dental materials Mcqs
151. The chemical used to etch enamel is_______________?
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A. Eugenol

B. Zinc oxide

C. Phosphoric acid

D. Methyl methacrylate

152. Cross linking in denture base resin is contributed by_____________?
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A. Glycol dimetharylate

B. Benzoyl peroxide

C. N-para toluidine

D. Methyl methacrylate

153. A restorative material which has a high proportional limit, compared with one with a lower proportional limit would have________________?
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A. More resistance to permanent deformation

B. Greater toughness

C. A higher modulus of elasticity

D. A higher modulus of elasticity

E. Greater ductility

154. Which of the following is NOT true of polymethyl methacrylate ?
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A. Knoop hardness number 18 to 20

B. Density of 1.13 g/cm3

C. Tensile strength of 60 MPa

D. Modulus of elasticity of 3.4 GPa
155. In self-cure acrylic resin, activator is_____________?
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A. Benzoyl peroxide

B. Quaternary ammonium compound

C. Toluidine

D. Tertiary amine
156. About polymerization shrinkage of composite all are true, except______________?
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A. Acid etching and priming will decrease polymerization shrinkage

B. Polymerization shrinkage is greater if bonded surface area is lesser than unbounded surface area

C. Microleakage can occur because of polymerization shrinkage

D. Polymerization shrinkage is high if within the enamel margins

157. A material behaves in certain ways above and below the proportional limit on a stress strin curve, which of the following is correct______________?
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A. Either A or B

B. Above the proportional limit a material function in a plastic manner, while below the proportional limit it behaves as an elastic

C. Neither A or B

D. Above the proportional limit a material functions in an elastic manner, while below the proportional limit it behaves as an plastic

158. When solid gets wet completely contact angle is______________?
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A. 0 90

B. >90

C. 0

D. 90

159. Ultimate tensile strength refers to_________________?
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A. Stress after rupture

B. Longitudinal compressive strength

C. Stress before rupture

D. Horizontal compressive strength

160. The modulus of elasticity is defined as_______________?
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A. The strain at the proportional limit

B. The stress at the proportional limit

C. None of the above

D. The stress/strain ratio within the proportional limit
161. Boiling point of methyl methacrylate________________?
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A. Is at normal room temperature

B. B.P of water

C. Equal of BP of water

D. < B.P of water

162. Back pressure porosity can be avoided by________________?
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A. Using a short and wide sprue

B. Preventing rapid heating the investment in burnout oven

C. Using asbestos linear

D. Placing the sprue at least one quarter inch away form the end of casting ring
163. Which of the following has the highest modulus of elasticity ?
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A. Enamel

B. Dentin

C. Amalgam

D. Composite Resin

164. For adhesion to be present between solid and liquid________________?
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A. Liquid should wet solid surface

B. Should have high contact angle

C. None of the above

D. Mechanical interlocking should be present

165. Insufficient closure of the flasks during packing of denture base resin can result in_____________?
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A. Less polymerization shrinkage

B. Poor colour stability

C. Decrease in vertical dimension

D. Increase in vertical dimension
166. The process wherein two or more chemically different monomers, each with some desirable property, can be combined to yield specific physical properties of a polymer is known as_____________?
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A. Step-growth polymerization

B. Addition polymerization

C. Condensation polymerization

D. Copolymerization
167. Gypsum product having least expansion_____________?
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A. Die stone

B. Model plaster

C. Stone plaster

D. Impression plaster

168. Hydrocolloid material, show all except______________?
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A. Imbibition

B. Recrytallisation

C. Hysterisis

D. Syneresis

169. Setting time of ZOE is best controlled by______________?
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A. Altering ratio of two pastes

B. Adding a drop of eugenol

C. Cooling the glass slab

D. Adding a drop of water

170. Which of the following impression material is rigid ?
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A. Polysulphide rubber

B. Reversible hydrocolloid

C. Alginate

D. Zinc oxide-eugenol
171. Solder and flux used for joining Elgiloy wires are_____________?
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A. Silver solder and fluoride flux

B. Gold solder and fluoride flux

C. Silver Solder and borax flux

D. Gold solder and borax flux

172. The impression for a diagnostic cast of a partial edentulous mouth should be taken in_______________?
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A. Modelling compound

B. Impression wax

C. Hydro-colloid

D. Hydro cal

173. Shape memory in NiTi is because of stress induced form__________________?
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A. Austenite to martensite

B. Ferrite to austenite

C. Austenite to ferrite

D. Martensite to austenite

174. Rapid removal of rubber impression with a single firm motion results in____________________?
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A. Improved adhesion of the impression to the tray

B. Minimal permanent deformation

C. Reduced contamination by saliva

D. Reduced dimensional instability

175. The porosity formed due to simultaneous nucleation of solid grains and gas bubbles at the first moment that metal freezes at the mold walls is called__________?
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A. Pinhole porosity

