Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Fixed > Impression Materials and Techniques for Fixed Prosthodontics > Flashcards

Impression Materials and Techniques for Fixed Prosthodontics Flashcards

1
Q

What are the other categories that alginate fits into?

A
  • elastic
  • hydrocolloid
  • irreversible (alginate)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a reversible hydrocolloid?

A

Softens under heat and solidifies when cooled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why is a reversible hydrocolloid reversible?

A

There is no chemical change making the changes permanent. Therefore, this is reversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is an irreversible hydrocolloid?

A

Chemical reaction that cannot revert to preset state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Is alginate a reversible or irreversible hydrocolloid?

A

Irreversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Alginate was developed as a substitute for _____ impression material when its supply became scarce during the WW II

A

Agar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is alginate based on?

A

a natural substance extracted from brown seaweed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When the soluble alginates are mixed with water, they form a…

A

gel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Alginate is hydrophilic or hydrophobic?

A

hydrophilic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

_________ is hydrophilic, so moist tissue surfaces are not a hindrance to the impression unlike PVS materials.

A

Alginate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a colloidal material?

A

any substance consisting of particles substantially larger than atoms or ordinary molecules but too small to be visible to the unaided eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is an example of a colloidal material?

A

Agar or Alginate dissolved in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is sol to gel?

A

a process that converts a colloidal solution (sol) into a gel-like network (gel)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Agar: reversible due to __________ change

A

temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Alginate: irreversible due to _________ reaction

A

chemical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are properties related to gel network?

A
  • Evaporation (shrinkage)
  • Syneresis: gel relaxation; water extruded from gel (shrinkage)
  • Imbibition: absorption of water causing expansion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is syneresis?

A

gel relaxation; water extruded from gel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is imbibition?

A

absorption of water causing expansion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Alginate is provided as a powder, which contains the following reacting ingredients:

A
  • Potassium or Sodium Alginate(15-20%): reacts with calcium ions
  • Calcium Sulphate Dihydrate (14-20%): reacts with Potassium Alginate to form a dihydrate insoluble alginate gel
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does the potassium/sodium alginate do?

A

reacts with calcium ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does calcium sulphate dihydrate do?

A

reacts with Potassium Alginate to form a dihydrate insoluble alginate gel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the powder part of alginate?

A

potassium or sodium alginate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the gel part of alginate?

A

calcium alginate
*formed by interactiuon b/w potassium alginate and calcium sulphate dihydrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

When mixing alginate you add ______ first and then ________

A

Add water first, then powder

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the mixing time for alginate?

A

45 – 60 sec

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Thickness of Alginate should be ___ mm in tray

A

3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

CDC recommend ______ dilution of household bleach for disinfection of impressions

A

1:10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How do you keep the impressions moist?

A

Impression placed in small Ziploc baggie or head rest cover with a few drops of water in the bottom of the baggie and is sealed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

After pouring the impression, the stone castshould not be separated for ___ min with yellow stone

A

60 minutes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

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

A

Storage temperature and moisture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

If you remove your impression from the mouth, rinse it off, and then wrap the impression with a wet paper towel, what will happen?

A
  • The alginate absorbs more water as it continues to harden and the material swells.
  • Now anything made from that impression will NOT fit because the model has distorted as it absorbed water.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

The diagnostic cast should be removed from the impression approximately_____ hour(s) after its final set.

A

one

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Small nodules and projections on the impression surface should be ___________

A

removed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

If you delay in pouring up impressions what problem arises?

A

dimensional changes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What can cause inadequate working or setting time?

A
  • high water temp
  • incomplete spatulation
  • low water/powder ratio
  • improper storage of alginate powder
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What can cause distortion of impression?

A
  • movement of tray during gelation
  • premature removal of tray
  • no snap quick removal of tray
  • delay in pouring cast
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What can cause tearing of impression?

A
  • impression removed before set
  • slow rate or removal of impression
  • thin mix used
  • presence of deep undercuts
  • inadequate material in tray
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What can cause of loss of detail of impression?

A
  • premature tray removal from the mouth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What can cause issues with consistency of impressions?

A
  • incorrect water/powder ratio
  • inadequate mixing
  • hot water used for mixing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What can cause dimensional changes to an impression?

A
  • delay in pouring the impression
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What can cause porosity issues in an impression?

A

air entrapped in the mix during spatulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What can cause poor stone surface?

A

delay in separating the cast from the impression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What is an analogue impression?

A
  • A negative likeness or copy in reverse of the surface of an object
  • An imprint of the teeth and adjacent structures for use in dentistry
  • Made from soft semi-fluid material allowed to set
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is an impression technique?

A

a method and manner used in making a negative likeness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is an impression tray?

A

a device that is used to carry, confine, and control impression material while making an impression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What do we look for in a dental impression?

A

-Exact duplication of the prepared teeth
-Includes uncut tooth structure beyond finish line
-Accurate reproduction of the other teeth and tissues
-Free of air bubbles specifically in the finish line and occlusal surfaces
-Extended enough to capture the vestibule, tuberosities, and retromolar pad is ideal

47
Q

How do you select what impression tray to use?

