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Dental materials > silicon impression > Flashcards

silicon impression Flashcards

1
Q

Was the first type of silicone impression material used in dentistry

A

CONDENSATION SILICONE

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2
Q

conventional silicones

A

CONDENSATION SILICONE

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3
Q

It is used to get impressions in the preparation of crowns, bridges,
onlays, and inlays.
And also used for an impression in the process of preparation for complete
dentures.

A

CONDENSATION SILICONE

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4
Q

introduced in 1955

A

CONDENSATION SILICONE

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5
Q

It is a type of silicone that forms from a condensation reaction

A

CONDENSATION SILICONE

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6
Q

ADA Specification No. 19

A

Dental Elastomeric Imp. Mat.

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7
Q

Supplied as a base paste and a low-viscosity
liquid catalyst, a two-paste system, or a twoputty system.

A

CONDENSATION SILICONE

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8
Q

Putty is used tray material in conjunction with
a low-viscosity silicone

A

putty-wash
technique

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9
Q

Hydroxyl-terminated polydimethylsiloxane
- undergoes cross-linking to form rubber
Insert filler such as silica, 35-75% (depending on viscosity)
- gives ‘body

A

PASTE (BASE) of condensation silicon

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10
Q

Alkyl silicate (e.g. tetraethyl silicate or orthoethyl silicate)
- acts as a cross-linking agent
Tin compound (e.g. dibutyl tin dilaurate or stannous octoate)
- acts as a reaction catalyst

A

LIQUID (ACCELERATOR) of condensation silicon

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11
Q

Working time of condensation silicon

A

2.5-4 mins

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12
Q

Setting time of condensation silicon

A

6-8 mins

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13
Q
  • GOOD WORKING TIME
  • BETTER ELASTIC PROPERTIES ON REMOVAL –LONG SHELF LIFE
    -CLEAN AND PLEASANT
    -ADEQUATE TEAR STRENGTH
    -EXCELLENT REPRODUCTION
    OF SURFACE DETAILS
A

Advantages of condensation silicon

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14
Q

-GREATER RIGIDITY
-POOR DIMENSIONAL STABILITY
-HYDROPHOBIC
-ALLERGIC REACTIONS
-EXPENSIVE

A

Disadvantages of condensation silicon

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15
Q

An elastomeric impression material of ethylene oxide and tetrahydrofluro copolymers that polymerizes under the influence of an atomic ester

A

POLYETHER

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16
Q

Supplied as a two-paste system in low, medium, and high consistencies.

A

POLYETHER

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17
Q

Commercial names are Impregum, Remitec, Polyjel etc

A

POLYETHER

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18
Q

2 types of polyether

A
  1. .Based on ring
  2. Based on an acid
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19
Q

opening polymerization of aziridine group

A

Based on ring

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20
Q

catalyzed condensation polymerization of
polyether prepolymer with alkoxysilane terminal groups

A

Based on an acid

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21
Q

Polyether - 80 - 85%
Colloidal silica (Filler)
Glycol ether or phthalate (Plasticizer)

A

polyether composition base

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22
Q

Alkyl-aromatic sulfonate (Initiator/crosslinking agent)
Colloidal silica (Filler)
Glycol ether or phthalate (Plasticizer)

A

polyether composition paste

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23
Q

The base paste of a polyether contains polyether
molecules that terminate in an

A

amine group.

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24
Q

Three-membered heterocycle
containing two methylene groups, and the nitrogen
is called an imine.

A

Aziridine rings

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25
Q

main chain of polyether

A

copolymer of ethylene oxide
and tetrahydrofuran.

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26
Q

An aromatic sulphonate ester in the activator paste
cross-links these polymer chains via the imine end
group

A

Cationic Polymerization

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27
Q

Whenever a ring is opened, the cation function remains what? , thus lengthening the chain as the
polymers further cross-links.

