Hydrocholliod MCQ PDF

What are colloids classified as in terms of matter? - A. A gas - B. A liquid - C. A fourth state of matter - D. A solid\ **Answer**: C. A fourth state of matter Which of the following best describes a \"true solution\"? - A. Heterogeneous mixture with two distinct phases - B....

What are colloids classified as in terms of matter? - A. A gas - B. A liquid - C. A fourth state of matter - D. A solid\ **Answer**: C. A fourth state of matter Which of the following best describes a \"true solution\"? - A. Heterogeneous mixture with two distinct phases - B. Homogeneous mixture with dissolved molecules or ions - C. Liquid with dispersed solid particles - D. Liquid dispersed in another liquid\ **Answer**: B. Homogeneous mixture with dissolved molecules or ions What is the main use of hydrocolloids in dentistry? - A. Creating permanent restorations - B. Making dental impressions - C. Coating dental tools - D. Cleaning teeth\ **Answer**: B. Making dental impressions 4. What is the key factor in the sol-gel transformation of hydrocolloids? - A. Physical reaction only - B. Chemical reaction only - C. Agglomeration of dispersed molecules forming a network - D. Temperature increase\ **Answer**: C. Agglomeration of dispersed molecules forming a network 5. Which type of hydrocolloid is alginate classified as? - A. Reversible - B. Irreversible - C. Permanent - D. Temporary\ **Answer**: B. Irreversible 6. Alginate impression material is primarily used for: - A. Permanent crown restorations - B. Study casts and denture impressions - C. Veneer impressions - D. Orthodontic braces\ **Answer**: B. Study casts and denture impressions 7. What is the preferred form of alginate packaging for hygiene purposes? - A. Bulk container - B. Small sealed packets - C. Open jars - D. Plastic bags\ **Answer**: B. Small sealed packets 8. Which of the following acts as the reactor in alginate composition? - A. Na/K alginate - B. CaSO4. 2H2O - C. Na3 PO4 - D. K. Ti fluoride\ **Answer**: B. CaSO4. 2H2O 9. The role of Na3 PO4 in alginate is to: - A. Act as a flavoring agent - B. Accelerate the setting time - C. Act as a retarder - D. Increase strength\ **Answer**: C. Act as a retarder 10. Fast-set alginate typically sets within: - A. 1-2 minutes - B. 2-3 minutes - C. 4-5 minutes - D. 5-6 minutes\ **Answer**: A. 1-2 minutes 11. The filler in alginate is used to: - A. Increase the gel\'s elasticity - B. Increase the gel's strength - C. Slow down the setting reaction - D. Change the gel\'s color\ **Answer**: B. Increase the gel's strength 12. Which substance in alginate serves as a gypsum hardener? - A. Na/K alginate - B. CaSO4. 2H2O - C. Na3 PO4 - D. K. Ti fluoride\ **Answer**: D. K. Ti fluoride 13. During mixing, alginate powder should be combined with: - A. Warm water first - B. Powder first, then water - C. Water first, then powder - D. Mixed without water\ **Answer**: C. Water first, then powder 14. Mechanical mixers for alginate impressions include all EXCEPT: - A. Vacuum mixer - B. Dynamic mechanical mixer - C. Manual spatula mixing - D. Rotating mixing bowl\ **Answer**: C. Manual spatula mixing 15. What is recommended if a perforated tray is not available for alginate impressions? - A. Add more water - B. Use adhesive lining on the tray - C. Use a larger tray - D. Reduce the alginate amount\ **Answer**: B. Use adhesive lining on the tray 16. To prevent dimensional changes in alginate impressions, disinfection should be: - A. Immediate - B. Delayed for an hour - C. Done after storage in a bag - D. Avoided completely\ **Answer**: A. Immediate 17. Which of the following is NOT a method to control alginate setting time? - A. Powder/water ratio - B. Type of water used - C. Tray size - D. Mixing rate\ **Answer**: C. Tray size 18. Increasing water temperature during alginate preparation will: - A. Decrease setting time - B. Increase setting time - C. Have no effect - D. Decrease gel strength\ **Answer**: A. Decrease setting time 19. Alginate\'s poor dimensional stability is due to: - A. Elastic recovery - B. Syneresis and imbibition - C. Incorrect mixing ratio - D. Use of tap water\ **Answer**: B. Syneresis and imbibition 20. How can you delay pouring an alginate