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Viva Question and Answers Related to Metallurgy in Dentistry

Here are 50 viva questions and answers related to metallurgy in dentistry:

  1. What is metallurgy in dentistry? Metallurgy in dentistry refers to the science and study of metals used in dental materials, such as alloys for dental restorations.
  2. What are the main types of metals used in dentistry? The main types of metals used in dentistry are noble metals (e.g., gold, platinum), base metals (e.g., stainless steel, cobalt-chromium alloys), and dental amalgam (a mixture of silver, tin, copper, and mercury).
  3. How is gold used in dentistry? Gold is used in dentistry for making crowns, bridges, and other restorations due to its biocompatibility, durability, and resistance to corrosion.
  4. What are the advantages of using stainless steel in dentistry? Stainless steel is preferred in dentistry for its strength, corrosion resistance, and affordability, making it suitable for orthodontic wires, crowns for temporary restorations, and surgical instruments.
  5. Explain the composition and properties of cobalt-chromium alloys used in dentistry. Cobalt-chromium alloys used in dentistry typically contain cobalt, chromium, and other elements like molybdenum and nickel. They offer high strength, corrosion resistance, and biocompatibility, making them suitable for dental prostheses and implants.
  6. What is the role of nickel in dental alloys? Nickel is often added to dental alloys to improve their mechanical properties, such as strength and ductility. However, some individuals may have allergic reactions to nickel, so its use is carefully regulated.
  7. How does the process of galvanic corrosion affect dental restorations? Galvanic corrosion occurs when two dissimilar metals are in contact in the presence of an electrolyte, leading to accelerated corrosion of one metal. In dentistry, this can occur between different metals in restorations, causing damage over time.
  8. What is the function of a dental casting machine? A dental casting machine is used to create precise metal castings of dental restorations, such as crowns and bridges, by melting and casting the metal into a mold.
  9. What are the steps involved in the investment casting process for dental restorations? The steps in the investment casting process include preparing the wax pattern, investing it in a refractory material, burning out the wax to create a mold, casting the metal, and finishing and polishing the restoration. Viva Question and Answers Related to Hypersensitivity Reactions
  10. How does porcelain fuse to metal in a porcelain-fused-to-metal (PFM) restoration? In a PFM restoration, the metal substructure is first fabricated, and then porcelain is applied and fired onto the metal at high temperatures, causing the porcelain to fuse to the metal surface, creating a strong bond.
  11. What is the purpose of the metal substructure in a PFM restoration? The metal substructure in a PFM restoration provides strength and support for the porcelain veneer, ensuring durability and stability of the restoration.
  12. Describe the process of electroplating in dentistry. Electroplating in dentistry involves depositing a thin layer of metal, such as gold or chrome, onto a dental prosthesis or instrument by using an electric current in an electrolyte solution.
  13. How does the composition of dental amalgam affect its properties? The composition of dental amalgam, which includes silver, tin, copper, and mercury, affects its strength, durability, and handling properties. The ratio of these metals determines the properties of the amalgam.
  14. What is the setting reaction of dental amalgam? The setting reaction of dental amalgam involves the formation of a hard mass through a chemical reaction between the metal powders (silver, tin, copper) and the liquid mercury, resulting in a stable restoration.
  15. What are the advantages and disadvantages of using dental amalgam? Advantages of dental amalgam include its durability, strength, and cost-effectiveness. Disadvantages include its silver color, potential for expansion and contraction leading to microleakage, and concerns about mercury content.
  16. How does stress corrosion cracking affect dental alloys? Stress corrosion cracking occurs when a metal is exposed to tensile stress in a corrosive environment, leading to cracking and failure of the material. This can affect the longevity and integrity of dental alloys.
  17. What is the role of heat treatment in the strengthening of dental alloys? Heat treatment is used to modify the microstructure of dental alloys, improving their mechanical properties such as hardness, strength, and ductility, making them suitable for various dental applications.
  18. Explain the concept of grain refinement in metallurgy and its importance in dental materials. Grain refinement involves reducing the size of crystal grains in a material, which can improve its mechanical properties, such as strength and fatigue resistance. In dental materials, grain refinement is essential for enhancing performance and longevity.
  19. What is the difference between wrought alloys and cast alloys in dentistry? Wrought alloys are formed by mechanical deformation, such as rolling or forging, while cast alloys are formed by casting molten metal into a mold. Wrought alloys often have better mechanical properties and are used for certain dental applications.
