1. Amalgam Flashcards
History of Dental Amalgam
lDeveloped in France..1800s
lFirst used in US 1833 ____ worked on a balanced formulation of silver and tin in 1896
l1920s Specification #1 of the ADA a standard test for dental amalgam. Amalgam alloy must be mostly Ag and Sn (____% Ag, ____% Sn)
Flagg and Black
65
29
History contd.
lln 1940 s and 1950 s changes in the shape of the particles to increase early ____. Lathe-cut alloys become ____-lathe cut alloys. (No improvement clinically
ll____ particles were introduced ll1960 s high-copper amalgams
____ (1963)-Admix High-Copper
Tytin was developed by Kamal Asgar
Single composition; High ____; Spherical
strength micro spheical disperalloy copper
Mercury
lMercury toxicity is a concern in dentistry because of its harmful effects on the kidneys and the ____.
lIts greatest risk is to office staff from mercury ____. It evaporates at room temperature and the lungs absorb most of the vapor.
l Mercury toxicity is not a problem for patients. Dentists who urge patients to replace amalgam restorations to cure medical problems are not practicing ethical dentistry.
l Mercury in the environment is an important problem. The role dentistry plays in contamination is under
investigation.
CNS
vapor
What is Dental Amalgam?
l Amalgam is a mixture of ____, tin, ____ and sometimes zinc, or a small amount of other metals with mercury
l Is a ____ alloy
l There are 2 basic particle shapes, lathe cut and spherical used to make three types of alloys: lathe cut, spherical and admixed
silver
copper
metal
Classification of Amalgam Alloys
Based on Particle Shape
____ – Irregular particles from filing on a Lathe
____ – Spherical particles from atomizing molten metal
____ – Mixture of spherical and lathe-cut particles
Based on composition High- and Low-Copper Zinc and Non-Zinc
lathe-cute
spherical
admix
Particle Classification
In the admix you have spherical and rod shaped particles.
Referring to pics above:
A) ____-cut rod shaped particles
B) ____ particles seen in EM of tytin
C) ____ that you would typically see in a class 2 restoration because the rods here give good packing and condensation in box unlike the spherical shaped particles
lathe
spherical
dispersalloy
Amalgam Phases
lGamma—– g ____
lGamma 1—— g1 ____ lGamma 2 —– g2 ____ lEpisilon ——–e
lEta ——– h
lSilver Copper Eutectic
Ag3-Sn
Ag2-Hg3
Sn8-Hg
Low Copper Dental Amalgam
llBlack s composition ____% Ag, ____% Sn, less than ____% Cu, and sometimes ____% Zn
llStrictly ____
llCu and Ag- causes setting expansion, ____ strength and corrosion resistance
lSn causes setting contraction and ____ strength and corrosion resistance
llZn-____, makes amalgam less brittle
65 25 6 1 historical increases decreases doxidizer
Low Copper Amalgams Process
Setting reaction
llg+Hg = g+g1+g2 Precipitation of
gamma 1 and gamma 2 continues until the mercury is consumed.
llThe bulk of the finished restoration consists of the ____ surrounded by reaction products
llAmalgam with lower ____ generally has better properties
original alloy
Hg
High Copper Amalgam Process
llState of the art. Dominate the market because the clinical performance is superior to even the best low copper amalgams.
llPerformance improved by elimination of the weak ____. (g2=Sn8-Hg)
llStrength ____
llCorrosion ____
llMarginal breakdown, ____ creep
gamma 2 phase
increases
decreases
decreases
High Copper Amalgam Process
Admix
Ag3Sn( ) + Ag-Cu + Hg = Ag2Hg3 ( 1)
+ Cu6Sn5(η ) + Ag3Sn( ) +Ag-Cu
At least ____ Cu needed to eliminate 2
Single Composition
Ag-Sn-Cu + Hg =Ag2Hg3( 1) +Cu6Sn5(η ) +Ag3Sn( ) +Ag-Sn-Cu
12%
High Copper Amalgams
In Admixed (Disperalloy) the ____ Ag3Sn powder and the ____ Ag-Cu eutectic particles are mixed with mercury. When the amalgam sets, the Ag2Hg3 (____ phase) forms as it did when the low-copper containing amalgam also set. However, rather than forming the tin-mercury phase, the tin reacts with copper and form the Cu6Sn5 phase (the eta phase of the Cu-Sn phase diagram).
Some of the dental amalgam alloy particles remain partly ____ after the amalgam has set. These unreacted particle parts ____ the amalgam.
lathe-cut spherical gamma-1 unreacted strengthen
High Copper Amalgams
l Spherical: The spherical particles contain both Ag3Sn (the gamma phase of the silver-tin phase diagram) and Cu3Sn (____ phase of the copper-tin phase diagram) phases, and these particles are mixed with mercury. When the amalgam sets, the Ag2Hg3 (____ phase) forms as it did when the low-copper containing amalgam also set. Again, rather than forming the tin-mercury phase, the tin reacts with copper and form the Cu6Sn5 phase (the eta phase of the Cu-Sn phase diagram).
Some of the dental amalgam alloy particles remain partly unreacted after the amalgam has set. These unreacted particle parts ____ the amalgam.
epsilon
gamma-1
strengthen
High Copper Amalgams
Two Groups
1)Admix High-Copper Amalgam (Dispersalloy)
Lathe-cut: Ag=____%, Sn=____%,Cu=____%,Zn=____%, Hg=____% with
Spherical: Ag=____%, Cu= ____%
2)Spherical High-Copper Amalgams (Tytin)
Ag=____%, Sn=____%, Cu=____%, Zn=____%
66-73 25-29 0-5 0-1 0-3
72
28
40-60
22-30
13-30
0-1
Amalgam Properties §§ \_\_\_\_ §§ Creep §§ \_\_\_\_ §§ Dimensional Change §§ \_\_\_\_
strength
corrosion
working/setting times