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Fixed Prosthodontics I > Impression Materials and Technique > Flashcards

Impression Materials and Technique Flashcards

1
Q

A negative likeness or copy in reverse of the surface of an object:

A

Analogue impression

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2
Q

List the characteristics of an ideal impression material: (14)

A
  1. easy to mix and handle
  2. suitable working time
  3. suitable setting time
  4. compatible with die and stone materials
  5. not toxic or allergenic to the patient
  6. dimensionally stable
  7. accurate to record the fine details
  8. acceptable odor and taste
  9. adequate stretch
  10. adequate shelf life
  11. ready to be disinfected without loss of accuracy
  12. fluid or plastic when inserted into the mouth
  13. it must be an exact record of all aspects
  14. economic
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3
Q

An impression should be an exact duplication of the prepared teeth including uncut tooth structure:

A

beyond finish line

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4
Q

The impression should be free of air bubbles especially in the:

A
  1. finish line
  2. occlusal surfaces
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5
Q

The impression should be extended enough to capture:

A
  1. vestibule
  2. tuberosities
  3. retromolar pad
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6
Q

The ability of a liquid to flow over a solid surface:

A

Wettability

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7
Q

Wettability is related to:

A

-surface energy of the solid
- surface tension of the liquid

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8
Q

A contact angle of greater than 90 degrees surface not wetted:

A

Hydrophobic

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9
Q

A contact angle of less than 90 degrees surface wetted:

A

Hydrophilic

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10
Q

Resistance of liquid to flow:

A

Viscosity

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11
Q

Viscosity is the reverse of:

A

fluidity

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12
Q

Viscosity is related to ____ , liquid material

A

unset

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13
Q

A fluid viscosity is not affected by shear rate; viscosity constant:

A

Newtonian

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14
Q

A fluid that does not follow; viscosity can be changed:

A

None-newtonian

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15
Q

Shear thinning:

A

Pseudoplasticity

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16
Q

What do the following describe?
- reduce viscosity with increase share
- material does not flow until under pressure
- less viscous with increased share

A

Pseudoplasticity

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17
Q

Why same material can be used in tray and syringe?

A

Pseudoplasticity

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18
Q

Characteristic of a solid that behaves as an elastic solid and viscous liquid:

A

Viscoelasticity

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19
Q

Viscoelacticity is related to:

A

the set impression

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20
Q

Mechanical properties of viscoelasticity are dependent on:

A

Loading rate

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21
Q

The loading rate of an impression material. is associated with:

A

viscous nature

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22
Q

As load rate of an impression material increased, the:

A

properties are improved

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23
Q

With an increased load rate, the impression material has an increase ___ and ___

A

tear strength and elastic limit

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24
Q

With quick removal of the impression material, there is:

A

decreased distortion

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25
Q

The ability to replicate the intra-oral surface details:

A

accuracy

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26
Q

Ability to retain its absolute dimensional size over time:

A

dimensional stability

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27
Q

The ability to resist tearing in thin sections, such as through the feather edge material within the gingival sulcus:

A

Tear resistance

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28
Q
  • Plaster
  • impression compound
  • ZOE
  • Impression waxes

These are all categorized as:

A

non-elastic impression material

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29
Q

What two categories does elastic impression material break down into?

A
  1. hydrocolloids
  2. non-aqueous elastomers
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30
Q

Hydrocolloids further break down into:

A

Agar reversible ; Alginate irreversible

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31
Q

Condensation silicone and addition silicone are examples of:

A

Non-aqueous elastomers

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32
Q

Classification of impression material described as:

Rigid, cannot be removed from undercuts:

A

Nonelastic

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33
Q

Classification of impression material described as:

Can be removed from undercuts without distortion

A

Elastic

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34
Q

Give an example of when you would use non-elastic impression material:

A

Edentulous impressions

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35
Q

Give an example of when you would use an elastic impression material:

A

dentate impessions

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36
Q

_____ were the first impression materials that were popular in the previous century:

A

non-elastic/ rigid

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37
Q
  • plaster of Paris
  • impression plaster
  • gutta percha
  • modeling compound
  • ZOE
  • Various waxes

These are all examples of:

A

Non-elastic/rigid impression material

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38
Q

Less commonly used now with the exception of recording atrophic edentulous ridges or flappy ridges:

A

Non-elastic/rigid impression material

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39
Q

What was the first elastic impression material (1925)

A

Reversible hydrocolloid (Agar)

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40
Q

Reversible hydrocolloid =

Irreversible hydrocolloid =

A

Agar

Alginate

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41
Q
  • Reversible Hydrocolloid
  • Irreversible Hydrocolloid
  • Polysulfide Rubber
  • Vinyl Poly Siloxanes
  • Polyether

These are all examples of:

A

elastic impression material

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42
Q

Aqueous elastomeric impression material =

A

hydrocolloids

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43
Q

Non-aqueous elastomeric impression material =

A

polymers

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44
Q

What is the major component of aqueous elastomeric (hydrocolloids) impression material?

