Restorative Materials Flashcards by Haider Chaudhry

What are the components of dental amalgam?

Liquid mercury (Hg)
Powder (metal alloy)

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What might a typical modern alloy contain in amalgam?

69% Silver
19% Tin

11% Copper
1% Zinc

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Which phase is responsible for corrosion, creep and decrease in strength?

Gamma 2

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The addition of what metal reduces the amount of gamma2?

Copper

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What are the differences between spherical and lathe cut particles?

Spherical: softer and more flowable
Lathe cut: less flowable, good for building up large amounts of missing tooth structure

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What are good properties of amalgam?

Good compressive strength, Good wear resistance, kind to opposing teeth, easy to use, chemical set, cheap, radiopaque

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What are disadvantages of amalgam?

Non adhesive, weak in thin sections, thermal conductor, unaesthetic, thermal expansion, corrosion
!! CREEP !! With use over time it deforms, localised reaction (Lichenoid reaction), plaque retentive factor if not handled properly

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What are the clinical indications of using amalgam?

class 1 and class 2 (where they are missing a marginal ridge)
where heavy occlusal forces are encountered
where aesthetics are not important
building up broken down teeth prior to crowning

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What should the cavo surface angle be for an amalgam cavity prep?

> 90 degrees

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What should the amalgam margin angle be?
(Where restoration meets prepared surface of the tooth to the margin of the restoration)

> 70 degrees

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What should the ideal cavity design be for an amalgam preparation?

must be 2mm deep minimum
undercut (wider at the base than at the top) - margins are not parallel

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Why are pins not used anymore?

Can drill into the pulp and make it non-vital
If it is too close to the ADJ it might weaken the tooth and cause fractures

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How long do you need to wait before you can polish amalgam?

24hrs

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What is the biggest reason for replacing restorations?

Secondary caries

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What is the risk of secondary caries in composite vs amalgam?

3.5x greater in the composite group
(The larger the restoration, the better amalgam performs compared to composite)

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What are the ingredients of composite?

Resin
Filler
Coupling agents
Pigments

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What is the composition of a composite?

Resin matrix and filler (and coupling agent)

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What are some of the advantages of composite?`

Conserved tooth structure whereas amalgam needs to be retentive
Aesthetics
Low thermal conductivity

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What are some of the disadvantages of composite?

Technique sensitivity (rubber dam)
Polymerisation shrinkage (cause marginal gaps, bacteria gets in, secondary caries)
Decreased wear resistance

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What type of polymerisation reaction does composite set by?

Free radical ADDITION polymerisation

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What are the steps in free radical?

Activation
Initiation
Propagation
Termination

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What are the ingredients in composite?

Resin, filler, coupling agents, pigments

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Why are fillers added to the resin matrix?

Makes it more stronger and without its not as good on its own

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What are some examples of filler particles?

Silica particles, quartz, glass

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What does filler size determine with composites?

Determines surface smoothness

Would a larger particle filler size be more or less rough than a smaller particle?

More rough

What properties would increasing the filler content do?

Increase in hardness/strength Increase in abrasion resistance Handling Aesthetics (As the filler content increases, the resin content decreases)

What does the coupling agent do?

Binds the filler particles (inorganic) to the resin matrix (organic)

What do pigments do in composites?

Provide translucency and opacity Tend to be metal oxide (titanium oxide/aluminium oxide)

How are composites usually classified?

Usually based on filler size

What can shrinkage lead to?

Microleakage Plaque could build up Secondary caries Can lead to staining/sensitivity

What are the contraindications for composite?

- where moisture control can’t be achieved (extend beyond gum margin/sub gingival) - composite polymerisation is reduced in the presence of Eugenol (it stops the composite from setting) - very deep restorations (?? Pulpal irritation due to unset monomers)

What is the purpos What is the purpose of etch on enamel?

- creates a micro porous layer - increases surface area creating micro pores - increases wettability

What is the purpose of etching dentine?

- removes the smear layer - unblocks and widens dentinal tubule orifices - exposes network of collagen fibres

What does coarse mean?

How rough something is

Indications for composite?

- aesthetics - diastema’s - change colour (fluorosis) - Bruxism

What is bruxism?

Clenching/grinding

What does GIC consist of?

Ion leach able glass (glass powder) and long poly acid chains in water

What are the 3 main stages for the setting reaction for GIC?

1. Dissolution 2. Gelation/hardening 3. Maturation (increased hardening/properties of the material)

What happens in dissolution stage of ~GIC?

1. Add water to the poly acid chain (comes as a powder)

What does Glass Ionomer particles contain?

Silica, calcium, aluminium, fluoride (Calcium-alumino-fluoro silicate glass

What happens in the maturation phase of GIC?

More and more calcium and aluminium ions cross loins with the acid chains (takes time)

Benefits of GIC?

Easy to use (doesn’t need a bond, tolerates moisture) Chemically bonds to enamel and dentine Releases fluoride

How does GIC adhere to dentine?

H+ released from poly acid chains can act similar to “etch” and attack tooth surface which releases calcium from the tooth and that can diffuse into the Glass ionomer

What can be used to improve chemical adhesion with GIC?

Dentine conditioning - 10% poly acrylic acid, leave for 20 seconds, wash and then dry - cleans the tooth surface prior to placing glass ionomer - removal of the smear layer

Disadvantages of GIC?

Weak compared to other materials Poor aesthetics compared to composite Poorer survival time compared to other materials

What does the addition of resin to GIC do to the properties?

Better aesthetics Command set More resistant to losing ions during maturation Stronger

WHat are the down sides of RMGIC?

Don’t chemically bond to the tooth Lower fluoride release Polymerisation shrinkage

What does adding smaller glass particles to GIC do?

Stronger

What is FUJI IX good for?

Suitable for molars (fairly long term temporary)

Problems with current GICS?

Weak (fracture easily, wear is high) Complicated to use (conditioning and coating required) Waiting time ( sticky at first, short workable time)

What is an example of a zinc-reinforced GIC?

CHemfill Rock

What are the advantages of Chemfil rock?

- bonds to enamel - bonds to dentine - no conditioning and varnish required - good if haven’t got long for a restoration (eg: cant get good moisture control) - Fluoride release

how long does chemfil rock last for?

Several months or around 2 years (semi-permanent)

Is Chemfil Rock suitable for anterior teeth?

No due to poor aesthetics

What GIC would you use for cavities extending below the CEJ?

RMGIC or GIC

What GIC would you use for temporisation?

Traditional GIC (eg: Fuji Triage - contrasting coloured)

When would you use traditional GIC (chemfil, Fuji triage, Fuji 9)

Subgingival restorations, temporary restorations, stepwise excavation - conditioner needed and varnish as soon as finished

When would you use RMGIC? Eg: Fuji II LC

Better aesthetics Cervical restorations Non-load bearing restorations - conditioner needed, light cure but no varnish Bonded amalgam where retention isn’t good

When would you use zinc reinforced GIC? Eg: chemfil ROCK

Long term temporary Caries management Fissure sealant

Restorative Materials Flashcards

(60 cards)