medical MCQs – Page 430

Practise multiple-choice questions from medical for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

8581. Which of the following is correct regarding chemical setting of condensation silicone_______________?
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A. Polymerization occurs with elimination of single byproduct

B. Condensation does not occur at all

C. Polymerization occurs with repeated elimination of small molecules

D. By condensation of repeated molecules of monomers

8582. Most rigid elastomer is___________________?
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A. Polyether

B. Condensation silicone

C. Polysulphide

D. Addition silicone

8583. Most ideally elastic among the following_______________?
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A. Polysulphide

B. Polyether

C. Condensation silicone

D. Addition silicone
8584. Disadvantage of having a short sprue is________________?
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A. Difficulty in removing casting from investment

B. Rapid solidification of metal

C. Incomplete evacuation of gases

D. No place for reservoirs

8585. Agar syringe material can be used with/as______________?
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A. Agar

B. Alginate impression material

C. Both of the above

D. Primary impression

8586. Rough surface of elastomeric impression results from_______________?
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A. Air bubbles

B. Incomplete polymerization caused by premature removal from mouth

C. Inadequate mixing

D. Too rapid polymerization

8587. Sol gel transformation is seen in________________?
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A. Elastomer

B. Hydrocolloids

C. Impression compound

D. Impression plaster

8588. Resistance to corrosion in a cobalt-chrome casting is due to presence of_______________?
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A. Cobalt

B. Chrome

C. Nickel

D. High quality iron

8589. Dimensional stability of hydrocolloid impressions may be achieved by_________________?
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A. Prolonged manipulation

B. Using humidor

C. Using less water powder ratio

D. Storing the impression under water

8590. The product, which is obtained by calcining gypsum under steam pressure at 120-130C or by dehydrating gypsum in the presence of sodium succinate is_______________?
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A. Alpha hemihydrates

B. Orthorhombic anhydrate

C. Beta hemihydrates

D. Calcium sulphate dihydrate

8591. Modiffiers are added to gypsum mainly to_______________?
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A. Modify setting expansion

B. Modify setting time

C. Decrease the porosity

D. Modify strength

8592. Elastomers are_________________?
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A. Imp. Compound

B. Alginate

C. Polyethers

D. Agar

8593. Alginates are made dust free by adding______________?
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A. Glycol

B. Glyecrol

C. alcohol

D. Glutamic acid

8594. Dimensional stability of elastomeric impression material can be given in descending order as_____________?
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A. Addition silicone > polyether > Polysulphide > Condensation silicone

B. Polysulphide > polyether > Condensation silicone > Addition silicone

C. polyether > Condensation silicone > Polysulphide > Addition silicone

D. Addition silicone> Condensation silicone > Polysulphide > polyether

8595. The ? (Beta) hemihydrate of gypsum requires more water to float its powder particles because______________?
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A. They are more dense and prismatic in shape

B. They are more irregular in shape and porous

C. They are more regular in shape and dense

D. They are more regular in shape and highly porous

8596. Suck back porosity is due to_________________?
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A. Attached impurities on undersurface of casting

B. No rapid cooling

C. Hot spot

D. Inadequate melting temperature

8597. Compared with noble metals, base metals show_______________?
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A. Better biocompatibility

B. Increased density

C. Increased ductility

D. Increased hardness
8598. Impression plaster is_____________?
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A. Less compressive than alginate

B. As compressive as alginate

C. More compressive than alginate

D. More compressive than hydrocolloids

8599. Impurities in casting is removed by________________?
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A. Conditioning

B. Pickling

C. Degassing

D. Annealing

8600. Binder used in Gypsum investment is_________________?
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A. Quartz

B. Silica

C. Calcium sulphate monohydrate

D. Cristobolite