Mechanical Properties of Dental Materials PDF

 Mechanical properties of dental materials Dr Omar Bio materials 1. What is the SI unit of force?  a) Joule  b) Pascal  c) Newton  d) Watt  Answer: c) N...

 Mechanical properties of dental materials Dr Omar Bio materials 1. What is the SI unit of force?  a) Joule  b) Pascal  c) Newton  d) Watt  Answer: c) Newton 2. What is the typical range of occlusal forces in Newtons?  a) 100-500 N  b) 200-3500 N  c) 4000-5000 N  d) 5000-6000 N  Answer: b) 200-3500 N 3. Occlusal forces are highest in which region of the teeth?  a) Incisors  b) Canines  c) Molars  d) Premolars  Answer: c) Molars 4. What does stress refer to in mechanical terms?  a) Deformation caused by force  b) Internal resistance to an external force  c) The unit of force applied  d) Force per unit area  Answer: b) Internal resistance to an external force 5. How is stress calculated?  a) Force divided by distance  b) Force divided by area  c) Area divided by force  d) Force multiplied by area  Answer: b) Force divided by area 1|Page Dr Omar Bio materials 6. Which type of strain is reversible?  a) Plastic strain  b) Elastic strain  c) Proportional strain  d) None of the above  Answer: b) Elastic strain 7. What is the definition of strain?  a) Force applied over an area  b) Change in length divided by original length  c) Energy stored in deformation  d) Resistance to deformation  Answer: b) Change in length divided by original length 8. Which testing machine is used to measure stress and strain?  a) Oscilloscope  b) Voltmeter  c) Instron  d) Seismograph  Answer: c) Instron 9. What does a stress-strain curve represent?  a) Force over distance  b) Force and elongation relationship  c) Heat transfer  d) Electrical resistance  Answer: b) Force and elongation relationship 10. Which point on the stress-strain curve represents the elastic limit?  a) Point A  b) Point B  c) Point C  d) Point D  Answer: b) Point B 2|Page Dr Omar Bio materials 11. Which property measures the stiffness of a material?  a) Ductility  b) Toughness  c) Modulus of elasticity  d) Flexibility  Answer: c) Modulus of elasticity 12. What does high Young’s modulus indicate?  a) The material is flexible  b) The material is rigid  c) The material has high ductility  d) The material is brittle  Answer: b) The material is rigid 13. Which term refers to a material’s ability to deform without fracture under compression?  a) Flexibility  b) Ductility  c) Malleability  d) Resilience  Answer: c) Malleability 14. Which property is important for orthodontic wires?  a) Flexibility  b) Brittleness  c) Malleability  d) Fracture strength  Answer: a) Flexibility 15. What is the term for resistance to fracture?  a) Ductility  b) Toughness  c) Malleability  d) Elasticity  Answer: b) Toughness 3|Page Dr Omar Bio materials 16. What material property is essential for dental restorations?  a) Low flexibility  b) High proportional limit  c) Low yield stress  d) High brittleness  Answer: b) High proportional limit 17. Which term describes the amount of energy required to deform a material to its proportional limit?  a) Resilience  b) Toughness  c) Flexibility  d) Ductility  Answer: a) Resilience 18. What is brittleness?  a) Ability to deform without fracture  b) Little or no plastic deformation before fracture  c) High elastic strain  d) High proportional limit  Answer: b) Little or no plastic deformation before fracture 19. Which property helps dental materials withdraw through undercuts without deformation?  a) Malleability  b) Elastic deformation  c) Ductility  d) Fracture toughness  Answer: b) Elastic deformation 20. Fracture strength refers to:  a) Strength at which material begins to yield  b) Maximum stress before fracture  c) Maximum deformation before breaking  d) The stress at the elastic limit  Answer: b) Maximum stress before fracture 4|Page Dr Omar Bio materials 21. Which term describes a material's ability to be drawn into wire? o a) Ductility o b) Brittleness o c) Malleability o d) Toughness o Answer: a) Ductility 22. What is the yield stress of a material? o a) The stress at which fracture occurs o b) The maximum stress before plastic deformation o c) The stress needed for elastic deformation o d) The stress where material begins to deform permanently o Answer: d) The stress where material begins to deform permanently 23. Which property is opposite to ductility? o a) Toughness o b) Flexibility o c) Brittleness o d) Malleability o Answer: c) Brittleness 24. Which material property allows it to return to its original shape after removing stress? o a) Plasticity o b) Elasticity o c) Toughness o d) Hardness o Answer: b) Elasticity 25. Proportional limit is significant in which of the following? o a) Adjusting a dental filling o b) Shaping an orthodontic wire o c) Permanent deformation resistance o d) Aesthetic dental material application o Answer: c) Permanent deformation resistance 26. Which term indicates the resistance to a force causing permanent deformation? o a) Toughness o b) Elasticity o c) Resilience o d) Malleability o Answer: c) Resilience 5|Page Dr Omar Bio materials 27. Which type of stress involves two opposite forces acting parallel to the surface? o a) Tensile stress o b) Compressive stress o c) Shear stress o d) Flexural stress o Answer: c) Shear stress 28. Flexibility