1

Stephen C. BayneStephen C. BayneDepartment of Operative DentistryDepartment of Operative DentistrySchool of DentistrySchool of DentistryUniversity of North CarolinaUniversity of North CarolinaChapel Hill, NC 27599Chapel Hill, NC 27599--74507450

Principles ofPrinciples ofAdhesion (Bonding)Adhesion (Bonding)

© 2004, Bayne and Thompson, UNC School of Dentistry.

It is key to understand the general principles of adhesion so that you can understand the design and limitations of dental bonding systems. The best approach is to envision adhesion is in terms of two processes – creating adhesion and destroying adhesion. They involve separate challenges.

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Adherend 1 Adherend 2

Adhesive Systemor Luting Cement

Interface 2Interface 1DENTALJOINT

ENAMEL, DENTIN >Liner, Base, Cement >

Post and Core >Dental Amalgam >

Implant >

< Composite, Amalgam< Cast Inlay, Onlay, or Crown< All-Ceramic Inlay, Onlay, or Crown< Veneers, Maryland Bridges< Orthodontic Brackets

AdhesiveInterface 1 DENTALADHESION

Adhesion involves an “adhesive” that is placed on a “substrate (adherend)” and which forms an “interface”. If the adhesive is intended to hold something in place, they one is effectively creating a joint (or dental joint) with the adhesive between two substrates and forming two interfaces. This can be seen in the schematic illustration above. One set of substrates (shown on the left) could be any number of dental ones (such as enamel, dentin, liner/base/cement, a post/core, remaining dental amalgam from a previous preparation, or a dental implant). The other substrate (shown to the right) is part of the new restoration (and could include a composite, amalgam, cast inlay/onlay/crown, an all-ceramic inlay/onlay/crown, veneer, Maryland bridge, or orthodontic bracket). The adhesive could be simply a bonding system or might be a two bonding systems coupled with an intervening composite. This complicated case will be discussed at the end of this presentation.

Adhesion, in almost all circumstances, depends on micromechanical interlocking of the adhesive with the substrate irregularities. To create this interlocking event a set of 5 very important prerequisites must occur. These are explained in the next slide.

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Steps in Forming Good Adhesion(1) Clean adherend

(2) Good wetting

(3) Intimate adaptation

(4) Bonding

(5) Good curing

physicalbonding

chemicalbonding mechanical

bonding

+–

In the figure above, the 5 prerequisites are shown in combination with a set of schematic representations of the interface of the adhesive with the substrate.

(1) Clean Adherend (Substrate): The adherend must not contain any surface debris or adsorbed films of oil or dirt that would prevent an adhesive from coming into good contact with the adherend. Surfaces can be cleaned with water, solvent, or acid.

(2) Good Wetting: The adhesive must spread onto the adherend with a low contact angle so that it wets the surface and develops good intimate contact. Unfortunately some adhesives are not well-matched to the surface energies of certain substrates. Hydrophilic materials do not wet hydrophobic surfaces very well, and vice versa. Enamel and dentin are hydrophilic while most composites are hydrophobic. The challenge for dental adhesives is to provide acceptable wetting for both of these materials.

(3) Intimate Adaptation: If good wetting occurs and the material flows adequately, then it can penetrate into all the surface interstices and develop good adaptation. This process should occur with entrapping air or leaving unfilled surface spaces.

(4) Bonding: The adhesive should interact in as many ways as possible with the substrate. It should develop physical bonding, chemical bonidng, and micromechanical bonding. The last is the most important and contributes the most (>90%) to the strength of the joint.

(5) Good Curing: The entire process depends on the adhesive (and restorative filling materials) becoming fully cured. Under-curing allows chemical erosion and/or debonding of the adhesive system.

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1 2 34

3a

3a 3c3b

3b3c

Debonding is a different process. The adhesive is now cured and contact angles are much less important. Failure of the adhesive generally occurs via fatigue cycling. Cracks are produced that emanate from defects along the interface or within the adhesive itself. This process can be envisioned schematically as shown above. The space labeled as 3a-3a is a defect in which wetting and contact is incomplete between the adhesive and adherend. During fatigue cycling, cracks develop that propagate outward from this space along the interface and sequentially disrupt bonding (shown as a series of changes 3b-3b to 3c-3c).

