Model and Die Material MCQ PDF

**What is the main requirement for model and die materials in dentistry?** - A\) High cost - B\) Ability to reproduce fine details - C\) Low mechanical strength - D\) Complex manufacturing process\ **Answer:** B) Ability to reproduce fine details **What is the primary component of g...

**What is the main requirement for model and die materials in dentistry?** - A\) High cost - B\) Ability to reproduce fine details - C\) Low mechanical strength - D\) Complex manufacturing process\ **Answer:** B) Ability to reproduce fine details **What is the primary component of gypsum products?** - A\) Calcium sulfate hemihydrate - B\) Sodium chloride - C\) Calcium carbonate - D\) Silicon dioxide\ **Answer:** A) Calcium sulfate hemihydrate **Which type of gypsum product is used for high-strength and high-expansion applications?** - A\) Model Plaster (Type II) - B\) Dental Stone (Type III) - C\) Improved Stone (Type IV) - D\) High-Strength, High-Expansion Dental Stone (Type V)\ **Answer:** D) High-Strength, High-Expansion Dental Stone (Type V) **What is the ideal water-to-powder ratio for dental stone (Type III)?** - A\) 100 gm powder / 50 ml water - B\) 100 gm powder / 30 ml water - C\) 100 gm powder / 22-24 ml water - D\) 100 gm powder / 18-22 ml water\ **Answer:** B) 100 gm powder / 30 ml water **What is the main advantage of using electroplated dies in dentistry?** - A\) Lower cost - B\) No dimensional change during setting - C\) Faster manufacturing time - D\) Compatibility with all impression materials\ **Answer:** B) No dimensional change during setting **Questions 6 - 20:** 6. **Which property is crucial for model and die materials to avoid dimensional changes?** - A\) Flexibility - B\) Dimensional stability - C\) Low cost - D\) High porosity\ **Answer:** B) Dimensional stability 7. **What type of gypsum product is commonly known as \"Plaster of Paris\"?** - A\) Type I: Impression Plaster - B\) Type II: Model Plaster - C\) Type III: Dental Stone - D\) Type IV: Improved Stone\ **Answer:** B) Type II: Model Plaster 8. **What does the process of \"calcination\" involve in gypsum production?** - A\) Mixing with water - B\) Removing water of crystallization - C\) Adding binding agents - D\) Reducing particle size\ **Answer:** B) Removing water of crystallization 9. **Which type of calcination produces plaster with irregular and porous particles?** - A\) Dry calcination - B\) Wet calcination - C\) Calcination under pressure - D\) Chemical calcination\ **Answer:** A) Dry calcination 10. **What type of gypsum product is created through wet calcination?** - A\) Model Plaster - B\) Dental Stone (Type III) - C\) Improved Stone (Type IV & V) - D\) Plaster of Paris\ **Answer:** B) Dental Stone (Type III) 11. **Which particle shape is associated with high-strength dental stones?** - A\) Irregular - B\) Needle-like - C\) Cubic - D\) Rounded\ **Answer:** C) Cubic 12. **In gypsum products, what is the function of \"excess water\"?** - A\) Improves setting reaction - B\) Increases strength - C\) Creates porosity after evaporation - D\) Reduces hardness\ **Answer:** C) Creates porosity after evaporation 13. **Which method is commonly used to measure the initial setting time of gypsum?** - A\) Gilmore test - B\) Vicat test - C\) Flexural test - D\) Tensile test\ **Answer:** B) Vicat test 14. **What is the primary disadvantage of gypsum as a die material?** - A\) Susceptibility to abrasion - B\) High cost - C\) Long setting time - D\) Low compressive strength\ **Answer:** A) Susceptibility to abrasion 15. **Why is calcium chloride sometimes added to gypsum products?** - A\) To increase cost - B\) To speed up setting time - C\) To improve compressive strength - D\) To enhance dimensional accuracy\ **Answer:** B) To speed up setting time 16. **What factor directly affects the setting expansion of gypsum products?** - A\) Water temperature - B\) Humidity - C\) Particle size and shape - D\) Mixing speed\ **Answer:** C) Particle size and shape 17. **What is the main purpose of \"vibration\" during the mixing of gypsum?** - A\) To speed up the setting time - B\) To prevent the formation of air bubbles - C\) To increase porosity - D\) To lower the temperature\ **Answer:** B) To prevent the formation of air bubbles 18. **Which material is used to make electroplated dies more abrasion-resistant?** - A\) Gypsum - B\) Silver or copper coating - C\) Sodium chloride - D\) Wax\ **Answer:** B) Silver or copper coating 19. **For which impression materials are epoxy resins NOT suitable?** - A\) Silicone - B\) Polyether - C\) Hydrocolloid - D\) Rubber\ **Answer:** C) Hydrocolloid 20. **What is the primary reason epoxy resins are favored over gypsum for certain dies?** - A\) Cost-effectiveness - B\) Abrasion resistance - C\) Rapid setting time - D\) No shrinkage\ **Answer:** B) Abrasion resistance 21. **Which chemical serves as a retarder in gypsum setting reactions?** - A\) Sodium chloride - B\) Borax - C\) Calcium sulfate - D\) Potassium sulfate\ **Answer:** B) Borax 22. **Which type of 3D printing technology is used to create dental models by solidifying photosensitive polymers layer-by-layer?