Glass Polyalkenoates

Question 1

what are GI’s derived from?

Answer 1

silicate cements

polycarboxylate cements

Question 2

what are polycarboxylate cements?

Answer 2

zinc oxide with polycarboxylic acid

set cement = adhesive to tooth, poor appearance, poor mech properties

Question 3

replace zinc oxide of polycarboxylate cements with what? Advantage?

Answer 3

replace zno with ion leachable glass
better appearance
less soluble
better mech. properites

Question 4

Glass ionomer came about when?

Answer 4

1970’s

Question 5

GI comes as?

Answer 5

powder to liquid
powder mixed with water
encapsulated

Question 6

powder of GI?

Answer 6

sodium aluminasilicate glass plus 20% caF

Question 7

liquid of GI?

Answer 7

aqueous solution of acrylic/iatonic acid copolymer

plus tartaric acid to control setting

Question 8

GI setting reaction essentially?

Answer 8

an acid base reaction

Question 9

unreacted what left?

Answer 9

glass cores

Question 10

powder/water gi, powder?

Answer 10

sodium aluminasilicate glass + 20% caf

plus vacuum dried polyacid

Question 11

powder reconstituted by mixing with?

Answer 11

either water or dilute aqueous solution of tartaric acid

Question 12

proportioning of powder and liquid

Answer 12

scoop/dropper bottle

encapsulated

Question 13

how to mix GI

Answer 13

spatula

mechanical by oscialltory/rotary

Question 14

what does hand spatulation cause?

Answer 14

more air incorporation

increased porosity

Question 15

porosity of viscous cements?

Answer 15

low porosity

Question 16

porosity causes stress of material which causes?

Answer 16

cracks

Question 17

properites of powder to water gi altered by?

Answer 17

p:l ratio

if encapsulated = consistent

Question 18

cored structure description?

Answer 18

outer is rich in calcium

inner rich in aluminium

Question 19

calcium 2+ allows?

al 3+

Answer 19

2 arms for cross linking the acid chain

3 arms

Question 20

in the initial set reaction what is there more of?

Answer 20

calcium ion predominates over al

Question 21

why is there more calcium in the initial set reaction?

Answer 21

calcium is at the outer surface so is the 1st thing the acid meets
calcium is more mobile in solution that Al
more likely that 2 chains will come along rather than 3

Question 22

why is mixing difficult if GI stored in the fridge?

Answer 22

initiates acid crystallisation

Question 23

how does GI bonded to the tooth?

Answer 23

by calcium ions

Question 24

how does GI bond to collagen?

Answer 24

by H bonding - metallic ion bridging

Question 25

how might bonding be boosted?

Answer 25

with a tooth cleanser

Question 26

what does citric acid do?

Answer 26

removes the smear layer | gives no increased bond strength

Question 27

what does polyacrylic acid do?

Answer 27

increases the bond strength

Question 28

can only enhance the bond strength to what point?

Answer 28

to the limit of the tensile strength of the glass polyalkenoate cement greater than tensile strength = failure of cement

Question 29

thermal diffusivity of GI close to? chemical set of GI is? what can GI release and uptake?

Answer 29

dentine exothermic fluoride

Question 30

GI has poor? is it brittle? what is GI susceptible to?

Answer 30

poor abrasion resistance brittle acid erosion = synergy of acid and mechanical wear

Question 31

GI has a lack of? | what is its appearance like?

Answer 31

lack of radiopacity | good appearance

Question 32

what are cermets?

Answer 32

Ag pellized mixture of glass and metal particles

Question 33

are cermets able to release fluoride? | appearance is?

Answer 33

yes some | poor appearance

Question 34

cermets have an increased?

Answer 34

compressive strength and fatigue limit

Question 35

what is modified composite?

Answer 35

The filler is replaced with aluminosilicate glass - aims to encourage F release

Question 36

how is modified composite set?

Answer 36

by light cured free radical polymerisation

Question 37

reaction of modified composite?

Answer 37

no acid base reaction until later in process | resin contains acidic groups, once resin is set, water enhances and ionises then acid base takes place

Question 38

what is a Giomer?

Answer 38

aluminasilicate glass is pre reacted with polyacid to give a prereacted glass polyalkenoate complex

Question 39

2 types of reaction of a giomer?

Answer 39

1) surface reaction - reaction happens at surface. Gives better physical properties 2) Full : reaction of all particles at expense of properties. Sold because of F release. Hema added

Question 40

how are giomers set?

Answer 40

both reactions are single paste VLC free radical polymerisation set

Question 41

what form does RMGIC come in?

Answer 41

Powder to Liquid or encapsulated

Question 42

what is the powder RMIGC?

Answer 42

ion leachable glass

Question 43

what is the liquid for RMGIC? and what does it enable?

Answer 43

methacrylate resin = enables setting by polymerisation

Question 44

what is the role of the polyacid in RMGIC?

Answer 44

reacts with glass by acid/base reaction

Question 45

what is the role of HEMA in RMGIC?

Answer 45

enables resin/acid components to co exist in aqueous solution

Question 46

what is the role of water in RMGIC?

Answer 46

essential for ionisation for acid/base reaction

Question 47

what can also be present in some RMGIC?

Answer 47

chemical activators

Question 48

on mixing RMGIC what happens? | if chem activators present what happens?

Answer 48

acid base starts light activation = resin polymerisation chem activators = further cure

Question 49

what do the 3 setting reactions of GI allow?

Answer 49

work more quickly | incremental cure

Question 50

the presence of the resin in RMGIC allows?

Answer 50

varnish not needed

Question 51

when can you finish a RMGIC?

Answer 51

immediately

Question 52

what is there significant amounts of with RMGIC?

Answer 52

shrinkage

Question 53

RMGIC's expand in what? | what can this benefit?

Answer 53

expand in water | can help seal

Question 54

RMGIC's are adhesive but are limited because? | what does this mean needs to be used?

Answer 54

- lack of free acid to form effective bond - lack of sufficient ionic character to form bon - lack of mobility of active spaces to form bond = some need extra agents to bond

Question 55

do RMGIC's release fluoride?

Answer 55

yes varies material to material | major release conventional with high initial burst and capacity to reuptake

Question 56

modified composite's fluoride release is?

Answer 56

a lower sustained release

Question 57

giomers and compomers have the same fluoride release because?

Answer 57

low pH allows greater release, at expense of material disintegration

Question 58

advantages of composite?

Answer 58

strong tough radiopaque quick set

Question 59

disadvantages of composite?

Answer 59

no inhert adhesion shrinkage no f release

Question 60

advantages of GI?

Answer 60

inhert adhesion little shrinkage F release biocompatible

Question 61

disadvantages of GI?

Answer 61

``` brittle not radiopaque wear prone slow set water sensitive ```