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TBSTBS

µµTBSTBS

18-35 MPa (typically ≅ 20 MPa)

10-12 MPa (typically ≅ 10 MPa)

40-80 MPa (typically ≅ 60 MPa)

SBSSBS

µµSBSSBS

40-80 MPa (typically ≅ 60 MPa)

BOND STRENGTH TESTINGBOND STRENGTH TESTINGWhat are good bond strengths?What are good bond strengths?

Macro SBS

µTBS

The resistance to de-bonding is measured in terms of bonding strengths (MPa). Remember that actual strength is related directly to the defect concentration. The magnitude of the measured strength will also depend on the type of test being conducted. Shear strength tests destroy interfacial bonding by sliding the adherends parallel to the interface. Tensile strength tests destroy interfacial bonding by pulling the adhesive perpendicularly away from the surface. When the samples are large, the tests are described as macro tests. When the sample being tested is a small specimens (representing only part of the actual interface), then the tests are called micro tests. The most common tests in dentistry are macro shear bond strength (SBS) tests, macro tensile bond strength (TBS) tests, and micro tensile bond strength (µTBS) tests. In macro tests, shear strength is often 50% to 100% greater in value than tensile strength. Micro tensile bond strengths tend to be much higher (often 2X to 4X that of macro TBS values) because the defect concentration in the small cross-sectional interfacial areas is much smaller. With a lower chance of defects, the interfaces behave much stronger. Dental manufacturers are intrigued the most by tests that show their products having high-valued strengths and prefer µTBS values. Recently, some labs have begun to test micro-shear as well. The behavior is very similar to micro-tensile testing.

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(1) OPERATORTechnical ability, Age, Eyesight, ...

(2) DESIGNSL, Bevels, Outline Form, ….

(3) MATERIALSComposition, Product age, T, %RH, ...

(4) INTRAORAL LOCATIONAnterior-Posterior, Maxillary-Mandibular, Lingual-Facial, Premolar-Molar, Tooth Flexure, ...

(5) PATIENTF-exposure, Diet, Oral Hygiene IQ, Caries Risk, ...

PERFORMANCE FACTORSPERFORMANCE FACTORS5 Categories of Factors Affecting Performance5 Categories of Factors Affecting Performance

Actual bond strength (and just about everything else in clinical dentistry) depends on 5 categories of factors as shown above.

(1) Operator Factors: These relate to the technical abilities of the operator.

(2) Design Factors: These include factors affecting the biomechanical design of the cavity preparation such as the presence of a smear layer, the actual outline form, and the depth of the cavity.

(3) Materials Factors: Materials factors depend on the composition, product age, temperature effects, and percent humidity effects.

(4) Intraoral Location Factors: The actual position of the restoration within the oral environment includes considerations of anterior-posterior location, maxillary-mandibular location, lingual-facial location, premolar-molar location, tooth flexure, and tooth rotation effects.

(5) Patient Factors: Individual patients have different fluoride exposures and histories of fluoride exposure, diets, oral hygiene IQs, caries risks, and epidemiological risk factors.

Of the categories, which is the most important? Operator factors are involved with at least 50% of the variability observed in dentistry. Which is the least important? Materials factors, despite our focus on different products, are the least important in the overall outcome of procedures.

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0 10 20 30 40

Shear Bond Strength (MPa Shear Bond Strength (MPa ++ s.d.)s.d.)

.

Lite

ratu

re C

itatio

nsLi

tera

ture

Cita

tions

DENTIN / SBMP / Z100DENTIN / SBMP / Z100

1.1. ConditioningConditioning2.2. PrimingPriming3.3. BondingBonding

A perfect example of this variation in bonding strengths is represented on this graph from work by Dr. Ken May. The values reported in the dental literature for 12 different research teams working on the bond strengths of Scotchbond Multipurpose bonded to dentin and Z100 composite are shown as the mean values plus or minus one standard deviation. Notice that although the average value for most are clustered around 20 MPa SBS, the range goes from 10 to 29 MPa. This is a wide variation for research tests that are performed under very well controlled conditions. Now imagine the variation that occurs clinically.

