Page 1 of 10 BDS SECOND PROFESSIONAL EXAMINATION 2007 SCIENCE OF DENTAL MATERIALS MODEL PAPER (MCQs) Marks: 45 Time: 45 minutes Total No. of MCQs 45 One mark for each MCQ Note: THE FINAL PAPER WILL BE SIMILAR TO THE MODEL PAPER BUT WILL FOLLOW “TOS” EXACTLY. 01. The knoop hardness number of which one of the following materials is closest to that of dentin (KHN 65)? a. Tooth enamel. b. Amalgam. c. Pure Gold. d. Silicate cement. e. Dentine. Key: d 02. KHN of enamel is: a. 90-100. b. 100.50. c. 300. d. 600. e. 60-90. Key: d 03. Which of the following impression materials is elastic? a. Impression compound. b. Zinc oxide – Eugenol paste. c. Wax. d. Polyether rubber base. e. Low fusing compound Key: d 04. Which one of the following is the safest and most reliable method of regulating setting time of gypsum products? a. Altering the water and powder ratio. b. Controlling the temperature of water to be used for mixing. c. Speed of hand spatulation. d. Length of hand spatulation. e. Adding salt in mixing. Key: bPage 2 of 10 BDS SECOND PROFESSIONAL EXAMINATION 2007 SCIENCE OF DENTAL MATERIALS MODEL PAPER (MCQs) 05. Which of the following impression materials can be electroplated without risk of distortion? a. Polysulphide. b. Condensation silicone. c. Addition silicone. d. Hydrocolloid impressions. e. Polyether. Key: a 06. Which of the following statements relates best regarding cavity varnish? a. Varnishes are synthetic resins dissolved in acetone. b. Varnishes are calcium hydroxide in a resin base. c. Varnishes are used to insulate the pulp thermally. d. Varnishes are used beneath restorative resins to insulate the pulp against chemical irritants. e. Varnishes are base of ZnO engenol. Key: a 07. Setting expansion of casting investment is approximately: a. 0.1-0.2%. b. 0.1-0.5%. c. 0.8-1%. d. 1.1-1.7%. e. 1.7%-2%. Key: b 08. Stiffness refers to a. Resistance to elastic deformation. b. Degree of elastic deformation. c. Expandability on heating. d. Shrinkage on cooling. e. Expansion on cooling. Key: a 09. What is trituration a. Surface discoloration of metal. b. Mixing of amalgam alloy with mercury. c. Same as erosion. d. Same as corrosion. e. Mixing of allow particles. Key: bPage 3 of 10 BDS SECOND PROFESSIONAL EXAMINATION 2007 SCIENCE OF DENTAL MATERIALS MODEL PAPER (MCQs) 10. The dental amalgam alloys and mercury are mixed in ratio of: a. 1:1 b. 2:1 c. 1:2 d. 1:3 e. 1:4 Key: a 11. Most common drawback of amalgam restoration is: a. Secondary expansion. b. Porosity. c. Marginal break-down. d. Contraction on setting. e. Contraction away from margins. Key: c 12. What are the consequences of prolonged heating of a dental casting investment? a. Disintegration of the investment. b. Rough moulds of investment. c. Contamination of the alloys. d. Any of the above. e. Expansion of alloys. Key: d 13. Regarding dental Amalgam: a. It is a mixture of silver alloy and mercury. b. It is be composed of spherical tin and mercury. c. It is a mixture of irregular particles of silver and tin. d. Amalgamation process is formed during heating of silver-mercury. e. The process of mixing amalgam is called Amalgamation. Key: a 14. Which part of an amalgam restoration has the highest mercury concentration? a. Marginal area. b. Centre of the restoration. c. Pulpal area. d. Proximal surface of restoration. e. Inclined plane. Key: aPage 4 of 10 BDS SECOND PROFESSIONAL EXAMINATION 2007 SCIENCE OF DENTAL MATERIALS MODEL PAPER (MCQs) 15. What is the maximum level of occupational exposure considered safe with regard to mercury vapors? a. 5gµof mercury b. 50 gµ of mercury c. 35 gµ of mercury d. 25 gµ of mercury e. 1 gµ of mercury Key: b 16. The cement which has antibacterial property is: a. Copper oxide cement. b. Glass informer cement. c. Polycarboxylate cement. d. Zinc phosphate cement. e. Zinc oxide Eugenol cement. Key: a 17. Cement extensively used for attachment of orthodontic brackets to teeth is. a. Silicate cement. b. Resin cement. c. Glass ionomer cement. d. Copper oxide cement. e. ZnO Eugenol cement. Key: b 18. Cement not irritant to pulpal tissue is. a. Calcium hydroxide cement. b. Silicate cement. c. Copper cement. d. Glass ionomer cement. e. Resins cement. Key: a 19. The main resin constituent of polishable composite resin is: a. Polymethymethacrylae b. Polycarbonate c. Cyanoacrylate d. Urethane e. Dimethacrylate. Key: dPage 5 of 10 BDS SECOND PROFESSIONAL EXAMINATION 2007 SCIENCE OF DENTAL MATERIALS MODEL PAPER (MCQs) 20. Fillers are added to composite resin to: a. Increase working time. b. Increase coefficient of thermal expansion. c. Inhibit matrix deformation. d. B+C. e. Decrease working time. Key: d 21. Activating compound for visible light curing system: a. Hycroquinone. b. Ubiquinone. c. Camphoquinone. d. Benzoin methyl ether. e. Patasium oxide. Key: c 22. In light cure system the wavelength of radiation is in excess of: a. 100 nm. b. 200 nm. c. 300 nm. d. 400 nm. e. 500 nm. Key: d 23. In UV curing system, the activator employed is: a. Benzoin methyl ether. b. Methylmethacrylate. c. Hydroquinone. d. Dibutylphthalate. e. Benzoic acid. Key: a 24. The stainless steel loses its resistance to corrosion if heated to a high temperature because: a. Precipitation of chromium carbide b. Precipitation of carbon carbide c. Precipitation of iron carbide d. Precipitation of nickle carbide e. Precipitation of cohalt carbide. Key: aPage 6 of 10 BDS SECOND PROFESSIONAL EXAMINATION 2007 SCIENCE OF DENTAL MATERIALS MODEL PAPER (MCQs) 25. What is the function of feldspar during preparation of dental porcelain of a metal ceramic Crown? a. Feldspar forms a glassphase that is able to soften and flow slightly at porcelain firing temperature b. It decreases viscosity of ceramic material so that it can be applied on the metal substructure with ease c. Feldspar due to its particle size interrupts crack propagation in the dental porcelain d. Feldspar forms a carbon layer that flows at porcelain firing temperature e. Feldspar helps to prevent porcelain cracking. Key: a 26. The firing temperature of high fusing porcelain lies in the range of: a. 1600-1950oF b. 2000-3400oF c. 2350-2500°F d. 2500 – 3400°F e. 1000 - 1500°F Key: c 27. Dicor is: a. Ceramic material