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Removable > Trays, Materials and Techniques > Flashcards

Trays, Materials and Techniques Flashcards

1
Q

What are impression trays?

A

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

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2
Q

What are the various types of impression trays

A

stock (denate and endentulous)
water cooled
custom
tripple

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3
Q

Describe custom trays?

A

Maintains optimal thickness of impression materials, 2.0 to 4.0 mm for elastomers

Require less impression material

Provide proper flange extensions

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4
Q

How should trays extend distally?

A

Trays should extend distally to cover the maxillary tuberosity and cover the mandibular retromolar pad for maximum anatomical reproduction

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5
Q

What height should trays be?

A

Tray height should fully cover the length of anterior and posterior teeth

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6
Q

How should trays extend regarding the facial aspect?

A

Tray should extend beyond the facial aspect of the teeth with ¼ inch of space between the tray and soft tissue

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7
Q

Utility wax beading

A

Wax may be added to the borders of the tray to extend its length or height

Wax can be placed in the palatal area of patients with high palates to eliminate voids in the palatal area

Wax may be placed around the tray periphery to protect and cushion the soft tissues in the oral cavity

The placement of utility wax on the posterior region of the maxillary tray prevents excessive alginate from flowing down the throat

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8
Q

What are the different types of impression materials?

A

Alginate Hydrocolloids

Agar Hydrocolloids

Elastomeric Impression Materials

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9
Q

Imbibition

A

to take in water

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10
Q

Syneresis

A

to give up water (dry out)

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11
Q

Tensile strength

A

ability to withstand tearing

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12
Q

Working time(WT)

A

time before the material begins to set; starts from the time you began mixing & includes the time you have to load material into a tray or syringe

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13
Q

Setting time(ST)

A

time it takes for the material to be completely set (from start to finish)

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14
Q

Mixing time

A

time you have to mix the material

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15
Q

Alginate is classified as an?

A

irreversible hydrocolloid

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16
Q

Why is alginate classified as a hydrocolloid?

A

Hydrocolloid because it is particles of a gelatinous (colloid) state in water (hydro).

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17
Q

What is alginate particles composed of?

A

Salts of alginic acid, a product of marine kelp (a type of seaweed)

An activator, usually calcium sulfate

A retarder like sodium phosphate

An inert filler to reduce stickiness, produce a smooth texture, and add strength

Flavoring

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18
Q

What are disadvantages of alginate?

A

Poor tear strength when thin

Poor dimensional stability

Distorts if shifted during setting

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19
Q

What are advantages of alginate?

A

Easy to mix and manipulate

No expensive equipment needed

Elastic and removes from undercuts easily

Cost effective

Pleasant taste and odor

20
Q

What is type 1 Fast set alginate?

A

WT 1 minute
ST 1-2 minutes

21
Q

What is type 2 normal set alginate?

A

WT 1-2 minutes
ST 2-4 minutes

22
Q

What temperature should water be for aliginate?

A

73

23
Q

How should impressions be removed?

A

with a snap-out motion

24
Q

Describe agar in agar hydrocolloids

A

13-17% for tray material and 6-8% for syringe materi

25
Q

Describe borates in agar hydrocolloids

A

Gel Strength, retards set of stone (disadvantage)

26
Q

Describe potassium sulphate in agar hydrocolloids

A

retards effect of borates

27
Q

Describe wax in agar hydrocolloids

A

filler

28
Q

Describe Thixotropic Materials in agar hydrocolloids

A

Plasticizer, Glycerine or Thymol (bactericide)

29
Q

Describe Alkylbenzoates in agar hydrocolloids

A

preservative

30
Q

Describe water in agar hydrocolloids

A

Dispersion Medium

31
Q

What are the types of elastomeric impression materials?

A

Polysulfide

Condensation Silicones

Addition Silicones (VPS- Vinylpoly Siloxanes and PVS- Polyvinyl Siloxanes)

Polyethers

32
Q

PolySulfides are commonly called what?

A

rubber base

33
Q

what are the two types of pastes?

A

base and reactor

34
Q

what is base paste?

A

Liquid polysulfide polymer

Inert fillers (titanium oxide, zinc sulfate, silica)

35
Q

What is reactor paste?

A

Lead dioxide
Dibutyl phthalate
Sulfur
Deodorants

36
Q

Disadvantages of polyethers

A

Flexibility is low, and stiffness high

Easy to break stone cast upon removal

Absorbs water so must be stored dry or will experience significant dimensional change

Allergic Reactions have been reported

37
Q

What is contact angle?

A

Contact angle measurement on unset material is a method used to determine hydrophilicity (having a tendency to mix with, dissolve in, or be wetted by water).

38
Q

What is the contact angle on hydrophilic surfaces?

A

less than 90 degrees

39
Q

What is the contact angle on hydrophobic surfaces?

A

greater than 90 degrees

40
Q

what is the cost comparison of impression materials?

A

Lowest to highest

Alginate
Agar = polysulfide
Condensation silicone
Addition silicone (PVS)
Polyether

41
Q

What is the rank of impression material by dimension stability?

A

Best to Worst

Addition silicone
Polyether
Polysulfide
Condensation silicone
Hydrocolloid

42
Q

What is gypsum?

A

Naturally Occurring Mineral

Calcium Sulfate Dihydrate + Water

Heated to 230-250o F to remove the water (Calcination)

Results in Calcium Sulfate Hemihydrate

Set by an Exothermic Reaction

43
Q

types of gypsum powder?

A

Plaster
Stone
Improved Stone
Investment Materials

44
Q

what is the difference in the different types of gypsum powders?

A

Principal difference between plaster, stone, and improved stone is in the shape and form of the hemihydrate crystals. Crystals of dental stone and improved dental stone are more dense and regular in shape.

45
Q

what choice of gypsum is recommended for study models?

A

Plaster or stone is the recommended choice of gypsum products for use in dentistry for study model construction for presentation purposes

46
Q

what are accelerators?

A

Increase in water temperature above 68 degrees F when mixing the plaster

Increase room temperature or humidity

Faster rate of spatulation time
will hasten the setting time

Pinch of table salt (sodium chloride)

Decrease the amount of water specified by the manufacturer

47
Q

What are retards?

A

Cooler than room temperature water

Decrease in room temperature and humidity

Slower rate of spatulation will slow down the setting time

Borax (calcium salts) in small concentrations

Increase in the amount of water specified by the manufacturer, although this weakens the cast

Removable (8 decks)

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