Composite Amalgam and gold were the primary restorative materials for posterior teeth. Some forms of metals were used in anterior teeth. Later a variety of direct-placement tooth-colored restorative materials were introduced



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116 DDA

Dr. Ru'a Baba'ier













Composite

  • Amalgam and gold were the primary restorative materials for posterior teeth.

  • Some forms of metals were used in anterior teeth.

  • Later a variety of direct-placement tooth-colored restorative materials were introduced.

  • In the 1960s composite resins were introduced & have been continually improved on ever since by making them more durable & color stable.

Direct-Placement Esthetic Restorative Materials

They can be placed directly into the cavity preparation or onto the tooth surface by the clinician w/o first being constructed outside of the mouth.



  • Esthetic Materials are those that are tooth colored.

  • The most commonly are:

  • Composite resin.

  • Glass ionomer cement.

  • Resin-modified GIC.

  • Compomer.

Composite Resin

  • A composite is a mixture of two or more materials with properties superior to any one component.

  • Are used in both the anterior & posterior parts of the mouth.

Composition

They are composed mainly of an organic resin (polymer) matrix & inorganic filler particles joined together by a silane coupling agent that sticks the particles to the matrix.



  1. Organic resin (polymer) matrix

Thick liquids made up of 2 or more organic molecules that form a matrix around filler particles.

  1. Inorganic filler particles

Fine particles of quartz, silica, or glass that give strength & wear resistance to the material.

  1. Silane coupling agent

A chemical that helps bind the particles to the matrix.

  1. Initiators & accelerators that cause the material to set.

  2. Pigments that give color matching the tooth.

Polymerization

It is a chemical reaction that occurs when low-molecular-weight resin molecules (monomers) join together to form long-chain, high-molecular-weight molecules (polymers).



scan0004.jpg

Classification of composite based on polymerization:

  1. Chemical Cure

  • Also called Self-cured composite resins, are two-paste systems (base & catalyst), supplied in jars or syringes.

Disadvantages:

  • Limited working time.

  • Voids & porosity due to manual mixing.

  1. Light Cure

  • They are the most common type used.

  • An intense visible light in the blue wave range activates these materials.

  • The depth of the cure depends on the location and the color of the restoration. The darker shade needs more curing time.

  1. Dual Cure

  • They are two-paste systems that contain the initiators & activators of both the light-activated &, to a smaller amount, the chemically activated materials.

  • The curing light initiates the setting reaction. The chemical setting reaction continues in areas not reached by the light.

Physical Properties of Composite

  • Biocompatibility

  • Strength

  • Wear

  • Polymerization Shrinkage

  • Thermal Conductivity

  • Coefficient of thermal Expansion

  • Elastic Modulus

  • Water sorption

  • Radiopacity

Classification of Composite

Macrofilled Composites

  • Relatively large particles as fillers, ranging in size 10-100 µm. scan0003.jpg

  • Difficult to polish, rough surface.

  • Stronger than composite w/ smaller particles.

  • No longer widely used.

Microfilled Composites

  • Much smaller particles as fillers, average about 0.04 µm. scan0003.jpg

  • Have a larger total surface area than one large particle of similar weight.

Therefore the volume of filler in microfilled composites is only 35% to 50%.

  • This results in poorer physical properties.

Hybrid Composite

  • Contain both macrofillers & microfillers in order to produce a strong composite that polishes well. scan0003.jpg

  • Their filler content is 75% to 80% by weight.

  • Microhybrid composites contain a mixture of small particles (0.5-3.0 µm) & microfine particles (0.04 µm).

  • Hybrids are versatile because of their strength & polishability.

  • Can be used as both anterior & posterior restorations.

Flowable Composites

  • Are low-viscosity, light-cured resins that may be lightly filled 40% or more heavily filled 70%.

  • The particles average in size 0.07-1.0 µm.

  • These composites flow readily & can be delivered directly into cavity preparations by small needles from the syringes in which they are packaged.

  • They adapt well to cavity walls & flow into microscopic irregularities created by diamonds & burs, because of their low viscosity.

  • They are well suited for use in conservative dentistry (PRR).

  • Many dentists use them in place of conventional pit & fissure sealants (higher filler content– more wear resistant).

  • They are useful as liners in large cavity preparations. Their low elastic modulus (more flexible) allows them to cushion stresses created by polymerization shrinkage or heavy occlusal loads when they are used as an intermediate layer under hybrid & packable composites.

  • They are useful for restoration of class V non-carious lesions as toothbrush abrasion, acid erosion, or occlusal stresses leading to abfraction.

  • They shrink when polymerized more than the hybrids, wear more & are weaker.

Pit and Fissure Sealants

  • They are low-viscosity resins that vary in their filler content from no filler to more heavily filled resins (same as flowable composites).

  • Used for prevention.

Packable Composites

  • Also called condensable composites.

  • They are highly viscous resins that contain a high volume of filler particles, which gives them a stiff consistency.

  • They shrink less when polymerized than less heavily filled composites, because there is less resin & more filler.

  • They are used for restoration of posterior teeth in areas of high function (stronger & more wear resistant).

  • They are marketed as substitutes for amalgams.

Core Buildup Composites

  • They are heavily filled composites used in badly broken-down teeth needing crowns.

  • They replace missing tooth structure lost from dental caries or tooth fracture so that there is adequate structure to retain a crown.

