8551. The American dental association (ADA) specification number for non-aqueous elastomeric dental impression material is______________?
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A. 21

B. 19

C. 20

D. 26

8552. Which of the following increases castability of base metal alloys________________?
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A. Carbon

B. Beryllium

C. Molybdenum

D. Tin

8553. Impression compound is characterized by all of the following except_______________?
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A. Is a thermoset material

B. Low coefficient of thermal conductivity

C. Shows increased flow when kneaded with water

D. Warps at room temperature

8554. During setting of alginate impression materials________________?
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A. Trisodium phosphate reacts with calcium sulphate

B. Material in contact with soft tissues sets last

C. Trisodium phosphate reacts with sodium alginate

D. Colloidal changes to sol

8555. The main difference between dental stone and dental plaster is______________?
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A. Chemical composition

B. Solubility in water

C. Self life

D. Sharpe and size of particles
8556. Cobalt-Chrominum alloys contains_______________?
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A. 20% gold

B. 30% cobalt and 60% chrominum

C. 1% palladium

D. 60% cobalt and 30% chrominum
8557. Glossy smooth margins of a casting are due to_____________?
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A. Investment breakdown

B. Incomplete wax elimination

C. Incomplete gas elimination

D. Shrinkage of alloy on cooling

8558. Finer particle size of silica______________?
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A. Normal setting expansion

B. Slower the hygroscopic expansion

C. No setting expansion

D. Greater the hygroscopic expansion
8559. The setting time of irreversible hydrocolloids can be decreased by_____________?
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A. None of the above

B. Lowering the temperature of water used for mixing

C. Raising the temperature of water used for maxing

D. Using excess water for maxing

8560. The setting expansion of gypsum products can be reduced by________________?
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A. Increased spatulation

B. Less water powder ratio

C. Adding potassium sulfate

D. Allowing setting under water

8561. Elastomers except: Polyether are_______________?
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A. Water loving impression materials

B. Hydrophilic

C. Hydrophobic

D. Potassium alginates

8562. Quartz in investment material is added for_______________?
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A. Expansion components for casting shrinkage

B. Contraction

C. Strength

D. Decrease strength

8563. Impression techniques are used for recording________________?
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A. Oral mucosal tissues

B. None of the above

C. Dental hard tissues

D. Oral mucosal tissues and dental hard tissues
8564. Which is best material for RPD impression_______________?
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A. Irreversible hydrocolloid

B. Impression plaster

C. None of the above

D. Reversible hydroollioid

8565. Most flexible impression material______________?
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A. Alginate

B. Addition silicone

C. Impression compound

D. Impression paste

8566. Corrosion of stainless steel is due to formulation of_________________?
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A. Nickel carbide

B. Chromium carbide

C. Carbon carbide

D. Iron carbide

8567. Which of the following is correct arrangement of impression material regarding linear contraction in ascending order ?
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A. Addition silicone < polyether < polysulfide < condensation silicone

B. condensation silicone < polysulfide < polyether < Addition silicone

C. condensation silicone < polyether < polysulfide < Addition silicone

D. Addition silicone < polysulfide < Polyether < condensation silicone

8568. Powders of dental plaster and dental stone differ mainly in____________?
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A. Particle porosity

B. Solubility

C. Shelf life

D. Chemical formula

8569. The process of changing the rubber base product or liquid polymer, to a rubber like material is generally known as_____________?
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A. Chain lengthening

B. Vulconization

C. Boiling

D. Condensation

8570. All of the following statements about an alginate impression are EXCEPT________________?
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A. It should be rapidly displaced from the mouth

B. It will take up water and expand if kept wet

C. It will shrink as a result of syneresis

D. It may exhibit fluid exudates on the surface as a result of imbibition of water
8571. Which one of the following increase the strength and reduce viscosity of agar hydrocolloid impression material_____________?
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A. Water

B. Sulfates

C. Borax

D. Carbonates

8572. Reduction in the fusion temperature of dental gold casting alloys is caused by presence of______________?
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A. Platinum

B. Silver

C. Gold

D. Copper
8573. Which one of the following impression materials is elastic, sets by a chemical reaction and is catalyzed by chloroplatinic acid_______________?
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A. Condensation silicone

B. Polyether

C. Polysulfide

D. Poly vinyl siloxane
8574. Inlay wax is used to_______________?
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A. Invest inlay patterns

B. Make inlay wax patterns

C. Box models

D. Temporarily cement inlays:

8575. Microstructure of cobalt chromium alloy in cast condition is______________?
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A. Fibrous

B. Homogeneous

C. Inhomogenous

D. amorphous

8576. To make the vinyl Polysiloxane hydrophilic the following is added_______________?
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A. Surfactant

B. Mineral oil

C. Plasticizer

D. Water

8577. The most commonly used Titanium alloy for dental and medical purposes is________________?
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A. Ti 5Al 4V

B. Ti 6Al 6V

C. Ti 6Al 4V

D. Ti 5Al 5V

8578. All of the following can be used to slow down the setting of Zinc oxide eugenol impression paste EXCEPT_________________?
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A. Adding a small amount of water

B. Altering the amounts of the two pastes used

C. Adding a small amount of glycerine

D. Cooling mixing slab

8579. Rubber base impressions are poured immediately as they_______________?
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A. Continue to polymerize

B. Show imbibition and syneresis

C. Become elastic

D. Show gelation

8580. The sprue in wax pattern should be placed________________?
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A. At 45C angle

B. It depend upon type of wax pattern

C. At obtuse angle

D. At right angle

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