** - A\) Stereolithography - B\) Laser sintering - C\) Extrusion molding - D\) Thermal printing\ **Answer:** A) Stereolithography 23. **What advantage do 3D printed dental models offer for educational purposes?** - A\) Lower cost than traditional models - B\) Precise reproduction of dental anatomy - C\) Increased setting time - D\) Enhanced durability\ **Answer:** B) Precise reproduction of dental anatomy 24. **The initial setting time in gypsum products can be estimated by observing which of the following?** - A\) Weight loss - B\) Loss of gloss - C\) Color change - D\) Odor release\ **Answer:** B) Loss of gloss 25. **What is the effect of increasing the water/powder ratio on the strength of gypsum products?** - A\) Increases strength - B\) Decreases strength - C\) No effect - D\) Increases setting expansion\ **Answer:** B) Decreases strength 26. **Which substance, when added in low concentrations, acts as an accelerator in gypsum setting?** - A\) Sodium chloride - B\) Potassium sulfate - C\) Borax - D\) Calcium oxide\ **Answer:** B) Potassium sulfate 27. **Which setting reaction mechanism in gypsum involves the precipitation of dihydrate crystals?** - A\) Solution theory - B\) Crystalline theory - C\) Hydration theory - D\) Oxidation theory\ **Answer:** B) Crystalline theory 28. **In electroplated dies, which element is often used for the anode in silver plating?** - A\) Copper - B\) Silver - C\) Nickel - D\) Gold\ **Answer:** B) Silver 29. **What is a significant disadvantage of copper-plated dies?** - A\) Costly materials - B\) Requires additional protective coating - C\) Potential for dimensional instability - D\) Short working time\ **Answer:** C) Potential for dimensional instability 30. **What is the purpose of adding fillers to polyurethane resin for dental models?** - A\) Decrease viscosity - B\) Reduce polymerization shrinkage - C\) Lower strength - D\) Increase setting time\ **Answer:** B) Reduce polymerization shrinkage 31. **Which type of impression material is compatible with flexible die materials?** - A\) Hydrocolloid - B\) Polyvinyl siloxane - C\) Silicone - D\) Epoxy\ **Answer:** B) Polyvinyl siloxane 32. **Why is it advised to use a mechanical mixer for gypsum products?** - A\) Prevents thermal reactions - B\) Reduces mixing time - C\) Controls setting temperature - D\) Enhances surface gloss\ **Answer:** B) Reduces mixing time 33. **What is the typical color of natural gypsum rock?** - A\) Green - B\) Black - C\) Yellowish-white - D\) Brown\ **Answer:** C) Yellowish-white 34. **Which of the following is NOT a property of ideal model and die materials?** - A\) Dimensional stability - B\) High porosity - C\) Accuracy - D\) Mechanical strength\ **Answer:** B) High porosity 35. **How long does it generally take for the dry compressive strength of gypsum to develop fully?** - A\) 1 hour - B\) 1 day - C\) 7 days - D\) 30 minutes\ **Answer:** C) 7 days 36. **Which factor controlled by the operator can reduce gypsum setting time?** - A\) High water/powder ratio - B\) Increased humidity - C\) Vigorous mixing - D\) Lower mixing temperature\ **Answer:** C) Vigorous mixing 37. **What is the effect of adding gum arabic to gypsum mixtures?** - A\) Increases hardness - B\) Reduces water requirement - C\) Increases setting time - D\) Reduces gloss\ **Answer:** B) Reduces water requirement 38. **What type of gypsum product is also known as \"Densite\"?** - A\) Model Plaster - B\) High-Strength Dental Stone (Type IV) - C\) High-Expansion Stone - D\) Improved Stone\ **Answer:** B) High-Strength Dental Stone (Type IV) 39. **Why is the temperature of 100°C significant in gypsum setting?** - A\) Increases setting time significantly - B\) Prevents gypsum from setting - C\) Enhances crystal growth - D\) Promotes hygroscopic setting expansion\ **Answer:** B) Prevents gypsum from setting 40. **What is the main reason hydrocolloid impressions cannot be used with epoxy resins?** - A\) High viscosity of epoxy - B\) Polymerization reaction is retarded by water - C\) Low abrasion resistance - D\) High temperature during epoxy setting\ **Answer:** B) Polymerization reaction is retarded by water 41. **What is one disadvantage of flexible die materials?** - A\) High cost - B\) High rigidity - C\) Long setting time - D\) Poor dimensional accuracy\ **Answer:** A) High cost 42. **Which of these factors does NOT affect the setting expansion of gypsum products?** - A\) Mixing time - B\) Particle size - C\) Chemical additives - D\) Storage container color\ **Answer:** D) Storage container color 43. **In gypsum setting, what are \"spherulites\"?** - A\) Porous bubbles - B\) Needle-like crystal clusters - C\) Mixed particles - D\) Round voids\ **Answer:** B) Needle-like crystal clusters 44. **What advantage does adding a die hardener to gypsum dies provide?** - A\) Reduces cost - B\) Increases setting time - C\) Improves abrasion resistance - D\) Reduces surface gloss\ **Answer:** C) Improves abrasion resistance 45. **Which type of gypsum has the lowest water/powder ratio requirement?** - A\) Plaster - B\) Stone - C\) High-strength, high-expansion stone - D\) High-strength, low-expansion stone\ **Answer:** D) High-strength, low-expansion stone 46. **Which type of die material provides the best contrast with inlay wax?