impression without dimensional changes? - A. Store in hot water - B. Store in dry air - C. Wrap in a wet towel in a sealed bag - D. Keep it in the freezer\ **Answer**: C. Wrap in a wet towel in a sealed bag 21. What is the typical elastic recovery percentage of alginate? - A. 90% - B. 92% - C. 95% - D. 97.3%\ **Answer**: D. 97.3% 22. Alginate impressions should ideally have a thickness of at least: - A. 1-2 mm - B. 2-3 mm - C. 3-4 mm - D. 4-6 mm\ **Answer**: D. 4-6 mm 23. Dust-free alginate is created by coating particles with: - A. Calcium - B. Glycol or glycerine - C. Sodium fluoride - D. Potassium sulfate\ **Answer**: B. Glycol or glycerine 24. Which form of alginate contains a color indicator for different stages of mixing? - A. Dust-free alginate - B. Chromatic alginate - C. Siliconized alginate - D. None of the above\ **Answer**: B. Chromatic alginate 25. Inhalation of alginate powder can potentially cause: - A. Eye irritation - B. Silicosis and pulmonary diseases - C. Tooth decay - D. None of the above\ **Answer**: B. Silicosis and pulmonary diseases 26. The reaction that causes alginate to set is: - A. Reversible - B. Physical - C. Chemical and irreversible - D. Instantaneous\ **Answer**: C. Chemical and irreversible 27. What is a disadvantage of using alginate impression material? - A. High tear strength - B. Dimension instability - C. Low flexibility - D. Hydrophobic nature\ **Answer**: B. Dimension instability 28. Which alginate additive helps control setting time by delaying gel formation? - A. CaSO4 - B. Na3PO4 - C. K. Ti fluoride - D. Diatomaceous earth\ **Answer**: B. Na3PO4 29. What factor can decrease the setting time of alginate? - A. Lower temperature water - B. Rapid mixing - C. Adding more powder - D. Increasing the amount of Na3PO4\ **Answer**: B. Rapid mixing 30. Which component in alginate is responsible for increasing the gel\'s strength? - A. CaSO4 - B. Fillers such as diatomaceous earth - C. Na3PO4 - D. Na/K alginate\ **Answer**: B. Fillers such as diatomaceous earth 31. Alginate impressions must be removed from the mouth: - A. Immediately after insertion - B. With a slow pull - C. Using a snap removal - D. By twisting\ **Answer**: C. Using a snap removal 32. The ideal storage condition for alginate powder is: - A. Warm and humid - B. Cold and dry - C. Open to air - D. Under sunlight\ **Answer**: B. Cold and dry 33. How does the pH change in chromatic alginate indicate readiness for use? - A. Color changes from pink to white - B. Color changes from blue to green - C. No color change - D. Color changes from yellow to red\ **Answer**: A. Color changes from pink to white 34. When using tap water instead of distilled water for alginate, setting time may: - A. Increase - B. Decrease - C. Remain unaffected - D. Double\ **Answer**: B. Decrease 35. Which term describes water loss in an alginate impression, leading to shrinkage? - A. Imbibition - B. Sol-gel transformation - C. Syneresis - D. Gelation\ **Answer**: C. Syneresis 36. Alginate impressions left in water will swell due to: - A. Gelation - B. Imbibition - C. Precipitation - D. Absorption\ **Answer**: B. Imbibition 37. Flexibility in alginate impression material is important for: - A. Easy removal from undercuts - B. Increased tear strength - C. Faster setting time - D. Lower cost\ **Answer**: A. Easy removal from undercuts 38. To avoid dimension instability, an alginate impression should be poured: - A. Within 10 minutes - B. After one hour - C. The next day - D. After 24 hours\ **Answer**: A. Within 10 minutes 39. The term \"viscoelastic\" in relation to alginate describes its: - A. Flexibility - B. High tear strength - C. Elastic recovery properties - D. Dimensional stability\ **Answer**: C. Elastic recovery properties 40. Which component prevents dust release in \"dust-free\" alginate? - A. Glycerine - B. Water - C. Sodium alginate - D. Calcium sulfate\ **Answer**: A. Glycerine 41. Poor tear strength in alginate impressions can be improved by: - A. Immediate pouring - B. Snap removal technique - C. Slow removal - D. Adding more water\ **Answer**: B. Snap removal technique 42. The effect of higher powder-to-water ratio in alginate preparation is: - A. Lower