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ENAMEL MICROSTRUCTUREENAMEL MICROSTRUCTUREQuick ReviewQuick Review

The figure above is a schematic summary of enamel formation during amelogenesis. (A) Ameloblast cell movement away from the DEJ producing enamel prismatic structure in regions behind cells to form enamel prisms. (B) Individual enamel prism with apatite crystals well packed longitudinally within the center of the prism but less-well packed along the peripheries. (Compliments of Scott and Symons) (C) Schematic end-on view of hydroxyapatite crystals packed together in the middle of a prism. (D) Geometry and dimensions of an apatite crystal. (E) TEM of packing arrangement of apatite crystals along tail of one prism (left) and head of another prism (right). (Compliments of Tim Wright, University of North Carolina School of Dentistry) (F) TEM section through tail of enamel rod showing regularity of hydroxyapatite crystal sizes. (G) SEM of enamel prisms at the margin of a cavity preparation.

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ENAMEL BONDING SYSTEMSENAMEL BONDING SYSTEMS89v/o HA, 6% Organic, 5% Water

FROSTYAPPEARANCE

SBS = 20 MPaSBS = 20 MPa

During conditioning (etching), acid is used to preferentially dissolve hydroxyapatite crystals from the exposed ends and side surfaces of enamel rods. Crystals do not dissolve at the same rate, and a pattern of relief develops with more dissolution at the enamel rod peripheries than at the cores (see images above). The most widely used acid is 37% phosphoric acid (pH=1.0). Other mineral acids do not work quite as well. Some organic acids are good etchants (e.g., citric acid) but do not etch quite as quickly. There is not much practical difference between 10% and 37% concentrations of phosphoric acid. Once this surface relief is created on enamel, the monomers in primers and bonding agents can penetrate into the spaces, become polymerized, and create micromechanical interlocking that is responsible for most of the bond strength (typically 20 MPa SBS).

In the 1980s, separate enamel bonding agents were sold that were based on BIS-GMA, TEGDMA, and some solvent. No fillers were included. The enamel bonding system matched the resin component of the composite. However, these bonding systems were hydrophobic and subject to problems if the enamel surface contained any moisture during applications of primer/bonding agent. By the 1990s, both enamel and dentin were routinely being etched, primed, and bonded. Systems were designed to be compatible with moist dentin. Dentin was left moist (glistening) and primers were based on hydrophilic monomers to readily penetrate into both dentin and enamel. Bonding agents were meant to bond to primers, but be more hydrophilic, similar to the overlying composites.

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3 v/o

28 v/o

DentinZones ?

DENTIN MICROSTRUCTUREDENTIN MICROSTRUCTUREQuick ReviewQuick Review

Now let’s consider dentin bonding by first reviewing odontogenesis. Use the schematic representations of dentin formation patterns shown above. (A) Odontoblast cell movement away from the DEJ producing a corresponding tubule pattern in forming dentin. (B) Relative position of original odontoblasts to fully formed dentin. (C) SEM cross-sectional view of primary dentinal tubules in the middle third of human dentin. (Compliments of Stephen C. Bayne, University of North Carolina School of Dentistry) (D) Schematic view of variation in tubule number and size from the DEJ to the edge of the dental pulp. (Compliments of David Pashley, Medical College of Georgia).

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Intertubular dentin

Peritubular dentin

Dentinal tubule

Residual smearlayer particles

Residual smearplug particles

Macrotag Microtag

Conditioning

Priming

Bonding

COMPOSITE

HYBRID LAYER: resin microtags that are withinintertubular dentin and surround collagen fibers.

Collagen fibers

B.B. Types that form Types that form ““hybrid layershybrid layers””

DENTIN BONDING SYSTEMSDENTIN BONDING SYSTEMSIntroductionIntroduction

A. Classification of dentin bonding systems:A. Classification of dentin bonding systems:1.1. Generations based on functionalityGenerations based on functionality2.2. Type of substrateType of substrate

(1) Clean adherend(2) Good wetting(3) Intimate adaptation(4) Bonding(5) Good curing

The earliest dentin bonding experiments were actually published in the 1950s. For almost 30 more years, dentin bonding work progressed very slowly. Then in the early 1980s, better understandings of the effect of smear layers and hydrophilic monomer systems began to be appreciated. By the late 1980s, dentin bonding systems could be demonstrated that produced strengths equal to bonding to enamel (SBS = 20 MPa).

During the early 1980s, it became popular to classify developments in dentin bonding systems in terms of “generations.” While this classification system still persists, there is not much practical value to it. The figure above presents examples of the enormous range of products that have been marketed and classifies them based on this scheme of generations. At the moment, many of the experts are philosophically arguing whether we are still in the 5th

or entering the 6th generation. No matter – it is not that important.

