dental amalgam

Question 1

metals that are a combination of several elements

Answer 1

ALLOYS

Question 2

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

Answer 2

AMALGAM

Question 3

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

Answer 3

AMALGAMATION

Question 4

Applications

Answer 4

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.

Question 5

CLASSIFICATION OF AMALGAM ALLOYS

Answer 5

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

Question 6

• 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

Answer 6

Silver

Question 7

• 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.

Answer 7

Tin

Question 8

• Increases hardness and strength.
• Increases setting expansion.

Answer 8

Copper

Question 9

• 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.

Answer 9

Zinc

Question 10

• Hardens the alloy and increases resistance to corrosion.

Answer 10

Platinum

Question 11

• Hardens and whitens the alloy.

Answer 11

Palladium

Question 12

• 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

Answer 12

Indium

Question 13

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

Answer 13

Mercury

Question 14

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

Answer 14

Self sealing

Question 15

• Net contraction or expansion of an amalgam during setting

Answer 15

DIMENSIONAL CHANGE

Question 16

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

Answer 16

STRENGTH

Question 17

• 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

Answer 17

CREEP

Question 18

 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

Answer 18

Tarnish

Question 19

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

Answer 19

Corrosion

Question 20

• 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)

Answer 20

CAVITY DESIGN

Question 21

• 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

Answer 21

FOUR WALL SUPPORT

Question 22

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

Answer 22

PREVENTING TENSILE FRACTURE

Question 23

• 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.

Answer 23

Cavosurface angle

Question 24

MANIPULATION

Answer 24

1. Trituration
2. Mulling
3. Condensation
4. Shaping and finishing

Question 25

* The objective of __ is to wet all the surfaces of the alloy particles with mercury. * it is achieved by: (2)

Answer 25

TRITURATION * Manually by hand * Mechanical mixing

Question 26

three factors to obtain a well mixed amalgam mass are:

Answer 26

* 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

Question 27

MERCURY: ALLOY RATIO (PROPORTIONING)

Answer 27

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

Question 28

Advantages of mechanical trituration: (3)

Answer 28

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

Question 29

 Dull, crumbly appearance  Poor compressive and tensile strength

Answer 29

 Under trituration

Question 30

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

Answer 30

 Over trituration

Question 31

shiny but offers resistance to condensation

Answer 31

 Properly triturated

Question 32

removes excess mercury using squeeze cloth

Answer 32

“Wringing out”

Question 33

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

Answer 33

MULLING

Question 34

 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

Answer 34

Transfer and Condensation

Question 35

 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

Answer 35

CARVING

Question 36

After the carving, the restoration is smoothened

Answer 36

BURNISHING

Question 37

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

Answer 37

POLISHING

Question 38

ADVANTAGES OF AMALGAM RESTORATIONS

Answer 38

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.