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D2: 621 Occlusion > 01: Dr Moon Alginate Lecture > Flashcards

01: Dr Moon Alginate Lecture Flashcards

1
Q

Rigid Impression Material

A

Not for Undercuts

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2
Q

Elastic Impression Material

A

Limited Undercuts

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3
Q

Irreversible Alginate

A

Not for Crown and Bridge

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4
Q

Reversible Agar

A

For crown and Bridge

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5
Q

Elastomeric rubber

A

For crown and bridge

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6
Q

What does accurate mean

A

+/- 0.2% dimensional change after 15 mins

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7
Q

What does stable mean

A

+/- 0.2% dimensional change at specific times like 1 hour, 1 day, 3 days, 1 week, etc.

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8
Q

How to keep alginate accurate?

A

Do not let it tear upon removal
Keep it bonded to tray
Do not distory

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9
Q

Is alginate expected to be stable?

A

No.

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10
Q

Why can’t we use alginate for crown and bridge prep

A

It doesn’t produce fine detail. It often permanently distorts when removed from preps

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11
Q

What are two reversible strains

A

elastic: stretches instantly and snaps back
viscoelastic: (soft tissue) stretches slowly on laoding and rebounds back slowly

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12
Q

Irreversible strains

A

Viscous strain: Strain begins and increases as long as load is applied as molecule flow in a solid
Plastic: Permanent strain in metals as stress exceeds yield strength of ductile metals

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13
Q

what would a tight watch on your skin be in terms of a strain

A

viscoelastic (reversible) retarded stretch and rebound

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14
Q

If you left a crayon or candle on its side for a year what type of strain would occur?

A

viscous (irreversible) strain. Continues as long as stress is still being applied

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15
Q

what type of strain happens to a rubber ball as it impacts the ground?

A

elastic (reversible) instantaneous strain and rebound

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16
Q

What percent of the population is allergic to alginate?

A

1%

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17
Q

How could you describe the chemical nature of alginate impression material

A

Irreversible hydrocolloid

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18
Q

What is alginate made from

A

brown seaweed

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19
Q

How does the alginate set

A

chemical reaction b/w Ca++ with COO-

20
Q

What is a hydrocolloid

A

mixture of water and particles (less that .5 microns)

21
Q

What is a sol thixotropic paste

A

Its a paste that mixes better the more you mix it

22
Q

How long do you have before it sets

A

45 seconds

23
Q

What happens upon setting

A

A gel forms with water and glass filler trapped in weak alginate fibrils

24
Q

Is alginate stretchy

A

not really, less than 10%

25
Q

Why do you have to be careful taking the impression out of the mouth

A

because a distorted impression will result in inaccurate occlusion

26
Q

What is an alginate retarder?

A

Sodium phosphate powder

The calcium reacts with the phosphate first and forms calcium phosphate

27
Q

What will accelerate the reaction

A

warm and hot water

28
Q

What temp water should we use?

A

Room temp ~70 degrees

29
Q

What provides dimensional accuracy?

A 
Impression not moved while setting
Impression completely set before removal
Prevent tearing by waiting 1 minute after set
Prevent tearing by removing with "snap"
Prevent tearing by "Smooth Creamy Mix"
Prevent tearing by eliminating air bubbles with good mixing
provide 3-5mm between tray and teeth
impression bonded securely to tray
30
Q

What spatula should we use to mix alginate

A

The thin flexible spatula

31
Q

How long to mix alginate

A

1 min/45 s

32
Q

load tray time

A

2 mins/1min

33
Q

Seat tray

A

2.24 min/1.25 min

34
Q

Initial gelation

A

2.75 min/1.75 min

35
Q

revome tray

A

4.75 min/3 min

36
Q

Rinse well

A

30 seconds

37
Q

Disinfect

A

10-15 mins

38
Q

Pour

39
Q

Separate impression from cast

A

under 30 mins and after 1 hour

40
Q

Sources of dimensional instability

A

Water evaporation
Imbibition
Syneresis (exposure to humidity)

41
Q

Steps to Dispense and Mix Alginate

A
  1. Tumble container to fluff powder
  2. Be sure bowl and spatula are clean and dry
  3. Fill scoops w/o packing
  4. Level scoops w/o packing
  5. Place powder in bowl
  6. Measure room temp H2O: 1 ring per scoop
  7. Don’t put powder in bowl if there is any water in bowl
  8. Reassure patient
  9. Wet powder gingerly and then mix vigorously in thin layer 1/2 around the bowl back and forth to eliminate air bubbles for .75 minutes
  10. Form a smooth creamy mix
42
Q

Why do we make mandibular impression first

A

To reduce chances of gagging

43
Q

How should the tray be put in the mouth

A

Sideways
Rotate and align
Seat posteriors first

44
Q

How much alginate should remain between tray and teeth upon seating

45
Q

Who should hold tray

A

You, not the patient

46
Q

Criteria for a good cast

A

Complete dentition
Min blebs/roughness
No voids on teeth
Base about 1/2 inch thick

D2: 621 Occlusion (2 decks)

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