generation Adhesives

Isolation with Rubber Dam to prevent contaminationUse an RMGI as liner / base (e.g. Vitrebond), especially in deep

cavitiesDo not over etch dentin – apply etchant to enamel first, then dentinThoroughly rinse off etching gelKeep dentin moist after etching – do not dry with air, but rather blot

excess moistureApply adhesive immediately after blottingApply adhesive generously – 2-3 coatsDo not air thin too aggressively – if all adhesive is blown away, there is

nothing to bond toContinue immediately with filling composite

FRQ

Self-Etch Adhesives (6th and 7th Gen)

Acidic monomers in formulation to provide etch pattern for retention and chemical bond (eg MDP, 4-META)

Introduced around 2000 (6th Generation, eg Clearfil SE Bond, first version of Prompt L-Pop)

Mild SE adhesives (pH >2) / Strong SE adhesives (pH <2)

Successful in USA, Japan, Western Europe Ease of use Low incidence of post-operative sensitivity

FRQ

Acidic, hydrophilic primer

Hydrophobic bond

(eg Clearfil SE Bond)

or

Acidic resin and aqueous phase

have to be mixed before application

(eg Xeno III, Adper Prompt L-Pop)

6th Generation Self-Etch Adhesives

A

Etch+

PrimeBond


B

FRQ

7th Generation Self-Etch AdhesivesAll components combined into one bottle

Usually „mild – ultra-mild“ (pH > 2)

Fastest growing segment in adhesives market

Intensely researched, but limited clinical evidence available

Etch+

Prime+

Bond


FRQ

Low POS with Self-Etch AdhesivesFirst version of Prompt L-Pop

0%2%4%6%8%

10%12%14%16%18%20%

Prompt Prime&Bond NT

1 month6 month

*Note: Data pertains to clinical study on original Prompt

formulation. U Iowa; Denehy et al.

% S

ensi

tive

FRQ

Total number of dentists

Number of dentists encountering post-operative sensitivity

Total numberof post-operative sensitivities

Total number of restorations placed

Percentage of restorations with post-operative sensitivity

100

7

26

5572

0.5%

Low POS with Self-Etch Adhesives Adper Easy Bond Application test 3M ESPE internal data

FRQ

Why do Self-Etch Adhesives reducePost-Operative Sensitivity?

No separate etching step – minimized danger of overetching and desiccation of dentin

Resin penetrates as far as demineralization of dentin – minimized danger of unimpregnated collagen layer under adhesive

FRQ

Self etch

2 steps

Demineralization Resin penetration

Risk of nanovoids

Demineralization

resin penetration+

- 2 consecutive steps- risk of nanovoids, if penetration depth of etchant and resin are not equal- higher risk of post-op sensitivity

- 1 single step- no risk of nanoleakage, since penetration depths are equal- lower risk of post-op sensitivity

Adper Easy One

FRQ




Adhesive is neutralized by basic hydroxyapatite during application

FRQ




Adhesive is neutralized by basic hydroxyapatite during application

Mild self-etch adhesives do not dissolve smear layer completely – most tubules remain protected by smear plugs

FRQ

7th Generation adhesive on dentin

lab-demineralized dentin

particle-filled adhesive

Clearfil Protect LinerClearfil Protect Liner

acid-resistant submicron hybrid acid-resistant submicron hybrid layerlayer

dentin tubuledentin tubule

smear plugsmear plug

TEM image courtesy of Prof. van Meerbeek, Univ. Leuven, Belgium

FRQ

What the Scientific World says...First glance:

MassesMasses Converting and using Converting and using Self-Etch Self-Etch

AdhesivesAdhesives

Opinion Opinion LeadersLeaders

Supporting Total-Etch Supporting Total-Etch Adhesives – even Adhesives – even

4th4th

FRQ

Van Meerbeek et al.2009, Dental Materials

FRQ

“3-step etch&rinse adhesives and (mild) 2-step self-etch adhesives are still the benchmarks

When bonding to enamel, an etch&rinse approach is definitely preferred

When bonding to dentin, a mild self-etch approach is superior, as it involves (like with glass-ionomers) additional ionic bonding

Altogether, … selective etching of enamel followed by the application of the 2-step self-etch adhesive to both enamel and dentin currently appears the best choice“

Van Meerbeek et al.2009 Conclusions

FRQ

Bond StrengthsReality check

FRQ

Bond StrengthsReality check

?

FRQ

Bond Strengths Bart van Meerbeek et al

„Relationship between Bond-strength tests and Clinical Outcomes“Dent Materials, 2009, 11, 148ff.

“A good correlation (…) was found between the annual failure ratesreported in the systematic review of Peumans et al and the “Battle of the Bonds” shear-bond strength data from Degrange et al.”

„The significantly highest bond strength was measuredfor OptiBond FL (Kerr) that somewhat surprisingly performed not significantly better than the relativelynew 1-step adhesive Easy Bond (3M ESPE).“

FRQ

Adper Easy Bond3M ESPE

Development Objectives A new self-etch formulation Fast and easy to use Robust application Moisture tolerant

+++++

http://www.dentaladvisor.com/index.shtml

FRQ

Adper™ Easy OneSelf Etch Application

FRQ


FRQ

Apply adhesive to tooth surface for a total of 20 sec


FRQ

Gentle agitation of adhesive maximizes penetration into etched dentin and enhances integrity of hybrid layer leading to

better bonds and less sensitivity.


FRQ

Dry for 5 sec


FRQ

Light cure for 10 sec


FRQ


FRQ

TEM-Interface AnalysisDentin (self-etch) - Prof. van Meerbeek

FRQ

TEM-Interface Analysis Cut Enamel (self-etch) - Prof. van Meerbeek

FRQ

The Formulation Meeting of the Generations

Adper Easy Bond

HEMA Bis-GMADimethacrylate Vitrebond™ CopolymerFillerEthanolWaterInitiatorsMethacrylated phosphoric esters

Adper Single Bond 2

HEMA Bis-GMADimethacrylateVitrebond™ CopolymerFillerEthanolWaterInitiators

pH = 2.7pH = 4.7

FRQ

THANKYOU!

Health & Medicine

Adhesives