Adhesion Myth or Magic

8/8/2019 Adhesion Myth or Magic

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ADHESIVE DENTISTRYMYTH OR MAGIC

LCDR ROD GUNNING, DC, USN


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ADHESIVE DENTISTRY MYTH OR MAGIC

Background1955-Buonocore applied acid to teeth to render the

tooth more receptive to adhesion.1956- First commercially available bonding agent.1978- Second generation adhesives introduced.

1980s- Total etch concept gains acceptance.1990s-Hybrid layer concept1990s- Multistep and one step adhesive systems.


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Present

Universal, all purpose, or multipurpose adhesivesystems claim to bond to enamel, dentin,amalgam, metal, and porcelain such that makingan appropriate product selection for use in daily

practice becomes difficult.


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erminologyAdhesion or bonding- The forces or energies betweenatoms or molecules at an interface that hold two phasestogether.Adherend- The surface or substrate that is adhered.Adhesive/ adherent/ bonding agent/ adhesive system- Amaterial that can join substances together, resistseparation, and transmit loads across the bond.


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erminologyAdhesive failure- The bond that fails at the interface

between the two substrates.Cohesive failure- The bond fails with in one of thesubstrates, but not at the interface.


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Potential Advantages>

Microleakage reduction.> Postoperative sensitivity reduction.> Marginal staining reduction.> Reinforce weakened tooth structure.> Does not act like a wedge.


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Potential Advantages>

Repair deteriorating or debonded restorations.without additional loss of tooth structure.> Expands range of esthetic possibilities.> Minimizes removal of sound tooth structure.


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I ndications

Replace carious and fractured tooth structure.Fill erosion or abrasion defects in cervical areas.Correct unaesthetic shapes, positions, dimensions,or shades.Bond silver amalgam restorations.Cement crowns.


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I ndications

Bond orthodontic brackets.Treat dentinal hypersensitivity.Repair fractured porcelain, amalgam, and resinrestorations.Pit and fissure sealants.Core build up foundations.


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Principles of Adhesion

Mechanical Theories Adsorption Theories Diffusion Theories Electrostatic Theories

Etched Enamel


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Adhesion to enamel is much easier to

achieve than is adhesion to dentin. Enamelcontains primarily hydroxyapatite, whichhas a high surface-free energy, whereasdentin is composed of two distinctsubstrates, hydroxyapatite and collagenwhich has a low surface free energy.

Parameters Affecting Adhesion to Enamel and Dentin


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Com positon of Enam el and Dentin by

W eight and Volume95

70

86

50

4

18

2

25

112 12

25

0102030405060708090

100

EnamelW t %

DentinW t %

EnamelVol %

DentinVol %

InorganicOrganicWater


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Changes in dentinSmear layer Internal and external dentinal wetnessWetting of the adhesivePolymerization contraction of restorative resins


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Parameters Affecting Adhesion to Enamel and DentinCompensation for polymerization contractionThermal expansion coefficientTransmission of stress across the restoration-toothinterface


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Parameters Affecting Adhesion to Enamel and DentinChanges in dentinSmear layer Internal and external dentinal wetnessWetting of the adhesivePolymerization contraction of restorative resins


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Physiologic dentinal sclerosisReactive sclerosisTertiary or reparative dentin


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ADHESIVE DENTISTRY MYTH OR MAGICParameters Affecting Adhesion to Enamel and Dentin

Changes in dentinSmear layer Internal and external dentinalwetnessWetting of the adhesive

Polymerization contraction of restorative resins


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Parameters Affecting Adhesion to Enamel and DentinThe smear layer is defined as any debris, calcific innature, produced by reduction or instrumentation of dentin, enamel, cementum, or as a contaminant that

precludes interaction with the underlying pure toothtissue.

The smear layer may reduce dentin permeability by asmuch as 86%.


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Parameters Affecting Adhesion to Enamel and DentinChanges in dentinSmear layer Internal and external dentin wetnessWetting of the adhesivePolymerization contraction of restorative resins


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Internal dentinal wetness occurs withsmear layer removal.