  • These composites can be light-cured, self-cured, or dual-cured.

  • They contain pigments that colorize them so that they can be easily differentiated from natural tooth structure.

Provisional Restorative Composites

  • They are used in place of acrylic resins for the construction of provisional onlays, crowns, & bridges.

  • They are more expensive but they wear less & shrink less, & release less heat as they cure.

  • They can be repaired easily with flowable composites.

  • They are more brittle than acrylic & tend to break more easily w/ longer-span bridges.

Clinical Handling of Composites

Uses of composite resins

  • They are used in all classes of restorations, from (I through VI).

  • Also used for provisional restorations, core-buildups. Fiber-reinforced posts, & laboratory –fabricated onlays & bridges.

Selection of Materials

This depends on:



  • The position weather anterior or posterior.

  • Is it in an area subjected to occlusal stresses or not?

Shade Guides

  • Many manufacturers include a shade guide w/ color tabs.

  • The color tab should be moist, held adjacent to the tooth to be restored, & viewed under different lighting conditions.

  • Apply & cure a small quantity of composite selected onto the clean, moist tooth before isolation if needed.

  • It may be necessary to mix a couple of different colors together to achieve the desired color match or to add special color modifiers.

Shelf Life

  • In general, avoiding heat & light can extend the shelf life. (Refrigerating)

  • The average shelf life is 2 to 3 years if stored properly.

Dispensing and Cross-contamination

  • Light –cured composites are supplied in compules or syringes.

  • All of these containers are opaque so that the material is not affected by light.

  • Single-use (unidose) as compules which are small containers of composite resin that fit into a delivery gun.

  • The delivery tip on syringes of flowable composites should be disposed of in a sharps container after use, & the syringes should be recapped & sprayed w/ disinfectant.

  • Composite in screw-type syringes should be dispensed after the shade is selected & covered in a light-protected container until used.

  • Chemical-cured composites come in jars or screw-type tubes.

Matrix Strips/ Bands

  • For class III & IV anterior restorations, a clear plastic (Mylar) matrix strip is used to contain & shape the composite.

  • For class II restorations. Metal matrix bands or precontoured plastic matrix strips that help shape the contact area are used.

  • Metal matrix bands are either circumferential bands or sectional bands.

  • A clear matrix forms for class V cavities are also available.

  • Appropriately sized & trimmed clear crown forms are used for rebuilding large portions of the tooth.

  • A wedge may be placed to seal the gingival margin or separate teeth to make up for the thickness of the matrix band.

  • Wedges can be wooden or transparent plastic.

Incremental Placement

  • For most moderately sized or large cavity preparations, the composite resin should be placed in small increments about 2mm thick.scan0007.jpg

  • Benefits:

  1. It minimizes polymerization shrinkage.

  2. It permits light from the curing unit to adequately penetrate & cure each increment.

Resin-to-Resin Bonding

  • Etched enamel & dentin is infiltrated with resin bonding agents to form the resin-rich hybrid layer.

  • The initial increment of composite resin will chemically bond to the resin bonding agent on the E & D.

  • Each additional increment will bond to the previously placed increment.

Contaminants

  • Newly etched D is kept moist for wet Dentin bonding.

  • After Dentin bonding any form of moisture (water, saliva, gingival fluids or blood) should be kept away from the tooth until the restoration is completed. (if it is contaminated we have to re-etch for 10-15 sec)

  • Don’t use alcohol to wet the plastic instrument. Instead, use bonding agent to prevent sticking.

  • Liners, bases, or temporary fillings containing eugenol should not be used because it inhibits the set of resins.

Light-curing

  • The light probe should be held as close as possible to the composite w/o touching it.

  • Typical curing times for thin layers are 20 to 40 seconds.

  • The light probe & handle are covered w/ a disposable barrier such as a clear plastic cover.

Finishing and Polishing

  • Excess composite can be removed w/ multifluted carbide finishing burs, fine & ultrafine diamonds, and sandpaper disks.

  • Small excesses at the gingival margin or interproximal can be removed w/ scalpel blade (no. 12), needle-shaped burs or diamonds, or abrasive strips.

  • Polishing can be achieved by using successively finer sandpaper disks and interproximal polishing strips; by rubber polishing points, cups, disks impregnated w/ abrasives; & by polishing pastes.

Clinical steps:

  1. Shade selection.

  2. Local anesthesia.

  3. Isolation using the rubber dam.

  4. Tooth preparation.

  5. Cleaning the tooth and cavity with pumice.

  6. Dry the cavity lightly.

  7. Apply the suitable matrix band and wedge.

  8. Apply the acid etchant (phosphoric acid 37%) for 15-20 seconds.

  9. Wash thoroughly then dry gently for 2-5 seconds. Don't over dry the dentin.

  10. Apply the primer with the microbrush and dry it with air then apply 2 layers of the bonding agent, air thin it then light cure it for 10-20 seconds as recommended. Note: some composite kit have the primer and the bonding agent in one bottle so after etching we add the bonding agent.

  11. Apply the composite with a plastic instrument in increments of 2mm in thickness and light cure each increment separately. The condenser and burnisher can be used in adapting and forming the composite.

  12. Remove the matrix and start finishing and polishing using the instruments explained earlier.

  13. Check the occlusion with an articulating paper.

References:

  • Refer to the practical manual for further explanation and pictures and different brands of composite.

  • Book: Dental Materials by Hatric and others.





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