Glass Polyakenoates

Question 1

name the two types of dental material derived from cement are?

Answer 1

1. silicate cement

2. polycarboxylate cement

Question 2

how is polycarboxylate cement made?

Answer 2

• ZnO
  and
• polycarboxylic acid
  = set cement

Question 3

what are some of the properties of polycarboxylate cement?

Answer 3

• adhesive to tooth substance
• poor appearance
• high solubility
• poor mechanical properties

Question 4

what is replaced to give you a glass polyalkenoate?

Answer 4

the ZnO is replaced with ion leachable glass

Question 5

what are the 3 benefits of a glass polyalkenoate over polycarboxylate cement?

Answer 5

• better appearance
• less soluble
• better mechanical properties

Question 6

what are the 3 ways of supplying a glass polyalkenoate?

Answer 6

1. powder / liquid
2. powder / water
3. encapsulated

Question 7

what is the setting reaction for glass polyalkeoate?

Answer 7

basically acid/base

Question 8

what gives the glass polyalkenoate a better appearance?

Answer 8

unreacted glass cores = translucent properties give

Question 9

what is in the powder for glass polyalkenoate?

Answer 9

sodium aluminosilicate glass with about 20% CaF

Question 10

what is the benefit of having CaF in the powder for glass polyalkenoate?

Answer 10

fluoride leaching

Question 11

what are the 2 component of the liquid for glass polyalkenoate?

Answer 11

• aqueous solution of acrylic / itaconic acid copolymer

- tartaric acid

Question 12

what is the function of the tartaric acid?

Answer 12

to control setting characteristics

Question 13

in addition to sodium aluminosilicate glass with CaF what is in the powder to make glass polyalkenoate with water?

Answer 13

vacuum dried polyacid

Question 14

what kind of mixing is most likely to give porosities? and why?

Answer 14

• hand spatulation due to more air incorporation

Question 15

are viscous cements more or less likely to get porosities?

Answer 15

less likely

Question 16

with fluid cements does mixing by hand or machine give more porosities?

Answer 16

more if mechanical as increased froth

Question 17

if carrying out an experiment on glass polyalkenoates then what type of supply would you use and why?

Answer 17

the encapsulated as more consistency with measurements

Question 18

why would you not store GI in the fridge?

Answer 18

• makes mixing difficult as initiation of acid crystalisation

Question 19

what can be placed on top of GI to prevent it from getting exposed to moisture?

Answer 19

• Varnish

- resin bonding agent or fissure sealant

Question 20

when does setting of a glass polyalkenoate begin?

Answer 20

when the acid comes into contact with the glass particles

Question 21

give two examples of a cored structure?

Answer 21

1. aluminosilicate glass

2. metals

Question 22

how does GI bond to enamel?

Answer 22

Ca2+ ions

Question 23

how does GI bond to dentine?

Answer 23

bonds to collagen with H bonding and metallic ion bridging

Question 24

what is the purpose of citric acid and what does it not do?

Answer 24

to remove smear layer

cannot increase bond strength

Question 25

what can increase bond strength of GI?

Answer 25

• polyacrylic acid

Question 26

give 8 properties of glass polalkenoate?

Answer 26

1. thermal diffusivity close to dentine
2. chemical set is exothermic (2-5%)
3. fluoride release and uptake
4. brittle
5. poor abrasion resistance
6. good appearance
7. susceptible to acid erosion
8. lack of radiopacity

Question 27

what are cermets?

Answer 27

silver (Ag) pelletised mixture of GLASS and METAL particles

Question 28

what are the properties of cermets?

Answer 28

• radiopacity
• poor apperance
• some F- release
• increased compressive stress
• increased fatigue limit
• some flexural strength and abrasion resistance

Question 29

what does RMGIC?

Answer 29

resin modified glass ionomer cement

Question 30

what is the difference between modified composite and conventional? what is the aim of this?

Answer 30

filler replaced with aluminosilicate glass - to encourage Fluoride release

Question 31

what is the setting reaction for modified composite?

Answer 31

light cured free radical polymerisation

Question 32

when does the acid base reaction occur during the setting of modified composite?

Answer 32

late on in the process

Question 33

why does it occur later?

Answer 33

(resin modified = contains acidic groups)

resin set water enters materials and ionised the acid and then acid base reaction