A

remains attached

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28
Q

Exothermic (polyether)

A

4-5 degrees Celcius

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29
Q

working time of polyether

A

3 minutes

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30
Q

setting time of polyether

A

6 minutes

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31
Q

tear strength of polyether

A

1800- 4800

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32
Q

PERCENT CONTRACTION of polyether

A

0.19-0.24

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33
Q

CONTACT ANGLE BETWEEN SET MATERIAL AND WATER of polyether

A

49 degrees

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34
Q
  • GETTING IMPRESSIONS FOR INLAYS AND
    ONLAYS
    -DURING PREPARATION FOR CROWNS
    AND BRIDGES
    -DURING THE CONSTRUCTION OF
    -FUNCTIONAL IMPRESSIONS,
    -CONSTRUCTION OF PARTIAL AND
    COMPLETE DENTURES
    -IMPLANT PROSTODONTICS
A

USES OF POLYETHER

35
Q

manipulation of polyether

A
  • Hand Mixing
  • Static Mixing
  • Dynamic Mechanical
    Mixing
36
Q

Dispense the same lengths of materials onto a mixing pad or glass slab.

A

Hand Mixing

37
Q

uses a gun for compressing materials in a two-cylinder cartridge.

A

Static Mixing

38
Q

Uses machine rotating mixers to blend materials as they are extruded through the tip

A

Dynamic Mechanical Mixing

39
Q

-High level of fidelity
-Tear strength
-Fast-setting
-Clean & easy to use
-Least hydrophobic of all elastomers
-Margins easily seen
-Good stability
-Shelf life: 2 yrs

A

ADVANTAGES OF POLYETHER

40
Q
  • stiff, high modulus
  • unpleasant (bitter) taste and smell
  • difficult handling
  • hard rigid material removal from mouth
  • absorbs water (may suffer expansion)
  • may cause allergic reaction
  • high cost
A

disadvantages of polyether

41
Q
  • final impression of full dentures and partial dentures
  • inlay and crown impressions
  • fixed bridge impression
A

common uses of polysulfide

42
Q

mid-1950s

A

polysulfide

43
Q

made of synthetic rubber and had a long setting time and were not as accurate

A

polysulfide

44
Q
  • first elastomer
  • homogenous (dentulous)
  • rubber base
  • lowest viscosity
  • least stiff
A

polysulfide

45
Q

order of impression materials (increasing stiffness)

A
  1. polysulfide
  2. condensation silicone
  3. addition silicone
  4. polyether
46
Q

3 viscosities of polysulfide

A
  1. regular permlastic
  2. light bodied permlastic
  3. heavy bodied permlastic
47
Q
  • partial/full dentures
  • high degree of flow that will capture all details
A

regular permlastic

48
Q
  • crowns, inlays, and fixed bridged impression
  • most free flowing
  • great accuracy and fine definition
A

light bodied permlastic

49
Q

results in optimum compression of the light bodied permlastic in a double mix

A

heavy bodied permlastic

50
Q

working time of polysulfide

A

4-7 mins

51
Q

setting time of polysulfide

A

7-10 mins

52
Q

tear strength of polysulfide

A

2500- 7000 gm/cm2

53
Q

dimensional stability of polysulfide

A

percent contraction .40-.45%

54
Q

loss of polymerization by product

A

SHRINKAGE

55
Q

lowest cell death count

A

biocompatibility

56
Q

caused by rocking the material while removal

A

deformation

57
Q

single swift pull

A

removal of polysulfide

58
Q

liquid polysulfide polymer
- 80-85%
inert fillers
- 16-18%
- titanium oxide, zinc sulfate, silica

A

base paste of polysulfide

59
Q

lead dioxide
- 60-69%
dibutyl phthalate
- 30- 35%
sulfur
- 3%
other substances
- 2%
- magnesium stearate and deodorant