** - A\) Epoxy resin - B\) Polyurethane resin - C\) Gypsum - D\) Electroplated dies\ **Answer:** C) Gypsum 47. **What is the primary material used in fused deposition modeling for 3D dental models?** - A\) Epoxy resin - B\) Thermoplastic resin (e.g., ABS) - C\) Copper alloy - D\) Silico-phosphate\ **Answer:** B) Thermoplastic resin (e.g., ABS) 48. **For best storage of gypsum products, which condition is ideal?** - A\) High humidity - B\) Air-tight container - C\) Open to air - D\) Mixed with stabilizers\ **Answer:** B) Air-tight container 49. **Which setting expansion type is associated with gypsum setting under water?** - A\) Hygroscopic expansion - B\) Thermal expansion - C\) Pressure-induced expansion - D\) Chemical expansion\ **Answer:** A) Hygroscopic expansion 50. **What is the working time for a standard gypsum mixture?** - A\) 1 minute - B\) 2 minutes - C\) 3 minutes - D\) 5 minutes\ **Answer:** C) 3 minutes 51. **What type of impression material is NOT compatible with epoxy resins due to water interference?** - A\) Rubber-based materials - B\) Hydrocolloid materials - C\) Polyether materials - D\) Silicone-based materials\ **Answer:** B) Hydrocolloid materials 52. **The addition of which chemical creates a dense, hard, and low-porosity gypsum product?** - A\) Sodium sulfate - B\) Calcium chloride - C\) Borax - D\) Aluminum oxide\ **Answer:** B) Calcium chloride 53. **What is the main disadvantage of silver electroplated dies?** - A\) Low strength - B\) Health risks with silver cyanide electrolyte - C\) Poor detail reproduction - D\) Limited to hydrocolloid impressions\ **Answer:** B) Health risks with silver cyanide electrolyte 54. **How is excess water in gypsum products eventually removed?** - A\) By chemical reaction - B\) Through evaporation - C\) By adding accelerators - D\) By using high-temperature storage\ **Answer:** B) Through evaporation 55. **What is the function of rubber bowl and spatula in gypsum preparation?** - A\) Vibration - B\) Mixing - C\) Drying - D\) Cooling\ **Answer:** B) Mixing 56. **What kind of setting expansion is typically observed in Type V gypsum?** - A\) Low expansion - B\) High expansion - C\) No expansion - D\) Rapid expansion\ **Answer:** B) High expansion 57. **What is the color of natural gypsum rock?** - A\) White to yellowish - B\) Blue to gray - C\) Green to black - D\) Pink to red\ **Answer:** A) White to yellowish 58. **Which additive improves the abrasion resistance of type IV gypsum?** - A\) Sodium chloride - B\) Cyanoacrylate adhesive - C\) Gelatin - D\) Silicone\ **Answer:** B) Cyanoacrylate adhesive 59. **How does adding borax to gypsum affect the setting time?** - A\) Shortens setting time - B\) No effect - C\) Extends setting time - D\) Reduces porosity\ **Answer:** C) Extends setting time 60. **What type of gypsum is best for impression plaster?** - A\) Type I - B\) Type II - C\) Type III - D\) Type IV\ **Answer:** A) Type I 61. **Which gypsum product type is commonly known as \"improved stone\"?** - A\) Type I - B\) Type II - C\) Type IV - D\) Type V\ **Answer:** C) Type IV 62. **Which setting expansion percentage is typical for dental stone?** - A\) 0.1% - B\) 0.2% - C\) 0.3% - D\) 0.5%\ **Answer:** B) 0.2% 63. **What effect does sodium chloride have when added in low concentrations to gypsum?** - A\) Increases setting time - B\) Decreases setting time - C\) Reduces hardness - D\) Increases porosity\ **Answer:** B) Decreases setting time 64. **What temperature range is required for dry calcination of gypsum?** - A\) 50-60°C - B\) 110-130°C - C\) 150-180°C - D\) 200-250°C\ **Answer:** B) 110-130°C 65. **How are epoxy resins typically supplied for dental applications?** - A\) Powder form only - B\) In cartridges with activators - C\) Pre-mixed paste - D\) In liquid form only\ **Answer:** B) In cartridges with activators 66. **What factor primarily controls the rate of crystal growth in gypsum?** - A\) Temperature of water - B\) Amount of accelerators - C\) Number of nuclei - D\) Mixing speed\ **Answer:** C) Number of nuclei 67. **What characteristic of high-strength dental stone enhances its suitability for die materials?** - A\) High porosity - B\) Dimensional stability - C\) Low tensile strength - D\) Short setting time\ **Answer:** B) Dimensional stability 68. **What primary material is used for stereolithography in 3D dental printing?** - A\) Epoxy resin - B\) Polycarbonate - C\) Photosensitive polymer - D\) Polyethylene\ **Answer:** C) Photosensitive polymer 69. **Which of these is a disadvantage of resin dies compared to gypsum?** - A\) Susceptibility to shrinkage - B\) Low hardness - C\) High cost - D\) Slow setting\ **Answer:** A) Susceptibility to shrinkage 70. **Which material is commonly used as the cathode in copper electroplating for dental models?** - A\) Aluminum - B\) Copper - C\) Zinc - D\) Nickel\ **Answer:** B) Copper 71. **What does the "induction period" refer to in gypsum setting?** - A\) Period of rapid reaction - B\) Time of mixing - C\) Initial phase of low reaction activity - D\) Time required for strength gain\ **Answer:** C) Initial phase of low reaction activity 72. **What effect does excessive spatulation have on gypsum setting?