Impression materials & Technique Flashcards
(146 cards)
1
Q
A negative likeness or copy in reverse the surface of an object:
A
Analogue impression
2
Q
List the characteristics of an ideal impression material: (8)
A
- easy to mix and handle
- suitable working time
- suitable setting time
- compatible with die and stone materials
- not toxic or allergenic to patient
- dimensionally stable
- accurate to record the fine details
- acceptable odor & taste
- adequate stretch
- adequate shelf life
- ready to be disinfected without loss of accuracy
- fluid or plastic when inserted into the mouth
- it must be an exact record of all the aspects
- economics
3
Q
An impression should be an exact duplication of the prepared teeth, including uncut tooth structure:
A
beyond finish line
4
Q
The impression should be free of air bubbles especially in the:
A
- finish line
- occlusal surfaces
5
Q
An impression should be extended enough to capture:
A
- vestibule
- tuberosities
- retromolar pad
6
Q
Ability of a liquid to flow over a solid surface:
A
wettability
7
Q
Wettability is related to ____ & ____
A
-surface energy of the solid
-surface tension of the liquid
8
Q
Contact angle of greater than 90 degrees surface not wetted:
A
hydrophobic
9
Q
Contact angle of less than 90 degrees surface wettled:
A
hydrophilic
10
Q
Resistance of liquid to flow:
A
Viscosity
11
Q
Viscosity is the reverse of:
A
fluidity
12
Q
Viscosity is related to ____, liquid material
A
unset
13
Q
a fluid viscosity is not affected by shear rate; viscosity constant:
A
Newtonian
14
Q
a fluid that does not follow; viscosity can be changed:
A
None-newtonian
15
Q
Shear thinning:
A
Pseudoplasticity
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
17
Q
Why same material can be used in tray and syringe?
A
psuedoplasticity
18
Q
Characteristic of a solid that behaves as an elastic solid & a viscous liquid:
A
Viscoelasticity
19
Q
Viscoelasticity is related to the:
A
set impression
20
Q
Mechanical properties contributing to viscoelasticity are dependent on:
A
loading rate
21
Q
The loading rate of an impression material is associated with:
A
viscous nature
22
Q
As load rate of impression material increases, the:
A
Properties are improved
23
Q
With an increased load rate, the impression material has an increased ____ and _____
A
tear strength; elastic limit
24
Q
Quick removal of the impression material results in:
A
decreased distortion
25
The ability to replicate the intra-oral surface details:
accuracy
26
The ability to retain its absolute dimensional size over time:
dimensional stability
27
The ability to resist tearing in thin sections, such as through the feather edge material within the gingival sulcus:
Tear resistance
28
-Plaster
-Impression compound
-ZOE
-Impression waxes
These are all categorized as:
Nonelastic impression material
29
Elastic impression material breaks down into what two main categories?
1. Hydrocolloids
2. Non-aqueous elastomers
30
Hydrocolloids further break down into what categories?
Agar reversible & alginate irreversible
31
Condensation silicone & addition silicone are examples of:
Non-aqueous elastomers
32
Classication of impression material described as rigid, & cannot be removed from undercuts:
Nonelastic
33
Classification of impression material described as being able to be removed from undercuts without distortion:
Elastic
34
Give an example of when you would use non-elastic impression material:
Edentulous impressions
35
Give an example of when you would you elastic impression material:
Dentate impressions
36
_____ were the first impression materials that were in popular in the previous century
Nonelastic/rigid
37
-plaster of Paris
-impression plaster
-gutta percha
-modeling compound
-ZOE
-various waxes
These are all examples of:
Nonelastic/rigid impression material
38
Less commonly used now with the exception of recording atrophic edentulous ridges or flappy ridges:
Nonelastic/rigid impression material
39
What was the first elastic impression material (1925):
Reversible hydrocolloid (agar)
40
Reversible hydrocolloid=
Irreversible hydrocolloid=
Agar
Alginate
41
-reversible hydrocolloid
-irreversible hydrocolloid
-polysulfide rubber
-vinyl poly siloxanes
-polyether
These are all examples of:
Elastic impression materials
42
Aqueous elastomeric impression materials=
hdyrocolloids
43
non-aqueous elastomeric impression materials=
polymers
44
What is the major component of aqueous elastomeric (hydrolloids) impression material?
Water
45
Aqueous elastomeric (hydrolloid) impression material may be ____ or ____
reversible or irreversible
46
Give examples of non-aqueous elastomeric (polymers):
1. polysulfide
2. vinyl polysiloxane
3. polyether
47
Label the following image:
1) Hydrocolloids
1a) agar (reversible)
1b) alginate (irreversible)
2) Non-aqeuous elastomers
2a) polysulfides
2b) polyethers
2c) condensation silicone
2d) addition silicone
48
Elastic polymers come in different consistencies such as:
light
medium
heavy
putty
49
What are the byproducts of condensation polymerization of non-aqueous elastomeric impression materials?
