Science of Dental Materials — MCQ ও উত্তর

ডেন্টাল ভর্তি · । এই অধ্যায়ে মোট 110টি প্রশ্ন আছে। নিচে প্রথম 10টি প্রশ্ন ও সঠিক উত্তর দেওয়া হলো।

এই অধ্যায়ে সব প্রশ্নে অনুশীলন করুন

1. Which of the following materials exhibits the greatest electrical conductivity?

   1. Silver
   2. Copper
   3. Aluminum
   4. Gold

   সঠিক উত্তর: Copper

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option B - Among the materials listed—Silver, Copper, Aluminum, and Gold—silver actually possesses the highest electrical conductivity due to its atomic structure and electron mobility.- However, in practical and medical device applications, copper is most commonly used because it offers an excellent balance of conductivity, cost-effectiveness, and durability. - While silver has the greatest conductivity, it is significantly more expensive and less practical for widespread use. - Copper's conductivity is only marginally lower than silver's, but it is much more abundant and affordable, making it the preferred choice in most medical and electrical applications.- Moreover, copper is less prone to oxidation than aluminum, maintaining good conductivity over time, and it is more conductive than gold, which is often used for its resistance to corrosion rather than conductivity. - Therefore, copper exhibits the greatest effective or practical electrical conductivity in real-world applications.Key Points:- Silver has the highest theoretical electrical conductivity. - Copper is preferred in practical applications due to its cost-effectiveness and durability. - Aluminum and gold have lower electrical conductivity than copper. - Copper balances performance with affordability, making it the best overall choice.Reference: Electrical Properties of Materials, Volume 2, Chapter 5 / Page 123

2. Which mechanical property refers to a material's capacity to undergo permanent shape change without breaking when subjected to stress?

   1. Elasticity
   2. Ductility
   3. Plasticity
   4. Toughness

   সঠিক উত্তর: Plasticity

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option C - Plasticity refers to a material’s ability to undergo permanent deformation or shape change without breaking when subjected to stress. - Unlike elastic deformation, which is reversible, plastic deformation means the material retains its new shape even after the applied stress is removed.- This property is crucial in processes like metal forming, shaping, and manufacturing.To clarify the other options: - Elasticity is the ability of a material to return to its original shape after the removal of stress (reversible deformation). - Ductility specifically refers to a material’s ability to undergo significant plastic deformation under tensile stress, often leading to stretching into a wire. - Toughness is a measure of how much energy a material can absorb before fracturing; it signifies resistance to impact and fracture but does not directly describe permanent shape change.Therefore, plasticity best describes the capacity for permanent shape change without breaking under stress.Reference: Materials Science and Engineering, Volume 1, Chapter 3, pp. 45-50

3. Which of the following best characterizes a material's chemical property?

   1. Its ability to conduct electricity
   2. Its reaction with acids or bases
   3. Its melting point
   4. Its density

   সঠিক উত্তর: Its reaction with acids or bases

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option B The question asks us to identify which option best characterizes a material's chemical property. - Chemical properties describe a substance’s ability to undergo changes that transform it into different substances. - These properties involve chemical reactions where the material's internal structure is altered. - Option 1: Its ability to conduct electricity – This is a physical property related to how free electrons move through a material without changing its chemical identity.- Option 2: Its reaction with acids or bases – This is a chemical property, as it describes how the material chemically interacts and changes when exposed to acids or bases.- Option 3: Its melting point – This is a physical property, describing the temperature at which the material changes state from solid to liquid without chemical alteration.- Option 4: Its density – This is also a physical property indicating mass per unit volume, without any chemical change. Therefore, "Its reaction with acids or bases" is the correct choice because it directly involves the material's chemical reactivity. Reference: Principles of Chemistry, Volume 1, Chapter 3: Chemical Properties and Reactions, Page 78.

