adehsives handout for classmates

8/8/2019 Adehsives Handout for Classmates

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Dental Adhesives

Terminology

Adhesive Bonding-Is the process of joining materials with the help of adhesives. Adhesion, defined as the

interaction between two surfaces. The initial substrate is called the adherend, whereas thematerial producing the interface is generally called the adhesive.

Composition

Three major ingredients that may be packaged separately or combined.

y Etchants also called conditioners are strong acid solutions that are mainly basedon phosphoric acid.

- organic (maleic, tartaric, citric, EDTA, acidic monomers),-polymeric (polyacrylic acid), and

-mineral (hydrochloric, nitric, hydrofluoric) acids

- phosphoric acid solutions and gels (37%, 35%, 10%) to produce the mostreliable etching patterns.

y Primers contain hydrophilic monomers to produce good wetting.-Acidic primers containing carboxylic acid groups are used in self-etching bonding agents. The solvents used in primers are acetone, ethanolwater, or

primarily water.

y Adhesives include typical dimethacrylate oligomers that are found in composites.

y Initiators and Accelerators: Most bonding agents are light cured and contain anactivator such as camphoroquinone and an organic amine.

y Fillers:some products contain inorganic fillers ranging from 0.5% to 40% by

weight. Filler particles include micro fillers, also called nanofillers, and sub-micron glass.

y Other Ingredients: may contain fluoride or antimicrobial ingredients. Oncebonding agent contains glutaraldehyde as a desensitizer, fluoride release from a

bonding agent has not been demonstrated.

PROPERTIES

Laboratory Properties Bond Strength produce bond strengths of 15 to 35 MPa. determined for deepdentin tend to be lower than superficial dentin.

Fatigue Strength Over long periods (>I0 years), the bonded interface willundergo extensive fatigue cycling. Weak or compromised interfaces will debond

and allow microleakage and fluid flow.

Biological PropertiesSolvents and monomers are typically skin irritants. 2 hydroxyethylmethacrylate(HEMA), is not considered biocompatible as a monomer. May produce local and

systemic reactions in dentists and dental assistants.Once the materials are polymerized, there is very little risk of side effects.


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Clinical PropertiesThe success of a bonding agent isevaluated indirectly by examining the

performanceof the restorations for:-postoperative sensitivity

-interfacial staining

-secondary caries-retention or fracture from insertion to 18 months.

Four mechanism of dental adhesive material Mechanical penetration of resin and formation of resin tags within the tooth

surface Adsorption chemical bonding into hydroxyapatite or organic component (type I

collagen) Diffusion precipitation of substances on the tooth surfaces to which can bond

mechanically or chemically. A combination of the previous three mechanisms

Indications for Adhesion Direct resin composite restorationsy caries, fractures, reshaping, masking

Bond all-ceramic restorationsy veneers, inlays, onlays, crowns

Bond amalgam

Steps in Forming Good Adhesion

Contraindications

1. Bonding Agent components are contraindicated for use with patients who have ahistory of severe allergic reaction to methacrylate resins or any of the components.2. Bonding Agent components are contraindicated for direct application to dental pulptissue (direct pulp capping).

DEVELOPMENTofDentin Bonding:

First Generation (1950-1970s)- Hydrophobic monomers- Very low bond strengths: 2 to 3 MPa


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Example: Cervident- SS White (1965)

o claimed chemical bond to calcium

Second Generation (late 70s to mid 80s)

- Phosphate-ester monomerso enhanced surface wettingo claimed chemical bond to calciumo smear layer predominately intact: fear of etching dentin

- Low bond strengths: 1 to 5 MPa

Examples: Clearfil Bond F, Scotchbond (3M ESPE, St. Paul, Minn), Bondlite (KerrCorporation, Orange, Calif), Prisma Universal Bond (Dentsply Caulk, Milford, Del)

The first- and second-generation bonding agents used did not recommend etching thedentin, but instead relied on adhesion to the attached smear layer. The weak bondstrength to the smear layer still allowed dentin leakage with clinical margin stain.

Third Generation (mid-80s)- Mechanism of action: mildly acidic hydrophilic monomer, modified/altered smear

layer- Moderate bond strengths : 3MPa13MPa- Improved short / long term success

Examples: Clearfil New Bond, Scotchbond 2 (3M ESPE, St. Paul, Minn)

The third-generation systems of the 1980s introduced acid etching of dentin and aseparate primer designed to penetrate the dentin tubules as a method to increase bondstrength. These systems increased bond strength to dentin and decreased dentin marginfailure. With time, however, margin staining caused clinical failure.