** - A\) Increases porosity - B\) Shortens setting time - C\) Weakens material - D\) No effect\ **Answer:** B) Shortens setting time 73. **How long is the typical setting time for most modern high-strength dental stones?** - A\) 10 minutes - B\) 20 minutes - C\) 30 minutes - D\) 45 minutes\ **Answer:** C) 30 minutes 74. **Which of the following accelerates the gypsum setting time?** - A\) Borax - B\) Hydrocolloid - C\) Sodium sulfate - D\) Alginate\ **Answer:** C) Sodium sulfate 75. **Which material is preferred for dental models used in patient education?** - A\) 3D-printed models - B\) Electroplated dies - C\) Gypsum plaster - D\) Epoxy resin\ **Answer:** A) 3D-printed models 76. **What is the ideal outcome for dimensional stability in model materials?** - A\) High expansion - B\) No expansion or contraction - C\) Moderate contraction - D\) Slight shrinkage\ **Answer:** B) No expansion or contraction 77. **Why is dental plaster less suitable for producing accurate dies than dental stone?** - A\) High cost - B\) High expansion - C\) Low compressive strength - D\) Low color contrast\ **Answer:** C) Low compressive strength 78. **What component in gypsum products primarily causes expansion during setting?** - A\) Hemihydrate particles - B\) Water/powder ratio - C\) Needle-like crystals - D\) Borax\ **Answer:** C) Needle-like crystals 79. **Which feature is critical for model and die materials in reproducing fine details?** - A\) Large particle size - B\) High porosity - C\) Smooth surface - D\) Low mechanical strength\ **Answer:** C) Smooth surface 80. **In flexible die materials, what enhances their compatibility with undercut regions?** - A\) Increased hardness - B\) High flexibility - C\) Longer setting time - D\) Increased viscosity\ **Answer:** B) High flexibility **Questions 81 - 100:** 81. **Which of the following can act as a retarder when added in high concentrations to gypsum?** - A\) Sodium sulfate - B\) Sodium chloride - C\) Calcium oxide - D\) Borax\ **Answer:** D) Borax 82. **Which gypsum type is recommended for study casts intended for record purposes only?** - A\) Dental stone - B\) Improved stone - C\) Model plaster - D\) Epoxy resin\ **Answer:** C) Model plaster 83. **What is the common disadvantage of both epoxy and polyurethane resins?** - A\) Low abrasion resistance - B\) Water sensitivity in hydrocolloid impressions - C\) Short shelf life - D\) Limited color options\ **Answer:** B) Water sensitivity in hydrocolloid impressions 84. **What is the main purpose of applying a vibration technique in gypsum mixing?** - A\) Increase porosity - B\) Decrease setting time - C\) Remove air bubbles - D\) Improve gloss\ **Answer:** C) Remove air bubbles 85. **Why are 3D-printed dental models advantageous for surgical simulations?** - A\) Lower cost - B\) Ease of sterilization - C\) Precise anatomical replication - D\) Reduced setting time\ **Answer:** C) Precise anatomical replication 86. **What factor controlled by the operator can increase the setting expansion of gypsum?** - A\) Increasing mixing speed - B\) Decreasing water/powder ratio - C\) Decreasing humidity - D\) Reducing mixing time\ **Answer:** A) Increasing mixing speed 87. **What is the ideal ratio of powder to water for high-strength dental stone?** - A\) 100 gm powder / 22-24 ml water - B\) 100 gm powder / 50 ml water - C\) 100 gm powder / 18-22 ml water - D\) 100 gm powder / 30 ml water\ **Answer:** A) 100 gm powder / 22-24 ml water 88. **What effect does humidity have on stored gypsum powder over time?** - A\) Shortens setting time - B\) Increases solubility - C\) Causes spontaneous setting - D\) Can result in delayed setting time\ **Answer:** D) Can result in delayed setting time 89. **Which method of gypsum calcination results in a uniform, prismatic particle shape?** - A\) Dry calcination - B\) Wet calcination - C\) Chemical calcination - D\) High-temperature calcination\ **Answer:** B) Wet calcination 90. **How does temperature above 37°C affect gypsum setting?** - A\) Increases setting rate significantly - B\) Decreases solubility of dihydrate, slowing setting - C\) Speeds up crystal growth indefinitely - D\) Causes immediate hardening\ **Answer:** B) Decreases solubility of dihydrate, slowing setting 91. **What is the main purpose of adding flexible die materials to dental procedures?** - A\) Improve hardness - B\) Enable easy fabrication of restorations - C\) Reduce cost - D\) Increase durability\ **Answer:** B) Enable easy fabrication of restorations 92. **What is the function of \"terra alba\" in gypsum products?** - A\) To improve gloss - B\) To act as a nucleating agent - C\) To reduce expansion - D\) To enhance color contrast\ **Answer:** B) To act as a nucleating agent 93. **What is the common color of dental stone (Type III)?** - A\) Yellow - B\) Pink - C\) White - D\) Gray\ **Answer:** A) Yellow 94. **Which additive is commonly used as a die hardener for gypsum?** - A\) Cyanoacrylate - B\) Sodium sulfate - C\) Copper powder - D\) Zinc oxide\ **Answer:** A) Cyanoacrylate 95. **What is the result of a high water/powder ratio in a gypsum mix?