2. OBJECTIVES
Introduction
Compositions and functions of each element
Classifications
Setting reactions
Clinical significance of each phases
Manipulation and types of mixes
Properties of Amalgam
3. INTRODUCTION
Amalgam technically means an alloy of mercury with any other
metal. It is an alloy made by mixing mercury with a silver-tin dental
amalgam alloy.
4. ADA specification : No.1 (amalgam alloy)
ADA specification : No.6 (mercury)
5. CLASSIFICATIONS
Based on copper content
1. Low copper alloy
2. High copper alloy
3. High copper admixed alloy
4. High copper unicompositional alloy
6. Based on particle shape
1. Lathe cut alloy
2. Spherical alloy
3. Admixed alloy
Based on size of alloy particle
1. Microcut
2. Macrocut
7. Based on zinc content
1. Zinc containing alloys
2. Zinc free alloys
Based on number of alloyed particle
1. Binary alloys
2. Ternary alloys
3. Quaternary alloys
9. FUNCTIONS OF ELEMENTS
Silver
1. Major component of alloy
2. Whitens the alloy
3. Increase strength
Copper
1. Increases strength
2. Resists tarnish and corrosion
3. Reduces creep
10. Tin
1. Reduces strength and hardness
2. Increases setting time
Zinc
1. To prevent oxidation of the other alloy constituents
2. Responsible for delayed expansion
16. SIGNIFICANCE OF EACH
PHASES
The Gamma 1 is somewhat strong and corrosion resistant but it is
also brittle . Its makes up approximately half of the amalgam and is
the matrix phase that holds the dental amalgam together .
17. The Gamma phase is typically the strongest and most corrosion
resistant phase .it s approximately one quarter of the volume of a
dental amalgam .
The Gamma 2 phase is the weakest and the most corrosion prone
. Its makes up approximately one teeth of the material and is the
weakest part of the dental amalgam .
18. MANIPULATION
The process of mixing alloy and mercury is called trituration .
It can be either ;
Hand trituration (mortar and pestle )
mechanical trituration ( amalgamators )
20. OVERTRITURATED MIX
Soupy consistency
difficult to handle
UNDERTRITURATED MIX
Grainy , dull in appearance
Low strength and poor resistance to corrosion due to rough
surface
21.
22. PROPERTIES
Compressive Strength : Admixed alloy has strength of 430MPa after 7 days.
Tensile strength : 50MPa after 24hrs
Increased mercury leads to increased expansion, creep and corrosion.
Zinc on contamination with water causes delayed expansion.
Creep is a time dependent plastic deformation that is common in amalgam.
Corrosion is less in high copper amalgam .
Non aesthetic hence used as posterior restorative material.
Easily condensable, finishable and polishable.