Dental adhesive systems

To increase the bonding strength of dental composites to the tooth structure bond-systems were created. All bond-systems can be divided into enamel adhesives, dentine adhesives and so called “one-bottle” bonding agents that are multi-purposed (enamel adhesive and dentine adhesive in one bottle).

Enamel adhesives. Acid-etching of the enamel, that was first introduced by М.G.Вuonосоrе (1955) is desirable before the application of enamel adhesive. Acid selectively dissolves peripheral and central zones of enamel prisms, and the surface of the enamel under the electronic microscope resembles the bee combs. As the result of mechanical cutting of enamel prisms and acid-etching of the enamel active surface of bonding to the composite widens, and hydrophobic adhesives can easier penetrate into the outer layer of the enamel.

Unfilled or lightly-filled mixes of diacrilates are used as enamel adhesives, that are included in composite’s matrix. Due to their high viscosity they penetrate into the etched enamel slowly. The set adhesive forms retentive tags within the enamel, similar to an interlocking jigsaw, thus providing microretention of a composite on the surface of the enamel.

Enamel etching includes etching enamel with 37% phosphoric acid (solution or gel), that is placed on the enamel surface for 20–30 sec. Gel is more convenient, because it is visible on the enamel and the quality of application and rinsing may be controlled, it may also prevent contact of the acid with mucose and skin.

Remember, that organic formations on the tooth surface (plaque, pellicle) interfere with enamel etching. That is why the suface cleanliness is necessary for the development of adhesion. Clean the tooth surface with rubber cup or rotary brush, stripes and fluoride-free polishing paste.

Dentine adhesives (primers) differ significantly from the enamel adhesives; they are applied on wet surface, which comprises a great part of organic material. That is why dentine adhesives must be water compatible, to be hydrophilic unlike enamel adhesives.

The IV generation adhesive systems– multi-component adhesive systems that form a hybrid layer (Pro Bond (Dentsply), Scotchbond MP Plus (3M), OptiBond (Kerr)).

The IV generation adhesive systems usually consist of 3 components:

- etching gel – is a phosphoric acid as a gel, used for etching of enamel and dentin;

- primer – a mix of hydrophilic low-molecular polymerizeable compounds;

- adhesive – a resin, that bonds composite to hybrid layer and tooth enamel.

Use of the IV generation adhesives:

1) Etching. Total etching is used – etching of enamel and dentine.

Etching gel is applied over the enamel and dentin (phosphoric acid). Recommended etching time: for enamel – not less than 15 sec. for dentin – no more than 15 sec.

Rinse with water, air-dry.

2) Application of primer.

Apply primer over the etched dentin and leave it for 15-30 sec. for penetration. Lightly air-dry. Surface must look wet. If primer is applied over enamel, that does not affect the bond strength. When only enamel is etched, primer application may be omitted.

3) Application of adhesive.

A thin layer of adhesive is applied over the etched and primed surfaces of enamel, dentin and protective layering. To reduce the thickness of adhesive layer, use air blow or a brush. Application with a brush is recommended, because air-blowing may enrich the adhesive with oxygen, and that may interfere with polymerization. But air-blowing allows acquiring of a thinner and even film. Do not use a strong air-blow, because air may be trapped in the adhesive and form bubbles. When polymerized, adhesive with bubbles looks like a white line between the composite and tooth hard tissues. Light-cure with halogen light.

Advantages of the IV generation adhesive systems: they bond composites to enamel, dentine, metal, ceramics, compomer; microretention due to the formation of hybrid layer.

Disadvantages of the IV generation are multi-component structure, difficulty of use, time consumption.

The V generation adhesive systems are one-component, light-cured, no-mixing systems (Single Bond (3M), Optibond Solo (Kerr)).

They combine properties of primer and adhesive. Their composition includes special low-molecular hydrophilic resins and elastomers, diluted in water, alcohol or acetone.

The Vgeneration adhesive systems require 2-step bonding technique:

1. Etching.

Etching gel is applied over enamel and dentine (phosphoric acid). Recommended etching time– not less than 15 sec. for dentine – no more than 15 sec. Rinse with water, air-dry.

1) Application of one-component adhesive. One-component adhesive is applied over the etched dentine, enamel, pulp protective layer ad is kept for 15-30 sec. for penetration. To increase the penetration of adhesive into the dentine, some manufacturers recommend to rub it in the cavity walls, others recommend double application of the adhesive.

Air-dry the adhesive with a light air blow. Surface must look gleaming. Light cure with halogen light.

The VI generation adhesives are self-etching multi-component adhesives (Adper Prompt L-Pop and Adper Prompt (3M ESPE), Xeno III (Dentsply)).