Adhesive Categories

1. Etch & Rinse

1a. Etch & Rinse (Three-Step)

Fourth Generation (early 1990s)

- Three-step Etch & rinsea. condition dentin: remove smear layerb. primerc. adhesive

-High bond strengths: 17-30MPa

Examples:All-Bond 2 (Bisco), OptiBond FL (Kerr), and Adper Scotchbond Multipurpose (3MESPE)

The fourth-generation adhesive systems of the early 1990s used chemistry thatpenetrated both etched and decalcified dentin tubules and dentin substrate, forming a


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hybrid layer of collagen and resin. These bonding agent systems have the longesttrack record as far as research goes and they perform well clinically. This system wasvery technique sensitive and required an exacting technique of controlled etching withacid on enamel and dentin, followed by two or more components on both enamel anddentin. Because of the complexity of multiple bottles and steps, dentists beganrequesting a simplified adhesive system.

1b. Etch & Rinse (Two-Step)-Conditioner-Combined primer and adhesive

- higher technique sensitivity- higher solvent-to-monomer ratio

- risk of applying too thin- apply multiple layers

Fifth Generation (late 1990s)- One-bottle, Total Etch Adhesives

-Attempt to simplify

o reduce number of bottles: combined primer and adhesive- High bond strengths

Examples:One-Step Plus ( Bisco), Bond1 (Pentron Clinical, Conn), Gluma Comfort Bond &Desensitizer (South Bond, Ind), Excite (Ivoclar Vivadent), OptiBond Solo Plus (Kerr),Prime and Bond NT (Dentsply), and Adper Singlebond (3M ESPE).

Unit-dose packaging introduced during this era provided fresh chemistry for eachprocedure. Controlled etching, surface wetness, and resin placement continued to be aclinical challenge for some clinicians.

2. Self-etch

2a. Self-Etch (Two-Step)

Sixth Generation (late 1990s)

- Self-Etching Primer system (SEPs): Non-rinsing conditioners- Combined conditioner and primer

o moderate bond strengths- Combined conditioner, primer and adhesive

o lower bond strengths

Examples:Clearfil SE Bond (Kuraray,Osaka,Japan), NRC Non-Rinse Conditioner (DentsplyDeTrey, Konstanz, Germany), Tyrian SPE (Bisco, Inc, Schaumburg, I11), Simplicity(Apex)

The separate acid-etching step was eliminated by incorporating an acidic primer thatwas placed on the enamel and the dentin after tooth preparation. Several variationsinvolved either mixing the acidic primer and adhesive before placement on the dentin


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and enamel, or leaving the primer on the tooth and then placing the adhesive over theprimer. These systems were also reported to reduce the incidence of post-treatmentsensitivity found in previous systems. However, the bond strength to dentin and enamelis lower than fourth- and fifth-generation systems.

2b. Self-Etch (One-Step)

Seventh Generation (most recent)

- All-in-one adhesiveso combined conditioner, primer and adhesive

- One-step self-etch- No mixing- Low bond strengths

Examples:Adper Prompt, and L-Pop (3M ESPE), Brush & Bond (Parkell Inc,Farmingdale,NY), iBond (Heraeus Kulzer), One-Up Bond T (Tokuyama Dental), Xeno(Dentsply)

The all-in-one adhesives are user-friendly, and most offer both a bottle and a unit-doseversion. There are variations on other attributes depending on the product used. Shearbond strength, a key attribute in dental adhesives, varies considerably depending on theself-etch adhesive used. Xeno IV self-etch seventh generation adhesive is available in abottle or unit dose delivery and does not require mixing. Xeno IV is pH balanced toreduce gingival irritation and sensitivity.

According to some independent studies provided by Kerr Corporation, OptiBond All-In-One delivers excellent penetration into dentin tubules, offering exceptional bond strengthand protection against microleakage and post-operative sensitivity.Its unique etching capability enables the most effective enamel etching of any single-component adhesive, creating a deeper-etched surface for higher mechanical retention

and chemical bonding.

Advantages of Adhesion Help offset polymerization shrinkage

y reduce marginal leakage staining sensitivity caries

Adhesiony conservation of

tooth structurey internal splinting

Esthetic restorations

Disadvantages:

. Interfacial debonding- crack formation

- propagation- subsequent joint failure.

. Interfacial contamination


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-Excess moisture-Trapped air bubbles

-Voids formed during solvent evaporation-Places of poor wetting

-Bubbles within the adhesive

-Curing shrinkage pores.

Conclusions Etch & rinse

y favorable long-term data Self-etch

y do not require rinsing demineralize and infiltrate to same depth

y reduced technique sensitivityy reduced application timey

potential decreased post-operative sensitivity??Conclusions If you prefer new trends where in it aims toward simplified application

y There will be reduced number of stepsy But, does not necessarily means it is better

Microleakage It is defined as the passage of bacteria and their toxins between restoration

margins and tooth. Bacterial can penetrate via:

1. Insufficient etch dentin2. Presence of smear layer

- So bacteria are able to survive or proliferate within the fluid filled marginal gapsand lead to pulpal inflammation.

Solution for Microleakage Remove the smear layer to seal the resin dentin interface Application of bonding agent on the resin to the tooth preparation. Or simply do the steps in good adhesion

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