A

catalyst of polysulfide

60
Q

hot and humid will what the setting of polysulfide

A

accelerate

61
Q

working time at 23 degree of polysulfide

A

6 mins

62
Q

working time at 37 degree of polysulfide

A

4.3 mins

63
Q

setting time at 23 degree of polysulfide

A

16 mins

64
Q

setting time at 37 degree of polysulfide

A

12.5 mins

65
Q
  • long working time
  • good tear strength/ high tear resistance
  • good flow before setting
  • good reproduction of surface detail
  • high flexibility for easier removal around undercuts
  • cheaper than silicones and polyether
A

advantages of polysulfide

66
Q
  • unpleasant odor and taste
  • long setting time
  • stains clothing (mercaptan)
  • shrinkage after setting
  • poor dimension stability
  • not as accurate as other elastomers
A

disadvantages of polysulfide

67
Q

Also known as polyvinyl siloxane or vinyl polysiloxane

A

ADDITION SILICONE

68
Q

most popular elastomeric impressions

A

ADDITION SILICONE

69
Q

Available as two-paste systems in four viscosities
○ Light
○ Medium
○ Heavy
○ Putty
Available in a range of colors

A

ADDITION SILICONE

70
Q

a polymerization reaction in which each polymer
chain grows to a maximal length in sequence

A

Addition reaction

71
Q

the component that forms the main three-dimensional structure of a final impression

A

Base Paste

72
Q

a chemical reaction that transforms small molecules
into large polymer chains

A

Polymerization

73
Q

Materials are based on silicone prepolymers with
vinyl and hydrogen side groups, which can polymerize by addition polymerization

A

Composition of addition silicon

74
Q
  1. Polymethylhydrosiloxane
    ○ undergoes cross-linking
  2. Divinylpolysiloxane
  3. Filler
    ○ Colloidal silica (35-75%)
    ○ Controls the viscosity
    ○ Increasing the filler content increases the consistency of the
    paste and the stiffness of the impression and decreases the
    coefficients of thermal expansion and contraction
A

base of addition silicon

75
Q

Colloidal silica (35-75%)
○ Controls the viscosity
○ Increasing the filler content increases the consistency of the
paste and the stiffness of the impression and decreases the
coefficients of thermal expansion and contraction

A

filler (base) of addition silicon

76
Q

Divinylpolysiloxane
○ Cross-linking agent
● Platinum salt
○ Chloroplatinic acid
○ Catalyst
○ Karstedt type
■ complex compound consisting of platinum and
1,3-divinyltetramethyldisiloxane
● Palladium
○ present in some products Hydrogen absorber
● Fillers

A

catalyst of addition silicone

77
Q

Vinyl siloxane + Hydrogen siloxane –Platinum salt-> Silicone rubber

A

setting reaction of addition silicone

78
Q

Increases the setting of addition silicone impressions
○ Result of sulfur contamination
○ Retardation or no polymerization in the contaminated area of the
impression
● Recommendations
○ Thorough washing of the gloves with detergent and water just
before mixing
○ Switching to vinyl and nitrile gloves

A

Complications with Latex Gloves

79
Q

No reaction by-products are formed, however secondary reaction may produce hydrogen gas which may produced porosity

A

setting reaction of addition silicone

80
Q

Residual monomer in acrylic provisional restorations and resin composite cores can also inhibit
the setting reaction
● Recommendations: use of 2% chlorhexidine to remove contaminants

A

Other Complications of addition silicone

81
Q

Working time of addition silicone

A

2- 4 mins

82
Q

setting time of addition silicone

A

4-6.5 mins

83
Q
  • Substitute for alginate
    impression
    ● Very precise impression
    ● High elastic recovery
    ● High stability
    ● Low creep
    ● Multiple usage
    ● Less irritation
    ● No unpleasant taste and
    smell
A

Advantages of addition silicone

84
Q

-Expensive
● Hydrophobic
● May release hydrogen gas
on setting
● Stiff
● Low Tear Strength

A

Disadvantages of addition silicone

Dental materials (1 decks)

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