External dentinal wetness may occur with humidity.


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Parameters Affecting Adhesion to Enamel and DentinChanges in dentinSmear layer Internal and external dentinal wetnessWetting of the adhesivePolymerization contraction of restorative resins


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The adhesive system must sufficientlywet the solid surface, have a viscositythat is low enough to penetrate themicroporosities, and be able to displaceair and moisture during the bonding

process.


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Wetting of a surface by a liquid is

characterized by the contact angle of adroplet placed on the surface. Sufficientwetting of the adhesive will only occur if itssurface tension is less than the surfaceenergy of the adherend.



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S u b s t r t

C t c t A l

U > 9 0 U < 9 0

U



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Parameters Affecting Adhesion to Enamel and DentinChanges in dentin

Smear layer Internal and external dentinal wetnessWetting of the adhesivePolymerization contraction of restorative resins


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Parameters Affecting Adhesion to Enamel and DentinCurrent resin composites shrink 3-7% by volume.

Bonding interface to tooth is a weak component.Bond strength should be in the range of 17-20 MPa.


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Parameters Affecting Adhesion to Enamel and DentinCompensation for polymerization contraction

Thermal expansion coefficientTransmission of stress across the restoration-toothinterface


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FlowHygroscopic expansionElasticity

Cervical sealing


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The coefficient of thermal expansion of resin isabout four times larger than that of tooth structurewhich may contribute to marginal gap formation.


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A true bond will transmit stress applied to therestoration to the remaining tooth structure.High masticatory stresses are likely to reduce thelongevity of adhesive restorations.


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Adhesion to EnamelEnamel etching and high surface energy.Clean etched field without moisture and saliva.Bond strengths 25-30 MPa.


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Type of Acid

Acid ConcentrationEtching timeEtchant formRinse time

Etching activationEnamel instrumentation

Enamel condition

Primary vs. PermanentPrism structureFluoridatedDemineralized

Stained

Parameters That Effect Etching On Enamel


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Development Of Resin Dentinal AdhesivesFirst generationSecond generationThird generationFourth generationFifth generation


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Development Of Resin Dentinal AdhesivesBuonocore in 1956 reported thatglycerophosphoric acid dimethacrylate (GPDM)could bond to etched dentin.First commercially available dentin bonding agent

introduced with N-phenylglycine glycidylmethacrylate (NPG-GMA).Bond strengths in 2-3 MPa range.


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Development Of Resin Dentinal AdhesivesBond strengths in 5-6 MPa range.Bond to smear layer.Based on phosphorous esters of methacrylatederivates.


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Development Of Resin Dentinal AdhesivesPrimer and adhesive systems introduced.Removal or modification of the smear layer.Hydrophobic and hydrophilic.Bond strengths 10 MPa


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Development Of Resin Dentinal AdhesivesTotal etch concept.Hybrid zone formation in dentin.Conditioners and primers.Low viscosity unfilled/ semifilled adhesive resin.Copolymerization.


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Development Of Resin Dentinal AdhesivesSingle component bonding systems.Does not represent improved bond strength or microleakage reduction.


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Adhesion to DentinConditioning of dentinPrimersAdhesive resinAdhesive strategies

Cross banded collagenCross banded collagen


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Adhesion to DentinConditioners such as acids or a calcium chelator (EDTA) chemically alters the dentin surface withthe objective to remove or alter the smear layer,simultaneously demineralize the dentin surface,and expose the microporous scaffold of collagenfibrils.


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Primer does not plug tubules.


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Adhesion to DentinHydrophilic wetting agentsCompatible with dentin and resinBifunctional moleculeMonomers include HEMA, NTG-GMA,NPG-GMA, PMDA, BPDA, and PENTA


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Adhesion to DentinHybrid layer stabilization

Resin tagsLow viscosityHydrophobic monomers (bis-GMA, UDMA)Hydrophilic monomers (TEGMA)Wetting agent (HEMA)Oxygen inhibited layer (15 micrometers)


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Adhesion to DentinHybridizationResin tag formationWet bonding


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Adhesion to Restorative MaterialsAmalgam bondingCeramic bondingGlass ionomer cements


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Adhesion to Restorative MaterialsSystems: All bond 2, amalgambond plus, panavia,scotch bond multi-purpose plus.Micromechanical mixing.Bond strength less than 10 MPa.

