Direct Restoratives Chapter 5 – 6 Dental Materials DAE/DHE 203.
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Transcript of Direct Restoratives Chapter 5 – 6 Dental Materials DAE/DHE 203.
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Direct Restoratives
Chapter 5 – 6
Dental Materials
DAE/DHE 203
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Part I: Metallic Restorations:
Amalgam Restorations Gold Foil Restorations Matrices and Margins
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Amalgam:
Metal Alloy + Mercury = Amalgam Alloy – a mixture of metals
– Copper, silver, tin, zinc
Mercury (Hg) – a metal with a low melting point making it liquid at room temperature– Makes the metal mixture moldable at room temp.– Allows for a direct restoration– A toxic metal – the root of current public concern
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Amalgam:
Used in dentistry for almost two hundred years Versatile, inexpensive, durable material Self-seals its interface (with corrosion products)
Does not chemically bond to tooth No studies of any major national & international
health organizations have ever linked it to disease or chronic illness
Considered safe & effective by industry & the profession
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Amalgam:
Using “high-copper” alloy since 1960’s
Compared to low-copper amalgams:– Require less mercury in the mix– Have increased strength– Less marginal breakdown– Less corrosion– Less creep (dimensional change under a constant stress)
Pre-dosed capsule:– Convenient– Less handling of mercury– Proper/consistent mix of amalgam
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Amalgam:
COMPOSITION OF HIGH-COPPER ALLOY
METAL % CHARACTERISTIC
SILVER 40-70% strength, corrosion,
expansion
TIN 22-30% expansion,
mixes with copper
COPPER 13-30% strength & hardness
ZINC 0-1% used in manuf. process
55 – 60 % ALLOY + 40 - 45% MERCURY
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Amalgam:
Three forms (shapes) of alloy:
1. Lathe-cut – “shavings” of metal Rough & sharp edges, irregular shape
2. Spherical – sprayed & “frozen” metal droplets Round or ovoid shaped
3. Admixed – lathe cut + spherical
Handling characteristics of amalgam vary with alloy shape.
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Amalgam: Mixing
GOAL: thorough mixing of alloy with mercury
“trituration”,“amalgamation” 5-20 seconds
Ideal - “plastic” mass– Shiny, moldable, cohesive
Over-triturated – – sticky, shiny
Under-triturated –– dull, dry, crumbly
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Amalgam: The Procedure
Tooth prepped, isolated, apply matrix Liner, base, varnish, as needed Triturate (per manufacturer) Dispense (amalgam carrier), repeat as needed Condense, repeat as needed Carve Check & adjust/carve occlusion & interproximally Burnish Polish – after 24 hoursPatients to avoid chewing/grinding for about 8 hours!
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Amalgam Setting:
High Copper Amalgam: Gamma-1 phase
– Silver combining with mercury– Form a crystalline matrix– 40% of total volume of filling
Tin reacts with Copper– Tin-copper compounds
Initial setting time = 5 minutes from trituration Final amalgamation continues for several hours
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Amalgam & Longevity:
Research: 20 years Private: 8 - 10 years Why replace amalgams?
1. Secondary decay2. Bulk fracture3. Marginal breakdown
Marginal gap decay?? Bonding agents help?
sensitivity life of margin strength & reinforce bond
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Amalgam & Corrosion:
Less of a problem with
high-copper amalgams Surface darkened by
tarnish Marginal breakdown Surface pitting – galvanism Reduced by:
– Thorough condensing– Burnishing & polishing– Good OH, acidity
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Mercury Handling Safety:
Avoid skin contact with mercury – wear gloves & eyewear, use kit to clean-up a spill!
Avoid mercury vapor – wear mask! Re-cap capsule immediately after opening/dispensing Dispose of empty capsules in a sealed plastic bag Place amalgam scraps in a sealed container
under x-ray fixer solution Use HVE & water when removing/drilling amalgam
When amalgam is set, mercury is bound to other metals!
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The Public Controversy:
"There is no sound scientific evidence supporting a link between amalgamfillings and systemic diseases or chronic illness," ADA President Robert M. Anderton says. "This is a position shared by the ADA and all major U.S. public health agencies and is a matter of public record."Spaeth, Dental Practice Report, Jul/Aug, 2002
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The Public Controversy:
“CDC officials also say there is no proof that removal of amalgam can cure some illnesses as ADA protesters claim. ‘While there have been a number ofcase studies and anecdotal reports about adverse effects from amalgam, no published controlled studies have demonstrated systemic adverse effects,’says the CDC. ‘There is also no scientific evidence that general symptoms are relieved by removal of existing amalgam restorations.”
