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Fixed Prosthodontics > Impression materials & Technique > Flashcards

Impression materials & Technique Flashcards

1
Q

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

A

Analogue impression

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2
Q

List the characteristics of an ideal impression material: (8)

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 patient
  6. dimensionally stable
  7. accurate to record the fine details
  8. acceptable odor & 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 the aspects
  14. economics
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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

An impression should be extended enough to capture:

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

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

Contact angle of greater than 90 degrees surface not wetted:

A

hydrophobic

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9
Q

Contact angle of less than 90 degrees surface wettled:

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

Psuedoplasticity

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17
Q

Why same material can be used in tray and syringe?

A

psuedoplasticity

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18
Q

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

A

Viscoelasticity

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19
Q

Viscoelasticity is related to the:

A

set impression

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20
Q

Mechanical properties contributing to 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 impression material increases, the:

A

Properties are improved

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23
Q

With an increased load rate, the impression material has an increased ____ and _____

A

tear strength; elastic limit

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24
Q

Quick removal of the impression material results in:

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

The 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

Nonelastic impression material

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29
Q

Elastic impression material breaks down into what two main categories?

A
  1. Hydrocolloids
  2. Non-aqueous elastomers
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30
Q

Hydrocolloids further break down into what categories?

A

Agar reversible & alginate irreversible

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31
Q

Condensation silicone & addition silicone are examples of:

A

Non-aqueous elastomers

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32
Q

Classication 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 being able to 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 you elastic impression material:

A

Dentate impressions

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36
Q

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

A

Nonelastic/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

Nonelastic/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

Nonelastic/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 materials

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42
Q

Aqueous elastomeric impression materials=

A

hdyrocolloids

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43
Q

non-aqueous elastomeric impression materials=

A

polymers

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44
Q

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

A

Water

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45
Q

Aqueous elastomeric (hydrolloid) 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 polysiloxane
  3. polyether
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47
Q

Label the following image:

A

1) Hydrocolloids
1a) agar (reversible)
1b) alginate (irreversible)

2) Non-aqeuous 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
putty

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49
Q

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

A

H2O or OH

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50
Q

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

A

Non 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 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

impression retention & adhesion

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53
Q

A fully or overextended of the arch with all anatomical landmarks

A

Preliminary impression

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54
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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55
Q

The final impression material is selected depending on:

A

the type of impression required for the procedure

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56
Q

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

A

Tissue retraction

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57
Q

Tissue retraction may be required for:

A

final impressions

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58
Q

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

A

light bodied consistency

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59
Q

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

A

Medium or heavy bodied

60
Q

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

A
  1. sulcus
  2. over & around prepared teeth
  3. surrounding tissues
61
Q

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

A

no downward pressure

62
Q

To traumatically 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

63
Q

The purpose of tissue manipulation gingival retraction is to atraumatically displace gingival tissues to allow access for impression material to record _____ and provide ____ of the impression

A

the finish line; sufficient thickness

64
Q

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

A
  1. mechanical
  2. chemo-mechanical
  3. surgical
65
Q

Impregnated retraction cords are an example of:

A

chemo-mechanical technique of gingival retraction

66
Q

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

A
  1. Electrosurgery
  2. rotary curettage
  3. laser
67
Q

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

A

surgical

68
Q

Classification of retraction cords are dependent on ____ and include:

A

configuration
-twisted
-knitted
-plain

69
Q

What surface finishes may be available for retraction cords?

A

waxed or unwaxed

70
Q

Describe the chemo-mechanical technique for gingival retraction:

A

pack retraction cord, soaked in hemostatic agent then dried; using cord packing instrument

71
Q

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

A

smaller diameter cord

72
Q

How long should you wait to remove the cord after packing?

(remember this time must be precise)

A

4 minutes

73
Q

What should you do immediately following the removal of the retraction cord (after sitting for 4 min):

A

inject impression material into sulcus

74
Q

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

A

4 min

75
Q

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

A

Irreversible hydrocolloid- alginate

76
Q

Made from a natural substance extracted from certain brown seaweed:

A

alginate

77
Q

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

A

sol gel

78
Q

alginate is _____, so moist tissue surfaces are NOT a problem

A

hydrophilic

79
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
80
Q

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

A

Calcium sulfate

81
Q

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

A

Sodium phosphate

82
Q

Component of alginate that reacts with calcium ions:

A

Potassium or sodium alginate

83
Q

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

A

calcium sulfate dihydrate

84
Q

Equation representing alginate reaction (powder to gel)

A

sodium alginate + CaSO4 –> Calcium alginate + Na2SO4

(powder –> gel)

85
Q

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

A

45-60 seconds

86
Q

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

A

accelerate the setting time

87
Q

The thickness of alginate should be:

A

3mm

88
Q

What is the CDC recommendation for disinfection of alginate impression?

A

1:10 dilution of household bleach

89
Q

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

A

60 min

90
Q

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

A

storage temp & moisture

91
Q

The diagnostic cast should be removed form the impression no longer than:

A

one hour after its final set (but also no sooner than 60 min according slides earlier)

92
Q

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

A

dimensional changes

93
Q

Non-aqueous elastic materials are typically made of:

A

synthetic rubber

94
Q

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

A

Non-aqueous elastic impression material

95
Q

Impression material also known as mercaptan or simply rubber:

A

polysulfide

96
Q

Now is polysulfide packaged?

