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Occlusion Lecture > Alginate and Stone > Flashcards

Alginate and Stone Flashcards

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1
Q

What are the charateristics of the ideal impression material?

A
  • easy to mix/handle
  • suitable working time
  • suitable setting time
  • compatible with stone
  • not toxic or allergenic
  • dimensionally stable
  • accurate to record fine details
  • has acceptable odor/taste
  • adequate strength
  • adequate shelf life
  • economical
  • can be disinfected
  • exact record of all aspects
  • free from air bubbles
    - Fluid or plastic when inserted into the mouth
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2
Q

What are the 3 key properties of impression materials?

A
  • accuracy (ability to replicate the intraoral surface details)
  • dimensional stability (ability to retain its absolute dimensional size over time)
  • tear resistance (ability to resist tearing in thin sections…such as the feather-edged material within the gingival sulcus)
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3
Q

(ability to replicate the intraoral surface details)

A
  • accuracy
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4
Q

(ability to retain its absolute dimensional size over time)

A
  • dimensional stability
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5
Q

(ability to resist tearing in thin sections…such as the feather-edged material within the gingival sulcus)

A
  • tear resistance
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6
Q

What are the nonelastic options for impression materials? (4)

A

gypsum (plaster)
impression compound
zinc oxide eugenol
impression wax

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7
Q

What are the elastic options for impression materials? (2 categories)

A
  • hydrocolloids (agar/alginate)
  • non-aqueous elastomers (polysulfides, polyethers, condensation silicone, addition silicone)
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8
Q

What weird ingredient is alginate made of?

A

based on a natural substance extracted from brown seaweed (aqnhydro-B-D-mannuronic acid; alginic acid)

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9
Q

What was alginate (irreversible hydrocolloid) developed as a substitute for?

A

agar impression material (it became scarce during WW2)

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10
Q

Identify this material as elastic or non-elastic: gypsum (plaster)

A

non-elastic

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11
Q

identify this material as elastic or non-elastic: impression compound

A

non-elastic

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12
Q

identify this material as elastic or non-elastic:
- hydrocolloids (agar/alginate)

A

elastic

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13
Q

identify this material as elastic or non-elastic:

  • non-aqueous elastomers (polysulfides, polyethers, condensation silicone, addition silicone)
A

elastic

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14
Q

identify this material as elastic or non-elastic:
polysulfides

A

elastic

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15
Q

identify this material as elastic or non-elastic:
-polyethers

A

elastic

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16
Q

identify this material as elastic or non-elastic:
condensation silicone

A

elastic

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17
Q

Identify this material as elastic or non-elastic: zinc oxide eugenol

A

non-elastic

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18
Q

Identify this material as elastic or non-elastic: impression wax

A

non-elastic

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19
Q

Why is alginate successful? (3)

A

easy to manipulate, comfortable for patient, relatively inexpensive (bc doesn’t require elaborate equipment)

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20
Q

What are the chief active ingredients of irreversible hydrocolloid material (alginate)? (3)

What is the composition of alginate?

A

1) sodium, potassium, or triethanolamine alginate*)

2)
sodium phosphate
diatomaceous earth
potassium titanium fluoride
zinc oxide
potassium alginate
calcium sulfate
triethanolamine alginate

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21
Q

What is the safest way to alter the setting time of alginate?

A

changing the temperature of water (hot = faster; cold = slower)

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22
Q

What impression material do we use for final impressions in the clinic?

A

condensation silicone

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23
Q

(alginate)

The typical sol-gel rxn can be described as a rxn of soluble alginate with calcium sulfate and the formation of an insoluble ______

A

-Calcium Alginate Gel

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24
Q

Is alginate impression material hydrophobic or hydrophilic?