Potential to weaken amalgam.May increase fracture resistance.May seal better than traditional cavity varnishes.


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Adhesion to Restorative Materials

A B C D E

Silanization with a bifunctional coupling agent.

F

Ceramic Bonding


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Adhesion to Restorative MaterialsAmalgam bondingCeramic bondingGlass ionomer cements


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PolyalkenoicAcid

Silica

CoreCa2+,Al3+,Na+,F-

PolycarboxylateSalt MatrixH+ COO-

Acid Base Setting Reaction of Conventional GI Cements


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Adhesion to Restorative MaterialsConventional Glass Ionomer Cements

Acid base reactionLong term release of fluorideAdhesion to tooth

Coefficient of thermal expansion


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Adhesion to Restorative MaterialsResin Modified Glass Ionomer Cements

Acid base reaction.Monomers include HEMA.Photoinitiator (camphorquinone).

Examples: Fugi IILC, Vitremere.Improved properties over conventional GI.


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Adhesion to Restorative MaterialsThe underlying mechanism of adhesion of glassionomer cements to tooth structure is thought to

be an ion-exchange process in which the polyalkenoic acid softens and infiltrates the toothsurface, displacing calcium and phosphate ions.


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Adhesion to Restorative MaterialsAn intermediate adsorption layer of calcium andaluminum phosphates and polyacrylates is formedat the glass ionomer cement-hydroxyapatiteinterface. A reversible breaking and reforming of calcium-carboxyl complexes in the presence of water is suggested to form a dynamic bond.


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Potential Problems with Dentin Adhesive SystemsCuring mechanisms: AccessResin pooling: Polymerization shrinkage 7-8%Film thickness: Solvent vs. aqueousProtocol variations: Application techniques


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Clinical SignificanceDentin bonding is technique sensitive andelimination of microleakage may be unreliable.Enamel bonding is much more predictable thandentin bonding. With more enamel at the marginsof a preparation, greater confidence can be givenfor the longevity of the adhesive restoration.


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WAYS TO HANDLE STRESS

When someone says have a nice day, tell themyou have other plans.Forget the diet center and send yourself acandygram.Make a list of things to do that you you have

already done.Go shopping. Buy everything. Sweat in it. Returnit the next day.


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WAYS TO HANDLE STRESS

Relax by mentally reflecting on your favoriteepisode of The Flintstones during thatimportant seminar.Read the dictionary upside down and look for important messages.

Write a short story using alphabet soup.Stare at people through the tines of a fork and

pretend that they are in jail.


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YOU MIGHT BE A RESIDENT IF.Instructors dont really care when you turn work inanymore.You start refering to stories like Snow White et al.

You frequently wonder how long you can live on pastawithout getting curvy.You look forward to taking time off to do laundry.You have given up trying to keep your books organized

and are now just trying to keep them all in the samegeneral area.You consider McDonalds real food.


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YOU MIGHT BE A RESIDENT IF.Everything reminds you of something in your discipline.There is a copier in the library that you consider yours.You look forward to summer because you are more

productive without the distraction of classes.You consider all projects as works in progress.You find the bibliographies of books more interestingthan the actual text.

You have accepted guilt as an inherent feature of relaxation.World War III could take place and youd be clueless.


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BEFORE I CAME TO RESIDENCYI WISH I HAD KNOWN..

That Sunday is a figment of the worldsimagination.That friends are what makes this placeworthwhile!A farewell is necessary before we can meet again,

and meeting again, after moments or a lifetime, iscertain for those who are friends.


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BEFORE I CAME TO RESIDENCYI WISH I HAD KNOWN..

That residents throw airplanes, too.That every clock shows a different time.That if I were smart in college- so what?That treatment plans require more time than allthe other classes put together.

That you can know everything and fail a test.That you can know nothing and ace a test.

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Adhesion Myth or Magic

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