** - A\) Increased hardness - B\) Increased porosity - C\) Reduced setting expansion - D\) Reduced setting time\ **Answer:** B) Increased porosity 96. **What type of gypsum product is typically used for crowns and bridges?** - A\) Type I: Impression plaster - B\) Type III: Dental stone - C\) Type IV: High-strength dental stone - D\) Type II: Model plaster\ **Answer:** C) Type IV: High-strength dental stone 97. **What chemical component is common in 3D printing resins for dental models?** - A\) Polyvinyl chloride - B\) Acrylonitrile butadiene styrene (ABS) - C\) Photosensitive polymers - D\) Polyethylene\ **Answer:** C) Photosensitive polymers 98. **Which test method is used to measure the final setting time of gypsum products?** - A\) Gilmore test - B\) Vicat test - C\) Loss of gloss method - D\) Crystalline theory method\ **Answer:** A) Gilmore test 99. **How long does it take for high-strength stone to be \"ready for use\"?** - A\) 10 minutes - B\) 20 minutes - C\) 30 minutes - D\) 1 hour\ **Answer:** C) 30 minutes 100. **What is the main disadvantage of model plaster (Type II) compared to dental stone?** - A) High cost - B) Low tensile strength - C) High water requirement - D) Poor dimensional stability\ **Answer:** B) Low tensile strength **Questions 101 - 120:** 101. **Which factor is essential to control for achieving accurate dimensional stability in gypsum models?** - A) Temperature - B) Water/powder ratio - C) Type of mixing bowl - D) Color contrast\ **Answer:** B) Water/powder ratio 102. **What does adding sodium sulfate in low concentrations do in gypsum?** - A) Extends setting time - B) Decreases setting time - C) Increases porosity - D) Prevents crystal growth\ **Answer:** B) Decreases setting time 103. **In which type of calcination does gypsum develop cubic-shaped particles?** - A) High-temperature calcination - B) Chemical calcination - C) Calcination under pressure - D) Open-air calcination\ **Answer:** C) Calcination under pressure 104. **What is the purpose of the boxing method in gypsum pouring?** - A) Increase strength - B) Improve color contrast - C) Contain gypsum for accurate cast shaping - D) Reduce expansion\ **Answer:** C) Contain gypsum for accurate cast shaping 105. **What type of mix consistency is ideal for dental stone?** - A) Watery - B) Creamy - C) Thick - D) Powdery\ **Answer:** B) Creamy 106. **In what setting do dental models exhibit "hygroscopic setting expansion"?** - A) In open air - B) Under water - C) Under pressure - D) At high temperature\ **Answer:** B) Under water 107. **Why is dental stone (Type III) preferred for creating working casts?** - A) High porosity - B) Low cost - C) High strength and accuracy - D) Quick setting time\ **Answer:** C) High strength and accuracy 108. **How does hand mixing affect the setting of gypsum?** - A) Extends setting time - B) Shortens setting time - C) Increases porosity - D) Reduces hardness\ **Answer:** B) Shortens setting time 109. **What effect does heating gypsum to 130°C in open air have?** - A) Produces porous particles - B) Produces prismatic particles - C) Creates smooth particles - D) Leads to high compressive strength\ **Answer:** A) Produces porous particles 110. **Which is a suitable accelerator for reducing gypsum setting time?** - A) Calcium sulfate - B) Terra alba - C) Zinc oxide - D) Borax\ **Answer:** B) Terra alba 111. **Why is polyurethane resin advantageous for making dies?** - A) Inexpensive - B) Low abrasion resistance - C) High edge strength and abrasion resistance - D) Poor dimensional accuracy\ **Answer:** C) High edge strength and abrasion resistance 112. **What is the effect of adding potassium sulfate to gypsum products?** - A) Increases setting time - B) Increases porosity - C) Reduces setting time - D) Reduces hardness\ **Answer:** C) Reduces setting time 113. **Which type of die material is often used for making temporary crowns?** - A) Flexible die materials - B) Electroplated dies - C) Gypsum plaster - D) Copper plating\ **Answer:** A) Flexible die materials 114. **What is a key disadvantage of using epoxy resins?** - A) Long setting time - B) Poor detail reproduction - C) High viscosity - D) Incompatibility with rubber impression materials\ **Answer:** C) High viscosity 115. **Which of the following is the preferred material for casting metal frameworks?** - A) Model plaster - B) High-strength dental stone - C) Flexible die materials - D) Dental wax\ **Answer:** B) High-strength dental stone 116. **What is the primary composition of natural gypsum?** - A) Calcium sulfate dihydrate - B) Sodium chloride - C) Magnesium oxide - D) Potassium sulfate\ **Answer:** A) Calcium sulfate dihydrate 117. **What kind of expansion occurs in gypsum products as they set?** - A) Hygroscopic expansion only - B) Linear expansion - C) Volume contraction - D) No expansion\ **Answer:** B) Linear expansion 118. **Why should gypsum powder be stored in a sealed container?** - A) Prevents color change - B) Avoids exposure to humidity - C) Maintains high gloss - D) Enhances hardness\ **Answer:** B) Avoids exposure to humidity 119. **In the Gilmore test, what is the criterion for final set time?