A

water

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45
Q

Aqueous elastomeric (hydrocolloid) impression material may be ____ or ___

A

reversible or irreversible

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46
Q

Give examples of non-aqueous elastomeric (polymers):

A
  1. polysulfide
  2. vinyl poly siloxane
  3. polyether
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47
Q

Label the following image:

A
  1. hydrocolloids
    1a. Agar (reversible)
    1b. Alginate (irreversible)
  2. Non-aqueous elastomers
    2a. polysulfides
    2b. polyethers
    2c. condensation silicone
    2d. addition silicone
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48
Q

Elastic polymers come in different consistencies such as:

A

light, medium, heavy, and putty

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49
Q

What are the byproducts of the condensation polymerization of non-aqueous elastomeric impression material?

A

H20 or OH

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50
Q

What is the byproduct of addition polymerization of non-aqueous elastomeric impression material?

A

No byproduct

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51
Q

Why must an impression tray be sufficiently rigid?

A
  1. carry the impression material into the oral cavity
  2. hold the material in close proximity to the teeth
  3. avoid breaking during removal
  4. prevent wrapping of the completed impression
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52
Q

Used to prevent impression distortion due to material pulling away from the tray

A

Retention & adhesion

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53
Q

What is the goal of a preliminary impression?

A

a fully or overextended impression of the arch with all anatomical landmarks

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54
Q

a fully or overextended impression of the arch with all anatomical landmarks

A

preliminary impression

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55
Q

List the purposes of a preliminary impression: (7)

A
  1. evaluate arch form
  2. anatomical landmarks
  3. musculature
  4. hard and soft tissue anomalies
  5. restorative space
  6. diagnostic wax up
  7. fabrication of custom tray
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56
Q

The final impression material is selected depending on:

A

the type of impression required for the procedure

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57
Q

Single or double cord technique; cord(s) removed right before impression making

A

Tissue retraction

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58
Q

Tissue retraction may be required for:

A

final impressions

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59
Q

In a final impression the ____ dispenses into the sulcus, over and around the prepared teeth and onto the surrounding tissues

A

Light bodied consistency

60
Q

What type of impression material is loaded into the custom tray with dried adhesive in a FINAL impression?

A

medium or heavy bodied

61
Q

Where do you place the light bodied impression material in a FINAL impression?

A
  1. sulcus
  2. over and around prepared teeth
  3. surrounding tissues
62
Q

Describe the pressure used with medium/heavy bodied impression material for a final impression?

A

No downward pressure

63
Q

To atruamatically displace gingival tissues to allow access for impression material to record the finish line and provide sufficient thickness of the impression

A

Tissue manipulation gingival retraction

64
Q

The purpose of tissue manipulation gingival retraction is to atruamatically displace gingiva tissues to allow access for impression material to:

A

record the finish line and provide sufficient thickness of the impression

65
Q

Describe the techniques that may be used in tissue manipulation gingival retraction:

A
  1. mechanical
  2. chemo-mechanical
  3. surfical
66
Q

Impregnated cords are an example of:

A

chemo-mechanical technique

67
Q

List the specific surgical techniques used in tissue manipulation gingival retraction:

A
  1. electrosurgery
  2. rotary curettage
  3. laser
68
Q

What form of tissue manipulation gingival retraction is not widely used?

A

surgical

69
Q

Classification of retraction cords are depend on ___ including:

A

configuration;
- twisted
- knitted
- plain

70
Q

What surfaces finishes may be available for retraction cords?

A

waxed or unwaxed

71
Q

Describe a chemo-mechanical technique for gingival retraction:

A

pack retraction cord soaked in hemostatic agent, then dried and use cord packing instrument

72
Q

With a double cord technique the ____ diameter cord will be deeper into the sulcus

A

smaller

73
Q

How long should you wait to remove the cord after packing? (remember this time must be precise)

A

4 minutes

74
Q

What should you do immediately following removal of the retraction cord after sitting for 4 minutes?

