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dental materials > dental amalgam > Flashcards

dental amalgam Flashcards

1
Q

metals that are a combination of several elements

A

ALLOYS

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2
Q

special type of alloy in which mercury is one of the components.

A

AMALGAM

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3
Q

The process of mixing liquid mercury with one or more metals or alloys to form an amalgam.

A

AMALGAMATION

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4
Q

Applications

A
  1. As a permanent filling material for
    —Class I and class II cavities, and
    —Class V cavities where esthetics is not important.
  2. In combination with retentive pins to restore a crown
  3. In retrograde root canal fillings
  4. As a core material.
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5
Q

CLASSIFICATION OF AMALGAM ALLOYS

A

BASED ON COPPER CONTENT
* Low copper alloy
* High copper alloys
BASED ON ZINC CONTENT
* Zinc-containing alloys
* Zinc-free alloys
BASED ON SHAPE OF THE ALLOY PARTICLE
Lathe cut alloys
Spherical alloys
Admixed

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6
Q
  • Major element in the reaction.
  • Whitens the alloy
  • Decreases the creep.
  • Increases the strength.
  • Increases the expansion on setting.
  • Increases tarnish resistance in the resulting amalgam
A

Silver

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7
Q
  • controls the reaction between silver and mercury. Without ___ the reaction would be too fast and the setting expansion would be unacceptable.
  • Reduces strength and hardness.
  • Reduces the resistance to tarnish and corrosion, hence the tin content should be controlled.
A

Tin

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8
Q
  • Increases hardness and strength.
  • Increases setting expansion.
A

Copper

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9
Q
  • In small amounts, it does not influence the setting reaction or properties of amalgam.
  • acts as a scavenger or deoxidizer during manufacture, thus prevents the oxidation of important elements like silver, copper or tin.
  • causes delayed expansion if the amalgam mix is contaminated with moisture during manipulation.
A

Zinc

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10
Q
  • Hardens the alloy and increases resistance to corrosion.
A

Platinum

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11
Q
  • Hardens and whitens the alloy.
A

Palladium

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12
Q
  • when added to the mercury reduces mercury vapor and improves wetting. __ can also added to the powder. Though it reduces early strength it increases the final strength. It reduces creep
A

Indium

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13
Q

 Only metallic element that is a liquid at room temperature
 __ + alloy = putty-like mass

A

Mercury

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14
Q

small amount of leakage under amalgam restorations seal the interface and reduce leakage. Leakage decreases as the restoration ages in the mouth.

A

Self sealing

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15
Q
  • Net contraction or expansion of an amalgam during setting
A

DIMENSIONAL CHANGE

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16
Q
  • Well designed amalgam restorations have sufficient compressive strength to withstand normal intraoral masticatory forces.
A

STRENGTH

17
Q
  • It is a slow progressive permanent deformation of set amalgam which occurs under constant stress (static creep) or intermittent stress (dynamic creep).
  • related to marginal breakdown of low-copper amalgams
A

CREEP

18
Q

 Surface phenomenon that can result in discolored restoration
 the result of silver sulfide forming on the surface and does not affect or change the mechanical properties of the amalgam

A

Tarnish

19
Q

 Results from chemical reactions that penetrate into the body of amalgam
 Eventually leads to failure of restoration

A

Corrosion

20
Q
  • Retention - amalgam does not adhere to tooth
    structure, cavity preparation is designed to provide
    maximum mechanical locking of the amalgam
  • walls diverge towards the floor of the cavity (or
    converge towards the mouth of the cavity)
A

CAVITY DESIGN

21
Q
  • For effective condensation, the cavity should have four walls and a floor. If one or more of the walls of the cavity is absent, a stainless steel matrix can compensate for the missing walls
A

FOUR WALL SUPPORT

22
Q
  • the cavity should have sufficient depth and width in order to provide sufficient bulk to the amalgam, especially those in high stress areas.
A

PREVENTING TENSILE FRACTURE

23
Q
  • The junction of the cavity with the external surface should be as close to a right angles as possible. Beveling is not indicated for amalgam as it can cause fracture of the amalgam at the margins.
A

Cavosurface angle

24
Q

MANIPULATION

A
  1. Trituration
  2. Mulling
  3. Condensation
  4. Shaping and finishing
25
Q
  • The objective of __ is to wet all the surfaces of the alloy particles with mercury.
  • it is achieved by: (2)
A

TRITURATION
* Manually by hand
* Mechanical mixing

26
Q

three factors to obtain a well mixed amalgam
mass are:

A
  • The number of rotations
  • The speed of rotation
  • The magnitude of pressure placed on the pestle. Typically a 25 to 45 second period is sufficient
27
Q

MERCURY: ALLOY RATIO (PROPORTIONING)

A

Eames Technique / minimal mercury technique
* Mercury/alloy 1:1

28
Q

Advantages of mechanical trituration: (3)

A

1.Shorter mixing time.
2.More standardized procedure.
3.Requires less mercury when compared to hand mixing technique.

29
Q

 Dull, crumbly appearance
 Poor compressive and tensile strength

A

 Under trituration

30
Q

 Soupy and adheres to the inside of the capsule
 Poor strength, creep and corrosion properties

A

 Over trituration

31
Q

shiny but offers resistance to condensation

A

 Properly triturated

32
Q

removes excess mercury using squeeze cloth

A

“Wringing out”

33
Q

actually a continuation of trituration. It is done to improve the homogeneity of the mass and get a single consistent mix.

A

MULLING

34
Q

 Goal: produce a mass without voids that adapts
closely to the cavity walls and margins
 30-40 N of force
 Delayed condensation - ↓ strength and ↑ creep

A

Transfer and Condensation

35
Q

 to reproduce the tooth anatomy. It should not be started until the amalgam is hard enough to offer resistance to the carving instrument.
 A scraping or ringing sound should be heard
carved.
 2 – 3 minutes after mixing

A

CARVING

36
Q

After the carving, the restoration is
smoothened

A

BURNISHING

37
Q

minimizes corrosion and prevents adherence of plaque. It should be delayed for at least 24 hours to ensure complete hardening of the filling.

A

POLISHING

38
Q

ADVANTAGES OF AMALGAM RESTORATIONS

A
  1. Reasonably easy to insert.
  2. Not overly technique sensitive.
  3. Maintains anatomic form well.
  4. Has adequate resistance to fracture.
  5. After a period of time prevents marginal leakage.

dental materials (7 decks)

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