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8/4/2019 Lecture 3 & 4- Composites (Slides)
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en a
materials
Direct and indirect esthetic
restorative materials
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Midterm exam
15/11/2011 Tuesday 12.15 pm
Location: 10H3,4, N2
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Direct placement restorativematerials
Esthetic materials are those materials thatare tooth colored.
Direct placement materials, are placeddirectly by the clinician in prepared teethwithout the need for extra-oral construction
of the restoration
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Replacement
o f amalgam
Re-contour ing
a p ig shapedla te ra l
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Uses
Maybe used forcosmetic purposes
Out of necessity
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Direct restorative materials
Composite
Glass ionomer cements (GIC)
Resin modified-GIC
Compomers
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Composite resin
Composite: mixture of two or morecomponents.
Major components:
Resin matrix
Fillers
Coupling agents (silane), join filler and matrix Pigments
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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 molecularweight monomers
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Fillers: silica, quartz, glasses composed ofbarium, strontium etc.
Why add fillers:
Add strength Increase wear resistance
Reduce 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 polymers
Initiators and activators cause the reaction to begin.
Side chains on polymers cross-link to form strongermaterial
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Polymerization1. Chemical cure (self-cure): 2-paste
system:
Base: composite and benzoyl peroxideas initiator
Catalyst: composite and tertiary amineactivator
Require manual mixing which may leadto air bubbles incorporation.
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Polymerization2. Light cure: blue light (400-500 nm) is
used to harden the composite. These
light curable composites containcomponents that start to react oncesubjected to the light:
1. Diketone2. Organic amines
Depth of cure? Depends on color and
location of restoration
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Polymerization
3. Dual cure: 2-paste system containingboth types of initiators and activators.Advantage: light starts thepolymerization rxn and the chemical
reaction continues in areas were lightcant reach them.
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Classification of composites
1. Macrofilled2. Microfilled
3. Small-particle composite4. Hybrid5. Flowable6. Pit and fissure sealant7. Packable composite8. Smart composite9. Core build up composite
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Macrofilled composites
First generation Filler particle size 10-100 m
Difficult to polish Stronger than composites with smaller
particles
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Microfilled composites
Filler particle size 0.04 m in diameter
Volume of filler is 35-50% (smallercompared to other composites due to the largervolume 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 m
Used to be used for posterior restorationsbut have been replaced by hybrid
composite
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Hybrid composite Mixture of macro and microfillers (75-80% by
weight)
Microhybrid composite: contains 2 particle sizes,small 0.5-3 m and microfine fillers 0.04 m
Hybrids have high polishability and strength sothey can be used for anterior and posterior
restorations
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Flowable composites Low-viscosity, light cured
Can be lightly filled (40%),or more heavily filled (70%)
Particle size 0.07-1 m
Delivered into cavity using
a syringe
Weaker and wear morecompared to hybrids
Used for PRR
Pit and fissure sealing
Liners (cushion stress
caused by polymerizationshrinkage of overlyingcomposite)
Class V
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Pit and fissure sealants
Range from no filler to more heavily filledcomposites similar to flowable composites
Low viscosity
Preventive material
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Packable composites
Highly viscous Heavily filled
Stiff and strong Posterior 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 torelease fluoride, calcium, hydroxyl ionswhen acidity increases
Effectiveness has not yet been proven
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Core buildup composites
Heavily filled Replace lost tooth structure in teeth
needing crowns
Colored to distinguish then from naturaltooth structure
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Provisional restorative composites
Replace acrylic resin in constructingprovisional onlays, crowns and bridges
More expensive than acrylic, but wear
less, and shrink less, and produce lessheat when polymerized. Easier to repair
with flowable composite However, they are more brittle than acrylic
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Physical properties
Biocompatibility Polished composites are tolerated by softtissue. Bonding agents protect pulp by
sealing tubules
Strength Larger filler composites are stronger intension and compression
Wear Lower filler content increases wear.Composites wear more than amalgams
Polymerization
shrinkage
Composite shrink away from cavity walls
Minimized 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 thermalexpansion (CTE)
Greater than tooth structure, causesdebonding & leakage. Filler content
CTE
Elastic modulus Determined by amount of filler. Fillerincreases stiffness. Important in
selection for anterior & posteriorrestorations
Water sorption resin content water sorption
Radiopacity Barium, strontium radiopacity. Quartz(radiolucent) used as filler in anteriorcomposites to improve shade
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Clinical handling of composites Composite is used for all sorts of
restorative procedures from class I toclass IV.
Selection criteria:Esthetic demands: ability to match tooth color
and achieve high polishability. 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 aportion of composite on tooth surface andcure it to observe the appropriate shade.
The tabs in the shade guide should bemoist and held adjacent to the tooth and
observed under different lights Shelf life: follow manufacturer instructions
but as a general rule, avoid heat and light.
Average shelf life 2-3 years.