A

inject impression material into the sulcus

75
Q

You should NOT let the retraction cord sit in the sulcus for more than:

A

4 minutes

76
Q

Developed as a substitute for agar impression material when its supply became scarce during WW2:

A

Irreversible hydrocolloid - alginate

77
Q

Based on a natural substance extracted from certain brown seaweed:

A

alginate

78
Q

When the soluble alginates are mixed with water, they form a ____ quite readily

A

sol gel

79
Q

alginate is ____ so moist tissue surfaces are NOT a problem

A

hydrophilic

80
Q

List the ingredients that make up alginate: (irreversible hydrocolloid):

A
  1. soluble alginates (sodium or potassium)
  2. calcium sulfate (reactor)
  3. zinc oxide
  4. potassium titanium fluoride
  5. diatomaceous earth
  6. sodium phosphate (retarder)
  7. coloring & flavoring agent
81
Q

What functions as the reactor in irreversible hydrocolloid (alginate)?

A

calcium sulfate

82
Q

What functions as the retarder in irreversible hydrocolloid (alginate)

A

sodium phosphate

83
Q

Component of alginate that reacts with potassium ions

A

potassium or sodium alginate

84
Q

Component of alginate that reacts with potassium alginate to form a dihydrate insoluble alginate gel:

A

Calcium Sulfate Dihydrate

85
Q

Equation representing alginate reaction (powder to gel):

A

Sodium alginate + CaSO4 —> Calcium alginate + Na2SO4

(Powder) —> (Gel)

86
Q

What is the mixing time for alginate? (based on fast or regular set)

A

45-60 seconds

87
Q

If the alginate is contaminated with components such as gypsum, this may:

A

accelerate the setting time

88
Q

The thickness of alginate should be:

A

3 mm

89
Q

What is the CDC recommendation for disinfection of alginate impression?

A

1:10 dilution of household bleach

90
Q

After pouring the impression, the stone cast should not be separated before:

A

60 min

91
Q

What are the two major factors that affect the shelf life of the impression?

A

storage temp & moisture

92
Q

The diagnostic cast should be removed from the impression longer than:

A

1 hour after its final set (no sooner than 60 minutes tho)

93
Q

If there is a delay in pouring the impression cast, this may result in:

A

dimensional changes

94
Q

Non-aqueous elastic material are typically made of:

A

synthetic rubber

95
Q

Offer potential solutions to the two main problems associated with hydrocolloids (poor tear resistance, poor dimensional stability)

A

Non-aqueous elastic impression material

96
Q

Impression material also known as Mercaptan or simply rubber:

A

polysulfide

97
Q

How is poly sulfide packaged?

A

It is provided as two tubes, a base and accelerator

98
Q

What is required for a polysulfide impression?

A

Custom tray

99
Q

“longer setting time, malodor, and stains clothes” describes:

A

polysulfide (elastomeric impression material)

100
Q

Describe the composition of BASE of polysulfide impression material:

A

polysulfide polymer mixed with inert fillers

101
Q

Describe the composition of the CATALYST of polysulfide impression material:

A

lead dioxide mixed with small amounts of sulfur and act as oxidation initiator

102
Q

Vinyl polysiloxane is considered a ____ impression material

A

elastomeric

103
Q

Describe the shelf life of VPS:

A

limited

104
Q

VPS requires a special:

A

tray adhesive

105
Q

Describe the packaging of VPS:

A

provided as auto-mix unit, syringe, and mixing tips

106
Q

With VPS, there is not syneresis or imbibition, however, responds with:

A

shrinkage over time

107
Q

VPS is more ____ so there is more of a chance of _____

A

flexible; distortion during removal

108
Q

What impression material is considered to have the best dimensional stability among impressions material?

A

VPS

109
Q

With VPS you should wait ____ before pouring for stress relaxation. It can be delayed with to ____.

A

20-30 min; 7-10 days

110
Q

Describe the composition of the following components of VPS (addition silicone):

  1. Base:
  2. Catalyst:
  3. Cross-linking agent:
  4. Filler
A
  1. Poly Dimethyl Siloxane
  2. Poly Vinyl Siloxane- platinum salt
  3. Alkyl Ortho Silicate or Organ Hydrogen Siloxane
  4. Filler- silica
111
Q

VPS may also be called:

A

addition silicone

112
Q

VPS undergoes a ___ reaction with ____ as the byproduct

A

addition; nothing!

113
Q

What characteristic of VPS contributes to uniform mixing, less air, and less mixing time?

A

auto mix

114
Q

What may inhibit the polymerization of VPS addition reaction?

A

Sulfur (for polymerization)

Latex gloves (retards the setting)

115
Q

Why is a dry field needed for VPS?

