Dentine bonding agents

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Dr syed sohaib gilani

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Dentine bonding agents :

Dentine bonding agents Dr Syed Sohaib Daud

Adhesion:

Adhesion The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking or both. (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.

Mechanism of resin bonding:

Mechanism of resin bonding Mechanical Adsorption Diffusion Combination of three

Adsorption:

Adsorption

Dentine adhesion :

Dentine adhesion Dentine bonding relies primarily of the penetration of adhesive monomer into the filigree of collagen fibers left exposed after etching with acid.

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Acid washing / rinsing Removes smear layer Dissolves HA Drying shrinks remaining Collagen polymer molecules Rehydration / priming Swells collagen Mechanism of dentine bonding

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Monomer penetration Mechanism of dentine bonding Monomer polymerisation And collagen entanglement

Challenges in dentine bonding :

Challenges in dentine bonding Dentine contains substantial amount of water and organic material as compared to enamel. It contains dens network of tubules . Smear layer prevents the penetration of adhesive into tubule by forming smear plug.

Development :

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 no ionic bonding develops between NPG-GMA and hydroxyaptite .

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1 st generation: Smear layer Adhesive resin Composite 1950-1970’s

Second generation :

Second generation Clearfill bond was the first product of second generation of dentine adhesives. It was a phosphate ester(phenyl-p and hydroxyethylmethacrylate [HEMA] in ethanol). Its mechanism of action was based on the polar interaction between negatively charged phosphate groups in the resin and positively 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 of hydrophilic groups posed major problems. Resistance to water was low.

Third generation :

Third generation The concept of acid etching was first introduced in 1979 by Fusayama . Clearfill new bond was introduced in 1984 and contained HEMA and 10-carbon molecule known as 10-MDP(10-methacryloxyethyl decyl dihydrogenphosphate ). Some materials were designed to modify smear layer and allow 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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3rd generation: 1 st step: -Total etching Leaving free minerals on surface -Rinse surface -Total drying of surface 2nd step : adding primer 3 rd step: Adding adhesive resin ,Then adding Composite Smear layer Residual water Primer Adhesive 3rd generation Composite

Fourth generation/Three step total etch adhesive:

Fourth generation/Three step total etch adhesive Fourth generation of dentine adhesives was introduced for use on acid etched dentine. This technique is also known as total etch or etch and rinse technique. Application of acid results in partial or total removal of smear layer and demineralization of underlying dentine up to depth of 7.5 microns.

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Fourth generation dentine adhesive include three components A phosphoric acid gel that is rinsed off. A primer containing reactive hydrophilic monomers in ethanol, acetone, or water. An unfilled or filled resin bonding agents containing hydrophobic monomer ( Bis -GMA) combined with hydrophilic molecules (HEMA).

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Acid etching also alter the free surface energy of dentine which is undesirable. Primer in three step technique is designed to increase critical surface energy of dentine. When primer and bonding agents are applied they results in formation of a hybrid layer and resin tags. This generation was proved successful both in vivo and in vitro with dentine resin bond strength of 13-80 Mpa .

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4th generation: 1 st step: -Total etching(removal of smear layer) Leaving free minerals on surface -Rinse surface - Without drying of surface ( residual water left) 2nd step : adding primer 3 rd step: Adding adhesive resin & then composite 4th generation Composite Smear layer Residual water Primer Adhesive resin

Fifth generation/one bottle, Total etch:

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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Primer Adhesive 5th generation: 5th generation Primer mixed with adhesive

Sixth generation/self-etching primer system:

Sixth generation/self-etching primer system These self etching primers, first introduced in Japan, include a phosphonated resin molecule that performs function of priming and etching simultaneously. They do not require rinsing off. The bonding mechanism is based on the simultaneous etching of enamel and dentine, forming a continuum in the substrate and incorporating smear plugs into the resin tags. It simplifies the bonding technique. Elimination of rinsing and drying reduce the possibility of over wetting or over drying. SEPs are less technique sensitive.

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Less discrepancy between the depth of demineralization and depth of resin infiltration. Less postoperative sensitivity. One disadvantage is that they do not etch enamel as well as phosphoric acid.

Self-etching primer adhesive system:

Self-etching primer adhesive system

Seventh generation/self etching adhesives(all in one):

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 contact the composite material directly. Presence of this un reacted acidic monomer is responsible for their incompatibility with self cured resin. These adhesives act as semi permeable membrane and hence result in degradation of dentine resin interface. These resin monomer might be too hydrophilic which make them susceptible to water degradation.

Comparison of the Classification and Components of Dental Adhesive Systems:

Comparison of the Classification and Components of Dental Adhesive Systems STEP 4 TH GEERATION 5 TH GENERATION 6 TH GENERATION 6 TH GEN (MIXING REQUIRED) 7 TH GEN SELF ETCHING ADHESIVE SELF ETCHING ADHESIVE Etching of enamel dentine Etchant Etchant Self etching primer Self-etching, self-priming resin/sealer Self-etching, self-priming resin/sealer desensitizer, disinfectant Priming of dentin Primer Self-priming resin/sealer Self –etching primer Self-etching, self-priming resin/sealer Self-etching, self-priming resin/sealer desensitizer disinfectant Sealing of enamel and dentine Resin/sealer Self-priming resin/sealer Resin/sealer Self etching, self priming resin/sealer Self-etching, self-priming resin/sealer desensitizer disinfectant

Comparison of the Number of System Components and Clinical Placement Steps of Dental Adhesive Systems:

Comparison of the Number of System Components and Clinical Placement Steps of Dental Adhesive Systems Generation steps Description Components 1 st 2 Etch enamel, apply adhesive 2 2 nd 2 Etch enamel, apply adhesive 2 3 rd 3 Etch enamel, apply primer 2-3 4 th 3 Total etch, apply primer 3-5 5 th 2 Total etch, apply adhesive. 2 6 th 1 Apply self etch adhesive 2 7 th 1 Apply self etch adhesive 1

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Thank you