4. Which characteristic of a material defines its resistance to surface deformation such as scratching or indentation?

   1. Hardness
   2. Toughness
   3. Ductility
   4. Elasticity

   সঠিক উত্তর: Hardness

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option A - The characteristic of a material that defines its resistance to surface deformation such as scratching or indentation is Hardness. - Hardness measures how well a material can withstand localized plastic deformation, which occurs when the surface is subjected to mechanical forces. - This property is crucial in applications where materials are exposed to wear and abrasion.- For example, harder materials are less likely to be scratched or indented compared to softer materials.- In contrast, Toughness refers to the ability of a material to absorb energy and plastically deform without fracturing, which relates to overall durability rather than surface resistance. - Ductility measures a material’s ability to undergo significant plastic deformation before rupture, typically associated with stretching or bending rather than surface resistance. - Elasticity is the ability of a material to return to its original shape after deformation, reflecting reversible deformation rather than permanent surface damage resistance.Understanding hardness is essential in selecting materials for surgical instruments, implants, or other medical devices where resistance to surface wear is imperative.Reference: Materials Science and Engineering: An Introduction, 10th Edition, Chapter 5 / Page 150

5. Which physical characteristic refers to the mass of a substance contained within a specific volume?

   1. Viscosity
   2. Density
   3. Surface tension
   4. Elasticity

   সঠিক উত্তর: Density

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option B The physical characteristic that refers to the mass of a substance contained within a specific volume is known as density. Density is defined as the mass per unit volume of a material and is mathematically represented as:Density (ρ) = Mass (m) / Volume (V)- This property helps us understand how compact or concentrated a substance is. - For example, a substance with a high density means it has a large amount of mass packed into a small volume. - It is an intrinsic property of materials and plays a crucial role in various fields such as physics, chemistry, engineering, and medicine.- Viscosity refers to a fluid’s resistance to flow.- Surface tension is the elastic tendency of a fluid surface that makes it acquire the least surface area possible.- Elasticity is the ability of a material to return to its original shape after deformation.Therefore, the correct answer is Density because it specifically describes the relationship between mass and volume of a substance.Reference: Principles of Physics, Volume 1, Chapter 3, Page 45.

6. Which of the following characteristics defines a biological property of dental materials?

   1. Biocompatibility
   2. Thermal conductivity
   3. Compressive strength
   4. Solubility

   সঠিক উত্তর: Biocompatibility

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option A The correct answer is Biocompatibility.In the context of dental materials, properties can be broadly categorized into biological, physical, and mechanical properties. - Biological properties relate to how the material interacts with the biological tissues in the oral environment. This includes the material's ability to perform without causing adverse reactions such as toxicity, allergy, or irritation. Therefore, biocompatibility is the key biological property that ensures the material is safe and compatible with the body’s tissues. - Thermal conductivity and solubility are examples of physical properties, as they describe how the material behaves physically under temperature change or in the presence of fluids. - Compressive strength is a mechanical property that measures the material's ability to withstand forces without failure.In summary, biocompatibility defines the biological property of dental materials, ensuring safe integration with oral tissues—a critical factor in the long-term success of dental restorations.Reference: Craig’s Restorative Dental Materials, 14th Edition, Chapter 2: Biological Properties of Dental Materials / Page 25

7. Which characteristic of a material is most essential for use in implantable medical devices?

   1. Corrosion resistance
   2. Tensile strength
   3. Biocompatibility
   4. Electrical conductivity

   সঠিক উত্তর: Biocompatibility

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option C When selecting materials for implantable medical devices, the most critical characteristic is biocompatibility. This is because the material must interact safely with the body's tissues and fluids without causing an adverse immune response or toxicity. While other properties such as corrosion resistance and tensile strength are important for the durability and functionality of the device, they are secondary to ensuring that the material is compatible with the biological environment. Electrical conductivity may be necessary for specific applications like pacemakers, but it is not universally essential across all implantable devices.In summary:- Biocompatibility ensures the material does not provoke inflammation, allergic reactions, or rejection by the body.- Corrosion resistance helps prevent degradation and release of harmful ions.- Tensile strength is important for mechanical stability.- Electrical conductivity is relevant only for devices requiring electrical function.Therefore, the primary and most essential characteristic is biocompatibility.Reference: Biomaterials Science: An Introduction to Materials in Medicine, 3rd Edition, Volume 1, Chapter 5, Page 120