  20. How does the microstructure of a dental alloy influence its properties? The microstructure of a dental alloy, including grain size, distribution of phases, and presence of defects, greatly influences its mechanical, chemical, and biological properties, impacting its performance in clinical use. Viva Question and Answers Related to Resin Impression Trays and Tray materials!
  21. What are the factors to consider when selecting a dental alloy for a specific application? Factors to consider when selecting a dental alloy include biocompatibility, mechanical properties (such as strength, hardness, and ductility), corrosion resistance, esthetics, ease of fabrication, and cost.
  22. Discuss the role of noble metals in dental alloys. Noble metals, such as gold and platinum, are used in dental alloys for their resistance to corrosion, biocompatibility, and ability to form strong bonds with porcelain in PFM restorations, enhancing the longevity and esthetics of dental prostheses.
  23. What is the significance of the elastic modulus in dental materials? The elastic modulus, also known as Young’s modulus, represents the stiffness of a material and is crucial in dental materials to ensure compatibility with natural teeth and surrounding tissues, minimizing stress and potential damage.
  24. How do dental alloys interact with oral tissues? Dental alloys must be biocompatible to avoid adverse reactions with oral tissues. Biocompatibility involves factors such as corrosion resistance, low toxicity, minimal allergic potential, and the ability to maintain a stable interface with tissues.
  25. Explain the principles of metal-ceramic bonding in dental restorations. Metal-ceramic bonding involves creating a strong bond between a metal substructure (such as cobalt-chromium or titanium) and a porcelain veneer through techniques like thermal expansion matching, surface treatment, and firing processes.
  26. What is the role of a porcelain veneer in a dental restoration? A porcelain veneer in a dental restoration provides esthetics, mimicking the natural appearance of teeth, while also offering strength, wear resistance, and biocompatibility when bonded to a metal or ceramic substructure. Viva Question and Answers Related to Instruments Used in Conservative and Endodontics
  27. How does the composition of dental casting investments affect casting quality? The composition of dental casting investments, including binders, refractory materials, and expansion agents, influences the accuracy, surface finish, and dimensional stability of castings, ensuring high-quality dental restorations.
  28. Describe the mechanism of corrosion in dental alloys and its impact on clinical performance. Corrosion in dental alloys can occur through chemical reactions with oral fluids, leading to degradation of the material, discoloration, microleakage, and potential tissue reactions. Proper alloy selection and maintenance are crucial to prevent corrosion-related issues.
  29. What are the characteristics of a high-noble dental alloy? A high-noble dental alloy contains a high percentage of noble metals (gold, platinum, palladium) and is designed for applications requiring superior esthetics, biocompatibility, and bonding with porcelain in PFM restorations.
  30. How does heat treatment affect the mechanical properties of dental alloys? Heat treatment can modify the microstructure of dental alloys, improving their hardness, strength, ductility, and resistance to deformation, which are critical for ensuring the longevity and performance of dental prostheses.
  31. Discuss the importance of surface finishing and polishing in dental alloys. Surface finishing and polishing of dental alloys are essential to remove surface irregularities, enhance esthetics, reduce plaque accumulation, and improve corrosion resistance, ensuring optimal clinical performance and patient satisfaction.
  32. What are the applications of titanium alloys in dentistry? Titanium alloys are used in dentistry for implants, orthodontic appliances, surgical instruments, and dental prostheses due to their biocompatibility, corrosion resistance, strength, and osseointegration properties.
  33. How does the galvanic couple effect influence the corrosion of dental alloys? The galvanic couple effect occurs when two dissimilar metals are in contact in an electrolyte (saliva), leading to accelerated corrosion of the less noble metal. Proper alloy selection and isolation techniques are crucial to prevent galvanic corrosion in dental restorations. Viva Question and Answers Related to Instruments Used in Periodontics
  34. What are the potential health risks associated with metal ions released from dental restorations? Metal ions released from dental restorations, such as nickel, chromium, and cobalt, can cause allergic reactions, oral mucosal reactions, and systemic health effects in sensitive individuals, highlighting the importance of biocompatibility testing and patient assessment.
  35. How does strain hardening affect the mechanical properties of dental alloys? Strain hardening, also known as work hardening, occurs when a metal is deformed plastically, leading to increased hardness, strength, and resistance to deformation in dental alloys. However, excessive strain hardening can also cause brittleness and fracture susceptibility.
  36. Explain the concept of creep in dental materials and its implications for long-term performance. Creep is the gradual deformation of a material under constant stress over time, which can occur in dental alloys subjected to occlusal forces. Understanding and minimizing creep are crucial for ensuring the stability and longevity of dental restorations.
