2015 Flashcards
Which of the following is a hydrocolloid?
A. Alginate
B. Polyether
A. Alginate
Which impression material is a reversible hydrocolloid?
A. Agar
B. Alginate
A. Agar
When making alginate impression, what is formed in gelation?
A. Calcium alginate
B. Potassium alginate
A. Calcium alginate
What is the accelerator for polysulfides?
A. Lead dioxide
B. Platinum
A. Lead dioxide
Which of the following causes shrinkage of hydrocolloids?
A. Imbibition
B. Syneresis
B. Syneresis
Contamination by sulfur from latex gloves inhibits the polymerization of which impression material?
A. Addition silicone
B. Polyether
A. Addition silicone
Which type of gypsum products is produced by steam and pressure?
A. Alpha hemihydrate
B. Beta hemihydrate
C. Densite
A. Alpha hemihydrate
Which type of gypsum is used for making diagnostic cast?
A. Type III
B. Type IV
C. Type II
A. Type III
Which stone has the highest compressive strength?
A. Type III
B. Type IV
C. Type II
B. Type IV
Which of the following is the most important as a manipulative factor of gypsum?
A. W\P ratio
B. Spatulation time
C. Vacuum mixing
A. W\P ratio
Which factor is the most important in setting expansion?
A. High w/p ratio
B. Crystals growth impinge upon each other exerting outward forces
B. Crystals growth impinge upon each other exerting outward forces
What will increase the compressive strength of gypsum?
A. Increase water content
B. Decrease water content
B. Decrease water content
What is the main constituent of inlay wax?
A. Bee wax
B. Parrafin
C. Candilila
B. Parrafin
Why is porosity needed in an investment material?
A. To allow air or gas to enter during casting
B. To allow air/gas to escape during casting
C. To allow the investment material to cool after casting
B. To allow air/gas to escape during casting
The amount of permanent deformation equals its elastic recovery. Permanent deformation depends on percent compression, time under compression, and time after removal of the compressive load.
A. Both statements are true
B. Both statements are false
C. The first statement is false; the second statement is correct
D. None of the above
C. The first statement is false; the second statement is correct
Compared to phosphate bonded investments, gypsum bonded investments are used for
A. Casting high melting point alloys
B. Limited to gold castings
B. Limited to gold castings
Which investment material is used to fabricate partial removable denture framework? A. Gypsum-bonded investment
B. Phosphate-bonded investment
C. Silica-bonded investment
B. Phosphate-bonded investment
Which of the following statements regarding metal grains is true?
A. Slow cooling helps form more grains
B. Seeding a melt in foreign body particles helps in decreasing grain size
B. Seeding a melt in foreign body particles helps in decreasing grain size
When there is increased supercooling, the critical radius size of nuclei is?
A. Increased
B. Decreased
B. Decreased
Which of the following is used for heterogeneous nucleation?
A. Iridium
A. Iridium
If a dental gold alloys of 1040C is poured in a cylindrical cast of 590C, the first solid form will:
A. Consist of small grains
B. Consist of dendritic shaped grains
A. consist of small grains
According to Hall-Petch theory, the yield strength is directly proportional to the diameter of the grains
A. True
B. False
B) False
Which of the following doesn't change after cold orking A. Elastic modulus B. Ductility C. Hardness D. Proportional limit
A. Elastic modulus
What occurs during the second stage of annealing?
A. Stress released
B. Nucleation of new grains
C. Strength and hardness return to near values before cold working
D. Both b and c
D. Both b and c
An alloy of 70%Au is poured then immediately quenched after, what properties would it have? A. Soft and ductile B. Hard and brittle C. Has a lot of ordered solid solutions D. Has a lot of random solid solutions E. Both A and D
E. Both A and D
