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23 Fixed Prosth > 8/22 - Retraction cord, Pindex Refresher, Impression Materials (Heavy Emphasis), S5-S8 > Flashcards

8/22 - Retraction cord, Pindex Refresher, Impression Materials (Heavy Emphasis), S5-S8 Flashcards

S5-S8 in above decks

1
Q

are we doing single or double retraction cord

A

single

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2
Q

about how much a retraction cord do we initially cut off

A

2 inches

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3
Q

placement of retraction cord is begun by pushing it where

A

sulcus on the mesial surface of the tooth. can also be tacked lightly into distal crevice

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4
Q

what are common problems students have when packing cord

A
  1. angulation
  2. packing too much cord at a time
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5
Q

what angle should cord be packed

A

30-45 degrees

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6
Q

what happens if the force of the instrument is directed away from area previously packed

A

cord already packed will be pulled outo

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7
Q

what to do if cord is not going in when packing

A

recheck angle

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8
Q

can you hold the cord with one instrument and packing it with a second instrment

A

YES

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9
Q

when packing, the instrment should be angled where

A

towards the root

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10
Q

what happens to the retraction cord if the instrument is held parallel to the long axis of the tooth

A

retraction cord will be pushed against the wall of the gingival crevice and will rebound

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11
Q

what is the thinnest retraction cord

A

000

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12
Q

T/F: it’s okay if the retraction cord just goes on side of margin. it does not need to physically go in.

A

FALSE! needs to physically go in

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13
Q

what to do with extra cord

A

cut it out or keep looping around

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14
Q

how long to keep retraction cord in

A

5-10 minutes

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15
Q

do you numb patient when placing retraction cord

A

YES

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16
Q

hardrock cast has ___ mm bevel

A

3 mm

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17
Q

how thick is hardrock cast B-L and O-G

A

15-18mm

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18
Q

short pins [lingual, buccal]
long pins [lingual, buccal]

A

short = lingual
long = facial

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19
Q

what side of pins enter stone, short or long

A

SHORT

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20
Q

gray sleeves on [short, long] pins
black sleeves on [short, long] pins

A

gray = short
black = long

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21
Q

how much flowstone to add

A

barely cover apical part of bevel

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22
Q

how many mm extension of flow stone

A

3-4 mm

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23
Q

how to trim die: start at occlusal or gingival

A

gingival

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24
Q

common mistakes when taking impressions

A
  1. voids and bubbles
  2. separation from tray
  3. embedded retraction cord
  4. prep debris
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25
Q

what does “the greater the contact angle, the greater the probability of air entrapment during pouring” in regard to

A

wettability

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26
Q

what do we look at when comparing the different types of ipressions

A

wettability and cost

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27
Q

large angle [bad, good] wetting

A

bad wetting/hydrophobic

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28
Q

acute angle [bad, good] wetting

A

good/hydrophilic

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29
Q

does hydrophilic or hydrophobic have a higher incidence of voids and is more readily repelled by hemorrhage or moisture in the gingival sulucs

A

phobic

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30
Q

is polysulfide, PVS, and condensation silicone hydrophilic or hydrophobic

A

phobic

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31
Q

what is effective in reducing both the contact angle and the number of voids trapped in resuling cast

A

surfactant

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32
Q

is hydrophilic or hydrophobic have a lower incidence of voids and more able to withstand hemorrhage or other moisture in gingival sulcus

A

hydrophilic

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33
Q

is hydrophilic or phobic less resistant to wetting by gypsum

A

hydrophilic

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34
Q

are revesible hydrocolloid, irreversible hydrocolloid and polyether hydrophilic or hydrophobic

A

hydrophilic

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35
Q

what is the decrease viscosity of the material under shear load

A

shear thinning

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36
Q

what is thick enough to stay in tray yet fluid enough to express thru syringe

A

thixotropic

37
Q

is light-body polysulfide and condensation silicone least or most viscous

A

least

38
Q

is heavy body sulfide least or most viscous

A

most

39
Q

what are examples of chemical disinfectants

A
  1. chlorine compounds
  2. combination synthetic phenolic compounds
  3. glltaraldehydes
  4. iodophors
  5. phenol-alcohol combinations
40
Q