A
  • Tray should feel comfortable to the patient
  • Extended slightly beyond the facial/buccal surfaces of the teeth
  • Extended approximately 2 -3 mm beyond the 3rd molar, retromolar, or tuberosity
  • Sufficiently deep to allow 2 -3 mm of material between the tray and the occlusal/incisal edges
  • Sufficiently rigid
48
Q

How much material should be b/w the tray and occlusal surfaces?

A

2-3mm

49
Q

An impression tray must be sufficiently rigid to:

A
  • Carry the impression material into the oral cavity
  • Hold the material in close proximity to the teeth
  • Avoid breaking during removal
  • Prevent wrapping of the completed impression
50
Q

What are stock trays?

A
  • Plastic or metal; perforated or rimmed
  • Complete arch, quadrant, or dual arch
  • Dentate or edentulous arch
51
Q

What are custom trays?

A
  • Made in advance
  • Light cured, auto cured, or thermoformed
  • Better fit than stock trays
  • Less material waste
  • Controlled thickness of material
  • Increased accuracy
52
Q

___________ is used to prevent impression distortion due to material pulling away from tray

A

Adhesive

53
Q

Adhesive provides a _______ adhesion

A

chemical

54
Q

What are the needs for adhesive?

A
  • Specific for each material; including Alginate
  • Should always be used
  • Apply and dry
55
Q

What are the ideal impression material characteristics?

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 the aspects
  • Economic
56
Q

What is the goal of a single crown impression technique?

A

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

57
Q

What is the purpose of impression techniques of a single crown?

A
  • Evaluate arch form
  • Anatomical landmarks
  • Musculature
  • Hard and soft tissue anomalies
  • Restorative space
58
Q

The impression material selected is dependent on….

A

the type of impression required for the procedure

59
Q

What is the tissue retraction part of a single crown impression?

A

single or double cord technique; cord/s removed right before impression making

60
Q

The _____ bodied consistency dispensed into the sulcus, over and around the prepared teeth and onto the surrounding tissues

A

light

61
Q

The custom tray for a single crown impression with dried adhesive is loaded with medium or heavy body material is seated with some downward pressure for approximately ______ min

A

4 – 6

62
Q

What is a nonelastic impression material?

A
  • Rigid, cannot be removed from undercuts
  • Best used for edentulous impressions
63
Q

What is an elastic impression material?

A
  • Can be removed from undercuts without distortion
  • Best for dentate impressions
64
Q

What are the first impression materials that were popular?

A
  • Plaster of Paris
  • Impression plaster
  • Gutta percha
  • Modeling compound
  • Zinc Oxide Eugenol
  • Various waxes

-less commonly used now

65
Q

What are the options for elastic materials?

A
  • Reversible Hydrocolloid (AGAR)
  • Irreversible Hydrocolloid (Alginate)
  • Polysulfide Rubber
  • Vinyl Poly Siloxanes
  • Polyether
66
Q

What is an aqueous elastomeric (hydrocolloids)?

A
  • Water is the major component
  • Hydrocolloid
  • Reversable and irreversible
  • Reversable is not commonly used today
67
Q

What is a non-aqueous elastomeric (polymers)?

A
  • Polysulfide
  • Vinyl Polysiloxane (silicone)
  • Polyether
68
Q

If the contact angle of wetting is less than 90 degrees what happens?

A
  • hydrophilic
  • surface wetted
69
Q

What is wettability?

A

ABILITY OF LIQUID TO FLOW OVER A SOLID SURFACE

  • RELATED TO SURFACE ENERGY OF THE SOLID AND SURFACE TENSION OF THE LIQUID
70
Q

Non-Aqueous Elastomers provide:

A

➢ Accuracy
➢ Dimensional stability
➢ Tear resistance
➢ Viscoelasticity

71
Q

If the contact angle of wetting is greater than 90 degrees what happens?

A
  • hydrophobic
  • surface not wetted
72
Q

What is accuracy?

A

Ability to replicate the intra-oral surface details

73
Q

What is dimensional stability?

A

Ability to retain its absolute dimensional size over time

74
Q

What is tear resistance?

A

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

75
Q

What is viscoelasticity?

A

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

76
Q

_______nature improves tear strength and elastic limit

A

Viscus

77
Q

What is a condensation polymerization reaction?

A

loses water as it combines

  • By product: H2O or OH
78
Q

What is an addition polymerization reaction?

A
  • No by product
79
Q

Elastic polymers can come in different consistencies. What are the examples?

A
  • Polysulfide or rubber base PS
  • Vinyl Polysiloxane VPS
  • Polyether PE
80
Q

What are nonaqueous elastomerics made of?

A

synthetic rubber

81
Q

Non aqueous elastomeric materials offer potential solutions to the two main problems associated with Hydrocolloids (alginate):

A
  • Poor tear resistance
  • Poor dimensional stability
82
Q

What are the characteristics of polysulfide?