** - A) Loss of gloss - B) Needle penetration resistance - C) Visual hardness - D) Increase in weight\ **Answer:** B) Needle penetration resistance 120. **Which material is commonly added to improve the abrasion resistance of type IV gypsum?** - A) Aluminum powder - B) Silica sol - C) Wax - D) Sodium chloride\ **Answer:** B) Silica sol **Questions 121 - 140:** 121. **Which setting time describes the period during which gypsum can be manipulated and poured?** - A) Working time - B) Mixing time - C) Final setting time - D) Hardening time\ **Answer:** A) Working time 122. **What is the primary purpose of dental stone (Type IV) in dental applications?** - A) Study casts - B) Model trimming - C) Precise dies for crowns and bridges - D) Training models\ **Answer:** C) Precise dies for crowns and bridges 123. **Why is it important to add water before powder when mixing gypsum by hand?** - A) Increases gloss - B) Prevents air bubbles - C) Speeds up setting - D) Enhances hardness\ **Answer:** B) Prevents air bubbles 124. **Which resin material for dies has a high filler content to reduce shrinkage?** - A) Epoxy resin - B) Polyurethane - C) Gypsum - D) Dental wax\ **Answer:** B) Polyurethane 125. **Which method involves measuring the loss of gloss to determine the setting time of gypsum?** - A) Gilmore test - B) Gloss test - C) Visual hardness test - D) Loss of gloss method\ **Answer:** D) Loss of gloss method 126. **What type of expansion occurs when gypsum is allowed to set under water?** - A) Hygroscopic expansion - B) Chemical expansion - C) Thermal expansion - D) Atmospheric expansion\ **Answer:** A) Hygroscopic expansion 127. **Which material is used to coat the impression in electroplating with copper?** - A) Silver powder - B) Graphite particles - C) Calcium sulfate - D) Sodium chloride\ **Answer:** B) Graphite particles 128. **How long does the initial setting time generally last for gypsum products?** - A) 1-2 minutes - B) 3-5 minutes - C) 8-10 minutes - D) 15-20 minutes\ **Answer:** C) 8-10 minutes 129. **What is the key advantage of using high-strength, high-expansion dental stone?** - A) Inexpensive - B) Increased accuracy - C) Suitable for detailed restorations - D) Reduced hardness\ **Answer:** C) Suitable for detailed restorations 130. **In what state is gypsum product strength the lowest?** - A) Dry - B) Wet - C) Powdered - D) Hardened\ **Answer:** B) Wet 131. **What is the result of using a low water/powder ratio in gypsum mixing?** - A) Increased setting time - B) Decreased hardness - C) Increased strength and density - D) Increased porosity\ **Answer:** C) Increased strength and density 132. **How is dimensional stability achieved in electroplated dies?** - A) Using flexible materials - B) Adding accelerators - C) No expansion or contraction occurs - D) Adding water/powder ratio\ **Answer:** C) No expansion or contraction occurs 133. **What is the main disadvantage of copper electroplating for dental dies?** - A) Requires prolonged immersion - B) Limited use with polysulfide impressions - C) Expensive to perform - D) Limited abrasion resistance\ **Answer:** B) Limited use with polysulfide impressions 134. **In gypsum manipulation, what is the primary purpose of proportioning?** - A) Reducing setting time - B) Ensuring correct water/powder ratio - C) Increasing color contrast - D) Reducing cost\ **Answer:** B) Ensuring correct water/powder ratio 135. **Which factor directly influences the hardness of gypsum materials?** - A) Type of impression material - B) Compressive strength - C) Rate of mixing - D) Thickness of casting\ **Answer:** B) Compressive strength 136. **What feature makes Type IV gypsum susceptible to abrasion?** - A) High porosity - B) Low hardness - C) Dense structure - D) Chemical additives\ **Answer:** C) Dense structure 137. **In what situation is model plaster (Type II) typically used?** - A) Precision dies - B) Study casts - C) Flexible dies - D) Impression molds\ **Answer:** B) Study casts 138. **Which component ensures better wettability of gypsum on rubber impressions?** - A) Water - B) Calcium sulfate - C) Vibration during pouring - D) Sodium sulfate\ **Answer:** C) Vibration during pouring 139. **What is the effect of using lower temperatures in gypsum setting?** - A) Faster setting - B) Decreased hardness - C) Prolonged setting time - D) Increased porosity\ **Answer:** C) Prolonged setting time 140. **How does adding sodium chloride in small amounts to gypsum affect setting expansion?** - A) Reduces setting expansion - B) Increases setting expansion - C) Increases gloss - D) Prevents bubble formation\ **Answer:** B) Increases setting expansion **Questions 141 - 160:** 141. **Which gypsum product type has the highest setting expansion?** - A) Type I - B) Type III - C) Type IV - D) Type V\ **Answer:** D) Type V 142. **What primary advantage does 3D printing offer for dental models?** - A) Reduced setup time - B) Increased porosity - C) Enhanced detail accuracy - D) Lower cost\ **Answer:** C) Enhanced detail accuracy 143. **What role does "terra alba" play in gypsum products?** - A) Acts as a retarder - B) Provides nuclei for crystal growth - C) Increases gloss - D) Decreases porosity\ **Answer:** B) Provides nuclei for crystal growth 144. **What is the primary disadvantage of resin-based die materials?