8. Which of the following materials is most commonly recognized for its biodegradability in medical applications?

   1. Polylactic acid (PLA)
   2. Polyethylene (PE)
   3. Polystyrene (PS)
   4. Polyvinyl chloride (PVC)

   সঠিক উত্তর: Polylactic acid (PLA)

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option A In medical applications, the biodegradability of materials is a crucial factor, especially for implants, sutures, and drug delivery systems where the material is expected to break down safely within the body over time.Among the given options:- Polylactic acid (PLA) is a biodegradable polymer derived from renewable resources like corn starch or sugarcane. It degrades into non-toxic lactic acid, which is naturally metabolized by the body. This makes PLA highly suitable for temporary medical devices such as resorbable sutures, implants, and tissue engineering scaffolds.- In contrast, Polyethylene (PE), Polystyrene (PS), and Polyvinyl chloride (PVC) are non-biodegradable synthetic polymers widely used in medical packaging and devices but do not break down within the body. Their persistence can lead to long-term foreign body reactions if implanted.Therefore, the correct answer is Polylactic acid (PLA) due to its biocompatibility and predictable biodegradation profile, making it the most commonly recognized biodegradable material in medical contexts.Reference: Biomaterials Science: An Introduction to Materials in Medicine, 3rd Edition, Volume 1, Chapter 5, pp. 130-135.

9. Which mechanical property is indicated by the slope of the linear portion of a stress-strain curve?

   1. Poisson's ratio
   2. Young's modulus (Elastic modulus)
   3. Yield strength
   4. Toughness

   সঠিক উত্তর: Young's modulus (Elastic modulus)

   ব্যাখ্যা: সমাধান সঠিক উত্তর: Option B - The slope of the linear portion of a stress-strain curve represents the material's stiffness or rigidity. - This linear region corresponds to the elastic behavior of the material, where the deformation is reversible upon removal of the applied stress. The property indicated by this slope is known as the Young's modulus, also referred to as the Elastic modulus.- Young's modulus is a fundamental mechanical property that measures the ability of a material to resist elastic deformation under load. - Mathematically, it is defined as the ratio of stress (force per unit area) to strain (proportional deformation) within the elastic limit:Young’s Modulus (E) = Stress / Strain- Poisson's ratio (Option 1) relates lateral strain to axial strain but does not describe the slope of the stress-strain curve.- Yield strength (Option 3) marks the transition from elastic to plastic deformation and is represented by the end of the linear region.- Toughness (Option 4) describes the total energy absorbed before fracture, represented by the area under the entire stress-strain curve, not just the slope.In summary, the linear portion slope effectively demonstrates how much a material will deform elastically under applied stress, which is quantified by the Young's modulus (Elastic modulus).Reference: Materials Science and Engineering: An Introduction, 10th Edition, by William D. Callister Jr., Chapter 5, Page 170

10. Which of the following dental materials exhibits the highest resistance to corrosion?

    1. Titanium
    2. Gold
    3. Stainless steel
    4. Cobalt-chromium alloy

    সঠিক উত্তর: Gold

    ব্যাখ্যা: সমাধান সঠিক উত্তর: Option B The correct answer is Gold.- Among the dental materials listed, gold exhibits the highest resistance to corrosion. - This is primarily due to gold's noble metal characteristics, meaning it is chemically inert and does not easily react with the oral environment. - Gold forms a stable surface that prevents the formation of oxides or other corrosion products.- Titanium, while highly biocompatible and resistant to corrosion due to its protective oxide layer, is more susceptible to mechanical wear and chemical attack compared to gold.- Stainless steel has a protective chromium oxide layer that confers good corrosion resistance, but it is still prone to pitting and crevice corrosion, especially in the chloride-rich environment of the mouth.- Cobalt-chromium alloys are corrosion resistant due to their chromium content; however, their corrosion resistance does not surpass that of pure gold.In clinical dentistry, gold has been used extensively as a restorative material owing to its durability, corrosion resistance, and biocompatibility. This makes it a preferred choice for long-lasting restorations without degradation caused by oral fluids.Reference: Craig's Restorative Dental Materials, 13th Edition, Chapter 3: Physical and Chemical Properties of Dental Materials, Page 85