Impression Materials and Technique Flashcards
1
Q
A negative likeness or copy in reverse of the surface of an object:
A
Analogue impression
2
Q
List the characteristics of an ideal impression material: (14)
A
- easy to mix and handle
- suitable working time
- suitable setting time
- compatible with die and stone materials
- not toxic or allergenic to the patient
- dimensionally stable
- accurate to record the fine details
- acceptable odor and 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 aspects
- economic
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
The impression should be extended enough to capture:
A
- vestibule
- tuberosities
- retromolar pad
6
Q
The 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
A contact angle of greater than 90 degrees surface not wetted:
A
Hydrophobic
9
Q
A contact angle of less than 90 degrees surface wetted:
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
Pseudoplasticity
17
Q
Why same material can be used in tray and syringe?
A
Pseudoplasticity
18
Q
Characteristic of a solid that behaves as an elastic solid and viscous liquid:
A
Viscoelasticity
19
Q
Viscoelacticity is related to:
A
the set impression
20
Q
Mechanical properties of 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 an impression material increased, the:
A
properties are improved
23
Q
With an increased load rate, the impression material has an increase ___ and ___
A
tear strength and elastic limit
24
Q
With quick removal of the impression material, there is:
A
decreased distortion
25
The ability to replicate the intra-oral surface details:
accuracy
26
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:
non-elastic impression material
29
What two categories does elastic impression material break down into?
1. hydrocolloids
2. non-aqueous elastomers
30
Hydrocolloids further break down into:
Agar reversible ; Alginate irreversible
31
Condensation silicone and addition silicone are examples of:
Non-aqueous elastomers
32
Classification of impression material described as:
Rigid, cannot be removed from undercuts:
Nonelastic
33
Classification of impression material described as:
Can 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 use an elastic impression material:
dentate impessions
36
_____ were the first impression materials that were popular in the previous century:
non-elastic/ rigid
37
- plaster of Paris
- impression plaster
- gutta percha
- modeling compound
- ZOE
- Various waxes
These are all examples of:
Non-elastic/rigid impression material
38
Less commonly used now with the exception of recording atrophic edentulous ridges or flappy ridges:
Non-elastic/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 material
42
Aqueous elastomeric impression material =
hydrocolloids
43
Non-aqueous elastomeric impression material =
polymers
44
What is the major component of aqueous elastomeric (hydrocolloids) impression material?
water
45
Aqueous elastomeric (hydrocolloid) impression material may be ____ or ___
reversible or irreversible
46
Give examples of non-aqueous elastomeric (polymers):
1. polysulfide
2. vinyl poly siloxane
3. polyether
47
Label the following image:
1. hydrocolloids
1a. Agar (reversible)
1b. Alginate (irreversible)
2. Non-aqueous elastomers
2a. polysulfides
2b. polyethers
2c. condensation silicone
2d. addition silicone
48
Elastic polymers come in different consistencies such as:
light, medium, heavy, and putty
49
What are the byproducts of the condensation polymerization of non-aqueous elastomeric impression material?
H20 or OH
50
What is the byproduct of addition polymerization of non-aqueous elastomeric impression material?
No 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 the 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
Retention & adhesion
53
What is the goal of a preliminary impression?
a fully or overextended impression of the arch with all anatomical landmarks
54
a fully or overextended impression of the arch with all anatomical landmarks
preliminary impression
55
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
56
The final impression material is selected depending on:
the type of impression required for the procedure
57
Single or double cord technique; cord(s) removed right before impression making
Tissue retraction
58
Tissue retraction may be required for:
final impressions
59
In a final impression the ____ dispenses into the sulcus, over and around the prepared teeth and onto the surrounding tissues
Light bodied consistency
60
What type of impression material is loaded into the custom tray with dried adhesive in a FINAL impression?
medium or heavy bodied
61
Where do you place the light bodied impression material in a FINAL impression?
1. sulcus
2. over and around prepared teeth
3. surrounding tissues
62
Describe the pressure used with medium/heavy bodied impression material for a final impression?