in dental materials is important for: o a) Resisting fracture o b) Withstanding compression o c) Adapting to undercuts in impression materials o d) Shaping of orthodontic wires only o Answer: c) Adapting to undercuts in impression materials 29. What happens to a material when it reaches its ultimate tensile strength? o a) It fractures o b) It undergoes elastic deformation o c) It reaches maximum resilience o d) It maintains its shape under stress o Answer: a) It fractures 30. Which property measures a material's ability to resist deformation under load? o a) Brittleness o b) Stiffness o c) Ductility o d) Hardness o Answer: b) Stiffness 31. Resilience is especially important for which dental applications? o a) Crown materials o b) Denture liners and tissue conditioners o c) Orthodontic brackets o d) Tooth enamel o Answer: b) Denture liners and tissue conditioners 32. What does a higher modulus of elasticity indicate about a material? o a) It is more flexible o b) It is more rigid o c) It has high toughness o d) It can withstand higher temperatures o Answer: b) It is more rigid 6|Page Dr Omar Bio materials 33. Which of the following materials is typically brittle? o a) Gold o b) Amalgam o c) Orthodontic wires o d) Rubber o Answer: b) Amalgam 34. What does toughness indicate in dental materials? o a) Flexibility under force o b) Resistance to deformation without fracture o c) Ability to withstand permanent deformation o d) Ability to resist fracture energy o Answer: d) Ability to resist fracture energy 35. The point where stress and strain are no longer proportional is known as: o a) Elastic limit o b) Yield point o c) Proportional limit o d) Fracture point o Answer: c) Proportional limit 36. What property of a dental material helps to create a tight seal at the margins? o a) Hardness o b) Ductility o c) Elasticity o d) Flexibility o Answer: b) Ductility 37. What is malleability? o a) The ability to be drawn into thin sheets o b) The resistance to indentation o c) Elastic strain under compression o d) The energy needed to deform o Answer: a) The ability to be drawn into thin sheets 38. Materials that have low yield stress are best suited for: o a) Orthodontic applications o b) High-load-bearing restorations o c) Temporary crowns o d) Permanent fillings o Answer: a) Orthodontic applications 7|Page Dr Omar Bio materials 39. What happens to a material at its fracture strength? o a) It deforms elastically o b) It becomes malleable o c) It fractures o d) It reaches yield strength o Answer: c) It fractures 40. Which of the following is a characteristic of ductile materials? o a) They are brittle o b) They break without significant deformation o c) They exhibit significant plastic deformation before fracture o d) They are flexible only under low stress o Answer: c) They exhibit significant plastic deformation before fracture 41. Which factor is most important for dental implants to resist biting forces? o a) Ductility o b) Toughness o c) Elastic modulus o d) Fracture toughness o Answer: d) Fracture toughness 42. What happens when stress exceeds the elastic limit? o a) The material deforms elastically o b) The material returns to its original shape o c) The material deforms permanently o d) The material becomes brittle o Answer: c) The material deforms permanently 43. Which property refers to the material’s ability to absorb impact energy? o a) Resilience o b) Toughness o c) Flexibility o d) Elasticity o Answer: b) Toughness 44. The ability of a material to withstand pulling or stretching force is called: o a) Compressive strength o b) Tensile strength o c) Shear strength o d) Flexural strength o Answer: b) Tensile strength 8|Page Dr Omar Bio materials 45. Which of the following is a flexible impression material? o a) Gold foil o b) Acrylic resin o c) Elastomer o d) Porcelain o Answer: c) Elastomer 46. The plastic strain in a material after reaching the elastic limit is associated with: o a) Brittleness o b) Elasticity o c) Flexibility o d) Ductility o Answer: d) Ductility 47. Which is a primary factor in the design of materials for removable dentures? o a) High modulus of elasticity o b) High resilience o c) Low tensile strength o d) High brittleness o Answer: b) High resilience 48. A material’s resistance to scratching or abrasion is known as: o a) Toughness o b) Hardness o c) Malleability o d) Ductility o Answer: b) Hardness 49. Which of these terms describes the force that opposes stretching? o a) Tensile stress o b) Compressive stress o c) Shear stress o d) Flexural stress o Answer: a) Tensile stress 50. Which property is desirable in orthodontic archwires? o a) High resilience o b) High brittleness o c) Low yield stress o d) High malleability o Answer: a) High resilience 9|Page Dr Omar Bio materials 51. What occurs in a material after reaching ultimate strength? o a) Elastic deformation o b) Plastic deformation o c) Yielding o d) Fracture o Answer: d) Fracture 52. Elasticity is crucial in which dental application? o a) Implants o b) Orthodontic braces o c) Denture linings o d) Restorative crowns o Answer: b) Orthodontic braces 53. Which material is not typically considered ductile? o a) Amalgam o b) Gold o c) Silver o d) Rubber o Answer: a) Amalgam 54. Which material property is essential for denture bases? o a) Brittleness o b) High