process of disinfecting impressions

A
  1. rinse
  2. trim
  3. spray
  4. seal
41
Q

what is agar made frmo seaweed

A

reversible hydrocolloid

42
Q

what is made of 85% water

A

reversible hydrocolloid

43
Q

what is water seeping rom surface

A

syneresis

44
Q

what is imbitition

A

absorbing water

45
Q

what are the risks of using reversible hydrocolloid

A

syneresis, evaporation, and imbitition

46
Q

when should you pour reversible hydrocolloid

A

ASAP

47
Q

why do you place reversible hydrocolloid in tempering batch

A

lowers temp to decrease viscosity and because it’s boiling from previous baths

48
Q

sodium tetraborate is also called what

A

borax

49
Q

modifiers placed in reversible hydrocolloid

A
  1. sodium tetraborate/borax
  2. potassium sulfate
  3. thymol
  4. plasticizers, fillers, flavoring agents and pigmetns
50
Q

since the set of gypsum is retarded by contact w/ any gel resulting in soft surface of cast, what is added

A

potassium sulfate (to accelerate set-up)

51
Q

irreversible hydrocolloid is also called what

A

alginate

52
Q

what is inexpensive and has low tear strenegth

A

irreversible hydrocolloid/alginate

53
Q

what material has less surface detail than other materials

A

irreversible hydroc

54
Q

what material is not as dimensionally stable as other materials

A

irreversible hydro

55
Q

how quick to pour irrversible hydro

A

15 minutes

56
Q

what is an elastomer known as mercaptan, thiokol, or rubber base

A

polysulfide

57
Q

is polysulfide hydrophilic or phobic

A

hydrophobic

58
Q

does hydrocolloid or polysulfide have greater dimensional stability

A

polysulfide

59
Q

what must you do when completing polysulfide impression

A

block out large undercut areas in inerproximal region with soft wax prior to impression making

59
Q

when must polysulfide impression be poures

A

within 1 hour

60
Q

what are the two tubes for polysulfide impression

A
  1. base
  2. accelerator
61
Q

what is a liquid polysulfide polymer mixxed with an inert filler

A

base

62
Q

what is usually a lead dioxide mixed wih small amounts of sulfur and oil

A

accelerator

63
Q

the accelerator in polysulfide is an oxidation iniator on what on the polymer

A

on terminal thiol groups

64
Q

do polysulfide acelerators have toxicity and tendency to irritate soft tissues

A

YES

65
Q

does the accelerator show up radioopaque

A

yes

66
Q

what impression material has a limited shelf life

A

organo-tin silicones

67
Q

is the two paste system of condensation silicone cross linked by reaction

A

ys

68
Q

what is a liquid silicone polymer w/ terminal hydroxyl groups, mixed w/ inert fillers

A

base paste of condensation silicone

69
Q

what is a viscous liquid, cross-linking agents, ethyl silicate with an organo-tin activator in tin

A

reactor of condensation silicone

70
Q

is condensation silicone dimensionally stable or insable

A

instable

71
Q

when to pour up condensation silicone impressions

A

ASAP

72
Q

process of putty/wash or putty/reline

A
  1. heavy body (putty) w/ stock tray and thin plastic spacer
  2. thin wash of light body material to reline the putty
73
Q

what is a copolymer of 1,2-epoxyethane and tetrahydrofuran
reacted with alpha, beta-unsaturated acid, such as
protonic acid to produce esterification of the
terminal hydroxyl groups

A

polyether impression

74
Q

is polyether impression resistant to tearing upon removal

A

yeS

75
Q

is polyether impression somewhat brittle

A

yeah

76
Q

is it okay if you dont block out for polyether impression

A

NO! stiff material so needs to be blocked out

77
Q

people with allergic rxns to polyether are allergic to what

A

aromatic sulfonate catalyst

78
Q

is polyether hydrophobic or hydrophilic

A

philic so imbibition likely

79
Q

is polyether accurate when poured weeks after removal from mouth

A

yes

80
Q

what impression material used in complete denture

A

polyether

81
Q

what is PVS also called

A

polyvinyl siloxane, addition silicone, vinyl polysiloxane, and vinl silicone

82
Q

what uses two pastes with mixing dispensers

A

PVS

83
Q

what are the two pastes in PVS

A
  1. silicone w terminal silane hydrogen groups and inert filler
  2. silicone w/ terminal vinyl groups, chloroplatinic acid catalyst, and filler
84
Q

is PVS hydrophilic or phobic

A

phobic

85
Q

are surfactants added to PVS

A

yes

86
Q

does PVS have less stability than condensation silicone

A

NO! it’s dimensional stabilit is GREATER than condensation silicone

87
Q

can you use latex gloves when doing PVS impression? why??

A

no - sulfur impedes material

88
Q

when to pour PVS impression

A

15-20 minutes after. still accurate after 1 week

23 Fixed Prosth (21 decks)

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