reaction rate - B. Faster setting time - C. Increased flexibility - D. Increased gel strength\ **Answer**: B. Faster setting time 43. If the alginate mix is overmixed, it may result in: - A. Stronger gel - B. Weaker gel strength - C. Faster setting - D. Better elasticity\ **Answer**: B. Weaker gel strength 44. The primary use of siliconized alginate is to: - A. Increase viscosity - B. Add color - C. Enhance tear strength - D. Reduce setting time\ **Answer**: C. Enhance tear strength 45. Which of the following is NOT a property of alginate impression material? - A. Hydrophilic nature - B. High tear strength - C. Easy manipulation - D. Poor dimensional stability\ **Answer**: B. High tear strength 46. What can result if there is an improper powder/water ratio in alginate mixing? - A. Perfect gel strength - B. Increased elasticity - C. Poor gel strength - D. Increased dimensional accuracy\ **Answer**: C. Poor gel strength 47. Flexibility in alginate material allows for: - A. Easier storage - B. Better tear strength - C. Easier removal from undercuts - D. Greater color variety\ **Answer**: C. Easier removal from undercuts 48. High concentration of sodium sulfate in alginate affects gypsum by: - A. Accelerating setting - B. Retarding setting - C. Improving elasticity - D. Increasing dimensional stability\ **Answer**: B. Retarding setting 49. Alginate with added disinfectant is beneficial because: - A. It eliminates the need for disinfection - B. It strengthens the gel - C. It changes color during setting - D. It improves flexibility\ **Answer**: A. It eliminates the need for disinfection 50. Modified alginate with a chemical indicator helps: - A. Improve elasticity - B. Control setting time - C. Reduce dimensional changes - D. Indicate stages in manipulation\ **Answer**: D. Indicate stages in manipulation 51. Which of the following factors increases the setting time of alginate? - A. High water temperature - B. Higher powder-to-water ratio - C. Rapid mixing - D. Increased amount of Na3PO4\ **Answer**: D. Increased amount of Na3PO4 52. The primary role of fillers in alginate is to: - A. Decrease tear strength - B. Add color - C. Improve gel strength - D. Increase water retention\ **Answer**: C. Improve gel strength 53. What is a major disadvantage of using alginate for dental impressions? - A. High dimensional stability - B. Excellent detail reproduction - C. Poor tear strength - D. Low flexibility\ **Answer**: C. Poor tear strength 54. What does snap removal help to prevent in alginate impressions? - A. Dimensional instability - B. Tear and permanent deformation - C. Color fading - D. Setting time reduction\ **Answer**: B. Tear and permanent deformation 55. Alginate is preferred for initial impressions because it is: - A. Hydrophobic - B. Expensive - C. Easy to manipulate - D. Highly tear-resistant\ **Answer**: C. Easy to manipulate 56. The best way to disinfect an alginate impression is to: - A. Use cold water - B. Heat sterilize it - C. Spray with disinfectant and wrap in a wet paper towel - D. Use no disinfection\ **Answer**: C. Spray with disinfectant and wrap in a wet paper towel 57. To minimize water evaporation from an alginate impression, it should be: - A. Exposed to air - B. Dried with a towel - C. Stored in 100% relative humidity - D. Placed in direct sunlight\ **Answer**: C. Stored in 100% relative humidity 58. Which chemical reaction initiates the setting of alginate? - A. Alginate + Na3PO4 - B. Na/K alginate + CaSO4 - C. Na3PO4 + water - D. CaSO4 + K. Ti fluoride\ **Answer**: B. Na/K alginate + CaSO4 59. Increasing the mixing speed for alginate will: - A. Increase setting time - B. Decrease setting time - C. Increase tear strength - D. Reduce gel strength\ **Answer**: B. Decrease setting time 60. Which of the following describes the sol-gel transformation? - A. The setting of alginate through cooling - B. A transformation from liquid sol to gel - C. The addition of gypsum to alginate - D. Heating of the alginate mixture\ **Answer**: B. A transformation from liquid sol to gel 61. Which additive is included in alginate to improve gypsum compatibility? - A. Glycerine - B. Na3PO4 - C. Diatomaceous earth - D. K. Ti fluoride\ **Answer**: D. K. Ti