A

it is provided as two tubes- a used and accelerator

97
Q

What is required for a polysufide impression?

A

custom tray

98
Q

-longer setting time
-malodor
-stains clothes

this describes

A

Polysulfide elastomeric impression material

99
Q

Describe the composition of the BASE of polysulfide impression material:

A

polysulfide polymer mixed with inert fillers

100
Q

Describe the composition of the CATALYST of polysulfide impression material:

A

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

101
Q

Vinyl polysiloxane is considered a ____ impression material

A

elasteromeric

102
Q

Describe the shelf life VPS:

A

Limited shelf life

103
Q

VPS requires a special:

A

tray adhesive

104
Q

Describe the packaging of VPS:

A

provided as auto-mix unit, syringe & mixing tips

105
Q

With VPS there is no syneresis or imbibition, however responds with:

A

shrinkage over time

106
Q

VPS is more _____ meaning there is more of a chance of _____ during removal

A

flexible; distortion

107
Q

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

A

VPS

108
Q

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

A

20-30 min; 7-10 days

109
Q

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

  1. base:
  2. catalyst:
  3. cross-linking agent:
  4. filler:
A
  1. poly dimethyl siloxane
  2. polyvinyl siloxane - platinum salt
  3. alkyl ortho silicate or organ hydrogen siloxane
  4. silica
110
Q

VPS may also be called:

A

addition silicon

111
Q

VPS undergoes a ______ reaction with _____ as the byproduct

A

addition; nothing

112
Q

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

A

auto-mix

113
Q

what may inhibit the polymerization of VPS addition reaction:

A

sulfur (for polymerization) & latex gloves (retards the setting)

114
Q

Why is a dry field needed for VPS?

A

because it is hydrophobic

115
Q

Surfactant may be added to VPS to:

A
  1. improve wettability
  2. less cast bubbles
116
Q

What is the secondary reaction of VPS? Describe

A

H2 release- a secondary reaction not a byproduct

117
Q

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

A

15-30 min

118
Q

With VPS’s secondary reaction, _____ acts as H2 scavengers

A

Platinum

119
Q

What are some key advantages to VPS:

A

Dimensional stability allowing for multiple pours & delayed pouring

120
Q

-Hydrophilic
-High elastic recovery
-Provided as hand auto-mix unit , or electronic mixing
-light, medium & heavy body consistencies

These describe what type of impression material?

A

Polyether (elastomeric impression material)

121
Q

Polyether impression material may be difficult to:

A

remove from mouth or cast (must block out undercuts)

122
Q

T/F: VPS is less stiff than polyether

A

False

123
Q

T/F: VPS & polyether are both hydrophobic

A

False- VPS is hydrophobic & polyether is hydrophilic

124
Q

T/F: VPS and polyether are both elastomeric impression materials

A

True

125
Q

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

A

marginal discrepancy

126
Q

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

A

increased water absorption

127
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
128
Q

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

A

addition; nothing

129
Q

Describe the setting time to polyether:

A

short

130
Q

Polyether impression materials provides excellent _____ & _____

A

accuracy & dimensional stability

131
Q

The excellent dimensional stability of polyether allows for:

A
  1. multiple pours
  2. delayed pouring
132
Q

Given the following types of impression materials- list the trays that must be used:

  1. Polysulfide (PS)
  2. Vinylpolysiloxane (VPS)
  3. Polyether (PE)
A
  1. custom tray
  2. custom or stock
  3. custom or stock
133
Q

Given the following types of impression materials- list the working/setting time in minutes:

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

1) working= 3-6
setting = 8-10

2) working= 2-4
setting= 4-6

3) working= 3
setting= 6

134
Q

Given the following types of impression materials- describe the pour (related to dimensional stability)

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

1)1 hour
2) 7d
3) 7d

135
Q

Given the following types of impression materials- describe the moisture tolerance/pouring ease:

  1. Polysulfide (PS)
  2. Vinylpolysiloxane (VPS)
  3. Polyether (PE)
A
  1. acceptable
  2. poor/adequate
  3. very good
136
Q

Given the following types of impression materials- describe the tear strength:

  1. Polysulfide (PS)
  2. Vinylpolysiloxane (VPS)
  3. Polyether (PE)
A
  1. highest
  2. adequate
  3. adequate
137
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 intraoral tip while syringing; presence of moisture

138
Q

You take an impression of 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

139
Q

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

  1. PS
  2. VPS
  3. PE
  4. alginate
A
  1. potential expansion w increased exposure time
  2. no adverse effects
  3. potential expansion w increased exposure time
  4. imbibition & expansion
140
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

141
Q

Acceptable impression disinfections include:

A
  1. glutaraldehyde
  2. iodophores
  3. sodium hypochlorite
  4. synthetic phenols
  5. dual or synergies quaternaries
  6. sodium bromide & chlorine
142
Q

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

A

true

143
Q

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

A

Digital impression (GPT9)

144
Q

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

A

digital scan

145
Q

Some available digital intraoral scanners include:

A
  1. CEREC Primescan
  2. Omnicam or Bluecam (Sirona)
  3. Tiors, 3 shape (3D biocad)
146
Q
A

Fixed Prosthodontics (13 decks)

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