H2O or OH
50
What is the byproduct of addition polymerization of non-aqueous elastomeric impression materials?
Non byproduct
51
Why must an impression tray be sufficiently rigid?
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
52
Used to prevent impression distortion due to material pulling away from the tray:
impression retention & adhesion
53
A fully or overextended of the arch with all anatomical landmarks
Preliminary impression
54
List the purposes of a preliminary impression: (7)
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
55
The final impression material is selected depending on:
the type of impression required for the procedure
56
single or double cord technique; cord(s) removed right before impression making:
Tissue retraction
57
Tissue retraction may be required for:
final impressions
58
In a final impression the ________ dispenses into the sulcus, over around the prepared teeth & onto the surrounding tissues
light bodied consistency
59
What type of impression material is loaded into the custom tray with dried adhesive in a FINAL impression?
Medium or heavy bodied
60
Where do you place the light bodied impression material in a FINAL impression?
1. sulcus
2. over & around prepared teeth
3. surrounding tissues
61
Describe the pressure used with medium/heavy bodied impression material for a final impression:
no downward pressure
62
To traumatically displace gingival tissues to allow access for impression material to record the finish line and provide sufficient thickness of the impression:
Tissue manipulation gingival retraction
63
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
the finish line; sufficient thickness
64
Describe the techniques that may be used in tissue manipulation gingival retraction:
1. mechanical
2. chemo-mechanical
3. surgical
65
Impregnated retraction cords are an example of:
chemo-mechanical technique of gingival retraction
66
List the specific surgical techniques used in tissue manipulation gingival retraction:
1. Electrosurgery
2. rotary curettage
3. laser
67
What form of tissue manipulation gingival retraction is not widely used?
surgical
68
Classification of retraction cords are dependent on ____ and include:
configuration
-twisted
-knitted
-plain
69
What surface finishes may be available for retraction cords?
waxed or unwaxed
70
Describe the chemo-mechanical technique for gingival retraction:
pack retraction cord, soaked in hemostatic agent then dried; using cord packing instrument
71
With double cord technique the ____ diameter cord will be deeper into the sulcus
smaller diameter cord
72
How long should you wait to remove the cord after packing?
(remember this time must be precise)
4 minutes
73
What should you do immediately following the removal of the retraction cord (after sitting for 4 min):
inject impression material into sulcus
74
You should NOT let the retraction cord sit in the sulcus for more than
4 min
75
Developed as a substitute for agar impression material when its supply became scarce during the WW2:
Irreversible hydrocolloid- alginate
76
Made from a natural substance extracted from certain brown seaweed:
alginate
77
When the soluble alginate are mixed with water they form a ____ quite readily
sol gel
78
alginate is _____, so moist tissue surfaces are NOT a problem
hydrophilic
79
List the ingredients that make up alginate (irreversible hydrocolloid)
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
What functions as the reactor in irreversible hydrocolloid (alginate)?
Calcium sulfate
81
What functions as the retarder in irreversible hydrocolloid (alginate)?
Sodium phosphate
82
Component of alginate that reacts with calcium ions:
Potassium or sodium alginate
83
Component of alginate that reacts with potassium alginate to form dihydrate insoluble alginate gel:
calcium sulfate dihydrate
84
Equation representing alginate reaction (powder to gel)
sodium alginate + CaSO4 --> Calcium alginate + Na2SO4
(powder --> gel)
85
What is the mixing time for alginate (based on fast or regular set)
45-60 seconds
86
If the alginate is contaminated with components such as gypsum, this may:
accelerate the setting time
87
The thickness of alginate should be:
3mm
88
What is the CDC recommendation for disinfection of alginate impression?
1:10 dilution of household bleach
89
After pouring the impression the stone cast should not be separated before:
60 min
90
What are the two major factors that affects the shelf life of the impression?
storage temp & moisture
91
The diagnostic cast should be removed form the impression no longer than:
one hour after its final set (but also no sooner than 60 min according slides earlier)
92
If there is a delay in pouring the impression casts, this may result in:
dimensional changes
93
Non-aqueous elastic materials are typically made of:
synthetic rubber
94
Offer potential solutions to the two main problems associated with hydrocolloids (poor tear resistance, poor dimensional stability)
Non-aqueous elastic impression material
95
Impression material also known as mercaptan or simply rubber:
polysulfide
96
Now is polysulfide packaged?
it is provided as two tubes- a used and accelerator
97
What is required for a polysufide impression?
custom tray
98
-longer setting time
-malodor
-stains clothes
this describes
Polysulfide elastomeric impression material
99
Describe the composition of the BASE of polysulfide impression material:
polysulfide polymer mixed with inert fillers
100
Describe the composition of the CATALYST of polysulfide impression material:
lead dioxide mixed with small amounts of sulfur and act as oxidation inhibitor
101
Vinyl polysiloxane is considered a ____ impression material
elasteromeric
102
Describe the shelf life VPS:
Limited shelf life
103
VPS requires a special:
tray adhesive
104
Describe the packaging of VPS:
provided as auto-mix unit, syringe & mixing tips
105
With VPS there is no syneresis or imbibition, however responds with:
shrinkage over time
106
VPS is more _____ meaning there is more of a chance of _____ during removal
flexible; distortion
107
What impression material is considered to have the best dimensional stability among impression materials?