No downward pressure
63
To atruamatically 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
64
The purpose of tissue manipulation gingival retraction is to atruamatically displace gingiva tissues to allow access for impression material to:
record the finish line and provide sufficient thickness of the impression
65
Describe the techniques that may be used in tissue manipulation gingival retraction:
1. mechanical
2. chemo-mechanical
3. surfical
66
Impregnated cords are an example of:
chemo-mechanical technique
67
List the specific surgical techniques used in tissue manipulation gingival retraction:
1. electrosurgery
2. rotary curettage
3. laser
68
What form of tissue manipulation gingival retraction is not widely used?
surgical
69
Classification of retraction cords are depend on ___ including:
configuration;
- twisted
- knitted
- plain
70
What surfaces finishes may be available for retraction cords?
waxed or unwaxed
71
Describe a chemo-mechanical technique for gingival retraction:
pack retraction cord soaked in hemostatic agent, then dried and use cord packing instrument
72
With a double cord technique the ____ diameter cord will be deeper into the sulcus
smaller
73
How long should you wait to remove the cord after packing? (remember this time must be precise)
4 minutes
74
What should you do immediately following removal of the retraction cord after sitting for 4 minutes?
inject impression material into the sulcus
75
You should NOT let the retraction cord sit in the sulcus for more than:
4 minutes
76
Developed as a substitute for agar impression material when its supply became scarce during WW2:
Irreversible hydrocolloid - alginate
77
Based on a natural substance extracted from certain brown seaweed:
alginate
78
When the soluble alginates are mixed with water, they form a ____ quite readily
sol gel
79
alginate is ____ so moist tissue surfaces are NOT a problem
hydrophilic
80
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
81
What functions as the reactor in irreversible hydrocolloid (alginate)?
calcium sulfate
82
What functions as the retarder in irreversible hydrocolloid (alginate)
sodium phosphate
83
Component of alginate that reacts with potassium ions
potassium or sodium alginate
84
Component of alginate that reacts with potassium alginate to form a dihydrate insoluble alginate gel:
Calcium Sulfate Dihydrate
85
Equation representing alginate reaction (powder to gel):
Sodium alginate + CaSO4 ---> Calcium alginate + Na2SO4
(Powder) ---> (Gel)
86
What is the mixing time for alginate? (based on fast or regular set)
45-60 seconds
87
If the alginate is contaminated with components such as gypsum, this may:
accelerate the setting time
88
The thickness of alginate should be:
3 mm
89
What is the CDC recommendation for disinfection of alginate impression?
1:10 dilution of household bleach
90
After pouring the impression, the stone cast should not be separated before:
60 min
91
What are the two major factors that affect the shelf life of the impression?
storage temp & moisture
92
The diagnostic cast should be removed from the impression longer than:
1 hour after its final set (no sooner than 60 minutes tho)
93
If there is a delay in pouring the impression cast, this may result in:
dimensional changes
94
Non-aqueous elastic material are typically made of:
synthetic rubber
95
Offer potential solutions to the two main problems associated with hydrocolloids (poor tear resistance, poor dimensional stability)
Non-aqueous elastic impression material
96
Impression material also known as Mercaptan or simply rubber:
polysulfide
97
How is poly sulfide packaged?
It is provided as two tubes, a base and accelerator
98
What is required for a polysulfide impression?
Custom tray
99
"longer setting time, malodor, and stains clothes" describes:
polysulfide (elastomeric impression material)
100
Describe the composition of BASE of polysulfide impression material:
polysulfide polymer mixed with inert fillers
101
Describe the composition of the CATALYST of polysulfide impression material:
lead dioxide mixed with small amounts of sulfur and act as oxidation initiator
102
Vinyl polysiloxane is considered a ____ impression material
elastomeric
103
Describe the shelf life of VPS:
limited
104
VPS requires a special:
tray adhesive
105
Describe the packaging of VPS:
provided as auto-mix unit, syringe, and mixing tips
106
With VPS, there is not syneresis or imbibition, however, responds with:
shrinkage over time
107
VPS is more ____ so there is more of a chance of _____
flexible; distortion during removal
108
What impression material is considered to have the best dimensional stability among impressions material?
VPS
109
With VPS you should wait ____ before pouring for stress relaxation. It can be delayed with to ____.