The two distinguishing features of classification by generations are the removal of the smear layer and the effective formation of a hybrid layer. Remember that the smear layer is simply a debris layer form cutting that was generated from the dentin. Collagen and water are vaporized during the cutting and crushed hydroxyapatite crystals form a compacted layer that is partially micro-porous.

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Prime&BondPrime&BondDentsply InternationalDentsply International(Acetone solvent system)(Acetone solvent system)

Single BondSingle Bond3M Dental Products Division3M Dental Products Division(Ethanol and water solvent system)(Ethanol and water solvent system)

Scotchbond Multipurpose Plus3M Dental Products Division(Ethanol and water solvent system)(Ethanol and water solvent system)

OneOne--StepStepBISCOBISCO(Acetone solvent system)(Acetone solvent system)

HOWHOWMUCHMUCH

SOLVENT?SOLVENT?

All of the bonding system components rely on solvent to dissolve components, mix with the water present in dentin, and provide a low contact angle for wetting. However, the levels of solvent are much greater than most would suspect. Dentsply’s Prime&Bond contains 90% acetone. 3M’s SingleBond contains 65% water. Generally two thirds or more of the material is solvent. This leads to a couple of problems. If the bonding system is sold in bottles rather than single-use containers, then the solvent can escape during opening and closing operations. Solvent also makes it easy for some of the components to volatilize into the air around the patient, assistant, and dentist. For the dental team, exposure to these monomers and solvents may lead to sensitization. Dentin bonding monomers represent the most hazardous materials in the dental operatory. You should use high volume evacuation to keep from contacting or breathing these materials. The patient is normally well isolated via the rubber dam and the suction operation.

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BONDED COMPOSITEBONDED COMPOSITEChallengesChallenges

50

1000

4000

3000

2000

BO

ND

ED C

OM

POSI

TE (1

mm

= 1

000µ

m)

[DENTIN][DENTIN]1

Bacteria

[Bonding System][Bonding System]

[COMPOSITE][COMPOSITE]

[COMPOSITE][COMPOSITE]

HL

RestorativeMaterial

NormalDentin

Now let’s foray into a real clinical situation and see what is going on. Imagine the schematic on the left represents a peek down into a 4 mm proximal box of a posterior DO preparation. How thick is the bonding agent going to be on the floor of the box? Bonding agent is loaded with solvent to improve its wetting and adaptation. After several coats, the thickness will still only be about 2-5 microns. After light-curing it, 2 mm of composite will be added and cured. Then a final increment of 2 mm of composite will be added and cured. All of this material will potentially pull on the bonding system during the initial shrinkage stages and try to disrupt it.

Next look at the expanded view of dentin that has been etched. When the bonding system is applied, its location of action is actually the region between the tubules and not the tubules. The SEM view of bonding agent penetrating into the tubules shows wasted bonding agent that is undercured, soft, and cheese-like that does not contribute to bonding. Only the microtags that form within the intertubular dentin, creating the hybrid-layer, actually produce bond strength. You can see this within the high resolution TEM layer where the white resin surrounds that darker collagen fibrils.

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Designing Bonding SystemsDesigning Bonding Systems

BONDING AGENTPRIMER

ETCHANT

E+nE+nPP++BB

US Companies

2 =

1 =

E+nE+nPPBB

Japanese Companies

= 2

= 1

or or nEnEPP++BBSelfSelf--EtchingEtching

PrimerPrimer

???

nEnEPPBBSelfSelf--EtchingEtching

AdhesiveAdhesive

hydrophilic tooth structure

hydrophobic “restorative material”

Total Etch SystemsTotal Etch Systems

Now – let’s consider the various flavors of bonding systems for composite restorations. Tooth structure is hydrophilic and restorative resins are hydrophobic. Therefore, it is crucial that the chemistry of the bonding system provide a rationale bridge between these two. Otherwise, components of the adhesive or substrates may not wet each other and bond failure would occur. As a starting point, consider the original 1990 bonding system as three components, an acid etchant, a primer, and a bonding agent. This is a 3-component system. The acid removes the smear layer, helps to clean the surface, and dissolves HA crystals within the outer 15-20 microns of intertubular dentin to create a place for adhesive to penetrate and lock onto dentin. A simple shorthand has been developed by Dr. John Kanca that is very useful in keeping track of the events (or components). Thus we would abbreviate this system as E+nP+B. The “n” is there to indicate that since primers contain solvent, they require multiple applications to build up sufficient material to work. The primer is designed to be hydrophilic so that it will penetrate into the etched by wet surface of dentin, mix with the water, and then polymerize. Solvent evaporation continually removes the original water and allows replacement with more primer. The bonding agent is required to bridge the hydrophilic primer layer with the hydrophobic restorative material.

