Casting Alloys, Wrought Alloys and Solders

This set of flashcards covers key concepts from the lecture on casting alloys, wrought alloys, and solders used in dentistry, including definitions, properties, classifications, and applications.

What is an alloy?

An alloy is a mixture of metallic and nonmetallic elements that possess improved properties for dental restorations compared to any single element.

What was the earliest material used for dental restorations?

The earliest restorations used pure gold because it was easy to purify, melt, and manipulate.

What is a cohesive gold foil used for in dentistry?

Cohesive gold is normally used in the form of a very thin gold sheet or ‘foil’ for dental restorations.

What are the two main categories of alloys used in dentistry?

They are cast metal alloys and wrought alloys.

What properties make a small grain size in alloys desirable?

A small grain size ensures uniform properties, making metals harder and giving them higher yield stress.

What are noble metal elements in dental alloys?

Noble metals are defined by their resistance to corrosion and are typically rare and precious.

Name three noble metals commonly used in dental casting alloys.

Gold (Au), Palladium (Pd), and Platinum (Pt).

What is the significance of the term 'carat' in relation to gold alloys?

'Carat' describes the amount of gold in an alloy, with pure gold being 24 carat.

What alloy properties are affected by mechanical forces?

Mechanical forces alter grain structure and can change the properties of the alloy.

What are the classifications of dental casting alloys according to the ADA?

High noble alloys, noble alloys (semi-precious), and base metal alloys.

What is the primary purpose of solders in dentistry?

Solders create junctions between different metals and alloys.

Why must the oxide layer be eliminated during soldering?

To allow wetting and flowing of solder on the alloy surfaces.

What are the required properties for ceramic-bonding metal alloys?

They must have strength and rigidity, a durable chemical bond with ceramic, a high melting range, and a compatible coefficient of thermal expansion.

What problems can arise from impurities during the firing of ceramic restorations?

Greening, or discoloration, occurs due to contamination of ceramic with vaporized metal during firing.

What is a wrought alloy?

A wrought alloy is created by mechanically shaping a cast alloy into a final form.

What is the composition of a high noble alloy?

At least 40% is gold from 60% or more noble metals, and the remaining is base metal.

What are common base metals used in dental alloys?

Copper (Cu), Silver (Ag), Zinc (Zn), Nickel, and Cobalt.

Define 'density' in the context of dental alloys.

Density is the amount of mass in grams that occupies a volume of 1 cubic centimeter.