** - A) Limited hardness - B) Dimensional shrinkage - C) High gloss - D) Limited strength\ **Answer:** B) Dimensional shrinkage 145. **What is a key feature of calcium sulfate in Type II plaster?** - A) Enhanced strength - B) Lower cost - C) High setting expansion - D) Abrasion resistance\ **Answer:** B) Lower cost 146. **Why are electroplated dies preferred in precision dental applications?** - A) High strength and abrasion resistance - B) Inexpensive - C) Easily manipulated - D) High water absorption\ **Answer:** A) High strength and abrasion resistance 147. **What is a disadvantage of using hydrocolloid with epoxy resin?** - A) Increased porosity - B) Retards polymerization - C) Causes shrinkage - D) Reduces gloss\ **Answer:** B) Retards polymerization 148. **What is the purpose of adding fillers to polyurethane resin?** - A) Reduce cost - B) Reduce polymerization shrinkage - C) Increase setting time - D) Improve gloss\ **Answer:** B) Reduce polymerization shrinkage 149. **What is the usual mixing time for hand-mixed gypsum?** - A) 10 seconds - B) 30 seconds - C) 1 minute - D) 5 minutes\ **Answer:** C) 1 minute 150. **What percentage of silica sols in water is often used for hardening gypsum models?** - A) 10% - B) 20% - C) 30% - D) 50%\ **Answer:** C) 30% 151. **Which test is most often used to measure the initial setting time of gypsum?** - A) Compression test - B) Flexural test - C) Vicat test - D) Gilmore test\ **Answer:** C) Vicat test 152. **Why is boxing used in gypsum casting?** - A) Reduce porosity - B) Improve dimensional stability - C) Contain gypsum within a specific area - D) Enhance gloss\ **Answer:** C) Contain gypsum within a specific area 153. **Which type of gypsum shows the least setting expansion?** - A) Plaster - B) Stone - C) High-strength stone (Type IV) - D) High-expansion stone\ **Answer:** C) High-strength stone (Type IV) 154. **What is the recommended time for immersing models in sodium hypochlorite for disinfection?** - A) 10 minutes - B) 15 minutes - C) 20 minutes - D) 30 minutes\ **Answer:** D) 30 minutes 155. **Which material is commonly used to improve the strength of high-strength dental stone?** - A) Silica sol - B) Wax - C) Calcium chloride - D) Borax\ **Answer:** A) Silica sol 156. **What type of material is polyether commonly used in?** - A) Impression materials - B) Wax patterns - C) Electroplated dies - D) Ceramic coatings\ **Answer:** A) Impression materials 157. **Which factor does NOT significantly affect the strength of gypsum?** - A) Water/powder ratio - B) Mixing speed - C) Amount of air bubbles - D) Temperature of the room\ **Answer:** D) Temperature of the room 158. **What component can increase the setting time if added in high concentrations to gypsum?** - A) Sodium chloride - B) Sodium sulfate - C) Borax - D) Calcium sulfate\ **Answer:** C) Borax 159. **How does hand mixing compare to mechanical mixing in terms of setting time for gypsum?** - A) Hand mixing decreases setting time - B) Hand mixing has no effect on setting time - C) Hand mixing increases setting time - D) Mechanical mixing reduces gloss\ **Answer:** A) Hand mixing decreases setting time 160. **Which material is typically used to improve abrasion resistance in electroplated dies?** - A) Copper - B) Silver - C) Nickel - D) Iron\ **Answer:** B) Silver **Questions 161 - 180:** 161. **Why should gypsum powder be kept in a tightly sealed container?** - A) To maintain the color - B) To avoid humidity exposure - C) To increase hardness - D) To prevent crystallization\ **Answer:** B) To avoid humidity exposure 162. **What does the initial setting time of gypsum represent?** - A) Time to reach maximum hardness - B) Duration to a semi-hard stage - C) Time before water is added - D) Time until full expansion\ **Answer:** B) Duration to a semi-hard stage 163. **What property does high-strength, high-expansion dental stone (Type V) possess?** - A) High porosity - B) Dimensional instability - C) Minimal setting expansion - D) High expansion for detailed work\ **Answer:** D) High expansion for detailed work 164. **What is the function of a die hardener in gypsum dies?** - A) Increase porosity - B) Improve abrasion resistance - C) Shorten setting time - D) Decrease compressive strength\ **Answer:** B) Improve abrasion resistance 165. **What is the effect of adding excess water to gypsum during mixing?** - A) Increases strength - B) Decreases porosity - C) Reduces overall hardness - D) Decreases setting expansion\ **Answer:** C) Reduces overall hardness 166. **What is a disadvantage of using plaster of Paris for dental casts?** - A) High strength - B) Low abrasion resistance - C) High dimensional stability - D) Fast setting time\ **Answer:** B) Low abrasion resistance 167. **What additive can increase the rate of setting in gypsum products?** - A) Sodium chloride (small amounts) - B) High concentration borax - C) Water/powder ratio increase - D) Adding cold water\ **Answer:** A) Sodium chloride (small amounts) 168. **What is the preferred water/powder ratio for dental stone (Type III)?