VPS
108
With VPS you should wait before pouring for stress relaxation. It can be delayed up to _____
20-30 min; 7-10 days
109
Describe the composition of the following components of VPS (addition silicon):
1. base:
2. catalyst:
3. cross-linking agent:
4. filler:
1. poly dimethyl siloxane
2. polyvinyl siloxane - platinum salt
3. alkyl ortho silicate or organ hydrogen siloxane
4. silica
110
VPS may also be called:
addition silicon
111
VPS undergoes a ______ reaction with _____ as the byproduct
addition; nothing
112
What characteristic of VPS contributes to its uniform mixing, less air, and less mixing time?
auto-mix
113
what may inhibit the polymerization of VPS addition reaction:
sulfur (for polymerization) & latex gloves (retards the setting)
114
Why is a dry field needed for VPS?
because it is hydrophobic
115
Surfactant may be added to VPS to:
1. improve wettability
2. less cast bubbles
116
What is the secondary reaction of VPS? Describe
H2 release- a secondary reaction not a byproduct
117
Due to the secondary reaction (H2 release) with VPS, you should delay pouring for:
15-30 min
118
With VPS's secondary reaction, _____ acts as H2 scavengers
Platinum
119
What are some key advantages to VPS:
Dimensional stability allowing for multiple pours & delayed pouring
120
-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?
Polyether (elastomeric impression material)
121
Polyether impression material may be difficult to:
remove from mouth or cast (must block out undercuts)
122
T/F: VPS is less stiff than polyether
False
123
T/F: VPS & polyether are both hydrophobic
False- VPS is hydrophobic & polyether is hydrophilic
124
T/F: VPS and polyether are both elastomeric impression materials
True
125
Water, saliva and blood affect the polyether material, increasing:
marginal discrepancy
126
With polyether impression material, _____ occurs if a thinning agent is used
increased water absorption
127
Describe the composition of the following components of polyether:
1. base:
2. catalyst:
3. cross-linking agent:
4. filler:
1. polyether
2. glycol based plasticizers
3. sulfate
4. silica
128
Polyether impression material undergoes a ____ reaction with _____ as the byproduct
addition; nothing
129
Describe the setting time to polyether:
short
130
Polyether impression materials provides excellent _____ & _____
accuracy & dimensional stability
131
The excellent dimensional stability of polyether allows for:
1. multiple pours
2. delayed pouring
132
Given the following types of impression materials- list the trays that must be used:
1. Polysulfide (PS)
2. Vinylpolysiloxane (VPS)
3. Polyether (PE)
1. custom tray
2. custom or stock
3. custom or stock
133
Given the following types of impression materials- list the working/setting time in minutes:
1. Polysulfide (PS)
2. Vinylpolysiloxane (VPS)
3. Polyether (PE)
1) working= 3-6
setting = 8-10
2) working= 2-4
setting= 4-6
3) working= 3
setting= 6
134
Given the following types of impression materials- describe the pour (related to dimensional stability)
1. Polysulfide (PS)
2. Vinylpolysiloxane (VPS)
3. Polyether (PE)
1)1 hour
2) 7d
3) 7d
135
Given the following types of impression materials- describe the moisture tolerance/pouring ease:
1. Polysulfide (PS)
2. Vinylpolysiloxane (VPS)
3. Polyether (PE)
1. acceptable
2. poor/adequate
3. very good
136
Given the following types of impression materials- describe the tear strength:
1. Polysulfide (PS)
2. Vinylpolysiloxane (VPS)
3. Polyether (PE)
1. highest
2. adequate
3. adequate
137
You take an impression on your patient and when you remove it, lots of voids are present, what may be the cause?
lifting intraoral tip while syringing; presence of moisture
138
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?
Early removal or sulfur contamination from gloves
139
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
1. potential expansion w increased exposure time
2. no adverse effects
3. potential expansion w increased exposure time
4. imbibition & expansion
140
Rather than soaking a paper towel with disinfectant and covering the impression material, it is probably better to:
rinse and spray the impression
141
Acceptable impression disinfections include:
1. glutaraldehyde
2. iodophores
3. sodium hypochlorite
4. synthetic phenols
5. dual or synergies quaternaries
6. sodium bromide & chlorine
142
T/F: All impression materials are not compatible with all disinfectants
true
143
Is NOT a negative likeness or copy & reverse of the surface of an object:
Digital impression (GPT9)
144
Capturing the optical image directly of the patients anatomy or indirectly of a definitive cast of the anatomy:
digital scan
145
Some available digital intraoral scanners include:
1. CEREC Primescan
2. Omnicam or Bluecam (Sirona)
3. Tiors, 3 shape (3D biocad)
146