B. Gas inclusion porosity

C. Subsurface porosity

D. Micro porosity

176. The impression material used to record the prepared areas on abutment teeth is______________?
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A. Low viscosity elastomeric impression material

B. Medium viscosity elastomeric impression material

C. None of the above

D. High viscosity elastomeric impression material

177. Incomplete casting is the result of_____________?
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A. Large reservoir

B. More porous investment in the mould

C. Narrow sprue diameter

D. Hollow sprue pin

178. The most mucostatic impression material is_______________?
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A. Free flowing wax

B. Reversible hydrocolloids

C. Thin mix of plaster of paris

D. Zinc oxide eugenol impression paste

179. Palatal secretions affect the setting of all the impression materials except_______________?
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A. Impression paste

B. Agar-agar

C. Silicone

D. Impression plaster

180. Flux is used during casting to________________?
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A. Remove the oxides formed on the gold alloy

B. Lower the melting point

C. Replace casting wax

D. Speed the burnout process

181. Impression compound base_____________?
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A. Crystalline structure

B. Low thermal conductivity

C. High fusion temperature

D. Formation of cross linkage with heating

182. Linear contraction of elostomeric impression with passage of time is highest in______________?
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A. Polysulphide

B. Polyetner

C. Addition silicone

D. Condensation silicone
183. The linear solidification shrinkage of Type IV Ni-Cr based alloys is_______________?
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A. 2.3%

B. 3%

C. 1.37%

D. 1.56%

184. Plaster of paris _____________?
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A. Has porous and irregular crystals

B. Has a W / P of 0.2

C. Is a hamihydrate

D. Is wet calcined hemihydrate

185. Immediate pouring of impressions is most critical in_____________?
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A. Condensation polysillicon

B. Polyether

C. Addition Polysilicon

D. A and B

186. The gold alloys used for casting contain at least. percent of precious metal according to ADA specification number 5________________?
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A. 85

B. 75

C. 65

D. 55

187. Titanium casting is done_____________?
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A. Under air pressure in nitrogen atmosphere

B. Under vacuum in argon atmosphere

C. In specially fabricated aluminium vanadium

D. Using CAD-CAM technique

188. Name the accelerator used in Zinc oxide eugenol paste______________?
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A. Linseed oil

B. Olive oil

C. All of these

D. Zinc acetate
189. Silver plated dyes use an electrolytic bath of_______________?
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A. Silver bromide

B. Silver iodide

C. Silver cyanide

D. Silver fluorides

190. The strength of the gypsum specimen when the water in excess of that required for the hydrate of the hemihydrate is left in the specimen is called____________?
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A. Dry strength

B. Compressive strength

C. Green strength

D. Water strength

191. Indium in metal alloys_______________?
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A. Improve bonding

B. Harden the metal ceramic Ag-Pd alloy

C. Both A and B

D. None of the above

192. Which of the following is true about Agar hydrocolloid impression material ?
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A. Cannot register fine surface details

B. Solidfies between 50 70C

C. Facilitates fabrication of metal dyes

D. Liquefies between 71 100C
193. Tublulence of molten gold is due to _____________?
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A. Improper venting

B. A and B

C. Impurities in gold

D. None of the above
194. Gap between true end of casting ring and wax pattern should be______________?
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A. one inch

B. inch

C. inch

D. 3/8 inch

195. Vulcanization refers to the setting of__________________?
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A. Zinc oxide-eugenol

B. Zinc Phosphate cement

C. Mercaptan impression material

D. Reversible hydrocolloid

196. Which of the following best describes the working time of impression material ?
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A. After the start of appearing elastic properties of impression material

B. The time for start of mixing till just before the start of appearing elastic properties of impression material

C. Just after the start of appearing elastic properties of impression material

D. Loss of lusture of impression material

197. A highly polished surface on a metallic dental restoration aids considerably in the prevention of the____________?
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A. Tarnish and corrosion

B. Warpage

C. Dimensional change

D. Thermal conductivity

198. The best way to remove a hydrocolloid impression from the patients mouth is____________?
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A. Sudden jerking of the impression to prevent tearing

B. Supporting the impression along with the tray to prevent disengaging of the tray alone

C. Wetting the periphery of the impression with moist cotton to break the peripheral seal

D. Slight rocking of the impression to disengage it from the undercut

199. Which of the following cast gold alloys is used for fabricating partial denture frameworks______________?
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A. Type IV Extra Hard

B. Type III Hard

C. Type I Soft

D. Type II Hard

200. The water powder ratio of alginate is______________?
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A. 40 ml of water to 15 gms of powder

B. 100 ml of water to 60 gms of powder

C. 15 ml of water to 40 gms of powder

D. 40 ml of water to 40 gms of powder