Spaeth, Dental Practice Report, Jul/Aug, 2002
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The Public Controversy:
Legislative bills are being introduced in states around the country by anti-amalgamists to abolish the use of mercury in dental amalgams or the use of dental amalgam altogether.
Anti-amalgam organizations have filed lawsuits against amalgam manufacturers and the ADA and local dental associations for “conspiring” to hide the truth about amalgam from the public.
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The Public Controversy:
“To Haley, the great amalgam debate is simple. Mercury is toxic. Keep it out of the mouth.
End of story.” “Can I prove that chronic exposure causes any one specific disease? Well, that takes a long time to do that kind of research. It’s hard to prove that.”…
Removing amalgam would take “an oxidated stress off the the body – a very significant one.”Boyd Haley, PhD; Chemistry Dept., University of Kentucky
Spaeth, Dental Practice Report, Jul/Aug, 2002 (www.dentalproducts.net)
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Direct Gold Fillings:
AKA “gold foil” Not used presently Great material, but
– NOT esthetic– Costly– Difficult procedure & time-consuming
Gold firmly condensed into “prep” & burnish – – Foil, mat or powdered gold
Pure gold can “weld” w/o heat Class V, buccal or lingual pits, small Class I
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Matrices & Margins:
Margins of a restoration are to be “flush” with the tooth surface – this may be most difficult interproximally
A matrix builds a border or “wall” for the restoration Wedges are placed to conform the matrix to the tooth Margin errors: Open margin – a gap is left between tooth & restoration Flash – a small amount of restorative above cavosurface margin Overhang – a large amount of restoration outside of margin Submarginal – the prep is “under-filled”
“Margination” – the removal of overhangs
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Part II: Esthetic Restorations
Polymers & PolymerizationDentin & Enamel AdhesivesDental CompositesGlass IonomersCompomer Restoratives
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Polymers & Polymerization:
POLYMERS: Long-chain of organic “monomers”
– “Bis-GMA”; “urethane dimethacrylates”– Comprised of carbon-carbon double bonds (C=C)– Monomers linked together thru Polymerization
POLYMERIZATION:– Creating a polymer through chemical reaction– Three methods (auto-, photo-, dual-cure)
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Polymerization:
Autopolymerization: “self-, or chemical- cure”– Monomer base + initiator (2 pastes/solutions)
– Chemical initiator in the catalyst
– Mixing of pastes begins reaction
– Setting time varies with product
– Disadvantages: no control of “working time”;
have to be mixed
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Polymerization:
Photopolymerization: “light-cure”– One paste– Reaction initiated by visible blue light (not
UV!)– Advantages: control of working time; no
mixing – less chance for bubbles– Disadvantages: must cure incrementally;
keep material from light
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Tips for Photopolymerization:
Hold light source (tip) as close to tooth surface as possible (1-2 mm)
Cure buccal, lingual & occlusal surfaces with Class II & III
Use eye protection – operator and assistant!
Follow manufacturer’s directions for exposure time
Test light intensity periodically
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Polymerization:
Dual-Cure:– Combination of auto- & photo- polymerization– 2 paste system + light-cure– Operator mixes pastes, applies material & light cures– Advantage: reassurance that material is curing at
depth of restoration
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Enamel & Dentin Adhesives:
Why? To improve the bond of the restoration with the tooth (dentin/enamel)
When? After the cavity prep is complete What? A 3-step process: etch, prime & bond;
enhances chemical bond between bonding agent (resin) and restoration
Remember! Don’t desiccate (dry-out) dentin!