A reduced number of components can be achieved by combining the actions of these three components. In the US and Europe the approach was to continue to utilize phosphoric acid as a bonding agent but merge together the primer and bonding agent. These materials can be re-designed or simply mixed together by adding more solvent into the system or a combination of these two strategies. Prime&Bond from Dentsply was the first commercial version of this strategy. Both 3-component and this 2-component approach are called “total etch systems.” The enamel and dentin is etched with phosphoric acid an maintained in a moist condition prior to application of the primer or primer/bonding agent.

In Japan, the approach was the reverse. The original bonding agents were retained, while the primer and etchant actions were combined by substituting acid functional water-soluble primer molecules. The primer etches and primers and became known as self-etching primer systems or SEPs. Taking this approach one further step, a self-etching 1-component system can be designed and these are called self-etching adhesives or SEAs.

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E + E + nnPP + + BB or or nEnEPP + + BBE + E + nnPPBB nEnEPPBBSelfSelf--Etching PrimerEtching Primer

SelfSelf--Etching Etching AdhAdh

nnPP ==HEMA, HEMA, …… , , (Polymers),(Polymers),Alcohol, HAlcohol, H22O, O, AcetAcet

E =E =HH33POPO44, , HH22OO

B =B =BisBis--GMA, TEGDMAGMA, TEGDMAAcetone or AlcoholAcetone or Alcohol

E =E =HH33POPO44, , HH22OO

nnPBPB ==HEMA, HEMA, …… , TEGDMA , TEGDMA (Polymers),(Polymers),Alcohol, HAlcohol, H22O, O, AcetAcet

B =B =MMA, MMA, BisBis--GMA, TEGDMA,GMA, TEGDMA,(Polymers),(Polymers),Acetone or AlcoholAcetone or Alcohol

Acid Monomer,Acid Monomer,HEMA,HEMA,HH22OO

nnEPEP ==Acid Monomer,Acid Monomer,HEMA, HEMA, Polymer,Polymer,(TEGDMA), (TEGDMA), HH22O, AlcoholO, Alcohol

nnEPEP ==

To prepare the surface of composites, there must be something that dissolves or dislodges the smear layer. Phosphoric acid, of all the acids tested, is the most effective at doing this. Bonding systems that utilized phosphoric acid are called total etch and are represented by the standard 3-component and the first 2-component types. Other bonding systems rely on acid monomers to accomplish the same thing (self-etching primers and self-etching adhesives).

In all of the typical components shown above there is some sort of solvent. Etching components must contain water so that the acidic species can dissociate. Primers generally contain some water but may rely heavily on alcohol or acetone as well. Bonding systems have some solvent but this is only added to enhance wetting.

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BONDING SYSTEM:BONDING SYSTEM: pHpH33--Component (Component (EE+P+B), +P+B), Total EtchTotal Etch•• 10% H10% H33POPO44 0.80.8•• 35% H3PO435% H3PO4 0.10.122--Component (Component (EE++PBPB), ), Total EtchTotal Etch•• OneOne--StepStep 0.80.8 + 4.74.7•• Bond 1Bond 1 0.80.8 + 3.93.9•• SingleBondSingleBond 0.80.8 + 3.6 (5.1)3.6 (5.1)•• OptibondOptibond SS 0.80.8 + 2.82.8•• Prime&BondPrime&Bond NTNT 0.80.8 + 2.6 (3.2)2.6 (3.2)•• CabrioCabrio 0.80.8 + 2.52.5•• PQ1PQ1 0.80.8 + 2.22.222--Component (Component (EPEP+B), +B), SelfSelf--Etching PrimerEtching Primer•• SE BondSE Bond 2.62.6•• TyrianTyrian SPESPE 0.40.411--Component (Component (EPBEPB), ), SelfSelf--Etching AdhesiveEtching Adhesive•• PanaviaPanavia 2.9 (A+B)2.9 (A+B)•• iBondiBond 2.42.4•• OneOne--UpUp 2.32.3•• Prompt LPrompt L--PopPop 1.31.3•• XenoXeno IIIIII 1.11.1