fluoride 62. Why is rapid mixing beneficial for alginate impressions? - A. It prevents air bubbles - B. It increases flexibility - C. It lengthens the setting time - D. It improves tear strength\ **Answer**: A. It prevents air bubbles 63. Alginate impressions should be removed after a minimum of: - A. 1 minute - B. 2 minutes - C. 3 minutes - D. 5 minutes\ **Answer**: C. 3 minutes 64. Which factor does NOT affect the gel strength of alginate? - A. Correct powder/liquid ratio - B. Sufficient spatulation - C. Use of high P/L ratio - D. Overmixing\ **Answer**: C. Use of high P/L ratio 65. The dimensional changes in alginate can be caused by: - A. High viscosity - B. Syneresis and imbibition - C. Chemical reaction only - D. Low flexibility\ **Answer**: B. Syneresis and imbibition 66. To prevent syneresis, an alginate impression should be: - A. Exposed to sunlight - B. Placed in the refrigerator - C. Stored in 100% relative humidity - D. Left in dry air\ **Answer**: C. Stored in 100% relative humidity 67. The primary setting reaction of alginate involves which ions reacting with soluble alginate? - A. Calcium ions - B. Sodium ions - C. Potassium ions - D. Magnesium ions\ **Answer**: A. Calcium ions 68. Alginate impressions that are not poured immediately may experience: - A. Improved detail accuracy - B. Reduced setting time - C. Dimensional distortion - D. Increased flexibility\ **Answer**: C. Dimensional distortion 69. Adding gypsum accelerator to alginate before pouring helps to: - A. Increase tear strength - B. Improve gypsum surface quality - C. Slow down setting - D. Reduce elasticity\ **Answer**: B. Improve gypsum surface quality 70. Modified alginate that contains quaternary ammonium salts provides: - A. Improved tear strength - B. Disinfectant properties - C. Reduced setting time - D. Better dimensional stability\ **Answer**: B. Disinfectant properties 71. What is a common issue with alginate impressions if there is movement of the tray during gelation? - A. Increased tear strength - B. Dimension distortion - C. Faster setting - D. Greater flexibility\ **Answer**: B. Dimension distortion 72. Which alginate type is suitable for patients with gagging reflexes? - A. Regular set alginate - B. Fast set alginate - C. Chromatic alginate - D. Siliconized alginate\ **Answer**: B. Fast set alginate 73. Alginate impressions are usually disinfected by: - A. Rinsing with water only - B. Spraying with disinfectant - C. Exposing to UV light - D. Immersing in hot water\ **Answer**: B. Spraying with disinfectant 74. The primary setting reaction of alginate is best described as: - A. Reversible gelation - B. Irreversible chemical reaction - C. Physical hardening - D. Ion exchange\ **Answer**: B. Irreversible chemical reaction 75. What is the function of sodium sulfate in alginate at low concentration? - A. Acts as a hardener - B. Retards gypsum setting - C. Accelerates gypsum setting - D. Improves elasticity\ **Answer**: C. Accelerates gypsum setting 76. How should alginate impressions be handled to reduce deformation? - A. Pull slowly and gently - B. Use a twisting motion - C. Remove with a snap technique - D. Leave in the mouth longer\ **Answer**: C. Remove with a snap technique 77. Which of the following improves alginate\'s tear strength? - A. Dust-free formulation - B. Snap removal - C. Chromatic indicator - D. Increased water temperature\ **Answer**: B. Snap removal 78. Alginate\'s hydrophilic property means it: - A. Repels water - B. Absorbs water easily - C. Requires drying before use - D. Is waterproof\ **Answer**: B. Absorbs water easily 79. The main reason for using chromatic alginate is to: - A. Improve flexibility - B. Show setting stages - C. Reduce dust formation - D. Increase tear strength\ **Answer**: B. Show setting stages 80. How does too much water in the alginate mix affect the gel? - A. Increases elasticity - B. Weakens the gel - C. Increases tear strength - D. Reduces setting time\ **Answer**: B. Weakens the gel 81. A properly mixed alginate impression material should: - A. Drip off the spatula - B. Be lumpy - C. Form a smooth, creamy mixture - D. Be thick and dry\ **Answer**: C. Form a smooth, creamy mixture 82. When is alginate\'s