20-30 min; 7-10 days
110
Describe the composition of the following components of VPS (addition silicone):
1. Base:
2. Catalyst:
3. Cross-linking agent:
4. Filler
1. Poly Dimethyl Siloxane
2. Poly Vinyl Siloxane- platinum salt
3. Alkyl Ortho Silicate or Organ Hydrogen Siloxane
4. Filler- silica
111
VPS may also be called:
addition silicone
112
VPS undergoes a ___ reaction with ____ as the byproduct
addition; nothing!
113
What characteristic of VPS contributes to uniform mixing, less air, and less mixing time?
auto mix
114
What may inhibit the polymerization of VPS addition reaction?
Sulfur (for polymerization)
Latex gloves (retards the setting)
115
Why is a dry field needed for VPS?
Because it is hydrophobic
116
Surfactant may be added to VPS to:
1. improve wettability
2. less cast bubbles
117
What is the secondary reaction of VPS (and describe it):
H2 release- a secondary reaction not a byproduce
118
Due to the secondary reaction (H2 release) with VPS, you should:
delay pouring for 15-30 minutes
119
With VPS secondary reaction, ____ acts as H2 scavengers
Platinum
120
What are some key advantages to VPS:
Dimensional stability allowing for multiple pours and delayed pouring
121
- 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?
Polyether (elastomeric impression material)
122
Polyether impression material may be difficult to:
remove from mouth or cast (must block out undercuts)
123
T/F: VPS is less stiff than polyether
False
124
T/F: VPS and Polyether are both hydrophobic
False- VPS is hydrophobic and Polyether is hydrophilic
125
T/F: VPS and Polyether are both elastomeric impression mateirals
True
126
Water, saliva, and blood affect the polyether material increasing:
marginal discrepency
127
With poly ether impression material, _____ occurs if a thinning agent is used
increased water absorption
128
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
129
Polyether impression material undergoes a ___ reaction with ____ as the byproduct
addition; none
130
Describe the setting time of polyether:
short
131
Polyether impression materials provide excellent ____ & ____
accuracy and dimensional stability
132
The excellent dimensional stability of polyether allows for:
multiples pours & delayed pouring
133
Give then following types of impression materials, list the trays that must be used;
1. Polysulfide (PS)
2. Vinyl polysiloxance (VPS)
3. Polyether (PE)
1. custom tray
2. custom or stock
3. custom or stock
134
Give then following types of impression materials, list the working/setting time (min):
1. Polysulfide (PS)
2. Vinyl polysiloxance (VPS)
3. Polyether (PE)
1) working= 3-6; setting = 8-10
2. working = 2-4; setting = 4-6
3. working = 3; setting = 6
135
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)
1) 1 hour
2) 7 days
3) 7 days
136
Give then following types of impression materials, describe the moisture tolerance/ pouring ease:
1. Polysulfide (PS)
2. Vinyl polysiloxance (VPS)
3. Polyether (PE)
1. acceptable
2. poor/ adequate
3. very good
137
Give then following types of impression materials, describe tear strength:
1. Polysulfide (PS)
2. Vinyl polysiloxance (VPS)
3. Polyether (PE)
1. highest
2. adequate
3. adequate
138
You take an impression on your patient and when you remove it, lots of voids are present. What may be the cause?
lifting intra-oral tip while syringing; or presence of moisture
139
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?
early removal or sulfur contamination from gloves
140
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
1. potential expansion with increased exposure time
2. no adverse effects
3. potential expansion with increased exposure time
4. imbibition and expansion
141
Rather than soaking a paper towel with disinfectant and covering the impression material, it is probably better to:
rinse and spray the impression material
142
Acceptable impression disinfectants include:
1. glutaraldehyde
2. iodophors
3. sodium hypochlorite
4. synthetic phenols
5. dual or synergized quaternaries
6. sodium bromide & chlorine
143
T/F: All impression materials are NOT compatible with all disinfectants
true
144
Is NOT a negative likeness or copy in reverse of the surface of an object
GTP-9 Digital impression
145
Capturing the optical image directly of the patients anatomy or indirectly of a definitive cast of the anatomy
Digital scan
146
Some available digital intraoral scanners include:
1. CEREC Primescan
2. Omnicam or Bluecam (Sirona)
3. Tiors 3 Shape (3D Biocad)
147
