Dental amalgam is an alloy made by mixing mercury with a silver-tin dental amalgam alloy. It is classified based on its copper, particle shape, zinc, and alloy content. The main constituents are silver, tin, copper and sometimes zinc. Silver whitens the alloy and increases strength. Copper increases strength and resistance to corrosion and creep. Tin reduces strength and hardness and increases setting time. Zinc prevents oxidation and causes delayed expansion. The setting reaction involves the mercury combining with the alloy particles to form different phases. The gamma 1 phase is strong but brittle, while the gamma 2 phase is weakest and most prone to corrosion. Amalgam must be properly manipulated, either by hand or machine, to ensure it

1. DENTAL AMALGAM
Material aspect

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

8. COMPOSITION
Constituents Low copper
%
Admixed % Unicompositi
onal %
Silver 63-70 69 40-60
Tin 26-29 17 22-30
Copper 2-5 13 13-30
Zinc 0-2 1

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

11. SETTING REACTIONS
 Alloy particle + mercury = Amalgam+ non reacted particle

12. LOW COPPER AMALGAM
 Ag Sn + Hg = AgHg +SnHg + unreacted AgSn
1. AgSn >>> gamma phase
2. AgHg >>> gamma 1 phase
3. SnHg >>> gamma 2 phase

13. HIGH COPPER ADMIXED
 PHASE 1:
AgSn + AgCu + Hg = AgHg + SnHg + AgSn + AgCu
1. AgSn >>> gamma phase
2. AgHg >>> gamma 1 phase
3. SnHg >>> gamma 2 phase

14.  Phase 2
SnHg + AgCu =CuSn + AgHg +AgCu
1. SnHg >>> Gamma 2 phase
2. CuSn >>> Etta phase
3. AgHg >>> Gamma1 phase

15. HIGH COPPER
UNICOMPOSITIONAL
ALLOYS
 AgCuSn +Hg = AgHg +CuSn +unreacted AgCuSn
1. AgHg >>> Gamma 1 phase
2. CuSn >>> Etta phase

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 )

19. TYPES OF MIXES
 NORMAL MIX
Warm
Homogenous
Shiny in appearance

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

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.

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