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BDS4 CDS Restorative, Pros & Endo > Rest: Materials > Flashcards

Rest: Materials Flashcards

Includes composite, bonding to enamel/dentine.

1
Q

COMPOSITE

What are the five components of composite ?

A
  • Glass filler particles i.e. alumina, silica, borosilicate.
  • Resin i.e. BisGMA.
  • Photoinitiator i.e. camphorquinoine.
  • Silane coupling agent.
  • Low weight dimethacrylates i.e. TEGDMA.
    *
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2
Q

COMPOSITE

What is the benefits/disadvanatges of smaller filler particle size vs. large ?

A
  • Small filler particles - better aesthetics, poorer mechanical properties.
  • Large filler particles - better mechnical properties, likely to stain and poorer aesthetics.
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3
Q

COMPOSITE

What is the function of resin ?

A
  • Resin is involved in setting reaction.
  • Long monomer chains with C=C.
  • Undergoes activation by photoinitiator.
  • Causes free radical polymerisation.
  • Crosslinking occurs generating monomer growth.
  • Which results in increased viscosity and mechnical properties.
  • Hydrophobic end also bonds with DBA.
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4
Q

COMPOSITE

What is the purpose of camphorquinoine ?

A
  • Photoinitiator.
  • Acivtated by blue light.
  • Causes release of free radical which initiates free radical polymerisation of resin.
  • Resulting in increased molecular weight, viscosity and mechnical properties.

Always some unreacted monomer - risk of leaching and pulp irritation.

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5
Q

COMPOSITE

What is the purpose of silane coupling agent ?

A
  • Removes moisture from the surface of glass particles which allows resin and glass particle bonding.
  • Methoxy group hydrolyses hydroxy group.
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6
Q

COMPOSITE

What is the purpose of low weight dimethacrylates ?

A

Changes viscosity and polymerisation rate.

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7
Q

COMPOSITE

What is the standard depth of cure for composite ?

A

2mm.

Knoop Hardness Test (ISO 4049).

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8
Q

COMPOSITE

What problems can arise which might affect light cure systems ?

A
  • Premature setting due to dental light.
  • Optimistic depth of cure (use increments - 2mm).
  • Polymerisation shrinkage (risk of cuspal fracture and microleakage).
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9
Q

COMPOSITE

List some benefical properties of enamel.

A

Aesthetics. Smooth surface. Biocompatible. Anticariogenic. Radiopaque. Low thermal diffusivity and conductivity. Similar mechnical properties to dentine.

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10
Q

COMPOSITE

What is the biggest disadvantage with composite’s properties ?

A
  • High thermal expansion coefficient.
  • High polymerisation contraction.
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11
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

Bonding to enamel - what material is used ?

A

37% phosphoric acid.

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12
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

How does acid etch improve bonding to enamel ?

A
  • Etch roughens long enamel prisms containing hydroxyapetite crystals - changing the structure to a ‘keyhole’ appearance.
  • Etch also increases the surface energy of enamel by removing the smear layer and increases surface wettability.
  • This allows micromechnical bonding of resin through interlocking.
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13
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

Explain why bonding to dentine is more difficult than bonding to enamel.

A
  • Non-inert surface and continuously releases water which prevents flow of DBA into the dentinal tubules and results in low surface energy.
  • There are also varying sizes/densities of dentinal tubules.
  • Also has smear layer.
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14
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

What properties should dentine bonding agent have ?

A
  • Low viscosity.
  • Able to make intimate contact with dentine.
  • Allow adhesion with resin.
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15
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

In what two ways does dentine bonding agent facilitate bonding between resin and tooth surface ?

A
  • Allows for interlocking forming mechnical bond.
  • Molecular entanglement occurs forming chemical bond.
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16
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

What are the three components of dentine bonding agent ?

A
  • Dentine conditioner.
  • Primer.
  • Adhesive.
  • Photoinitiator.
17
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

What is the function of a dentine conditioner in DBA ?

A

Removal of smear layer.

18
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

What is the purpose of primer (HEMA) in DBA ?

A
  • Forms hydrophillic bond with dentine (hydroxyl group and collagen).
  • Forms hydrophobic bond with resin (C=C).
19
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

What is the purpose of adhesive (BisGMA or HEMA) in DBA ?

A
  • Helps with micromechnical bond by infiltating tubules and encourages molecular entanglement.
  • Forms hybrid layer by encorperating collagen and smear layer into bond.
20
Q

BONDING SYSTEMS - COMPOSITE TO ENAMEL/DENTINE

What is the difference between total etch vs. self etch ?

A
  • Total etch - removes entire smear layer.
  • Self etch - encorporates smear layer (organic materials) into bond, resulting in hybrid layer.
21
Q

CAVITY LINING MATERIALS

What is the aims of a cavity lining material ?

A
  • Protection from thermal and chemical irritation.
  • Protection from bacterial microleakage.
  • Reduce inflammation and pain.
22
Q

CAVITY LINING MATERIALS

How thin should cavity lining material application be ?

A

0.5mm

23
Q

CAVITY LINING MATERIALS

What are the ideal properties of a cavity lining material ?

A
  • Low thermal properties - prevent recurrent nerve stimulation.
  • High mechnical properties - used under deep restorative materials.
  • Provide good marginal seal - prevent microleakage.
  • Be radiopaque - to see secondary caries formation.
  • Cariostatic - prevent microleakage.
24
Q

CAVITY LINING MATERIALS

Name three different types of cavity lining materials.

A
  • CaOH.
  • ZOE or resin modified ZOE.
  • Glass ionomer.
25
Q

CAVITY LINING MATERIALS

What is the setting reaction for CaOH lining material ?

A
  • Chelation setting reaction.
  • Zinc oxide (base) and butylene glyco disilicate (catalyst).
26
Q

CAVITY LINING MATERIALS

What is the properties of CaOH lining material ?

A
  • Bactericidal (pH12).
  • Pulpal irritant causing necrosis of odontoblasts & causing teritary dentine formation.
27
Q

CAVITY LINING MATERIALS

What are the disadvantages of CaOH lining material ?

A
  • Low compressive strength.
  • Soluble and unstable.
  • Requires RMGI to be placed over the top.
28
Q

CAVITY LINING MATERIALS

What are the benefits of using RMGI as cavity lining material ?

A
  • Bonds and seals dentine - prevents microleakage.
  • Resin filling materials can bond.
  • Low thermal conductivity & diffusivity.
  • Thermal expansion coeffient similar to dentine.
  • High compressive strength.
  • Provides good marginal seal.
  • Benzoyl idodines and bromides released as products from polymerisation reaction have bactericidal effects.
29
Q

CAVITY LINING MATERIALS

What is the main disadvantage of using RMGI as cavity liner ?

A
  • Possibility of unreacted monomer (HEMA).
  • Cytotoxic and causes pulpal irritation.
30
Q

CAVITY LINING MATERIALS

When should CaOH (Dycal) and RMGI (Vitrebond) be used ?

A
  • CaOH - direct or indirect pulp caps with RMGI over the top to prevent dissolution of CaOH.
  • RMGI on its own - on deep cavities under amalgam & composite restorations.
31
Q

CAVITY LINING MATERIALS

ZOE cavity lining can ONLY be used under what material ?

A

Amalgam - prevents resin setting in composites.

But poor compressive strength - not used first choice for cavity lining.
Can be used as temporary restorations, root canal sealant, PD dressings.

BDS4 CDS Restorative, Pros & Endo (13 decks)

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