A

Because it is hydrophobic

116
Q

Surfactant may be added to VPS to:

A
  1. improve wettability
  2. less cast bubbles
117
Q

What is the secondary reaction of VPS (and describe it):

A

H2 release- a secondary reaction not a byproduce

118
Q

Due to the secondary reaction (H2 release) with VPS, you should:

A

delay pouring for 15-30 minutes

119
Q

With VPS secondary reaction, ____ acts as H2 scavengers

A

Platinum

120
Q

What are some key advantages to VPS:

A

Dimensional stability allowing for multiple pours and delayed pouring

121
Q
  • Hydrophilic
  • High elastic recovery
  • Provided as hand, auto-mix unit, or electronic mixing
  • light, medium, and heavy body consistency

These describe what type of impression material?

A

Polyether (elastomeric impression material)

122
Q

Polyether impression material may be difficult to:

A

remove from mouth or cast (must block out undercuts)

123
Q

T/F: VPS is less stiff than polyether

A

False

124
Q

T/F: VPS and Polyether are both hydrophobic

A

False- VPS is hydrophobic and Polyether is hydrophilic

125
Q

T/F: VPS and Polyether are both elastomeric impression mateirals

A

True

126
Q

Water, saliva, and blood affect the polyether material increasing:

A

marginal discrepency

127
Q

With poly ether impression material, _____ occurs if a thinning agent is used

A

increased water absorption

128
Q

Describe the composition of the following components of Polyether:

  1. Base:
  2. Catalyst
  3. Cross-linking agent
  4. Filler
A
  1. polyether
  2. glycol based plasticizers
  3. sulfate
  4. silica
129
Q

Polyether impression material undergoes a ___ reaction with ____ as the byproduct

A

addition; none

130
Q

Describe the setting time of polyether:

A

short

131
Q

Polyether impression materials provide excellent ____ & ____

A

accuracy and dimensional stability

132
Q

The excellent dimensional stability of polyether allows for:

A

multiples pours & delayed pouring

133
Q

Give then following types of impression materials, list the trays that must be used;

  1. Polysulfide (PS)
  2. Vinyl polysiloxance (VPS)
  3. Polyether (PE)
A
  1. custom tray
  2. custom or stock
  3. custom or stock
134
Q

Give then following types of impression materials, list the working/setting time (min):

  1. Polysulfide (PS)
  2. Vinyl polysiloxance (VPS)
  3. Polyether (PE)
A

1) working= 3-6; setting = 8-10
2. working = 2-4; setting = 4-6
3. working = 3; setting = 6

135
Q

Give then following types of impression materials, describe the pour time (related to dimensional stability)

  1. Polysulfide (PS)
  2. Vinyl polysiloxance (VPS)
  3. Polyether (PE)
A

1) 1 hour
2) 7 days
3) 7 days

136
Q

Give then following types of impression materials, describe the moisture tolerance/ pouring ease:

  1. Polysulfide (PS)
  2. Vinyl polysiloxance (VPS)
  3. Polyether (PE)
A
  1. acceptable
  2. poor/ adequate
  3. very good
137
Q

Give then following types of impression materials, describe tear strength:

  1. Polysulfide (PS)
  2. Vinyl polysiloxance (VPS)
  3. Polyether (PE)
A
  1. highest
  2. adequate
  3. adequate
138
Q

You take an impression on your patient and when you remove it, lots of voids are present. What may be the cause?

A

lifting intra-oral tip while syringing; or presence of moisture

139
Q

You take an impression on your patient and when you remove it you notice tacky, unset VPS material in the preparation area. What is the cause?

A

early removal or sulfur contamination from gloves

140
Q

Describe the effects of a disinfectant soaked paper towel placed on the following materials for 10 minutes:

  1. PS
  2. VPS
  3. PE
  4. Alginate
A
  1. potential expansion with increased exposure time
  2. no adverse effects
  3. potential expansion with increased exposure time
  4. imbibition and expansion
141
Q

Rather than soaking a paper towel with disinfectant and covering the impression material, it is probably better to:

A

rinse and spray the impression material

142
Q

Acceptable impression disinfectants include:

A
  1. glutaraldehyde
  2. iodophors
  3. sodium hypochlorite
  4. synthetic phenols
  5. dual or synergized quaternaries
  6. sodium bromide & chlorine
143
Q

T/F: All impression materials are NOT compatible with all disinfectants

A

true

144
Q

Is NOT a negative likeness or copy in reverse of the surface of an object

A

GTP-9 Digital impression

145
Q

Capturing the optical image directly of the patients anatomy or indirectly of a definitive cast of the anatomy

A

Digital scan

146
Q

Some available digital intraoral scanners include:

A
  1. CEREC Primescan
  2. Omnicam or Bluecam (Sirona)
  3. Tiors 3 Shape (3D Biocad)
147
Q
A

Fixed Prosthodontics I (13 decks)

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