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Dental materialsDirect and indirect esthetic

restorative materials

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Midterm exam

15/11/2011Tuesday 12.15 pmLocation: 10H3,4, N2

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Direct placement restorative materials

Esthetic materials are those materials that are tooth colored.Direct placement materials, are placed directly by the clinician in prepared teeth without the need for extra-oral construction of the restoration

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Replacement of amalgam

Re-contouring a pig shaped lateral

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Uses

Maybe used for cosmetic purposes

Out of necessity

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Direct restorative materials

CompositeGlass ionomer cements (GIC)Resin modified-GICCompomers

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Composite resin

Composite: mixture of two or more components.Major components:

Resin matrixFillers Coupling agents (silane), join filler and matrixPigments

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Components Resin matrix:

bis-GMA (bisphenol A-glycidyl methacrylate). UDMA (Urethane dimethacrylate)These resins are made of oligomers (organic molecules) and low molecular weight monomers

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Fillers: silica, quartz, glasses composed of barium, strontium etc.

Why add fillers:Add strengthIncrease wear resistanceReduce polymerization shrinkage

Size of filler?Ratio or weight of filler to resin matrix?

Coupling agent: silane, binds filler to matrix and reduces wear.Pigments: to produce different colors and shades.

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Varity of filler size, A, Macrofilled.

B, Microfilled. C, Hybrid

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Polymerization Monomers join polymersInitiators and activators cause the reaction to begin.Side chains on polymers cross-link to form stronger material

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Polymerization 1. Chemical cure (self-cure): 2-paste

system:Base: composite and benzoyl peroxide as initiatorCatalyst: composite and tertiary amine activator Require manual mixing which may lead to air bubbles incorporation.

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Polymerization 2. Light cure: blue light (400-500 nm) is

used to harden the composite. 3. Depth of cure? Depends on:

1. color and location of restoration2. Thickness of the layer3. Light intensity4. Distance between light source and

restoration

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Polymerization 3. Dual cure: 2-paste system containing

both types of initiators and activators. Advantage: light starts the polymerization rxn and the chemical reaction continues in areas were light can’t reach them.

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Classification of composites

1. Macrofilled2. Microfilled3. Small-particle composite4. Hybrid5. Flowable6. Pit and fissure sealant7. Packable composite8. Smart composite9. Core build up composite

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Macrofilled composites

First generationFiller particle size 10-100 µmDifficult to polishStronger than composites with smaller particles

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Microfilled compositesFiller particle size 0.04 µm in diameterVolume of filler is 35-50% (smaller compared to other composites due to the larger volume of several small particles as opposed to one large particle of the same weight) Lower physical properties

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Small particle composite

Particle size 1-5 µmUsed to be used for posterior restorations but have been replaced by hybrid composite

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Hybrid compositeMixture of macro and microfillers (75-80% by weight)Microhybrid composite: contains 2 particle sizes, small 0.5-3 µm and microfine fillers 0.04 µm Hybrids have high polishability and strength so they can be used for anterior and posterior restorations

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Flowable composites

Low-viscosity, light curedCan be lightly filled (40%), or more heavily filled (70%)Particle size 0.07-1 µmDelivered into cavity using a syringe

Weaker and wear more compared to hybrids

Used for PRR Pit and fissure sealingLiners (cushion stress caused by polymerization shrinkage of overlying composite)Class V

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Pit and fissure sealants

Range from no filler to more heavily filled composites similar to flowable compositesLow viscosityPreventive material

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Packable composites

Highly viscousHeavily filledStiff and strongPosterior restorations (as a substitute for amalgam)Shrink less due to higher filler content

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Smart composites

Combat caries by having the ability to release fluoride, calcium, hydroxyl ions when acidity increasesEffectiveness has not yet been proven

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Core buildup composites

Heavily filledReplace lost tooth structure in teeth needing crownsColored to distinguish then from natural tooth structure

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Provisional restorative composites

Replace acrylic resin in constructing provisional onlays, crowns and bridgesMore expensive than acrylic, but wear less, and shrink less, and produce less heat when polymerized. Easier to repair with flowable compositeHowever, they are more brittle than acrylic

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Physical propertiesBiocompatibility Polished composites are tolerated by soft

tissue. Bonding agents protect pulp by sealing tubules

Strength Larger filler composites are stronger in tension and compression

Wear Lower filler content increases wear. Composites wear more than amalgams

Polymerization shrinkage

Composite shrink away from cavity wallsMinimized by incremental placement.Can cause postoperative sensitivity, &

pressure on tooth

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Shrinkage outcomes

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Thermal conductivity Low thermal conductivity, close to that of natural tooth structure

Coefficient of thermal expansion (CTE)

Greater than tooth structure, causes debonding & leakage. Filler content

CTE Elastic modulus Determined by amount of filler. Filler

increases stiffness.

Water sorption resin content water sorption

Radiopacity Barium, strontium radiopacity. Quartz (radiolucent) used as filler in anterior composites to improve shade

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Clinical handling of composites

Composite is used for all sorts of restorative procedures from class I to class IV.Selection criteria:

Esthetic demands: Microfills and microhybrids are suitedStrength demands: in posterior teeth and stress bearing areas, hybrids are more suited

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Shade guide: Some practitioners apply a portion of composite on tooth surface and cure it to observe the appropriate shade. The tabs in the shade guide should be moist and held adjacent to the tooth and observed under different lightsShelf life: follow manufacturer instructions but as a general rule, avoid heat and light. Average shelf life 2-3 years.

