Glass ionomer cements

Question 1

luting

Answer 1

joining underlying tooth material to a fixed prosthesis using cement

Question 2

what are the 2 components and there constituents that make up conventional glass ionomer cements

Answer 2

liquid acid - usually polyacrylic

powder base - usually aluminium, silica and calcium fluoride

Question 3

why is tartaric acid added to glass ionomer cements

Answer 3

to control setting characteristics

Question 4

what is the effect of having small powder particles in conventional GICs

Answer 4

quicker setting time and more opaque

Question 5

what is the effect of having a greater molecular weight of the acid in conventional GICs

Answer 5

better mechanical properties

however more viscous and difficult to hand mix

Question 6

what are the 3 phases of conventional GICs setting

Answer 6

1 - dissoloution - dissolving of glass powder in acid
2 - gelation - initial setting
3 - hardening - aluminium ions cross link

Question 7

describe the dissolution phase of conventional GICs

Answer 7

glass particles are dissolved in acid
H+ ions attack glass surface
ions are released and silica gel forms around the unreacted glass

Question 8

describe the gelation phase of conventional GICs

Answer 8

Ca ions bind with carboxyl groups on polyacrylic chains
calcium is bivalent so can bond with 2 groups and crosslinking them however also potential to bind with 2 groups on same chain
takes several minutes to form calcium polyacrylate which appears hard in the mouth

Question 9

describe the hardening phase of conventional GICs

Answer 9

trivalent aluminium ions further cross link which increases strength
aluminium polyacrylate can take days to fully form
greatly improves mechanical properties

Question 10

why must conventional GICs be protected after placement with varnishes , resins or gel

Answer 10

to prevent moisture contamination, moisture contamination between gelation and hardening can cause aluminium ions to diffuse out which will result in a weaker material

Question 11

since there is no need for an intermediate how do GICs bond to the tooth

Answer 11

via carboxyl groups from GIC bonding with Ca ions in hydroxyapatite
acid - base reaction

Question 12

what is a common conditioner used prior to GIC placement

Answer 12

polyacrylic acid

Question 13

what are 3 advantages to using conventional GICs

Answer 13

no polymerisation contraction when setting
fluoride release
thermal expansion properties are similar to dentine

Question 14

how does conventional GICs mechanical properties compare to composite

Answer 14

decreased compressive and tensile strength , hardness and wear resistance

Question 15

what is the concept of a ‘fluoride sink’ when discussing GICs

Answer 15

rather than GICs releasing fluoride throughout their life their are theories that they take in fluoride from the environment e.g toothpaste and gradually re release it

Question 16

what are the 2 components and there constituents that make up resin modified glass ionomer cements

Answer 16

base powder - aluminium, silica, calcium fluoride (same as conventional) but may have added redox catalyst so resin can cure in the dark
liquid acid - HEMA (monomer), polyacrylic acid with added methacrylate groups, tartaric acid, phot- initiator (usually camphorquinone)

Question 17

HEMA

Answer 17

water miscible resin

Question 18

what is the difference between dual and tri curing

Answer 18

tri curing also sees a REDOX reaction

Question 19

describe the process of dual curing RMGICs

Answer 19

initial mixing seees acid base reaction begin like seen in conventional
light activation sees a free radical methacrylate reaction resulting in a resin matrix formation

Question 20

describe the process of tri curing RMGICs

Answer 20

Acid - base reaction like conventional
REDOX reaction - gives confidence material will set even if light doesnt penetrate deeply
light activation - sees free radical methacrylate formation resulting in a resin matrix formation

Question 21

what are the advantages and disadvantages of using RMGIC rather than GIC

Answer 21

better physical properties and aesthetics
lower solubility

polymerisation contraction
exothermic setting reaction
risk of HEMA leaching - HEMA = toxic to pulp

Question 22

what can be used to protect conventional GICs inbetween gelation and hardening

Answer 22

varnishes and resins = best but can also use petroleum jelly or gels e.g vaseline but this is quickly removed