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DMS :( > GICs > Flashcards

GICs Flashcards

1
Q

types

A

conventional: anhydrous vs original

resin modified: self/light cure

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2
Q

uses

A 
restorative filling material
core build up
lining
luting cement
FS
dressing
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3
Q

chemistry

A

acid - liquid

base - glass powder

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4
Q

chemistry - liquid

A 
polyacrylic acid
tartaric acid (control setting characteristics)
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5
Q

tartaric acid

A

control setting characteristics

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6
Q

chemistry - base - glass powder

A

SiO2
Al2O3
CaF2
strontium and lithium salts

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7
Q

strontium and lithium salts

A

increase radiopacity

no role in reaction

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8
Q

aluminium/silica ratio

A

alters translucency

more silica = more translucent

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9
Q

variations in composition

A

anhydrous

encapsulated

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10
Q

anhydrous

A

acid freeze dried and added to powder
liquid distilled water
easier handling

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11
Q

encapsulated

A

consistent

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12
Q

variations

A

powder particle size

molecular weight of acid

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13
Q

variations - powder particle size

A

<20um for luting cement to give low film thickness

smaller=quicker setting reaction=more opaque set cement

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14
Q

variations - molecular weight of acid

A

higher = better mechanical properties

but more viscous - difficult to mix

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15
Q

setting reaction

A

acid base

glass+acid = salt+silica gel

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16
Q

setting reaction stages

A

dissolution
gelation
hardening

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17
Q

dissolution

A

H+ ions attack surface of glass
Ca, Al, Na, F ions released
leaves silica gel around unreacted glass

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18
Q

gelation

A

form calcium polyacrylate
Ca ions crosslink with polyacid by chelation with the carboxyl groups
Ca ions bivalent - can react with 2 carboxyl groups on the same molecule

19
Q

hardening

A

form aluminium polyacrylate
trivalent - better mechanical properties
takes long time

20
Q

protection

A

from moisture and desiccation following gelation
- when ‘set hard’ in mouth but before maturation begun
contamination
- excessive drying
- absorb water

protection at later date if working on other areas of mouth

21
Q

protection mechanisms

A

varnishes
resins - best
greases/gels e.g. vaseline

22
Q

handling

A

better now due to tartaric acid - working time similar but setting time shortened

23
Q

aesthetics

A

lack translucency (opaque)
increased silica content better
translucency improves over 24+ hours when extra X-linking
not suitable where aesthetics really important
once set less susceptible to staining and colour change than composite

24
Q

mechanical properties

A

poor tensile strength
low compressive strength
poor wear resistance
low hardness

25
Q

F release

A

can release F without damage to their structure
initial fluoride release but diminishes v quickly
F reservoir/sink - can take it up from the env then release when ambient conc falls

26
Q

bonding

A

bonds to E and D
low bond strength compared to composite
cohesive strength low
good sealing ability

chelation between carboxyl groups in cement and Ca on tooth surface
H bonding/metallic ion bridging to collagen
acid base reaction between poly acrylic acid and Ca ions in HA

27
Q

good bond requires:

A

clean surface

conditioned surface - polyacrylic acid

28
Q

physical properties

A 
higher solubility than composite
 - dissolution during gelation
 - long term erosion by acids
no contraction on setting
lower modulus - cervical margin - flexing is good as tooth moves when bite
29
Q

thermal properties

A

good - expansion similar to dentine

30
Q

cermets

A

developed to overcome GI brittleness
silver added to glass to increase toughness and wear resistance
just ended up making a silver GIC

31
Q

disadvantages

A 
brittle
poor wear resistance
moisture susceptible when first placed
poor aesthetics
poor handling characteristics
susceptible to acid attack and drying out over time
possible problems bonding to composite
32
Q

advantages

A 
stable chemical bond to E and D
low microleakage
F release
good thermal properties
no contraction on setting
much easier to use than composite
33
Q

RMGIC chemistry

A

powder and liquid

34
Q

RMGIC chemistry - powder

A 
F-Al-Si glass
barium glass (radiopacity)
vacuum dried polyacrylic acid
potassium persulfate (redox catalyst)
ascorbic acid
pigments
35
Q

RMGIC chemistry - barium glass

A

radiopacity

36
Q

RMGIC chemistry - redox catalyst

A

potassium persulfate

37
Q

RMGIC chemistry - liquid

A 
HEMA - water miscible resin
polyacrylic acid with pendant methacrylate groups - acid base and polymerisation reactions
tartaric acid
H2O
photoinitiators
38
Q

RMGIC chemistry - tartaric acid

A

speeds setting

39
Q

RMGIC chemistry - H2O in liquid

A

allows reaction between poly acid and glass

40
Q

advantages of RMGIC

A 
bonds to E and D
better physical properties
lower solubility
F release
handling
better translucency and aesthetics
41
Q

dual curing

A 
acid base reaction
 - starts initially on mixing
free radical methacrylate reaction
 - light activation
 - complete 20s

acid base reaction continues within resin matrix for several hours

42
Q

tricuring

A

will set even if insufficient light penetration
- but in absence of light physical properties reduced by 25%

acid base
redox (continues around 5mins)
free radical methacrylate reaction

43
Q

RMGIC disadvantages

A

polymerisation contraction
exothermic setting reaction - both polymerisation and dark cure
swelling due to uptake of water - HEMA extremely hydrophillic
monomer leaching
reduced strength if not light cured
light curing slows down acid base reaction
benzoyl iodides and bromides can be released which are cytotoxic
moisture sensitive

DMS :( (18 decks)

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