Dental Amalgam Alloy Powder At Dentalkart

Dental Amalgam Alloy Powder At Dentalkart

Classify silver alloys. (June 2014, 5 Marks)
Or
Write a short note on the classification of silver amalgam.
Answer:

The following are the classifications for silver amalgam:

Classification of Dental Amalgam (Adapted from Marzouk, 1997)

Amalgam alloy can be classified as

• According to the content
• Copper amalgam
• Silver amalgam
• Preamalgamated alloys
• Amalgam with noble metals

According to the number of alloy metals

• Binary alloys (silver–tin)
• Ternary alloys (silver–tin–copper)
• Quaternary alloys (silver—tin—copper—indium)

According to whether the powder consists of unmixed or admixed alloys

• Admixed/dispersion or blended alloys
• Single compositional/uni-compositional alloys

According to the shape of the powdered particles

• Spherical shape (smooth-surfaced spheres)
• Lathe—cut (irregular, ranging from spindles to shavings)
• Combination of spherical and lathe-cut (admixed)

According to the powder’s particle size:

• Microcut
• Finecut
• Coarsecut

According to the copper content of powder:

• Low-copper content alloy: Less than 6%
• High-copper content alloy: 6% to 30%

According to the addition of noble metals:

• Platinum
• Gold
• Palladium

 According to the presence of zinc:

• Zinc containing (more than 0.01%)
• Non-zinc-containing (less than 0.01%)

Additional classification based on the generations of amalgam

•  The first-generation amalgam was that of GV Black, i.e. three parts silver and one part tin (peritectic alloy)
•  Second-generation amalgam alloys: Three parts silver, one part tin, 4% copper to decrease the plasticity and to increase the hardness and strength, and 1% zinc which acts as an oxygen scavenger and decreases brittleness
• Third-generation: First-generation + spherical amalgam— copper eutectic alloy
• Fourth-generation: Adding copper up to 29% to original silver and tin powder to form ternary alloy so that tin is bound to copper
• Fifth-generation: Quaternary alloy, i.e. silver, tin, copper, and indium
•  Sixth-generation consists of a eutectic alloy containing silver (62%), copper (28%), and palladium (10%) which is lathe-cut and blended into the first-, second-, or third-generation amalgam in the ratio of 1:2.