Direct Restoratives

Chapter 5 – 6

Dental Materials

DAE/DHE 203

Part I: Metallic Restorations:

Amalgam Restorations Gold Foil Restorations Matrices and Margins

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

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

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

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

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.

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

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!

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

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

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

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!

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

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

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.

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)

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

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

Part II: Esthetic Restorations

Polymers & PolymerizationDentin & Enamel AdhesivesDental CompositesGlass IonomersCompomer Restoratives

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)

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

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

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

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

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!

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

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

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

Esthetic Restoration: Posterior Composite

Decay: #30 MOD, plus restoring buccal pit

Cavity Prep drill, etch, prime & bond

Restored

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

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

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:

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)

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

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

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

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

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

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

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

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

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)

Part III: Preventive Restorations

Dental (Enamel) Sealants Preventive Resin Restorations

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

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

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