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Isolation

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Single paste, light activated composite

Instruments for placing composite

Syringe for injecting composite

Self-cure 2 paste composite, and bonding agent bottle

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Matrix strips/ bands: Mylar strip is used in class III, IV. Metal matrix bands are used for class II cavities (curing is from an occlusal direction then after the band is removed, light is directed from facial and lingual aspects). Clear crown forms are used for build up restorations. A wedge is also used to seal gingivally. Incremental placement: 2 mm thick is recommended:

To minimize polymerization shrinkageAllow curing light to properly penetrate and cure

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Etching and bonding:Etching is achieved using phosphoric acid ( 34-37%). After etching, tooth surface is washed and gently dried, etched enamel will appear frosty white.Bonding agent is applied in a thin layer and light-cured according to manufacturer instructions. (remember micromechanical retention).

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Etching and bonding

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Etching

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Acid etched enamel

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Resin to resin bonding: proper isolation, no contamination is necessary for proper bonding of successive composite layers. The surface layer is a thin layer of unpolymerized composite (air-inhibited), is removed by polishing

Enamel etching

Bonding agent

Composite (bonds chemicallyto bonding agent)

2nd layer of composite, etc.

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Contaminants: After etching and bonding, dentine surface should be kept contaminant free. Otherwise re-etching for 10-15 seconds is necessary. Eugenol containing cements should be avoided. Bonding agent can be used to prevent sticking of composite to instrument during filling.

Light-curing: Should be held as closely as possible to composite20-40 seconds for thin layersThicker layers, darker shades, deeper locations require more time

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Finishing and polishing: sandpaper discs, fine, ultra-fine diamonds.Abrasive strips and needle-shaped diamond burs are used. Polishing pasts can also be used.Surface sealers: unfilled resin maybe added after cleaning and etching the surface. It is thought to be useful to reseal margins opened by polymerization shrinkage, or surface porosities.

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Light curing unitsHalogen light bulbs are used as a light source. Light delivery probe or tip is glass or glass encased in metal or plastic casing. Should be covered in a disposable cover

Cordless curing unitsPlugged into an electric outlet

High intensity light units: curing timePlasma arc curing units (PAC)Argon laser units

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Precautions for light curing

1. Inadequate light output: monthly check on light source, to examine output (using radiometers), any scratches on light probes or darkening due to disinfection.

2. Premature set of composites: caused by operatory light which should be moved away during placement of composite.

3. Eye protection: light-shielding protective device, glasses for patient.

4. Heat generation: may cause pulp irritation in deep cavities (1 mm or less of dentine).

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Light curing unit, protective glasses and shield

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Compomers Composites modified with polyacid (polyacid-modified resin). The resin contains MMA and polycarboxylic acid. Light activation chemicals are included and also fluoride containing glasses. Fluoride release is small compared to conventional GIC due to resin binding the glass fillers after light activation.Setting rxn occurs in 2 stages

Same as light-cured compositeAcid-base rxn

Bonding to tooth structure occurs as in composites

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Indirect esthetic materialsInlaysOnlaysVeneersPFM All-ceramicCrowns with composite resin facing Indirect composites

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Indirect composite restorations

Veneers: can be porcelain or composite. Veneers are used to treat staining, close diastemas, lighten teeth color, reshape crooked teeth.

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Indirect composites: inlays, onlays, veneers. Preparation is done in the clinic, followed by an impression and construction of the restoration on a die, then cementation in the preparation. With resin cements and bonding agent.

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Laboratory processed composites

Procedure: Preparation is performed by dentistImpression and bite registration Restoration constructionCementation

Shrinkage occurs outside the cavity, therefore less stress is created as opposed to direct restorations

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Restorative materials used: Conventional compositeFiber reinforced composite. Fiber source is carbon Kevlar, glass fiber, polyethylene ( to improve strength).Particle-reinforced composite: heavily filled (70-80% by weight) with ceramic particles to improve wear resistance.

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Indirect chair-side technique

Tooth preparationAlginate impressionPoured in fast setting die stone or PVS die material (sets in 2 minutes)Composite restoration is made and light curedAdjustment and cementation

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Shade taking

Patient

Dentist Assistant

1. Hue

2. Chroma

3. value

54Vita shade guide and shade selection

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Guidelines for taking the shade:Group effortShould be taken before preparationTaken before rubber dam placementTeeth should be clean, free of stains and moistTwo different lights should be used (Metamerism): dental offices usually have fluorescent light (blue), or incandescent light (yellow). Natural light is a good source except in morning or late afternoon (more yellow and orange, and less green and blue)

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Continue, A neutral background should be used (e.g. blue apron)Female patients should be asked to remove lipstick, and colorful clothes should be coveredSeveral tabs are held close to patients teeth and kept moist. Separate shades for cervical part of the tooth might be necessary.

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Characterizing the shadeSurface texture (affects light scatter from tooth) and luster (the degree to which the surface appears shiny) should be noted. These two properties affect how the tooth reflects light and scatter it.The amount of translucency (especially near the incisal edge) should also be noted.

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Continue,

Any surface characteristics should be replicated if the patient demands that the restoration matches existing teeth. A photograph of the patients teeth and adjacent shade guide tab maybe helpful.

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Reference

Dental materials, clinical applications for dental assistants and dental hygienistsChapter 6