10/2: Impression Material and Technique Flashcards
1
Q
- What is a GPT-9 impression?
A
Digital impression
NOT a Negative likeness or copy in reverse of the surface of an object
2
Q
- This is a method and manner used in making a negative likeness
A
a. Impression technique
3
Q
- An impression should include tooth structure beyond
A
a. The finish line
4
Q
- An impression should include tooth structure beyond the finish line to facilitate
A
a. Die ditching
5
Q
- Should an impression extend to capture the vestibules, tuberosities, and retromolar pad?
A
Yes
6
Q
- Do you want to have air bubbles?
A
No
7
Q
- This is the ability of liquid to flow over a solid surface
A
Wettability
7
Q
- Wettability related to the surface energy of the ______ and the surface tension of the ______
A
a. Solid
b. Liquid
8
Q
- What is the contact angle of a hydrophobic?
A
a. >90
9
Q
- What is the contact angle of a hydrophilic?
A
a. <90
10
Q
- This is the resistance of liquid to flow, reverse of fluidity
A
a. Viscosity
11
Q
- Viscosity relates to _____, liquid material
A
a. Unset
12
Q
- This is when a fluid viscosity is NOT affected by shear rate, velocity is the same
A
a. Newtonian
13
Q
- This is a fluid that does not follow newtonian, velocity can be changed
A
a. Non-newtonian
14
Q
- This is shear thinning
A
a. Pseudoplasticity
15
Q
- This is when you have reduced viscosity and viscous with increased shear
A
a. Pseudoplasticity
16
Q
- This is characteristic of solid that behaves as an elastic solid and viscous liquid
A
a. Viscoelasticity
17
Q
- The mechanical properties of viscoelasticity is dependent on
A
a. Loading rate
18
Q
- As you increase the loading rate of viscoelasticity, what happens?
A
a. Properties improve
19
Q
- This is the ability to replicate the inrta-oral surface details
A
a. Accuracy
20
Q
- This is the ability to retain its absolute dimensional size over time
A
a. Dimensional stability
21
Q
- This is the ability to resist tearing in thin sections, such as through feather edge material within
the gingival sulcus
A
a. Tear resistance
22
Q
- What are the 2 types of impression materials?
A
a. Elastic
b. Non-elastic
23
Q
- What are the types of non-elastic materials?
A
a. Plaster
b. Impression compound
c. Zinc oxide eugenol
d. Impression wax
24
25. What are the types of hydrocolloids?
a. Agar reversible
b. Alginate irreversible
25
26. What are the types of non-aqueous elastomers?
a. Polysulfides
b. Polyethers
c. Condensation silicone
d. Additional silicone
26
27. This are rigid and cannot be removed from undercuts
a. Nonelastic
27
28. Edentulous impressions are
Nonelastic
28
29. These can be removed from undercuts without distortion
Elastic
29
30. Dentate impressions are
Elastic
30
31. Is reversible agar commonly used today?
No
31
32. The soften under heat and solidify when cooled (temperature)
a. Reversible hydrocolloid
32
33. What kind of bonds do you see in reversible hydrocolloids?
a. Secondary bonds
33
34. This is a chemical reaction that cannot revert back to present state
a. Irreversible hydrocolloids
34
35. What kind of bonds do you see in irreversible hydrocolloids?
a. Primary bonds
35
36. Agar and alginate go from _____ to _____
a. Sol to gel
36
37. What are the gel properties?
a. Evaporation (shrinkage)
b. Syneresis: gel relaxation, water extruded from gel (shrinkage)
c. Imbibition: water absorbed causing expansion
37
38. Vinyl polysiloxane is known as
PVS
38
39. What is the byproduct of condensation?
a. H2O or OH
39
40. What is the byproduct of addition?
a. No byproduct
40
41. How far back should the tray extend?
a. 2-3mm beyond 3rd molars, retromolar, or tuberosities
41
42. How much material do you want between tray and occlusal/incisal edges?
a. 2-3mm
42
43. What are the types of trays?
a. Stock
b. Custom trays
43
44. This is used to prevent impression distortion due to material pulling away from the tray
a. Chemical Adhesion
b. Mechanical perforations or rims
44
45. Adhesive materials are
a. Specific for each material
b. Should always be used
c. Apply and dry
45
46. The goal of this is to get a fully or overextended impression of the arch
a. Preliminary impression
46
47. Good impressions are
a. Made not taken
47
48. Describe tooth retraction
a. 1 or 2 cords packed and removed right before taking final impression
48
49. After you take out the cord, what do you do?
a. Light body on sulcus
b. Medium and heavy impression on top
49
50. What are the techniques for gingival retraction?
a. Mechanical
b. Chemo-mechanical → cord
c. Surgery
50
51. How often is surgery used?
a. Very rarely
51
52. What are the types of cord?
a. Twisted
b. Knitted
c. Plain
52
53. How long should you leave the cord?
a. 4 minutes
53
54. Alginate is extracted from
a. Brown seaweed
54
55. What is the alginate equation?
a. Potassium or Sodium alginate + Calcium sulfate → insoluble calcium alginate
55
56. What is the accelerator for alginate?
a. Potassium titanium
56
57. What is the retarder for alginate?
a. Sodium phosphate
57
58. What are the fillers in alginate?
a. Zinc oxide
b. Diatomaceous earth
58
59. Thickness of alginate should be
3mm
59
60. What are the 2 major factors determining shelf life?
a. Storage temperature
b. Moisture
60
61. After pouring the impression, the stone cast should not be separated for
a. 60 minutes
61
62. You will get dimensional changes due to what?
a. Delay in pouring the impression
62
63. Non-aqueous elastic material is
a. Synthetic rubber
63
64. Non-aqueous materials offer what solutions?
a. Better dimensional stability
b. Better tear strength
64
65. Polysulfide is also known as
a. Metacarptan
65
66. Describe Polysulfide (how it comes, requirements, base, etc..)
a. 2 tubes, base and accelerator
b. Custom tray required
c. Base: polysulfide polymer
d. Catalyst: lead oxide
66
67. Describe PVS (how it comes, requirements, base, etc...)
a. Auto-mix unit
b. Special adhesive required
c. Base: poly dimethyl siloxane
d. Catalyst: poly vinyl siloxane
e. Cross-linking: alkyl ortho silicate
f. Filler: silica
67
68. What inhibits polymerization? (acts as a retarder)
a. Sulfur
68
69. Platinum acts as a scavenger for H2 in what reaction?
a. PVS/addition
69
70. What has the best dimensional stability?
PVS
70
71. Describe polyether (how it comes, requirements, base, etc...)
a. Hydrophilic
b. Automix, hand-mix, electronic mix
c. Base: polyether
d. Catalyst: glycol
e. Cross-link: sulfate
f. Filler: silica
71
72. What material has the highest tear strength?
a. Polysulfide