A
  • It is known also as Mercaptan or simply rubber base
  • It is provided as two tubes of base and accelerator
  • It requires a custom tray
  • Longer setting time, malodor, stain cloths
83
Q

What is the composition of polysulfide?

A
  • Base: polysulfide polymer mixed with inert fillers
  • Catalyst: lead dioxide mixed with small amounts of sulfur and act as oxidation initiator
84
Q

What are the characterisitics of vinyl polysiloxane?

A
  • Limited shelf life
  • Requires special tray adhesive
  • It is provided as an auto-mix unit, syringe, and mixing tips
  • No syneresis or imbibition, however, responds with shrinkage over time
  • More flexible; so, there is more chance for distortion during removal
  • Best dimensional stability among impression materials (addition silicon)
85
Q

Wait _____ min before pouring up a vinyl polysiloxane impression for stress relaxation. It can be delayed up to 7- 10 days

A

20 – 30

86
Q

What is the composition of addition silicon?

A
  • Base
  • Catalyst
  • Cross-linking agent
  • Filler
87
Q

What type of reaction occurs with VPS?

A

addition reaction, no by-product

88
Q

Is vinyl polysiloxane hydrophilic or hydrophobic?

A

Hydrophobic
. dry field needed
. surfactant added; improve wettability & less cast bubbles

89
Q

What can change the setting of vinyl polysiloxane?

A
  • Sulfur inhibits the polymerization
  • Latex gloves retards the setting
90
Q

What is release during setting of vinyl polysiloxane?

A

H2
*secondary reaction NOT a by product

91
Q

How long should you delay before pouring up vinyl polysiloxane?

A

15 – 30 min delay before pouring

92
Q

What are the characteristics of polyether?

A
  • Hydrophilic
  • High elastic recovery
  • It is provided as hand, auto-mix unit, or electronic mixing
  • Light, medium, and heavy body
  • Difficult removal from mouth or cast: need to block out undercuts
  • More stiff than VPS
93
Q

How do you remove a polyether impression?

A

When removing the impression, break the seal and rock slightly to prevent tearing

94
Q

What affects polyether in terms of marginal discrepancy?

A

Water, saliva, and blood affects the material; increase the marginal discrepancy

95
Q

What causes increased water absorption with polyetehers?

A

thinning agent used

96
Q

What is the composition of polyethers?

A
  • Base
  • Catalyst
  • Cross-linking agent
  • Filler
97
Q

What type of reaction occurs with polyethers?

A

addition reaction; no by product

98
Q

Polyethers are known for their…

A

hydrophilic properties and good flowability

99
Q

Polyvinyl siloxanes are known for their…

A

excellent elasticity, high tear strength and stability

100
Q

The preferred elastomeric impression materials on the market are…

A

polyvinyl siloxanes (PVS) and polyethers (PE)

101
Q

Polyethers are considered to have the ________ tear strengths

A

highest

102
Q

hydrocolloids have relatively ______ tear strengths

A

low

103
Q

Polysulfide impression materials have a _______ resistance to tearing but stretch and do not recover completely elastically

A

high

104
Q

What are unacceptable impressions?

A
  • voids
  • tacky unset VPS material in the preparation area
105
Q

How do you disinfect impressions?

A

➢ Rinse and spray the impression
➢ Acceptable disinfectants include: glutaraldehyde, iodophors, sodium hypochlorite, synthetic phenols, dual or synergized quaternaries, and sodium bromide and chlorine
➢ All impression materials are not compatible with all disinfectants

106
Q

How does disinfectant soaked paper towel effect the different impression materials?

A
  • no adverse effect on VPS
  • potential expansion for PS and PE
  • imbibition and expansion for alginate
107
Q

Are all impression materials compatible with all disinfectants?

A

NO

108
Q

What is the purpose of tissue retraction?

A

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

109
Q

What are the techniques for tissue retraction?

A
  • Mechanical
  • Chemo- mechanical (Impregnated cords)
  • Surgical:
    –Electrosurgery
    –Rotary curettage (handpiece)
    –Laser
110
Q

What are the classifications of retraction cords?

A

▪ Depending on the configuration:
-Twisted
-Knitted
-plain
▪ Depending on the surface finish:
-waxed
-unwaxed

111
Q

What is the chemo-mechanical technique for tissue retraction?

A
  • Pack the retraction cord, soaked in hemostatic agent, then lightly dried; use cord packing instrument to place
  • Double or single cord technique (two knitted cords with different diameters are used;smaller diameter will be deep into the sulcus)
  • Remove cords after 4 minutes
  • Impression material is injected into the sulcus once the cords are removed
112
Q

What is GPT-9?

A

A digital impression: is NOT a negative likeness or copy in reverse of the surface of an object

113
Q

What is a digital scan?

A

capturing the optical image directly of the patient’s anatomy or indirectly of a definitive cast of the anatomy

114
Q

What are some digital impression systems?

A
  • CEREC Primescan, Omnicam or Bluecam (Sirona)
  • Tiors, 3 Shape (3D Biocad)

Fixed (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions