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BDS2.5 Dental Materials - operative dentistry > Plastic restorations - resin modified glass Ionomer cements > Flashcards

Plastic restorations - resin modified glass Ionomer cements Flashcards

1
Q

What type of reaction is the polymerisation component?

A

light activated free-radical methacrylate reaction

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2
Q

What is the maximum depth of the cement which can be light cured (polymerisation)?

A

0.5mm

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3
Q

Why is the max depth of light curing for the polymerisation reaction 0.5mm?

A

limited light transmission through these material

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4
Q

What is a tri-cured glass ionomer resin?

A

material can be light cured and chemically cured

a second chemical initiator system has been incorporated into some RMGIC products to compensate for the limited light-cure polymerisation reaction

to set the resin

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5
Q

What are the 2 types of reactions in order to set the resin part?

A

polymerisation reaction - free radical methacrylate reaction effected by light activation
- light

+ redox reaction
- chemical

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6
Q

How any stages are in the dual-cured RMGIC reaction?

A

4

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7
Q

What are the 4 clinical stages of the dual-cured RMGIC reaction?

A
  1. commences when powder and liquid mixed together
  2. light activation of polymerisation reaction
  3. light activation stopped
  4. restoration complete
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8
Q

What are the 4 sages of the dual-cured RMGIC setting reaction?

A
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9
Q

What are the stages of the tri-cured RMGIC setting reaction?

A
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10
Q

Do the acid-base and polymerisation setting reactions need to be initiated at the same time?

A

yes

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11
Q

Why do the acid-base and polymerisation setting reactions need to be initiated at the same time?

A

as the material wont fully set at the same time

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12
Q

Why is does the acid-base and polymerisation reactions rarely start at the same time?

A

as the addition of HEMA retards the setting rate of the acid-base reaction

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13
Q

Why does shrinkage occur?

A

polymerisation phase

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14
Q

What kind of setting reaction occurs when HEMA polymerises?

A

exothermic

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15
Q

What are the 2 mechanisms for bonding to the tooth?

A

calcium chelation

subsidiary collagen bonding

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16
Q

What are factors limiting the success of the adhesive bond?

A
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17
Q

What can cause excessive expansion?

A

affinity for polyHEMA for water can cause excess expansion if not mixed correctly (i.e too much monomer)

18
Q

What happens as the polyEMA absorbs water?

A

mechanical properties begin to fall

19
Q

What is the fluoride release like?

A

sustained release

20
Q

When is the most fluoride released form the cement?

A

first 10-15 days

21
Q

What allows fluoride release long-term?

A

slow setting of glass ionomer phase of the cement

polyHEMA matrix provides n easier pathway for the ionic species to migrate through the cement

HEMA is hydrophilic

22
Q

What is occurring as fluoride is released?

A

the restoration is degrading

23
Q

is R,GIC prone to staining?

A

yes, intrinsic staining

24
Q

When should a tri-cure system be used?

A

where the material cannot be fully light cured

25
Q

What can occur if the material is not fully cured?

A

unconverted monomer can easily leach out from incompletely cured RMGIC

Adverse reactions reported with HEMA

risk of damage to pulpal tissue if in contact

26
Q

What are the advantages of RMGIC?

A

Fluoride ion release

early strength

adhesion - molecular bonding

long working time

limited moisture sensitivity

low solubility or erosion of cement margins

simple to use

command set

can be finished immediately after light curing (resin part might be cured but the acid -base reaction will be going on for some time)

seals dentinal tubules

27
Q

What can be released as part of the setting reaction?

A

benzoyl iodides and benzoyl bromides

28
Q

What are the benefits/disadvantages of releasing benzoyl iodides and benzoyl bromides during the setting reaction?

A

they are cytotoxic and can potentially mop up ay residual cavity bacteria

29
Q

What are the disadvantages of RMGIC?

A

EXOTEERMIC REACTION ON CURNG

SHRINKAGE ON CURING

INCOMPLETE CURE PROCEDES WEAK MATERIAL

MONOMER LEACH

SWELLIG DUE TO MOISTURE UPTAKE

powder is moisture sensitive (storage problem)

releasing benzoyl iodides and benzoyl bromid

30
Q

Why is there shrinkage on curing?

A

due to the polymer in it (resin)

31
Q

Why is phase separation a disadvantage?

A

lead to expansion and potentially fracture of the teeth

32
Q

where is the material weaker?

A

where redox setting of the resin phase is used

33
Q

When would you use the RMGIC?

A

Small-sized class I cavities

class III and V cavities

non-carious tooth surface loss lesions

core build ups

Can be used as a lining material and composite on top

deciduous teeth

blocking undercuts

bonding dental amalgam

34
Q

How much tissue do you need remaining to use RMGIC?

A

> 50%

35
Q

Why ca you use RMGI on deciduous teeth?

A
36
Q

How are RMGICs predominantly used?

A

lining material

37
Q

What does increasing the powder in the RMGIC do?

A

increase strength of the material and decrease its retention to tooth tissue and vice versa

38
Q

What 3 forms can the RMGIC come in?

A

powder/liquid

encapsulated (best)

paste/paste systems

39
Q

What does the paste/paste system claim to enhance?

A

the polishability and wear resistance

by utilising nanotechnology

40
Q

Why can the paste/paste presentations lead to non-uniform mix?

A

may become separated during storage

41
Q

Do some RMGIC requirre a primer?

A

yes

42
Q

What is the role of a primer?

A

usually infiltrate the dentine and make alternative adhesive restorations less successful

modify smear layer, wet tooth surface and facilitate adhesion of the RMGIC

BDS2.5 Dental Materials - operative dentistry (22 decks)

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