Theme 9. Compensation of metal shrinkage. Investing materials. Wax modeling of a framework. Alloys for a cast RPD framework.

Q1.The channel which allows molten metal to flow from the crucible to the mold cavity during the casting procedure is called a __________.

a. *sprue

b. barrel

c. peanut

d. cannula

Q2.All of the following statements concerning beryllium are correct, except

a. *is used as a scavenger in casting alloys

b. is not found in all base metal alloys

c. is biologically hazardous

d. in small percentages, in nickel-based alloys, lowers the melting temperature of the alloy

e. the addition of beryllium to an alloy may allow the use of calcium sulfate investments

Q3. In dental casting alloy the metal ingredient which is considered to be the scavenger is

a. *zinc

b. gold

c. tin

d. silver

e. copper

Q4.The tripping action of Stone refers to

a. *the removal of an infrabulge clasp

b. the removal of a suprabulge clasp

c. the framework is more retentive on a cast than in the mouth

d. the water / powder proportion of the mix

e. none of the above

Q5. Which of the following are true about gypsum bonded casting investments?

1. should be allowed to set a minimum of 45 minutes

2. should be heated no longer than 30 minutes at 900 degrees F

3. the mold temperature should not exceed 1200 degrees F

4. used for alloys with melting temperatures exceeding 1800 degrees F

5. ideal mold temperature for hygroscopic technique is 875 degrees F

a. *1, 3, 5

b. 1, 2, 3, 5

c. 2, 3, 4

d. all of the above

e. none of the above are correct statements

Q6.Chromium, Nickel, Molybdenum, Manganese, Aluminum, and Beryllium are the component elements of Ticonium. One important biological consideration is that in patients with a history of nickel sensitivity, 80% will react to a nickel chromium based alloy.

*T or F

Q7.Low fusing metal is associated with which of the following procedures?

A. *The RPD remount cast.

B. Physiological adjustment of the framework.

C. The altered cast impression.

D. Making records for RPDs.

Q8.10. After the investment cast has been dried it is sealed by dipping it in molten boxing wax.

T or *F

Q9.During construction, the framework whose metal covers exostoses or inclined slopes of alveolar bone located between the edentulous segment and its nearest rest must be

a. *relieved

b. stripped

c. polished

d. deplated

Q10.Cast RPD was made for a patient’s upper jaw. In anamnesis the patient has high sensitivity to chrome. What material was used?

A. *Gold alloy 750

B. Co Chr

C. Gold alloy 900

D. NiChr

E. Pd 250

Q11. Cast RPD is fabricated for a patient’s upper jaw. Casting of the framework will be performed on a refractory model. Electrical and thermal conduction of metal depend on:

A. *Quantity of electrons

B. Quantity of positive ions

C. Location of ions

D. Valence of atoms

E. Freedom in electrons movement inside lattice

Q12. Cast RPD is fabricated for a patient’s upper jaw. Casting of the framework will be performed on a refractory model. Metal crystallization is –

A. *Metal’s conversion from liquid to rigid

B. Effect of subcooling

C. Atoms movement

D. Development of crystal grain

E. Metal’s conversion from rigid to liquid

Q13. Cast RPD is fabricated for a patient’s upper jaw. Casting of the framework will be performed on a refractory model. Mechanical properties of metals depend on:

A. *Quantity of granularity

B. Speed of cooling

C. Presence of insoluble mixtures

D. Presence of soluble mixtures

E. Quantity of electrons

Q14. Cast RPD is fabricated for a patient’s upper jaw. Casting of the framework will be performed on a refractory model. Mechanical properties of metals are higher when:

A. *Fine-grained texture

B. Coarse-grained texture

C. Doesn’t depend on granularity

Q15. What is the most accurate method of framework casting?

A. *Casting on refractory model

B. Casting in special form

C. Casting with soldering of separate parts of a denture

D. Swaging

Q16. What metal is widely used for making framework of cast RPD?

A. *CoChr

B. Stainless steel

C. Gold alloy 750

D. Gold alloy 900

E. PdAg

Q17. What is used for processing metal after casting?

A. *Sandblasting

B. Brush

C. Paste of Goi

D. Scaler

E. Carbide stone

Q18. What temperature investing material should resist?

A. *1400° - 1600°;

B. 800° - 900°;

C. 1000° - 1200°;

D. 1250° - 1350°;

E. 1800° - 2000°.

Q19. What is the temperature of CoChr melting?

A. *1460°с;

B. 1000°с;

C. 1250°с;

D. 1300°с;

E. 1600°с.

Q20. What amount of cobalt is in the Co-Chr alloy? A. *66%; B. 36%; C. 58%; D. 25%; E. 81%;