modulus of elasticity o c) High flexibility o d) Low resilience o Answer: c) High flexibility 55. Which of these has the highest modulus of elasticity? o a) Acrylic resin o b) Porcelain o c) Dentin o d) Elastomer o Answer: b) Porcelain 56. Why is toughness important in dental materials? o a) Provides elasticity o b) Prevents deformation o c) Resists cracking and fractures o d) Enables hardness o Answer: c) Resists cracking and fractures 10 | P a g e Dr Omar Bio materials 57. What type of deformation occurs first when a force is applied to a material? o a) Plastic deformation o b) Elastic deformation o c) Fracture o d) Compression o Answer: b) Elastic deformation 58. The term "yield point" indicates: o a) The material’s maximum elasticity o b) The start of permanent deformation o c) The beginning of fracture o d) Maximum flexibility o Answer: b) The start of permanent deformation 59. Flexibility is vital for which dental application? o a) Amalgam fillings o b) Orthodontic brackets o c) Crown frameworks o d) Dental impressions o Answer: d) Dental impressions 60. Which property is required for burnishing metallic restorations? o a) High elasticity o b) High malleability o c) High resilience o d) Low toughness o Answer: b) High malleability 61. What is the opposite of resilience in dental materials? o a) Toughness o b) Elasticity o c) Hardness o d) Brittleness o Answer: d) Brittleness 62. In the stress-strain curve, which portion represents the elastic region? o a) Area under plastic deformation o b) Area under the elastic limit o c) Beyond the fracture point o d) After yield point o Answer: b) Area under the elastic limit 11 | P a g e Dr Omar Bio materials 63. How does adding zirconia to porcelain affect dental materials? o a) Increases brittleness o b) Increases fracture toughness o c) Decreases resilience o d) Reduces malleability o Answer: b) Increases fracture toughness 64. What is the effect of higher proportional limits in restorative materials? o a) Increased brittleness o b) Reduced fracture resistance o c) Greater tolerance to stress without deformation o d) Reduced toughness o Answer: c) Greater tolerance to stress without deformation 65. Which material property allows for the creation of intricate orthodontic devices? o a) Ductility o b) Hardness o c) Brittleness o d) Modulus of elasticity o Answer: a) Ductility 66. Which property is crucial for dental materials exposed to occlusal forces? o a) Low toughness o b) High fracture strength o c) High ductility o d) Low modulus of elasticity o Answer: b) High fracture strength 67. A material's resistance to stress-induced deformation is measured by: o a) Elasticity o b) Resilience o c) Stress-strain curve slope o d) Modulus of elasticity o Answer: d) Modulus of elasticity 68. Stress beyond the proportional limit leads to: o a) Reversible deformation o b) Irreversible deformation o c) Elastic deformation only o d) Strain reduction o Answer: b) Irreversible deformation 12 | P a g e Dr Omar Bio materials 69. Which dental material is known for high ductility? o a) Amalgam o b) Porcelain o c) Gold o d) Resin o Answer: c) Gold 70. Which of these best resists crack propagation? o a) High resilience materials o b) Toughened dental porcelain o c) High brittleness materials o d) Low modulus of elasticity materials o Answer: b) Toughened dental porcelain 71. Which property is essential for orthodontic aligners? o a) High modulus of elasticity o b) High resilience o c) High fracture strength o d) High brittleness o Answer: b) High resilience 72. What is the significance of flexibility in dental impression materials? o a) Ensures rigidity o b) Allows withdrawal without deformation o c) Increases malleability o d) Decreases brittleness o Answer: b) Allows withdrawal without deformation 73. Which material is often used for its high modulus of elasticity in dental applications? o a) Porcelain o b) Elastomer o c) Resin o d) Rubber o Answer: a) Porcelain 74. High fracture toughness is necessary for: o a) Filling materials o b) Temporary crowns o c) Dental implants o d) Retainers o Answer: c) Dental implants 13 | P a g e Dr Omar Bio materials 75. Which dental property is essential for materials resisting repeated biting forces? o a) High toughness o b) High resilience o c) High hardness o d) High flexibility o Answer: a) High toughness 76. Which material property allows dental crowns to withstand chewing? o a) Low modulus of elasticity o b) High fracture toughness o c) Low brittleness o d) High flexibility o Answer: b) High fracture toughness 77. Which factor contributes to the durability of maxillofacial materials? o a) Hardness o b) Resilience o c) Elasticity o d) Malleability o Answer: b) Resilience 78. Elastic deformation occurs up to which point on the stress-strain curve? o a) Fracture point o b) Ultimate strength point o c) Elastic limit o d) Yield point o Answer: c) Elastic limit 79. Which term refers to the material’s ability to be shaped without cracking? o a) Ductility o b) Flexibility o c) Malleability o d) Resilience o Answer: c) Malleability 80. A material that is brittle will most likely: o a) Withstand high strain o b) Deform significantly before breaking o c) Fracture with little deformation o d) Stretch under tensile forces o Answer: c) Fracture with little deformation 14 | P a g e