GICs

Question 1

types

Answer 1

conventional: anhydrous vs original

resin modified: self/light cure

Question 2

uses

Answer 2

restorative filling material
core build up
lining
luting cement
FS
dressing

Question 3

chemistry

Answer 3

acid - liquid

base - glass powder

Question 4

chemistry - liquid

Answer 4

polyacrylic acid
tartaric acid (control setting characteristics)

Question 5

tartaric acid

Answer 5

control setting characteristics

Question 6

chemistry - base - glass powder

Answer 6

SiO2
Al2O3
CaF2
strontium and lithium salts

Question 7

strontium and lithium salts

Answer 7

increase radiopacity

no role in reaction

Question 8

aluminium/silica ratio

Answer 8

alters translucency

more silica = more translucent

Question 9

variations in composition

Answer 9

anhydrous

encapsulated

Question 10

anhydrous

Answer 10

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

Question 11

encapsulated

Answer 11

consistent

Question 12

variations

Answer 12

powder particle size

molecular weight of acid

Question 13

variations - powder particle size

Answer 13

<20um for luting cement to give low film thickness

smaller=quicker setting reaction=more opaque set cement

Question 14

variations - molecular weight of acid

Answer 14

higher = better mechanical properties

but more viscous - difficult to mix

Question 15

setting reaction

Answer 15

acid base

glass+acid = salt+silica gel

Question 16

setting reaction stages

Answer 16

dissolution
gelation
hardening

Question 17

dissolution

Answer 17

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

Question 18

gelation

Answer 18

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

Question 19

hardening

Answer 19

form aluminium polyacrylate
trivalent - better mechanical properties
takes long time

Question 20

protection

Answer 20

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

Question 21

protection mechanisms

Answer 21

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

Question 22

handling

Answer 22

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

Question 23

aesthetics

Answer 23

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

Question 24

mechanical properties

Answer 24

poor tensile strength
low compressive strength
poor wear resistance
low hardness

Question 25

F release

Answer 25

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

Question 26

bonding

Answer 26

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

Question 27

good bond requires:

Answer 27

clean surface | conditioned surface - polyacrylic acid

Question 28

physical properties

Answer 28

``` 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 ```

Question 29

thermal properties

Answer 29

good - expansion similar to dentine

Question 30

cermets

Answer 30

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

Question 31

disadvantages

Answer 31

``` 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 ```

Question 32

advantages

Answer 32

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

Question 33

RMGIC chemistry

Answer 33

powder and liquid

Question 34

RMGIC chemistry - powder

Answer 34

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

Question 35

RMGIC chemistry - barium glass

Answer 35

radiopacity

Question 36

RMGIC chemistry - redox catalyst

Answer 36

potassium persulfate

Question 37

RMGIC chemistry - liquid

Answer 37

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

Question 38

RMGIC chemistry - tartaric acid

Answer 38

speeds setting

Question 39

RMGIC chemistry - H2O in liquid

Answer 39

allows reaction between poly acid and glass

Question 40

advantages of RMGIC

Answer 40

``` bonds to E and D better physical properties lower solubility F release handling better translucency and aesthetics ```

Question 41

dual curing

Answer 41

``` 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

Question 42

tricuring

Answer 42

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

Question 43

RMGIC disadvantages

Answer 43

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