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Fixed Prosthodontics > Lecture 1- intro (part 2) > Flashcards

Lecture 1- intro (part 2) Flashcards

1
Q

Advantages of Agar Hydrocolloid (6)

A
  1. Elastomeric and Reproduces undercuts accurately
  2. Recovers from Distortion
  3. Hydrophilic, so good model surface
  4. Cheap
  5. Can be reused as a duplicating material
  6. Pleasant tase and odor
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2
Q

Disadvantages of Agar Hydrocolloid (6)

A
  1. Warm upon insertion
  2. Tears easy
  3. Expensive Equipment
  4. Only pour once
  5. Requires greater gingival retraction
  6. Contamination due to reuse
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3
Q

Name the 4 types of Elastomeric impression materials

A
  1. Polysulfides
  2. Condensation Silicones
  3. Addition Silicones (VPS, PVS (polyvinyl siloxanes)
  4. Polyethers
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4
Q

Name the parts of a Polysulfide impression material

A
    • also called Rubber base
      1. Base paste
    • Liquid polysulfide polymer
    • Innert fillers (titanium oxide, zinc sulfate, silica)
  1. Reactor paste
    - Lead dioxide
    - Dibutyl phthalate
    - Sulfur
    - Deodorants
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5
Q

Advantages of Polysulfide material (6)

A
  1. Long working time
  2. Accurate
  3. High tear resistance
  4. Inexpensive
  5. Less hydrophobic
  6. Long shelf life
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6
Q

Disadvantages of Polysulfide material (7)

A
  1. Pour immediately
  2. Potential for distortion
  3. Odor
  4. Long setting time
  5. Stains, messy
  6. Re-our is not as accurate as first pour
  7. Requires a custom tray, most accurate 2.0 to 4.0 mm thick
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7
Q

Contents of Condensation silicones

A
  • *First type of silicone impression material
    1. Base and accelerator paste
    2. Low, medium and putty viscosity
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8
Q

Advantages of Condensation silicones (5)

A
  1. Good working time
  2. Pleasant odor
  3. No staining
  4. Elastic properties for removal
  5. Less distortion
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9
Q

Disadvantages of Condensation silicones (5)

A
  1. Poor immediately
  2. Poor dimensional stability
  3. Expensive
  4. Technique sensitive to wash
  5. Potential for distortion
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10
Q

Which has better properties, condensation silicones or addition silicones?

A

Addition silicones

** Also known as poly vinyl siloxane (PVS) (VPS)

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11
Q

Advantages of Addition silicones (5)

A
  1. Short working time
  2. Good tear strength
  3. Highly accurate
  4. Minimal distortion
  5. Dimensionally stable
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12
Q

Disadvantages of Addition silicones (3)

A
  1. Hydrogen gas release can cause dimensional change
  2. Requires very dry conditions
  3. Expensive
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13
Q

Advantages of Polyether (5)

A
  1. Excellent dimensional stability, when dry
  2. Can delay in pouring
  3. Good accuracy, surface detail
  4. Low shrinkage
  5. Fast setting
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14
Q

Disadvantages of Polyether (4)

A
  1. Flexibility is low and stiffness high
  2. Easy to break stone cast upon removal
  3. Absorbs water so must be stored dry or will experience significant dimensional change
  4. Allergic reactions
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15
Q

What is a contact angle used for?

A

To determine hydrophilicity

  • Less than 90 degrees –> hydrophilic
  • Greater than 90 degrees –> Hydrophobic
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16
Q

Cost comparison of materials (Lowest to highest price)

A
  1. Alginate
  2. Agar = Polysulfide
  3. Condensation silicone
  4. Addition silicone
  5. Polyether
17
Q

Dimensional stability comparison of materials (Best to worst)

A
  1. Addition silicone
  2. Polyether
  3. Polysulfide
  4. Condensation silicone
  5. Hydrocolloid
18
Q

Wet ability comparison (best to worst)

A
  1. Hydrocolloids
  2. Polyether
  3. Hydrophilic addition silicone
  4. Polysulfide
  5. Hydrophobic addition silicones = Condensation silicone
19
Q

Stiffness Comparison of materials (Most to least)

A
  1. Polyether
  2. Addition silicone
  3. Condensation silicone
  4. Polysulfide = hydrocolloids
20
Q

Tear strength comparison (Greatest to Least)

A
  1. Polysulfide
  2. Addition silicone
  3. Polyether
  4. Condensation silicone
  5. Hydrocolloids
21
Q

Define an Impression Tray

A
  • A device used to carry, confine, and control impression material while making an impression
22
Q

Name the types of impression trays

A
  1. Stock trays
  2. Water cooled trays
  3. Custom trays
  4. Triple trays
23
Q

Attributes of a Custom tray (3)

A
  1. Maintains optimal thickness of impression materials, 2.0 to 4.00 mm for elastomers
  2. Require less impression material
  3. Provide proper flange extensions
24
Q

Attributes of Gypsum (5)

A 
Naturally occurring mineral
Calcium sulfate dihydrate + water
Heated to 230-250 F to remove water (calcination)
Results in calcium sulfate hemihydrate
Set by an exothermic reaction
25
Q

Types of gypsum

A

Plaster
Stone
Improved stone
Investment materials

26
Q

What is the difference between all of the types of gypsum?

A

Is the shape and form of the hemihydrate crystals. Crystals of dental stone and improved dental stone are more dense and regular in shape

27
Q

The types of gypsum (I, II, III, IV and V) and their classification as plaster or stone

A

Plaster

  • Type I –> Mounting plaster
  • Type II –> Model plaster

Stone

  • Type III –> Dental stone
  • Type IV –> Improved stone
  • Type V –> High-strength, high-expansion dental stone
28
Q

Desired characteristics of Gypsum stone or plaster: (9)

A
  1. Compatibility with impression materials
  2. Acceptable working and setting times
  3. Adequate flow properties
  4. Ease of manipulation
  5. Reasonable cost
  6. Adequate shelf life
  7. Acceptable strength and durability
  8. Excellent dimensional stability
  9. Capable of duplicating fine detail of hard and soft tissues
29
Q

5 examples of accelerators

A
  1. Increase in water temperature above 68 degrees F when mixing plaster
  2. Increase room temperature or humidity
  3. Faster rate of spatulation time will hasten the setting time.
  4. Pinch of table salt (sodium chloride)
  5. Decrease the amount of water specified by manufacturer
30
Q

5 examples of retarders

A
  1. Cooler than room temperature water
  2. Decrease in room temperature and humidity
  3. Slower rate of spatulation will slow down setting time
  4. Borax (calcium salts) in small concentrations
  5. Increase in the amount of water specified by the manufacturer, although this weakens the cast.
31
Q

T or F, When mixing gypsum, sprinkle the powder into the water to obtain better mixing and reduce the chance for trapping air bubbles

A

True

Fixed Prosthodontics (8 decks)

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