Composition of a VI generation adhesive system (two-component). Ex.: Adper Prompt L-Pop (3M ESPE): №1 – methacrylated phosphoro-acid ethers, initiators, stabilizers; №2 – water, fluoride comound, stabilizers.

Adhesive is ready for use after mixing of 2 components.

Use of adhesive systems of the VI generation:

1) Application of adhesive to the prepared cavity (15 sec.). Blow adhesive for 4-5 sec. The surface must look wet. Light cure.

Clinical advantages of the adhesives:

- minimizes possibility of a mistake (minimum steps, no risk to take the wrong bottle, no etching, rinsing, drying);

- provides good initial and prolonged adhesion (nanoretention) to enamel and dentine without etching;

- bond strength to dentine – 18-23 mPa;

- acetone-free, hydrophilic;

- greatly reduces the postoperative sensitivity (due to the formation of a hybrid layer);

- compatible with most of dental restorative materials, compomers.

The adhesion of those materials to unprepared enamel is discussable.

The VII generation of adhesive systems – are one-step adhesives, which combine etching, application of primer and adhesive in one step. I Bond (Heraeus Kulzer) is a VII generation adhesive.

Use of I Bond:

1) Apply 3 coats of adhesive or more on the entire surface of the cavity. Lightly rub it in and mix for 30 sec. Surface must look gleaming. Lightly blow I Bond and air-dry for a few seconds. Polymerization time - 20 sec.

Clinical advantages of the adhesive: convenient, time-efficient (one-component one-bottle adhesive);no mixing is required; bond strength to dentine 18-25 Mpa; includes active component Glumа Desensitizer, thus greatly reduces the postoperative sensitivity;does not cause overwetting or overdrying of the cavity;bond strength to dentine and enamel is the same.

Adhesive systems of the VI and VII generations are the most convenient for use in pediatric dentistry, because of “impatience” of most of patients, and low mineralization of hard tooth tissues. The safe adhesion is very important also during period of tooth tissue formation.

Direct restoration with self-cured composite materials:

1. Cleaning. Clean the tooth and adjacent teeth with rubber cup, rotatory brush and pumice or a prophy paste and water.

2. Shade selection (if available).

3. Cavity preparation.

The basic principle of cavity preparation is minimal possible preparation. High adhesive properties of composites allow minimal intervention, on the contrary to Black’s principles. It is very important to remove necrotic, softened or pigmented dentine before placing the composite restoration. Remove all necrotic, discolored enamel. The enamel edge is cut on 45º - that is so called groove. It is formed for the vertical opening of enamel prisms, to increase the contact area between the enamel with adhesive and composite, to hide the cavo-marginal line. In class I and II groove should not be formed.

4. Tooth isolation from saliva.

5. Wash with water spray and air-dry.

6. Pulp protection.

7. Enamel etching. Etch the enamel for 15-20 sec. Wash thoroughly with water spray (45-60 sec.). Air-dry. Etched enamel looses its natural shine and looks matte white.

8. Bonding treatment. Bonding system is applied with a brush over the etched enamel and pulp protective layering as a thin film.

9. Placement of composite into the cavity as a single portion.

10. Finishing and polishing (after material is completely set). Finish and polish using diamond burs, polishing points and discs. To obtain a high gloss, polishing pastes can be used. Contact surfaces are polished with stripes, that can be metal, plastic or textile.

11. Postbonding. Apply an adhesive or a special varnish to the set and polished filling to fill the microcracks.

12. Fluoridation of the enamel surface, adjacent to the filling. Fluoride gel and liquid are used to remineralize the enamel. If postbonding is done, fluoridation is not necessary.

Direct restoration with light cured composite materials:

1. Cleaning. Clean the tooth and adjacent teeth with rubber cup, rotary brush and pumice or a prophy paste and water.

2. Shade selection. Shade is usually selected by referring to the "Vita" shade guide. Tooth surface and the shade guide must be wet, natural sunlight is preferred.

3. Cavity preparation (as described in direct restoration with self-cured composite materials).

4. Enamel and dentine etching. Etching time is 30 sec., 15 of which are the dentine etching time. Gel etchant is first placed on the enamel. After 15 sec. it is also applied to dentine. If the self-etching adhesive is used, this step is omitted.

5. Etching gel is rinsed off with water for 45-60 sec. Water spray must not be too strong.

6. Air-dry the cavity. Be careful not to damage the etched dentine surface, do not overdry it. Blow the air unperpendicularly to the enamel surface.

