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Dental materials > L13: prosthetic polymer and resins > Flashcards

L13: prosthetic polymer and resins Flashcards

1
Q

denture base materials are available as ___

A

powder (polymer)
liquid (monomer )

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2
Q

colorless material used in fabrication of denture :

A

polymethyl methacrylate

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3
Q

how does polymethyl methacrylate polymerize?

A

under heat and pressure

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4
Q

curing of denture base polymer :
type I class I :
type II class I:
type IV:

A

type I class I : heat cured powder/liquid

type II class I: chemical/self polymerized powder liquid

type IV:light cured

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5
Q

list the polymer powder and monomer liquid present in heat cured polymethyl methacrylate :

A

polymer powder : polymethylmethacrylate beads

monomer liquid : methyl meth acrylate

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6
Q

what is the most commonly used denture base?

A

heat activated (type 1 class 1) polymethyl methacrylate

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7
Q

how are heat activated PMMA shaped?

A

compression modeling

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8
Q

molds of heat activated PMMA are prepared by :

A

dental gypsum in dental flask

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9
Q

denture base is made with :

A

wax, missing teeth are also positioned in wax

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10
Q

what is the ratio of polymer to monomer in heat cured acrylic resin?

A

3:1. using this ratio , volumetric shrinkage can be limited to 2.3%

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11
Q

5 distinct stages that occur after mixing of powder and liquid of PMMA :

A

sandy stage : little or no interaction occurs immediately after mixing

stringy stage : monomer liquid is absorbed into beads, causing swelling . polymer chains now uncoil and increase viscosity of mix ( stringiness or stickiness)

dough-like stage : ideal consistency for compression molding , pliable dough no longer stringly or sticky . packing is done in this stage

rubbery stage : no longer flows freely , initial setting

stiff or hard stage : dry mixture resistant to mechanical deformation

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12
Q

controlled heating process used for polymerization of heat activated acrylic is termed ____

A

polymerization cycles or curing cycles

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13
Q

when does benzyl peroxide decompose ?

A

65C to form free radicals

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14
Q

resin is processed :

A

at 74 C For 2 hours and increasing the temperature of the water bath to 100C for 1 hour

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15
Q

boiling point of liquid MMA monomer ?

A

100.8C

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16
Q

What happens if you over heat the monomer ?

A

gaseous porosity

17
Q

insufficient monomer produces :

A

dry mix and granular porosity

18
Q

insufficient dough and inappropriate pressure causes :

A

contraction porosity

19
Q

initiator used in chemically activated denture base resin is activated by ____

A

tertiary amine such as dimethyl para-toludine added to liquid monomer

20
Q

what happens when liquid and powder of chemically activated denture base resin are mixed?

A

tertiary amine causes decomposition of benzoyl peroxide which results in free radical production and polymerization occurs similarly to the way it does in heat activated PMMA

21
Q

Residual monomer in which type of denture material is higher ?

A

chemically activated ( high residual monomer figures decrease the strength and serve as a potential tissue irritant (compromises biocompatibility )

22
Q

which denture base material has slightly less shrinkage

A

chemically activated , they have greater dimentional accuracy

23
Q

which denture base material has better color stability ?

A

heat activated

24
Q

which denture base material has smaller polymer beads which disolve quicker ?

A

chemically activated resins

25
Q

light activated denture base polymers are supplied in __

A

pre mixed sheets or bars

26
Q

what’s the major pro of light activated denture base polymers?

A

reduced working time by eleminating need for flasks, wax , boiled out , packing

27
Q

which denture base polymer is very useful for production of the hallow denture bases for obturators ?

A

light cured denture base polymer

28
Q

density ____ with polymerization

A

increases

29
Q

change in density results in ___

A

volumetric shrinkage of 21%

30
Q

volumetric shrinkage exhibited by polymerized mass___

A

7%

31
Q

linear shrinkage within a denture base rarely exceeds :

A

1%

32
Q

production flaws , micro leakage due to internal stress is termed ___

A

crazing

Dental materials (15 decks)

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