Dentistry Quiz: Metals and Alloys

Forms of Pure Gold Fillings

• Classified into:
  • Cohesive Gold (also known as Cohesive Gold Foil)
  • Mat Gold
  • Electralloy
  • Electrolytic Gold

Manipulating Cohesive Gold Fillings

• Steps to carry out a Class 1 filling:
  • Selection of the proper tooth preparation
  • Isolation of the operating field
  • Wedging and condensing the gold
  • Carving and finishing the gold

Cold Working

• Definition: the process of shaping or deforming metals at room temperature
• Properties changed:
  • Increases hardness and strength
  • Decreases ductility
• Examples in dentistry:
  • Shaping dental instruments
  • Forming metal matrices for direct filling gold restorations

Eutectic and Peritectic Alloys

• Eutectic Alloy:
  • Definition: an alloy that has a single melting point (lowest possible temperature)
  • Example: 72% Gold, 14.5% Silver, 9.5% Copper, and 4% Zinc
• Peritectic Alloy:
  • Definition: an alloy that has a specific temperature at which it changes from a solid to a liquid
  • Example: 75% Gold, 20% Silver, and 5% Copper

Classification of Dental Alloys (ADA 1984)

• Classified according to their nobility:
  • Noble Alloys (gold, platinum, palladium)
  • Semi-Precious Alloys (silver, copper, zinc)
  • Base Metal Alloys (nickel, chromium, iron)

Ideal Requirements of Dental Casting Alloys

• Properties required:
  • High strength and resistance to corrosion
  • Low melting point and high fluidity
  • Biocompatibility and non-toxicity
  • Good casting properties and accuracy
  • Aesthetically pleasing color
  • Cost-effective and easy to manipulate

This quiz covers various aspects of metals and alloys in dentistry, including pure gold filling, cold working, and classification of dental alloys.