7. Bonding treatment (special peculiaties of different generations of adhesive systems are described above).

8. Placement of composite. Filling material is placed into the cavity with carvers and burnishers, preferably with Teflon or titan coating. Every layer of a composite must not be thicker than 1,5-2 mm. Layering technique of composite placement allows the maximal polymerization and reduction of shrinkage. When light-curing a composite, direct the light through enamel of previous layers of composite, if possible, in order to bond composite to the enamel or to the adjacent layers. Second light-curing is done perpendicularly to the composite’s surface. Remember, shrinkage is directed to the source of light.

Hybrid composites do not require directed polymerization technique, because they demonstrate minimal shrinkage.

9. Postbonding. Apply the enamel adhesive on the surface of polymerized and carved filling to fill the microspace on the surface of the composite and between the filling and the enamel.

10. Finishing and polishing of a composite filling is done in order to create the final shape and natural-looking gloss. Diamond finishing burs, carborund finishing burs are used. Stripes and flosses are used for contact surfaces. The last step is polishing, that is done with special polishing heads of different shapes and polishing pastes.

When working with light-cured materials follow the recommendations to reduce the polymerization shrinkage:

- use an adequate polymerization light source with the wave length 450-500 nm;

- if possible, direct the light from the side opposite to the filling material, start the light-curing through the enamel (not obligatory for hybrid materials);

- follow the recommended curing-time for every layer according to the a manufacturer’s recommendations (remember: curing-time of darker shades is longer than curing-time of the lighter shades);

- light source must be put as close as possible to the surface of filling material;

- when working with halogen lamp follow the precautions: work in protective glasses and with protective shield;

- at the completion of filling the cavity do the last light-curing (finishing light-curing) of the material. Finishing polymerization is done in Class I and V cavities – from vestibular and occlusal surfaces.

When working with light cured composite materials to restore the natural color and translucency of a tooth it is obligatory to use opaque. Usually the lost dentine is restored with the opaque or dentine shades of a composite. When the lost enamel is restored, it is important to keep in mind the difference between shades of body, cervix and cutting edge. Cutting edge usually is lighter in shade and is more translucent than tooth body. Cervical area usually has darker and more yellowish shade.

Flowable composites have a modified polymer matrix based on highly flowable resin. Usually their filling rate is 55-60% in weight. The filler is microhybrid («Filtek Flow», «Aeliteflo», «Arabesk Flow») or microfill («Durafill Flow», «Glase»). Some of materials contain fluoride («Ultraseal XT plus», «Tetric Flow»). Flowable composites are sufficiently strong, aesthetic, radioopaque, highly elastic.

Condensable («packable») composites consit of a modified „thick” polymer matrix and hybrid filler with particle size up 3,5 mcm («Solitaire» (Heraeus/Kulzer), «Filtek P-60» (ЗМ), «Synergy» (Coltene), «Piramid» (Bisco)).

Compomers - is a new class of filling materials that somehow combines properties of composites and glass-ionomer cement.

Particles of reactive fluorine-aluminium-silicate glass with additives serve as a filler. That can be silanized barium-fluorine-silicium aluminium or strontium-aluminium-fluorine-silicium glass (Dyract) with particle size 0,2-2,5 mcm. Filler’s ratio is 52-60%. Initiators, stabilizers and dye are also included in the composition. Organic matrix is a monomer that has polimerizable groops of composite resin and acid carboxyl groups of glass ionomer polymer. This is a resin with active functional acid and acrylic groups: aromatic (Bis-GMA), urethane (UDMA), alyphatic (TEGDMA), dimethacrylates (dimethacrylate monomer with two carboxyle groups in its structure). Compomers, unlike the hybrid glass-ionomer cements, do not contain water, that is why they can be a stable paste, not a powder-liquid system.

Advantages of compomers: durability,good aesthetics,excretion or fluoride,compatibility with adhesive systems, that do not require the etching.

Disadvantages of moderm compomers are contraindication for use in cavities with high occlusal intensity (ex.: MOD cavity), insufficient polishing (compared to composites), possible cavo-marginal pigmentation due to the hygroscopic widening of the material, insufficient caries-preventive effect.

Indications for compomers: class III and V lesions and cavities in permanent teeth;all classes in deciduous teeth;minimal class I and II cavities in permanent teeth (after ART preparation with the use of reinforced compomers like Dyrаct AP);temporary and semi-permanent restoration of class I and II cavities in permanent teeth;small cavities filling prior to prosthodontics (except for the ceramic crowns);fissure filling (with special hermetics like Dyract Seal);dentine substitution when using an open type “sandwich technique”;crown, bridge and orthodontic appliances cement (luting compomers like Dyract Cem);root-to-crown filling of the root canal; root wall perforations.

Дата добавления: 2014-01-05