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Radiology > fixed > Flashcards

fixed Flashcards

1
Q

Does impression material get larger or shrink upon setting

A

shrink

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2
Q

Rigid impression materials:

A

zinc oxide and eugenol impression paste

impression plaster

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3
Q

For synthetic elastomers, ____ polymerize into elastomers?

A

oligomers

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4
Q

LIGHT body has ___ viscosity and ____ setting contraction

A

low viscosity

high setting contraction

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5
Q

Thermoplastic polymer:

Thermoset:

A

thermoplastic: no-cross linking. physical state reversible by temp (wax)
thermoset: has cross-linking

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6
Q

Condensation polymerization results in a:

A

by-product

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7
Q

POLYSULFIDE needs a _____ of impression material to stay accurate

A

minimum amount

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8
Q

Silicones (Polysiloxanes) are inherently ____ but the addition type can be made more ______

A

hydrophobic

hydrophilic

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9
Q

Addition silicone (polyvinylsiloxane) you should wait to pour model until:

A

hydrogen liberated

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10
Q

Most hydrophilic impression material?

A

polyether

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11
Q

Good wetting = ____ contact angle

A

low

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12
Q

Die stone has __% expansion.

Gold alloy can shrink up to __%

A

0.1%

Gold=2%

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13
Q

Starting material for gypsum is calcium sulfate __hydrate

A

di-hydrate

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14
Q

Typical water-to-powder ratio of high-strength die stone:

A

0.2-0.3

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15
Q

Common accelerator:
Common retarder:
What can be used for both:

A

accelerator: potassium sulfate
retarder: borax
both: NaCl

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16
Q

Which die stone type has lowest setting expansion and contain larger amounts of modifiers?

Which die stone is high strength AND high expansion (for “modern” use)?

A

Type IV

Type V

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17
Q

Gypsum has very _____ compressive strength, but very ___tensile strength

A

high compressive

low tensile

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18
Q

Composition of gypsum-bonded casting investment powder:

A

refractory (quartz): 1/2 - 2/3
binder (stone): 30-45%
chemical modifiers: 3% or less

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19
Q

Gypsum is _____ form in set material

A

dihydrate

20
Q

Cristobalite, quartz, and tridymite are versions of ____.

Which has highest thermal expansion?

A

SiO2

Critobalite

21
Q

Normal thermal expansion with temp increase..
Cristobalite:
Quartz:

A

Cristobalite: 200-270C
Quartz: 575C

22
Q

What is special solution?

A

Silica sol in water

23
Q

Advantage of phosphate-bonded investment:

A

withstand burnout temp of 900*C

24
Q

Effect of length of deflection:

Effect of connector height on deflection:

A

D=L^3

D=1/(H^2)

25
Q

Crown/root ratio

A

2:3

26
Q

Modified hygienic pontic just has ____ connectors than normal

A

wider

27
Q

What is an ovale pontic

A

goes into gum space

28
Q

Retention form:

Resistance form:

A

retention: POW
resist: lateral

29
Q

1 cause of FPD failure:

A

caries (23%)

30
Q

Glass will adhere to _______ metal if covered with _____ and temp raised where _____ is partially dissolved into the metal

A

clean, gas free

adherent oxide

31
Q

You want 90* metal/porcelain junction (T/F)

A

True

32
Q

Zinc _____ cement has moderate pulp irritation. Adequate strength. Use cool glass slab.

Zinc _____ is only used for single metal units with less stress.

A

phosphate

polycarboxylate

33
Q

Why is glass ionomer cement hard to use?

A

any moisture ruins it.

34
Q

Which cement has highest compressive strength?

Which cements release flouride

A

glass ionomer

glass ionomers

35
Q

which cement is highest strength?

A

composite resin

36
Q

Pretzel has high ___ and low ___.

Twizzler has high ____ ability

A

high strength, low strain

strain

37
Q

What has higher tensile strength (dentin or enamel)

A

dentin

38
Q

Mechanisms to improve alloy mechanical properties:

A

solid solution hardening + grain refining

39
Q

Small amounts of _____ produce metals with very fine grains

A

Ir + Ru

40
Q

Casting alloy hardness classification..

Type I is ____ while Type IV is _____

A 
I = softest
IV= hardest
41
Q

3 components of dental porcelain

A

potash feldspar
quartz
kaolin (clay)

42
Q

what kinds of bonds does ceramic have?

A

ionic and covalent

43
Q

Building block of dental porcelain:

A

SiO4

44
Q

Melting point of porcelain must be ____ than metal

A

LOWER

45
Q

Porcelain must ____ the surface of metal

A

wet

Radiology (5 decks)

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