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Enamel & Dentin Adhesives:
1. Acid Etching: Improves the retention of the restoration Increases the surface area of the dentin Removes “smear layer” from prep Allows for penetration of bonding agent into dentin Protect pulp exposures before using! Phosphoric acid (35-37%) gel or liquid Isolate teeth, apply etchant, wait (5-15 seconds) Rinse – don’t desiccate! – blot prep to remove water
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Enamel & Dentin Adhesives:
2. Primer: Resin - monomer Improves wettability of prep Penetrates etched dentin tubules Applied in a thin layer; thinned with air; blot May require light-curing
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Enamel & Dentin Adhesives:
3. Bonding Adhesive: Un-filled or lightly filled resin Adhesive bonds to collagen fibers in dentin –
mechanically “locks-in” – “Hybrid Layer” Applied in a thin, uniform layer Light-cured 10-20 seconds New “generations” being developed
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Esthetic Restoration: Posterior Composite
Decay: #30 MOD, plus restoring buccal pit
Cavity Prep drill, etch, prime & bond
Restored
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Dental Composites:
Mixture of materials: polymers (resins) + glass particles (fillers)– plus pigments for shade variety– plus silane as a coupling agent (bond fillers to resin)
– plus chemical to initiate the polymerization Many types available:
– Filler material, particle size, and filler volume vary– Conventional, Microfill, Hybrids
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Dental Composites:
A challenge for users of resins…
“Polymerization Shrinkage” When monomer molecules are polymerized they take up
less space/volume than when uncured (2% shrinkage)
Solutions: – Incremental Curing: Allow for curing between layers– Use dentin bonding adhesives in prep site
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CONVENTIONAL COMPOSITES:
Resin base + large quartz fillers (50-60%) Good strength & hardness Difficult to polish well – rough surface Stains and discolors; poor esthetics Uses: not used for restorations anymore; may
be used as an ortho cement
Dental Composites:
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Dental Composites:
MICROFILLED COMPOSITES: Resin base + silica particle fillers (30-55%) Weaker material ( fillers) Very high polish – excellent esthetics May be used as final layer of deep restoration Use: Great for anterior restorations (III, V)
(NOT Class IV)
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Dental Composites:
HYBRID COMPOSITES: Resin + quartz or glass fillers (65-70%) Small or midsize particles
– Minifills (largest particles are 1 – 2 um)– Midfills ( average particle size is 3 – 8 um)– Metals added to glass to make them radiopaque
Combination of esthetics & durability Universal use
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Dental Composites:
“Flowable” Composites:– Hybrid with smaller and
fewer particles– Dispensed thru canula tip– Maybe OK for Class V
“Packable” Composites:– Hybrid with larger and
more particles– Condensed with an
instrument
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Dental Composites:
Handling Tips: Prevent cross-contamination of self-cure solutions Take care to not incorporate bubbles upon mixing Protect light-cure solutions from white light exposure Protect composites from heat Store composite materials in the refrigerator Should have 2-year shelf life May use metal instruments and matrices
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Dental Composites:
Able to use a more conservative prep Offer great esthetics – perhaps even tinting Biggest reasons for failure in anteriors are discoloration
& recurrent caries – adhesion is the key! Reason for failure in posterior is marginal failure &
secondary caries Should have a 5 –10 year duration (Posterior & Class IV
have lesser duration) May have limited success with Class V fillings The composites can be layered to build strength &
adaptation to prep/margins
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Glass Ionomers:
Used for liner, luting cement & restoration Powder: liquidInorganic Glass & Organic Polymer + water/acid
– glass: calcium aluminofluorosilicate– particle size: restorations 40 um - thicker
lining/luting 25 um – more flow
– Liquid: polyacrylic acid + tartaric acid + water– plus pigments for shades
Adheres to tooth surface & releases fluoride
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Glass Ionomers:
Used for Class III and V restorations (non-stress bearing areas)
Some forms strengthened with metal particles for use as a core build-up material (gray color)
Shrinkage of 3-4% - not as detrimental to bond Tooth must be moist for adhesion Soluble in water – protect with resin or varnish Not yet equal to esthetics of composites
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Glass Ionomers:
Conventional G.I.’s:– Liquid + powder– Mix on paper pad or glass slab with spatula – Add ½ powder at a time– Finish mix in 30 seconds
OR– Triturate capsule for 10 seconds– Place into tooth (“working time” = 2.5 minutes)
– Use matrix to form surface– Will appear glossy when mixed
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Glass Ionomers:
RESIN-MODIFIED GLASS IONOMER: Resin added to mixture Light-cure material - one paste – no mixing! Uses: liners, bases
– Added fillers have allowed use of
Resin-Modified G.I.’s as core material or “packable” primary molar Class I material
Not recommended for high-stress areas
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Compomer:
A combination restorative material =Composite + Glass Ionomer
Packaged and handle like composites Formulated to releases fluoride – less than G.I.’s Excellent esthetics Not widely used as direct restorative A few products on the market
(Brands: Compoglass, Dyract, 3M F2000)
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Part III: Preventive Restorations
Dental (Enamel) Sealants Preventive Resin Restorations
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Dental Sealants:
Applied to the pits & fissures of healthy enamel
Prevent decay as long as sealant retained on tooth
Provides a physical barrier against decay-causing food/bacteria
Non-invasive; conservative Use acid-etch technique on
enamel surface to be sealed
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Dental Sealants – Composition:
Highly flowable monomer (resin) material
– Unfilled vs, Filled
Self-cure or light-cure Layer of air-inhibited uncured resin Many various delivery systems Opaque, clear, tinted May be glass ionomer
www.nidcr.nih.gov/health/pub/sealants
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Preventive Resin Restoration “PRR”:
Conservative, preventive restoration When frank decay is present in a groove or pit
of the occlusal surface Combines a composite filling with an enamel
sealant. Both procedures are performed.– Decay is removed with a small, round bur– Composite is placed to fill the prep site– Sealant is placed to protect the filling & rest of tooth