dental materials Mcqs
251. 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

252. Elastomers are_________________?
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A. Imp. Compound

B. Alginate

C. Polyethers

D. Agar

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

B. Glyecrol

C. alcohol

D. Glutamic acid

254. 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

255. 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

256. 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

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

B. Increased density

C. Increased ductility

D. Increased hardness
258. 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

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

B. Pickling

C. Degassing

D. Annealing

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

B. Silica

C. Calcium sulphate monohydrate

D. Cristobolite

261. With indirect spruing. Which one of the following porosities can be minimised_______________?
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A. Back pressure porosity

B. Micro porosity

C. Pin hole porosity

D. Localized shrinkage porosity
262. Hysteresis in a hydrocolloid gel is______________?
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A. Phenomenon of conversion of gel into sol

B. Temperature lag between gelation and liquefaction temperature

C. Moisture absorption

D. All of the above

263. The best pickling solution for gypsum bonded investment is_______________?
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A. Hydrochloric acid

B. Phosphoric acid

C. Sulphuric acid

D. Nitric acid

264. Function of carnauba wax_________________?
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A. Increase toughness

B. To provide a smooth and glossy surface

C. Decrease toughness

D. Decrease flow at room temperature
265. Crucible indicated for casting base metal alloys is______________?
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A. High melting plastic crucible

B. Clay crucible

C. Quartz crucible

D. Carbon crucible

266. Stages of annealing in order_________________?
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A. Recrystallization recovery, grain growth

B. Grain Growth Recrystallization recovery

C. Recovery recrystallization grain growth

D. Melting point, grain growth, Recrystallization

268. The impression materials with lowest viscosity is_____________?
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A. Elastomers

B. Plaster of paris

C. Zinc oxide eugenol

D. Agar agar

269. The relative hardness of elastomere is determined using________________?
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A. Knoop pyramid

B. Rockwell tester

C. Barcol indenter

D. Shore durometer
270. Masterial causing minimum tissue distortion is______________?
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A. Impression plaster

B. Zinc oxide eugenol paster

C. Polysulphide

D. Silicone

271. Wax pattern is ideally invested immediately to decrease the dimensional changes caused by_______________?
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A. Water loss

B. Decrease flow

C. Relaxation of the internal stresses

D. Continuous expansion

273. 4th state of matter is______________?
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A. Liquid

B. Solid

C. Gas

D. Colloid
274. Which material is the most difficult to remove from the patients mouth ?
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A. Silicone impression material

B. Reversible hydrocolloid

C. Impression plaster

D. Metallic oxide paste
275. Impression compound has which of the following characteristic property ?
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A. Degradation is presence of moisture

B. High flow property

C. Remain distortion free up to 72 hrs. pouring can be safely delayed

D. Low thermal conductivity
276. When making a polysulphide impression for a caste crown, custom trays are usually preferred over stock trays for all of the following reasons except_______________?
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A. Custom trays facilitate uniform contraction of impression material

B. Custom trays require less impression material

C. Impressions made n the custom trays are easier to remove from the mouth

D. Stock trays may be short in the flange area

278. A common electrolyte used for plating copper indirect dies is_______________?
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A. Ionic copper

B. Acidic copper sulfate

C. Copper cynide

D. Silver cyanide

279. Which of the following is not affected by saliva ?
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A. Impression paste

B. Silicon impression material

C. None of the above

D. Impression plaster

280. Perforated impression tray are used for_______________?
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A. Zinc oxide-eugenol

B. Impression compound

C. Alginate

D. Agar-agar

282. Hypersensitivity reactions like contact dermatitis can be caused by______________?
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A. Polyether

B. Condensation silicones

C. polysulfides

D. addition silicones

283. Which of the following is function of fluoride flux in soldering process ?
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A. Increase the strength of solder

B. It prevents the formation of chromium oxide or dissolves chromic oxide layer

C. It prevents the formation of copper oxide

D. It prevents the flow of material in undesirable area

284. Which of the following is used as surface hardener in Impression material ?
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A. 2% Potassium sulfate

B. 2% sodium sulfate

C. 0.2% Potassium sulfate

D. 4% Potassium sulfate

286. Polysulfide material is routinely not recommended because of_______________?
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A. Least permanent deformation

B. Unpleasant odor and taste

C. Low accuracy

D. Highest curing shrinkage

288. The function of a sprue is to_______________?
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A. Help polish cast restorations

B. Reproduce fine detail

C. Form an opening of molten metal to enter the mold

D. Eliminate air bubbles on the wax pattern

290. Function of wetting agents used in casting procedure is_________________?
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A. To felicitate mixing investment

B. To felicitate wetting of ring liner

C. For better wax elimination

D. To reduce contact angle of liquid with max surface
292. Two in one stage impression materials include______________?
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A. All of the above

B. Elastomeric impression material

C. Zinc Oxide eugenol impression paste

D. Hydrocolloid impression material

293. Type III Dental gypsum is__________________?
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A. Model or lab plaster

B. Class I stone or hydrocal

C. Densite

D. Class II stone

296. Stainless steel is used mostly in dentistry_________________?
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A. To strength amalgam

B. To replace internal gold restorations

C. To construct clasps for partial dentures

D. In orthodontic wires
297. Which of the following decrease with strain hardening______________?
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A. Surface hardness

B. Proportion limit

C. Strength

D. Corrosion resistance
298. Which one of the following categories of dental materials has the highest thermal conductivity_________________?
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A. Gold alloys

B. Zinc phosphate cements

C. Porcelains

D. Unfilled acrylic plastics

299. Before pouring an elastic impression it is washed with slurry of water and stone to______________?
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A. Prevent distortion

B. Prevent syneresis

C. Wash off saliva on impression

D. Increase gel strength

300. Type I and Type II zinc oxide impression paste differ with respect to_______________?
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A. Eugenol content

B. Their hardness after setting

C. Their use

D. Water content