7 Mouth Prep, Survey CR, Impressions, Alloys

Question 1

Krotachvil proximal plate preparation - Occlusal gingival height?

Answer 1

Long, from marginal ridge to gingiva with physiologic relief

Question 2

Krol proximal plate preparation - Occlusal gingival height?

Answer 2

1 mm of contact at junction of occlusal and middle thirds

Question 3

Demer proximal plate preparation - Occlusal gingival height?

Answer 3

1 mm from marginal ridge

Question 4

What is the temperature for working with green thermoplastic modeling plastic compound?

Answer 4

123 degrees

Question 5

Irreversible hydrocolloid?

• Tear strength
• Surface detail
• How many pours
• Dimensionally stable
• Hydrophilic/phobic

Answer 5

1. Poor tear strength
2. Poor surface detail
3. Only one pour
4. Not dimensionally stable
5. Hydrophilic

Question 6

Polysulfide (rubber base)

• Tear strength
• How many pours
• Dimensionally stable
• Border molding?

Answer 6

1. High tear strength
2. Pour within one hour
3. More stable than alginate
4. Border molds well

Question 7

Polyether (impregum)

• Tear strength
• Surface detail
• Dimensionally stable, when to pour
• Hydrophilic/phobic
• Border molding

Answer 7

1. Low to mod tear strength
2. Good surface detail
3. Stable - pour w/in 2 hours
4. Hydrophilic
5. Great for border molding

Question 8

Addition Silicones

• Tear strength
• Surface detail
• Dimensionally stable
• Hydrophilic/phobic

Answer 8

1. High tear strength
2. Great surface detail
3. Very dimensionally stable - low distortion/shrinkage
4. Hydrophilic and hydrophobic

Question 9

Base Metal ANSI/ADA Specification #14

• Chromium, cobalt and nickel amounts
• Elongation %, yield strength, elastic modulus

Answer 9

Chromium - 20% minimum
Chromium, Co, Ni - 85% minimum
- 1.5% elongation, 500 MPa yield strength, 170 GPa elastic modulus

Question 10

Chromium

• Properties
• What happens if more than 30%

Answer 10

Tarnish/corrosion resistance

If 30%+, difficult to cast/brittle

Question 11

Cobalt - Properties

Answer 11

Elastic modulus, strength, and hardness

Question 12

Nickel - Properties

Answer 12

Increases ductility, but decreases hardness

Question 13

Aluminum

Answer 13

Forms Ni3Al which increases tensile, yield strength, and hardness

Question 14

Carbon

- What percent makes it brittle?

Answer 14

Increases hardness

0.2% increase over ideal makes it too hard and brittle

Question 15

Molybdenum - Percentage and properties

Answer 15

3-6% - Lowers CTE and improves corrosion resistance

Question 16

Beryllium - Percentage and properties

Answer 16

1-2% for nickel based alloys

• Lowers melting range by 100%, enhance casting and grain refinement
• May affect ductility to decrease corrosion resistance

Question 17

Silicon, Manganese, Iron, Carbon

Answer 17

Improve alloying

Question 18

Wironium, Vitalium

- Co, Cr, Mn, Si percentages

Answer 18

1. 62.5% Co
2. 30% Cr
3. 0.5% each Mn and Si (enhances fluidity and molten state of alloy)

Question 19

Melting temp of base metals
(wironium, vitalism, ticonium)
- What does Beryllium do for Ni-Cr alloys?

Answer 19

Over 1300 degrees except Ticonium melts at 1275

Beryllium - Lowers melting temp by 100 degrees

Question 20

Disadvantages of Chromium based metals

• Clasp success?
• Adjustments/polishing
• Hardness?
• Allergies?

Answer 20

1. Clasp more likely to fail during function/adjustment
2. More difficult due to low ductility, high strength, high hardness
3. Can wear opposing and adjacent
4. Nickel allergy up to 9% in females

Question 21

How to disinfect RPD’s?

Answer 21

Sodium hypochlorite for 15 minutes