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Dispensing and cross-contamination:composites are usually dispensed insyringes. Disposable small containers are
used to avoid cross-contamination. Oncecomposite is dispensed, it should be
covered with a light-protected container
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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 bandis removed, light is directed from facial and lingual
aspects). Clear crown forms are used for build uprestorations. A wedge is also used to seal gingivally.
Incremental placement: 2 mm thick isrecommended:
To minimize polymerization shrinkage
Allow 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 iswashed and gently dried, etched enamel willappear frosty white.
Bonding agent is applied in a thin layer andlight-cured according to manufacturerinstructions. (remember micromechanical
retention).
Etching and bonding
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Etching and bonding
Bonding
and
light
curing
Etch ing
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Acid etched enamel
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Resin to resin bonding:proper isolation, nocontamination is
necessary for properbonding of successivecomposite layers. Thesurface layer is a thinlayer of unpolymerized
composite (air-inhibited), is removedby polishing
Enamel etching
Bonding agent
Composite (bonds chemicallyto bonding agent)
2nd layer of composite, etc.
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Contaminants: After etching and bonding, dentinesurface should be kept contaminant free. Otherwise re-etching for 10-15 seconds is necessary. Eugenolcontaining cements should be avoided. Bonding agentcan be used to prevent sticking of composite toinstrument during filling.
Light-curing: Should be held as closely as possible to composite
20-40 seconds for thin layers
Thicker layers, darker shades, deeper locationsrequire more time
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Finishing and polishing: sandpaper discs,fine, ultra-fine diamonds. For gingival orinterproximal areas, scalpel knife, abrasive
strips and needle-shaped diamond bursare used. Polishing pasts can also beused.
Surface sealers: unfilled resin maybeadded after cleaning and etching the
surface. It is thought to be useful to resealmargins opened by polymerizationshrinkage, or surface porosities.
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Light curing units
Halogen light bulbs are used as a light source.Light delivery probe or tip is glass or glassencased in metal or plastic casing. Should becovered in a disposable cover
Cordless curing units Plugged into an electric outlet
High intensity light units: curing time
Plasma arc curing units (PAC) Argon laser units
Precautions for light curing
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Precautions for light curing
1. Inadequate light output: monthly check on lightsource, to examine output (using radiometers), any
scratches on light probes or darkening due todisinfection.
2. Premature set of composites: caused by operatory
light which should be moved away during placement ofcomposite.
3. Eye protection: light-shielding protective device,
glasses for patient.
4. Heat generation: may cause pulp irritation in deepcavities (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-modifiedresin). The resin contains MMA and polycarboxylic acid.
Light activation chemicals are included and also fluoridecontaining glasses. Fluoride release is small comparedto conventional GIC due to resin binding the glass fillers
after light activation. Setting rxn occurs in 2 stages
Same as light-cured composite
Acid-base rxn Bonding to tooth structure occurs as in composites
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Indirect esthetic materials Inlays
Onlays Veneers
PFM All-ceramic
Crowns with composite resin facing Indirect composites
I di t it
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Indirect compositerestorations
Veneers: can beporcelain or composite.Veneers are used to treatstaining, close diastemas,lighten teeth color,reshape crooked teeth.
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Indirect composites:inlays, onlays, veneers.Preparation is done inthe clinic, followed by an
impression andconstruction of therestoration on a die,
then cementation in thepreparation. With resincements and bonding
agent.
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Laboratory processed composites
Procedure:Preparation is performed by dentist
Impression and bite registration
Restoration constructionCementation
Shrinkage occurs outside the cavity,therefore less stress is created asopposed to direct restorations
R t ti t i l d
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Restorative materials used:
Conventional composite
Fiber reinforced composite. Fiber source is
carbon Kevlar, glass fiber, polyethylene ( toimprove strength).
Particle-reinforced composite: heavily filled
(70-80% by weight) with ceramic particles toimprove wear resistance.
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Indirect chair-side technique Tooth preparation
Alginate impression
Poured in fast setting die stone or PVS die
material (sets in 2 minutes) Composite restoration is made and light
cured
Adjustment and cementation
Sh d t ki
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Shade taking
Patient
Dentist Assistant
1. Hue
2. Chroma
3. value
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Guidelines for taking the shade: Group effort by dentist, assistant and patient
Should be taken before preparation
Taken before rubber dam placement Teeth should be clean, free of stains and moist
Two different lights should be used (Metamerism):
dental offices usually have fluorescent light (blue), orincandescent light (yellow). Natural light is a goodsource except in morning or late afternoon (more
yellow and orange, and less green and blue)
Continue
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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 cervicalpart of the tooth might be necessary.
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Characterizing the shade Surface texture (affects light scatter from
tooth) and luster (the degree to which thesurface appears shiny) should be noted.These two properties affect how the toothreflects light and scatter it.
The amount of translucency (especially
near the incisal edge) should also benoted.
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Reference Dental materials, clinical applications for
dental assistants and dental hygienists
Chapter 6