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BDS2.5 Dental Materials - operative dentistry > Glass Polyalkenoate/Glass ionomer cement > Flashcards

Glass Polyalkenoate/Glass ionomer cement Flashcards

1
Q

What is another name for glass polyalkenoate cement?

A

glass ionomer cements

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2
Q

What are the 2 basic ocmponents of GPC?

A

glass

acid (usually polyacrylic acid)

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3
Q

What type of reaction occurs in GPC?

A

acid-base reaction

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4
Q

Is fluoride released from GPC?

A

yes, throughout its life

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5
Q

What is the liquid component, acid or base?

A

acid, usually polyacrylic

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6
Q

Can glass ionomer cements be light cured?

A

no, only chemically

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7
Q

When can the GIC be light cured?

A

if resin is in there, but at that point it is not a cement, it is likely a resin modified glass ionomer

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8
Q

What is the glass component of the GIC?

A

fluoro-alumino-silicate

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9
Q

Where is the source of fluoride in GIC?

A

from the glass component,… fluoro-alumino-silicate

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10
Q

What is the effect of adding in elements strontium and lithium into glass?

A

impoact radiopacity

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11
Q

What is the effect of altering the aluminium/silica ratio?

A

make it more translucent

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12
Q

What is the effect f altering ion release of the glass?

A

determines the solubility, setting characteristics and fluoride release

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13
Q

What are the main components of glass?

A
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14
Q

What has the highest percentage composition of glass?

A

silica (silicon oxide)

it does vary though

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15
Q

How is the glass made?

A

glass mixture heated to between 1150 and 1450

molten mass poured onto metal plate and then cooled into water (shock cooling)

broken up to form a glass frit

wet or dry milled to produce small particles of glass

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16
Q

What is the max size of particle which can be used for restoration?

A

20um

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17
Q

What is shock cooling?

A

molten mass is poured onto a metal plate and then into water

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18
Q

What is the process called to reducing glass reactivity?

A

passivation treatment

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19
Q

What does passivation treatment involve?

A

washed with acetic acid for up to 24 hours and then dried

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20
Q

What acid is used in passivation treatment?

A

acetic acid

21
Q

How does passivation treatment reduce the reactivity of glass?

A

leads to ion depletion of the glass surface - fewer ions immediately available to form the salt matrix at start of mix

22
Q

When is passivation treatment maximised?

A

it has greater significance when the particle size of cement is reduced (smaller particle size the more rapid the set; volume: surafce area)

23
Q

Polacrylic acid is the main acid in GIC, what are the others in the series?

A

polymaleic acid

number of copolymers of polyacrylic acid

24
Q

What group is common to all of the acids?

A

carboxylate

25
Q

Why is the carboxylate common to all of the acids?

A

as water ionises to carboxyl and hydrogen ions to facilitate chemical reaction

facilitate the chemical reaction

26
Q

What can be added to the GIC acid component to sharpen the set?

A

polyphosphonic acid to provide a short sharp set

27
Q

What does an cement with a higher molecular weight determine?

A

it will have better mechanical properties

28
Q

What is the disadvantage of the high molecular weight of cement?

A

higher viscosity and harder to work with

29
Q

How do some manufacturers package the GIC?

A

vacuum dry the acid solution and then mix the anhydrous powder so formed with the glass

activation of the cement is achieved by adding water

just adjust the water to powder ratio

30
Q

What can molecular weight of the cement also influence?

A

the working and setting time

higher molecular weight, shorter the working time

31
Q

What acid has been used to facilitate encapsulation of the cement?

A

maleic acid, makes it les viscous

32
Q

What acid is added to the cement to accelerate setting reaction?

A

tartaric acid - it maintains the working time

33
Q

What is the structure of the GIC?

A

Cored structure

34
Q

What is the unreacted powder material (glass) encased in? (after setting)

A

salt matrix

35
Q

What do the surface soluble components of glass react with?

A

acid from the matrix

36
Q

What is the setting reaction of GIC?

A

(DONT NEED TO MEMORISE)

37
Q

What gel forms around the glass particles?

A

silica gel

38
Q

What come out of the silica gel around the glass core?

A

calcium, aluminium and fluoride ions

39
Q

What do the calcium, aluminium and fluoride ions form? (form the silica gel)

A

calcium and aluminium polysalts

40
Q

When does the condensation reaction occur more rapidly?

A

with the calcium ions

41
Q

What gel the calcium ions form? (condensation)

A

calcium polyacrylate gel formed- within a minute

42
Q

Why does the aluminium take longer to form polyacrylate gel compared to calcium ions? (condensation)

A

aluminium ion is triple charges and less mobile

43
Q

What occurs after the polyacrylate gel has formed by condensation?

A

cement goes through a period of maturation

44
Q

What occurs during the maturation period of setting?

A

further cross-linking of the matrix and more cations become bound onto the polyanion chain

45
Q

What properties increase during the maturation phase of the setting reaction?

A

increase in mechanical properties

46
Q

How long can the maturation phase take?

A

months

47
Q

What is the compressive and flexural strength like of GIC?

A

relatively low but increase very time as the martial matures (maturation stage)

48
Q

Do you place a protective layer over GIC and why?

A

yes, varnish can be put over

longer the restoration is protected from moisture, better resistance it is to erosion (not good with oral fluids)

BDS2.5 Dental Materials - operative dentistry (22 decks)

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