shelf life affected? - A. At high moisture and temperature - B. At low moisture and high temperature - C. When stored in dry conditions - D. When used immediately\ **Answer**: A. At high moisture and temperature 83. Which type of alginate is safest for minimizing airborne particles? - A. Regular set alginate - B. Chromatic alginate - C. Dust-free alginate - D. Fast set alginate\ **Answer**: C. Dust-free alginate 84. Why should alginate impressions not be removed prematurely? - A. Prevent dimensional stability - B. Improve gel strength - C. Avoid tearing - D. Ensure smoothness\ **Answer**: C. Avoid tearing 85. Which factor can reduce the setting time when mixing alginate? - A. Adding more powder - B. Using cold water - C. Increasing mixing speed - D. Adding Na3PO4\ **Answer**: C. Increasing mixing speed 86. When an alginate impression is stored in low humidity, it will: - A. Expand due to water absorption - B. Shrink due to water loss - C. Remain dimensionally stable - D. Harden further\ **Answer**: B. Shrink due to water loss 87. If an alginate impression appears grainy, it is likely due to: - A. Overmixing - B. Prolonged gelation - C. Insufficient mixing or improper water/powder ratio - D. High temperature mixing\ **Answer**: C. Insufficient mixing or improper water/powder ratio 88. A rough or chalky stone model can result from: - A. High mixing speed - B. Inadequate impression cleaning - C. Low powder ratio - D. Low setting temperature\ **Answer**: B. Inadequate impression cleaning 89. What happens if an impression is stored in open air for a prolonged time? - A. It absorbs more moisture - B. It retains all details perfectly - C. It undergoes shrinkage - D. It hardens permanently\ **Answer**: C. It undergoes shrinkage 90. An alginate impression is considered irreversible because: - A. It can be melted and reused - B. The setting reaction is chemical and cannot be reversed - C. It can revert to sol state with heat - D. It loses elasticity permanently\ **Answer**: B. The setting reaction is chemical and cannot be reversed 91. A major disadvantage of alginate impressions for fixed restorations is: - A. Poor dimensional stability - B. High cost - C. Poor hydrophilicity - D. Flexibility\ **Answer**: A. Poor dimensional stability 92. Alginate is considered dimensionally unstable primarily due to: - A. Its setting speed - B. Syneresis and imbibition effects - C. High viscosity - D. Low flexibility\ **Answer**: B. Syneresis and imbibition effects 93. A delay in pouring the impression leads to dimensional changes. To avoid this, alginate impressions should be: - A. Dried before storage - B. Sealed in airtight containers - C. Wrapped in a wet towel - D. Kept in a freezer\ **Answer**: C. Wrapped in a wet towel 94. For increased setting time, one should use: - A. Cold water - B. Higher powder-to-water ratio - C. Fast mixing - D. Less retarder\ **Answer**: A. Cold water 95. Alginate impressions are not suitable for electroplating because they: - A. Are hydrophobic - B. Have poor elasticity - C. Are dimensionally unstable - D. Are difficult to handle\ **Answer**: C. Are dimensionally unstable 96. The primary component in alginate responsible for the gel formation is: - A. Na3PO4 - B. Na/K alginate - C. K. Ti fluoride - D. Diatomaceous earth\ **Answer**: B. Na/K alginate 97. Alginate is classified as a hydrocolloid because: - A. It is water-based - B. It has hydrophobic properties - C. It contains organic solvents - D. It is thermoplastic\ **Answer**: A. It is water-based 98. Which factor can lead to a failed alginate impression with air bubbles? - A. Mixing at a slow speed - B. Allowing too much time before insertion - C. Proper storage in humidity - D. Rapid spatulation incorporating air\ **Answer**: D. Rapid spatulation incorporating air 99. The brush heap structure formed during gelation is due to: - A. Sol-gel transformation - B. Rapid water evaporation - C. Low ion exchange - D. Reduced temperature\ **Answer**: A. Sol-gel transformation 100. An ideal alginate impression material for children with gag reflex would be: - A. Chromatic alginate - B. Fast set alginate - C. Dust-free alginate - D. Regular set alginate\ **Answer**: B. Fast set alginate