A

hydrophilic

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25
What type of impressions are alginate mostly used for?
preliminary impressions (used to construct a custom tray)
26
Mixing time of alginate:
45 sec to 1 min
27
What are the steps to making an alginate impression?
1. measure powder in a clean rubber bowl 2. powder is incorporated into the water by carefully mixing with a spatula until all of the powder is dissolved 3. mixing time of 45 seconds-60 seconds 4. result is smooth, creamy mixture 5. should have sufficient body so it does not flow out of tray and gag patient 6. place in a tray and then into mouth 7. at least 3 mm of thickness between tray and tissues
28
What are the different types of stock trays?
rim lock tray perforated tray
29
T/F: Alginate is very weak
True
30
The thickness of the alginate impression between the tray and the tissues should be:
at least 3mm
31
Alginate Hydrocolloid materials are ______-dependent. The tear strength is ____ when the impression is removed with a snap
--strain-rate dependent --increaased
32
How should you disinfect an impression?
disinfectant-soaked paper towel/plastic bag for 10 minutes
33
Hydrocolloids-- Imbition: expansion after ___ Polysulfide, Polyether-- Potential expansion ____ with expst
--10 min -potential expansion, increased exposure time
34
What is the future of impressions?
digital impressions (scan and then send electronic file)
35
What are some current digital impression systems?
Sirona (CEREC, Omnicam, bluecam) Align Tech (Itero) Midmark (LAVA True Definition Scanner)
36
Why do we use gypsum in dentistry?
1) For prep of study models for oral/max structures 2) important auxiliary materials for dental laboratory operations that are involved in the production of dental prostheses
37
What is gypsum almost entirely made of?
calcium sulfate dihyrate (CaSO4--2H2O)
38
What is a gypsum dental investment?
plaster is mixed with fillers (different forms of silica; high heat resistant*)
39
What is the principle constituent of gypsum-based products?
calcium sulfate hemihydrate
40
What is the colloidal theory of gypsum? | What mechanism is involved?
when mixed with water, plaster enters into the colloidal state through a sol-gel mechanism
41
What is the hydration theory of gypsum? | What mechanism is involved?
rehydrated plaster particles join together through hydrogen bonding to the sulfate groups to form the set material
42
What is the dissolution-precipitation theory of gypsum?
dissolution of plaster and instant recrystallization of gypsum, followed by interlocking of the crystal to fm the set solid
43
What is the setting reaction of gypsum?
1. dissolution of calcium sulfate hemihydrate 2. formation of saturated solution of calcium sulfate 3. aggregation of less soluble calcium sulfate dihydrate 4. precipitation of the dihydrate crystals
44
What is the mixing time (MT) for Gypsum?
the time from the addition of the powder to the water until the mixing is completed
45
What is the average mechanical mixing time of stones and plasters? What is the average hand-spatulation mixing time of stones and plasters?
20-30 seconds 1 minute
46
time available to use a workable mix, noe that maintains a uniform consistency to perform one or more tasks
working time (WT)
47
time that elapses form the beginning of mixing until the material hardens
setting time (ST)
48
What is the best way to control the setting time of stone/plaster? if decreases setting time it is called: if increases setting time:
the addition of certain chemical modifiers such as accelerators or retarders ---if added chemical decreases setting time, it is known as an accelerator; if it increases setting time it is known as a retarder
49
What is the crystallization?
outgrowth of crystals from nuclei of cyrstallization
50
What is the most effective method for controlling the setting expansion?
addition of chemicals from the manufactor (potassium sulfate, sodium chloride, borax)
51
What are the types of gypsum?
- Impression plaster (type 1) - Model plaster (type 2; white) - Dental stone (type 3; yellow stone) - Dental stone, high strength (type 4) - Dental stone, high strength and expansion (type 5)
52
- condyle is in the most anterior-superior position - first contact when leaf gauge is in place on the anterior teeth
centric relation
53
- made of plaster of paris - rarely used anymore
impression plaster (type 1)
54
- white color w contrasting colored stones - relatively weak (compressive strength as low as 9 MPa and a tensile strength of 0.6MPa
model plaster (type 2)
55
What are the characteristics of dental stone (type 3)?
- used to process dentures
56
(type of dental stone) - hard surface - necessary for a die stone
dental stone type 4
57
What are the characteristics of dental stone type 5?
- high strength and expansion than type 4
58
What dental stone is used to process dentures?
dental stone (type 3) ... yellow stone
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# T/F: Alginate is an elastic impression material
yes--hydrocolloid

Occlusion Lecture (20 decks)

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