7.07.0

5.05.0

4.04.0

3.03.0

2.02.0

1.01.0

0.00.0

--1.01.0

6.06.0

BasicBasic

AcidicAcidic

Variable Etching EffectivenessVariable Etching Effectiveness

In addition to choosing a functional acid of sufficient pH strength, it is crucial that the acid have good buffering capacity. However, this does not happen easily with some of the bonding systems. Total etch systems employ phosphoric acid that has a low pH (0.2 to 0.8) and outstanding buffering capacity. Phosphoric acid is only partially dissociated and continues to contribute more hydrogen ions during the etching process so that the pH stays in this low range. It is the most effective of all etching options. However, for acidic monomers used with SEPs and SEAs the acids rarely have as low a pH and may be less acidic by 100-fold. In addition, they have poor buffering capacity. Therefore, any special challenges may prevent them from dissolving the smear layer and/or totally dissolving the HA crystals in the outer layer of dentin.

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E+nE+nPP++BB E+E+nPBnPB nEPnEP++BBSelfSelf--EtchingEtching

PrimerPrimer

nEPnEPBBSelfSelf--EtchingEtching

AdhesiveAdhesive

TotalTotal--Etch SystemsEtch Systems SelfSelf--Etch SystemsEtch Systems

Reliable BondingReliable Bonding No Postoperative SensitivityNo Postoperative Sensitivity

1. Store in the refrigerator and use quickly.2. Use steel or carbide burs (not diamonds) for

dentin surfaces to be bonded.3. Apply multiple layers and agitate applicator.4. SEPs (and SEAs) should be “air dried” >10s,

and “not air thinned.”5. Consider H3PO4 etch, as well, if significant

enamel involved in preparation surfaces.

HybridLayer

HybridLayer

HybridLayer

HybridLayer

hydrophilic

hydrophobic

These effects can be reviewed in the animations above. One of the things that you will immediately notice, is that the self-etch systems tend not to remove the entire smear layer and smear plugs. While this complicates the formation of a good hybrid layer, it also tends to keep the surface sealed and prevent any post-operative sensitivity.

An additional complication for the self-etching systems is that the chemistries are hard to stabilize. Therefore, there are a series of important considerations in using these materials. Store them in the refrigerator but recognize that that shelf-life is still very short, generally no more than about 3 months. Whenever possible use carbide burs to finish the preparatoin so that the smear layer is weaker and easier to penetrate with these weaker acids. Apply multiple layers to insure that the SEPs and SEAs completely saturate the outer dentin and any undissolved smear layer particles. Becareful that air drying does not move the material around and potentially remove adhesive. Finally, if there are any suspicions that this will not work, then choose to etch with phosphoric acid first to create a total-etch like system.

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TIME EFFECTSTIME EFFECTSon hydrophilic leachingon hydrophilic leaching

Water blisters

Tay FR, Frankenberger R, Krejci I, BouillaguetS, Pashley DH, Carvalho RM, Lai CNS. Single-bottle adhesives behave as permeable membrances after polymerization. I. In vivo evidence.J Dent 2004; 32:611-621.

One of the recently confirmed side-effects of these systems is moisture contamination from underlying water in dentin that is wicked through the predominantly hydrophilic material. Thus, it is critical to work quickly. Do not let any more than 1-2 minutes elapse between adhesive application and placement of the composite restoration. In many circumstances this is complicated and may not happen. The true effects of this contamination are not fully understood at this point. All of the different adhesive approaches seem to be susceptible to this problem. An important conclusion is that despite the history of using dentin bonding systems, there is still no reasonable assurance that they will automatically work well.

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BONDING SYSTEMSBONDING SYSTEMS2-COMPONENT SYSTEMS (nEP + B)• Clearfil SE Bond & LinerBond 2v (Kuraray)• Tyrian SPE (Bisco)• Optibond Solo SE Plus (Kerr)• Fluoro Bond (Shofu)• UniFil Bond (GC)• Mac Bond II (Tokuyama)• NanoBond (Pentron)

1-COMPONENT SYSTEMS (nEPB)• AQBond (Sun Medical)• or Touch-and-Bond (Parkell)• Adper Prompt or LP3 (3M-ESPE)• Solist (One-bottle-bond) (DMG Hamburg)• iBond (Hereaus-Kulzer)• Xeno III (Dentsply)

3-COMPONENT SYSTEMS (E + nP + B)• Scotchbond Multipurpose Plus (3M)• Permaquick (Ultradent)• Bond-It (Jeneric / Pentron)• All-Bond 2 (BISCO)• Tenure A/B/S (Denmat)• ProBond (Dentsply)

