dental materials Mcqs
201. Modern dental noble metal casting alloys generally have equiaxed fine grain structures because of the incorporation of small amounts of______________?
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A. Irridium

B. Indium

C. Palladium

D. Chromium

202. Setting of POP is result of______________?
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A. Reaction between hemihydrate and hihydrate

B. Nucleation and growth of CaSo4 H2O crystals

C. Difference in solubility of CaSo4 H2O + CaSO4+ 2H2O

D. Reaction between CaSO4+ 2H2O and water

203. Brush heap structure is found in______________?
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A. Polyether

B. Condensation silicone

C. Agar

D. Zinc oxide impression material

204. Placing cast under tap water is to be avoided as______________?
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A. H2O interferes with hygroscopic expansion

B. H2O interferes with Crystallization of dihydrate

C. Gypsum is slightly soluble in water and the surface of the cast will be eroded

D. H2O inhibits polymerization of dental resin

205. The main ingredient in dental plaster in_______________?
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A. Calcium sulphate hemihydrate

B. Calcium anhydrate

C. Calcium phosphate

D. Calcium sulphate dihydrate

206. Minimum flow of Type-I impression compound at mouth temperature is___________________?
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A. 6%

B. 10%

C. 8%

D. 4%

207. Boxing wax is also called as________________?
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A. Utility wax

B. Sticky wax

C. Carding wax

D. Inlay wax

208. Impression plaster containing potato starch is called______________?
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A. Anti expansion solution

B. Soluble plaster

C. Die stones

D. Plaster of paris

209. Dustless alginate is produced by______________?
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A. Adding heavy metal salts

B. Coating with dihydric alcohol

C. Altering the matrix

D. Reducing the diatomaceous earth

210. Which of the following impression materials is easy to pour and difficult to remove the stone cast from the impression ?
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A. Polyether

B. Condensation polysilicone

C. Polysulfide

D. Addition polysilicone

211. 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

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

B. Beryllium

C. Molybdenum

D. Tin

213. 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

214. 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

215. 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
216. 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
217. 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

218. 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
219. 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

220. 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

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

B. Hydrophilic

C. Hydrophobic

D. Potassium alginates

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

B. Contraction

C. Strength

D. Decrease strength

223. 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
224. 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

225. Most flexible impression material______________?
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A. Alginate

B. Addition silicone

C. Impression compound

D. Impression paste

226. 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

227. 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

228. 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

229. 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

230. 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
231. 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

232. 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
233. 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
234. 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:

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

B. Homogeneous

C. Inhomogenous

D. amorphous

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

B. Mineral oil

C. Plasticizer

D. Water

237. 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

238. 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

239. 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

240. 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

241. 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

242. Most rigid elastomer is___________________?
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A. Polyether

B. Condensation silicone

C. Polysulphide

D. Addition silicone

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

B. Polyether

C. Condensation silicone

D. Addition silicone
244. 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

245. 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

246. 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

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

B. Hydrocolloids

C. Impression compound

D. Impression plaster

248. 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

249. 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

250. 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