  37. What are the methods used for evaluating the mechanical properties of dental alloys? Methods for evaluating the mechanical properties of dental alloys include tensile testing, hardness testing (e.g., Vickers, Rockwell), fatigue testing, flexural testing, and impact testing, providing insights into their strength, ductility, and resilience.
  38. How does cold working affect the properties of dental alloys? Cold working, such as rolling or drawing, can increase the strength and hardness of dental alloys by inducing strain hardening and refining the microstructure. However, excessive cold working may lead to material embrittlement and reduced ductility.
  39. What are the factors influencing the corrosion resistance of dental alloys? Factors influencing the corrosion resistance of dental alloys include alloy composition, surface finish, presence of protective oxide layers, pH and chemical composition of oral fluids, galvanic effects, and exposure to environmental contaminants. Viva Question and Answers Related to Sterilization of Dental Instruments
  40. Discuss the challenges and advancements in the development of bioactive dental alloys. Bioactive dental alloys are designed to promote tissue integration, reduce bacterial adhesion, and enhance biocompatibility. Challenges include balancing mechanical properties with bioactivity, optimizing corrosion resistance, and ensuring long-term clinical performance.
  41. How do metal allergies manifest in the oral cavity, and how are they diagnosed? Metal allergies in the oral cavity can manifest as oral mucosal reactions (e.g., erythema, ulceration, lichenoid reactions) or systemic symptoms (e.g., dermatitis, respiratory distress) upon exposure to allergenic metals. Diagnosis involves patient history, patch testing, and biocompatibility assessments.
  42. What are the principles of metal-ceramic compatibility in dental restorations? Metal-ceramic compatibility involves matching the thermal expansion coefficients of the metal substructure and porcelain veneer to minimize thermal stresses, ensure proper fit, and prevent porcelain chipping or delamination in PFM restorations.
  43. How does the biocompatibility of dental alloys influence their clinical acceptance? The biocompatibility of dental alloys, including low toxicity, minimal allergenic potential, tissue compatibility, and stability in the oral environment, is critical for patient safety, comfort, and long-term success of dental treatments.
  44. What are the key considerations in the design and fabrication of removable partial dentures using dental alloys? Key considerations for removable partial dentures include selecting appropriate alloys (e.g., cobalt-chromium, titanium), ensuring proper fit and retention, minimizing tissue irritation, optimizing esthetics, and providing functional stability for masticatory efficiency.
  45. Discuss the role of surface treatments (e.g., passivation, anodization) in enhancing the performance of dental alloys. Surface treatments in dental alloys can improve corrosion resistance, biocompatibility, esthetics, and mechanical properties by modifying surface chemistry, texture, and morphology, leading to enhanced clinical performance and longevity. Viva Question and Answers Related to Routes of drug Administration in Pharmacology
  46. How does the phase transformation of dental alloys influence their mechanical behavior? Phase transformations, such as martensitic transformation, can occur in dental alloys under specific conditions (e.g., heating, cooling, stress), affecting their mechanical properties, shape memory, and resilience to deformation, which are critical for clinical applications.
  47. What are the potential complications associated with metal-ceramic restorations in dentistry? Potential complications with metal-ceramic restorations include porcelain chipping or fracture, marginal discrepancies, galvanic corrosion, allergic reactions to metal ions, esthetic challenges (e.g., metal show-through), and occlusal wear, requiring careful clinical management and maintenance.
  48. How does thermal cycling testing evaluate the performance of dental alloys? Thermal cycling testing involves subjecting dental alloys to alternating temperature cycles (e.g., hot and cold water baths) to simulate oral conditions, evaluating their dimensional stability, resistance to thermal stresses, and long-term durability in clinical use.
  49. What are the principles of electrochemical testing for assessing the corrosion behavior of dental alloys? Electrochemical testing, such as potentiodynamic polarization and electrochemical impedance spectroscopy, provides insights into the corrosion kinetics, passive film formation, galvanic effects, and localized corrosion susceptibility of dental alloys under simulated oral environments.
  50. How do regulatory standards and guidelines (e.g., ISO, FDA) influence the development and use of dental alloys in clinical practice? Regulatory standards and guidelines set by organizations like the International Organization for Standardization (ISO) and the U.S. Food and Drug Administration (FDA) ensure the safety, efficacy, quality control, and biocompatibility of dental alloys, guiding their design, manufacturing, testing, and clinical application. Viva Questions and Answers Related to the Matrix Technique in Dentistry

 

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