** - A) 100 gm powder / 50 ml water - B) 100 gm powder / 30 ml water - C) 100 gm powder / 22 ml water - D) 100 gm powder / 10 ml water\ **Answer:** B) 100 gm powder / 30 ml water 169. **What characteristic of epoxy resin is beneficial in die material applications?** - A) High flexibility - B) High abrasion resistance - C) No shrinkage - D) Requires hydrocolloid impressions\ **Answer:** B) High abrasion resistance 170. **Why are high-strength stones (Type IV) preferred for precision die work?** - A) High gloss finish - B) Low cost - C) Dimensional stability - D) Quick setting\ **Answer:** C) Dimensional stability 171. **What effect does excessive hand mixing have on gypsum?** - A) Reduces gloss - B) Shortens setting time - C) Lowers strength - D) Increases gloss\ **Answer:** B) Shortens setting time 172. **Which type of gypsum is primarily used for study casts?** - A) Type I - B) Type II - C) Type IV - D) Type V\ **Answer:** B) Type II 173. **What is a significant property of silico-phosphate dies?** - A) Flexibility - B) High abrasion resistance - C) Quick setting time - D) High expansion rate\ **Answer:** B) High abrasion resistance 174. **What happens if gypsum is mixed with warm water?** - A) Extends setting time - B) Slows down setting - C) Speeds up setting - D) Reduces strength\ **Answer:** C) Speeds up setting 175. **Why is silver often used in electroplated dies?** - A) Improves cost-effectiveness - B) Provides dimensional stability - C) Increases porosity - D) Softens the die material\ **Answer:** B) Provides dimensional stability 176. **Which of the following properties is critical for impression materials to be compatible with die materials?** - A) Flexibility - B) Gloss - C) Accurate reproduction of detail - D) High temperature resistance\ **Answer:** C) Accurate reproduction of detail 177. **Which setting time describes the point when gypsum can safely be handled without fracture?** - A) Initial setting time - B) Working time - C) Mixing time - D) Final setting time\ **Answer:** D) Final setting time 178. **What effect does adding a small amount of calcium oxide to gypsum have?** - A) Increases setting time - B) Reduces required water - C) Increases gloss - D) Enhances porosity\ **Answer:** B) Reduces required water 179. **Which type of gypsum is often referred to as "improved stone"?** - A) Type I - B) Type II - C) Type III - D) Type IV\ **Answer:** D) Type IV 180. **What temperature condition prevents gypsum from setting at all?** - A) Below freezing - B) 20°C - C) 100°C - D) 37°C\ **Answer:** C) 100°C **Questions 181 - 200:** 181. **What is the primary use of flexible die materials?** - A) Long-term models - B) Interim restorations and composite inlays - C) Permanent dentures - D) Surgical planning models\ **Answer:** B) Interim restorations and composite inlays 182. **Which material requires extra care when using silver electroplating due to toxicity?** - A) Sodium chloride - B) Copper sulfate - C) Silver cyanide - D) Polyurethane\ **Answer:** C) Silver cyanide 183. **Which type of calcination results in the densest and hardest gypsum particles?** - A) Wet calcination - B) Calcination under pressure - C) Dry calcination - D) Open-air calcination\ **Answer:** B) Calcination under pressure 184. **What color contrast is desirable in die materials when compared to inlay wax?** - A) High contrast - B) Low contrast - C) Medium contrast - D) No contrast\ **Answer:** A) High contrast 185. **What property is most desirable for the surface of a model used in dental castings?** - A) High gloss - B) Smoothness - C) Low strength - D) Porosity\ **Answer:** B) Smoothness 186. **How can the setting expansion of gypsum be reduced?** - A) Decrease water/powder ratio - B) Increase mixing time - C) Add more water - D) Add calcium chloride\ **Answer:** D) Add calcium chloride 187. **What is the main disadvantage of 3D-printed dental models?** - A) Dimensional instability - B) Limited material choices - C) Long setup time - D) Low accuracy\ **Answer:** B) Limited material choices 188. **Why are resin dies generally preferred over gypsum for some applications?** - A) Faster setting time - B) Better abrasion resistance - C) Lower cost - D) Reduced shrinkage\ **Answer:** B) Better abrasion resistance 189. **In gypsum, what does "wet strength" refer to?** - A) Strength with excess water present - B) Strength after setting completely - C) Compressive strength after drying - D) Hardness immediately after mixing\ **Answer:** A) Strength with excess water present 190. **Which gypsum type is known for high strength and low expansion?** - A) Type I - B) Type II - C) Type IV - D) Type V\ **Answer:** C) Type IV 191. **What disadvantage is associated with high-strength dental stones?** - A) Susceptibility to abrasion - B) High porosity - C) Low dimensional stability - D) High cost\ **Answer:** A) Susceptibility to abrasion 192. **Which factor helps accelerate the setting time of gypsum?** - A) Lowering the room temperature - B) Vigorous hand mixing - C) Increased water/powder ratio - D) Reduced mixing time\ **Answer:** B) Vigorous hand mixing 193. **What additive serves as a practical retarder in gypsum products?** - A) Sodium chloride - B) Potassium sulfate - C) Borax - D) Calcium chloride\ **Answer:** C)