Casting Alloys, Wrought Alloys and Solders:
Alloys:
➢ Alloys are mixtures of metallic and nonmetallic elements that have better
properties for dental restorations than any single element
➢ Alloys have been used in dentistry for thousands of years to replace natural
tooth structure.
➢ The earliest restorations used pure gold because it was very easy to purify,
melt, and manipulate
○ Gold in foil form probably was used first as a dental restorative
material several thousand years ago.
Most Common Alloys Used in Dentistry:
➢ Cast Metal Alloys: ➢ Wrought Alloys: ➢ Solders:
- For inlays, onlays, - For orthodontic wires, - a molten filler metal
crowns, bridges endodontic files, and that is used to connect
- Partial or complete implants pieces of metal.
denture bases
- Denture bases
, Crystal Structures and Grains of Alloys:
➢ Dental alloys like ice, salt, sugar, or many other solids have a crystal
structure
➢ When a molten (liquid) alloy freezes, crystals (grains) form and grow as the
alloy cools
➢ Each crystal consists of a crystal lattice of metal atoms.
➢ The boundaries where individual crystals meet are called grain boundaries.
Grain Size:
➢ A small grain size is generally more desirable as it ensures uniform
properties of the alloy
➢ Metals with finer grain structure are generally harder and have higher
values of yield stress than those with coarser grain structure.
➢ Achieve Grain Structure By:
○ Quenching: Rapid cooling of the molten metal or alloy following
casting.
○ Refined Grain Structure: seeding the molten material with an
additive metal (iridium and indium) which forms nuclei for
crystallization.
Grain Structure:
➢ Significantly altered by mechanical forces
○ Wrought Alloy: If the alloy is rolled into a sheet or drawn into a
wire and the grain structure takes on a fibrous appearance.
➢ Heating of the alloy after casting or mechanical work may change its grain structure
○ These changes may lead to significant changes in the
properties of the alloy.
○ Ex: heat treatment of Au-Cu ally can produce a stronger
alloy.
■ The copper atoms can be induced to change
lattice positions depending on how the alloy is
cast (or reheated) and cooled.
Major Elements In Dental Alloys:
1. Noble Metal Elements
2. Base Metal Elements
1.Noble Metal Elements:
➢ Defined by their resistance to corrosion even under extreme conditions that occur in the oral
cavity
➢ Noble metals are expensive simply because they are rare (precious)
➢ Out of 7 elements, the 3 mainly used in dentistry are gold, palladium, platinum.
Alloys:
➢ Alloys are mixtures of metallic and nonmetallic elements that have better
properties for dental restorations than any single element
➢ Alloys have been used in dentistry for thousands of years to replace natural
tooth structure.
➢ The earliest restorations used pure gold because it was very easy to purify,
melt, and manipulate
○ Gold in foil form probably was used first as a dental restorative
material several thousand years ago.
Most Common Alloys Used in Dentistry:
➢ Cast Metal Alloys: ➢ Wrought Alloys: ➢ Solders:
- For inlays, onlays, - For orthodontic wires, - a molten filler metal
crowns, bridges endodontic files, and that is used to connect
- Partial or complete implants pieces of metal.
denture bases
- Denture bases
, Crystal Structures and Grains of Alloys:
➢ Dental alloys like ice, salt, sugar, or many other solids have a crystal
structure
➢ When a molten (liquid) alloy freezes, crystals (grains) form and grow as the
alloy cools
➢ Each crystal consists of a crystal lattice of metal atoms.
➢ The boundaries where individual crystals meet are called grain boundaries.
Grain Size:
➢ A small grain size is generally more desirable as it ensures uniform
properties of the alloy
➢ Metals with finer grain structure are generally harder and have higher
values of yield stress than those with coarser grain structure.
➢ Achieve Grain Structure By:
○ Quenching: Rapid cooling of the molten metal or alloy following
casting.
○ Refined Grain Structure: seeding the molten material with an
additive metal (iridium and indium) which forms nuclei for
crystallization.
Grain Structure:
➢ Significantly altered by mechanical forces
○ Wrought Alloy: If the alloy is rolled into a sheet or drawn into a
wire and the grain structure takes on a fibrous appearance.
➢ Heating of the alloy after casting or mechanical work may change its grain structure
○ These changes may lead to significant changes in the
properties of the alloy.
○ Ex: heat treatment of Au-Cu ally can produce a stronger
alloy.
■ The copper atoms can be induced to change
lattice positions depending on how the alloy is
cast (or reheated) and cooled.
Major Elements In Dental Alloys:
1. Noble Metal Elements
2. Base Metal Elements
1.Noble Metal Elements:
➢ Defined by their resistance to corrosion even under extreme conditions that occur in the oral
cavity
➢ Noble metals are expensive simply because they are rare (precious)
➢ Out of 7 elements, the 3 mainly used in dentistry are gold, palladium, platinum.