2-COMPONENT SYSTEMS (E + nPB)• Syntac Single Component (Ivoclar)• Ecusit Primer/Mono (DMG Hamburg)• One Coat Bond (Coltene / Whaledent)• Bond-1 (Jeneric / Pentron)• Tenure Quik with Fluoride (Denmat)• Solid Bond (Hereaus-Kulzer)• Imperva Bond (Shofu)• EG Bond (Sun Chemical)• PQ1 (Ultradent)• Easy Bond (Parkell)• Paama 2 and Stae (SDI)• Prime&Bond NT (Dentsply)• Single-Bond (3M)• Optibond Solo and Solo Plus (Kerr)• One-Step (BISCO)• Excite (Ivoclar/Vivadent)• OSB Bonding System (ESPE)• IntegraBond (Premier)

Examples of most of the contemporary systems are shown above. Notice that at the moment, the 2-component total etch and SEPs seem to dominate the landscape – and are typical of the US market. In Europe, there is a strong tendency to use and promote that total etch systems. In Japan the SEPs dominate.

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ENAMEL orDENTIN

DENTALAMALGAM

AMALGAMBONDING SYSTEM

Amalgam ReactionProduct MatrixResidualAmalgam Alloy

AMALGAM BONDINGAMALGAM BONDINGMechanical InterlockingMechanical Interlocking

Interfacial Interlocking of phases

Amalgambond Plus(Parkell)

Amalgam bonding agents serve two purposes, sealing of dentin and retention of enamel or dentin to amalgam. If dental amalgam is placed into a cavity preparation with conventional undercuts, then there is no need for retention. Sealing is easily accomplished with a standard dentin bonding system or a dentin sealer. However, if additional retention is desirable or necessary for non-retentive cavity preparations, then it is possible to make bonding occur by increasing the thickness of the bonding system several fold. Instead of a thin bonding layer, a thick one is placed. This is done by adding thickening modifiers (generally PMMA) and applying several layers. Amalgam bonding systems are self-curing systems since there is no opportunity to get visible-light to the system after amalgam placement. The thick and viscous bonding system slowly cures after the amalgam has been placed. During amalgam condensation, pressure of the viscous amalgam mass against the bonding layer causes the materials to become intermixed. They are not truly compatible but do become micromechanically interlocked. Once they both harden, this works just as well as a hybrid layer and produces a 20 MPa SBS.

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ENAMELENAMELCERAMICCERAMICINLAYINLAY

AcidAcid--etchedetchedenamel enamel and dentinand dentin

DentinDentinbondingbondingsystemsystem

SilanatedSilanated //Bonded surfaceBonded surface

HF acidHF acid--etchedetchedsurfacesurface

RESININLAY

CEMENT

CERAMIC BONDINGCERAMIC BONDING

Resin CementResin Cement= Composite= Composite

HF ETCHINGHF ETCHING•• HighHigh--LeuciteLeucite PorcelainsPorcelains•• HighHigh--Alumina PorcelainsAlumina Porcelains•• Alumina Cores (Alumina Cores (ProCeraProCera))•• Zirconia Cores (Zirconia Cores (CerconCercon, Lava), Lava)

DENTINDENTIN

Probably the most complex case of bonding involves cementing of ceramic inlays. Enamel and dentin are etched, primed, and bonded. The ceramic inlay is etched with hydrofluoric acid and bonded with silane coupling agent. Composite cement is used to attach the bonded dental surfaces to the silanated ceramic surfaces. Four interfaces are actually involved – tooth structure / bonding agent / cement / silane / ceramic. The principles are all the same for the situation as in others.

While some the bonding system can be visible-light cured, the composite cement is generally self-cured or dual cured. It is important not to mix the chemistry of VLC and self-cured or dual-cured materials. The accelerator for self-cured or dual-cured systems (which is basic) can neutralize the photo-sensitizer (photoinitiator) for VL systems that is acidic. The interfaces between the materials are therefore not cured and bonding fails.

A complete treatment of composite bonding should consider the reactivity of the bonding or coupling systems at the ceramic interface. However, for brevity in this shortened treatment only the dentin bonded interface will be considered.

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THANK YOUTHANK YOU

Thank you. [The scene above is looking through the park and a giant water fountain toward the convention center that sits on the bay. It is symbolic of tubules full of water.]