Flashcards in 1. Amalgam Deck (37):
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
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
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
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
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
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
lGamma----- g ____
lGamma 1------ g1 ____ lGamma 2 ----- g2 ____ lEpisilon --------e
lEta -------- h
lSilver Copper Eutectic
Low Copper Dental Amalgam
llBlack s composition ____% Ag, ____% Sn, less than ____% Cu, and sometimes ____% Zn
llCu and Ag- causes setting expansion, ____ strength and corrosion resistance
lSn causes setting contraction and ____ strength and corrosion resistance
llZn-____, makes amalgam less brittle
Low Copper Amalgams Process
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
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)
llMarginal breakdown, ____ creep
gamma 2 phase
High Copper Amalgam Process
Ag3Sn( ) + Ag-Cu + Hg = Ag2Hg3 ( 1)
+ Cu6Sn5(η ) + Ag3Sn( ) +Ag-Cu
At least ____ Cu needed to eliminate 2
Ag-Sn-Cu + Hg =Ag2Hg3( 1) +Cu6Sn5(η ) +Ag3Sn( ) +Ag-Sn-Cu
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.
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.
High Copper Amalgams
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=____%
§§ Dimensional Change
lADA SPECIFICATION NO. 1
- helps control the qualities of dental
- three physical properties used as a measure
b) ____ (1 hr.-80 MPa)
lIdeally amalgam should be ____
lNo Severe ____...
lNo Excessive expansion... lGood ____ ratio
lIncreased condensation pressure favors ____
AMALGAM PROPERTIES Dimensional Change
llInitial contraction – first 20 mins related to the solubility of ____ and ____ particles
llThen ____ – the reaction of Hg with Ag and Sn
ll6-8 hrs ____
ll24 hrs ____
llContamination of Zn containing alloys with H2O results in excessive ____ dimensional change
llADA --- + or – 20 microns/cm
A is ____, b is ____ and C is ____ amlagam.
Seeing the initial contractions that happens with the low copper amalgams. Has to do with the ____ phase. The low copper amalgam use alot more mercury
In A can see initial contraction but as u condense and remove excess amalgam then u have expansion which cancels each other out - resulting in a ____ amalgam restoration.
AMALGAM PROPERTIES Compressive Strength
- resistance to compressive forces
- dependent on ____ design
l Variables affecting strength
Hg content -weakens
l High Copper 1hr – 250 MPa
l Lathe Cut 1hr 45 MPa
l Low Copper 1hr – 88MPa
l ADA 80MPa (11000psi)
l Needs support of tooth structure because tensile and shear strengths are low
llHigh Cu vs. Low Cu Amalgams.
Mercury ____ is very important.
If Hg ____ increases more than ____, strength decreases.
AMALGAM PROPERTIES Tensile strength
llThe high early ____ strengths of the high copper unicompositional alloys resist fracture by premature biting stresses
llCavity designed to reduce ____ stresses
llOver- and under- triturating decrease ____ of spherical alloys
1) The amalgam was not ____ properly.
2) the dovetail is fairly large, the isthmus is narrow and the box is fairly large so you have a narrow ____ supporting a large bulk of amalgam.
3) If the axial pulpal line angle was left very ____
4) Not condensed properly, so when patient tried to function on marginal ridge, stresses occured.
lTime dependent deformation of a material under a ____ load or stress
In pic 1 you see that its burnished very well and margins are sealed. Then patient comes back and in pic 2 u see that amalgam is extruding from the restoration.
This suggests that there was ____ contamination when the amalgam was being condensed.
Contamination is not as severe if occurs during burnishing or carving as it is when u r condensing.
This is a ____ restoration and it is very hard to prevent the moisture from the gingival sulcus to coming in contact with the restoration, most of the time u see creep or an extrusion from the restoration its usually in the class 5.
Its even worse if you try to place a ____ in a wet environment. Placing the amalgam is less technique sensitive, it is important to keep it dry, but it is very technique sensitive if you want to place a composite
TARNISH AND CORROSION
llAmalgam corrodes in much the same way that ____ rusts. Reaction with environment.
llTarnish – the formation of surface ____ or loss of ____
Low Cu amalgams
Sn7Hg + 1/2O2 + H2O + Cl- = ____ + Hg
High Cu Amalgams
Cu6Sn5 + 1/2O2 + H2O + Cl- = ____ + SnO
llCorrosion process can liberate free ____ which can contaminate and ____ gold restoration
There is a hare and a tortoise button in the preclinical lab - goes on about the hare and tortoise story. Hare is the fast one.
The high copper amalgams need to have ____ speed triturations so you would press the hare button
These can also be used to mix ____ not just amalgam. The speeds are different depending on the type of cement u are mixing
Should be familiar with the different types of capsules. 1 is ____ and 2 is ____.
If you under triturate you get a very ____ mix as seen in pic labelled a) on previous slide. You cant pick it up with amalgam carrier. And by the time u get it into the prep and start condensing it will be very dry and they layers wont stick to each other.
Pic labelled b) is an ____ mix
Pic labelled c) is ____. This also weakens the strength. It looks falt , shiny instead of solid round.
lIncreased triturating time and/or speed ____ the working and setting times.
lHigh copper alloys require ____ speed triturating
lOver- and under- triturating reduces ____ and ____ and increases ____
- Select almagam based on ____ time, particle size and shape, composition, and the presence or absence of ____.
l Large restorations....
- Capsule - 400, 600, 800mg of alloy color coded. If large amounts are required several ____ mixes are recommended.
l “a ____ setting amalgam, used by a slow condensing dentist, can result in a ____ amalgam”
The amount of Hg that remains in the restoration influences ____, creep, and ____ strength.
Moisture contamination during mixing and condensation may produce excessive ____ (Zn alloys)
l Condensation pressure influences the amount of ____
l Size of ____ and direction and magnitude of force
lAmalgam should be condensed promptly
Condensation of a
partially set amalgam breaks up the ____ already formed.
lWith the development of adhesive bonding systems attempts were made to bond amalgam to tooth structure. Adhesive monomers containing ____ are most successful ;
Amalgam to dentin – ____ MPa Composite to Dentin – ____ MPa
4_META (4-methacryloxyethyl trimellitic anhydride)
lIncreased fracture resistance (2x) – dependent on ____ of restoration
lDecreased ____ in Class V restorations compared to not bonding
lThe amalgam restoration is unique in that ____ decreases as the restoration ages. This is due to corrosion products that form between the tooth and the restoration
Uses of Dental Amalgam
ll____ direct restorations
ll____ treatment following an apicoectomy