Dental Amalgam

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Types of Amalgam Alloys

1.Based on copper content

A.Low copper alloys

B.High copper alloys

i.Admixed

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ii.Single composition

2.Based on zinc content

A.Zinc containing alloys

B.Zinc free alloys

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3.Based on shape of the alloy particle

A.Lathe cut alloys

B.Sperical alloys

C.Speroidal alloys

4.Based on number of alloyed metals

A.Binary alloys

B.Ternary alloys

C.Quaternary alloys

5.Based on size of alloy

A.Microcut alloy

B.Macrocut alloy

PROPERTIES OF AMALGAM

1.Microleakage

  • Dental amalgam has tendency to minimize marginal leakage
  • It is a self sealing material
Microleakage

2.Dimensional change

  • Amalgam may expand or contract, depending on its manipulation.Ideally, dimensional change should be small

3.Strength

  • Hardened amalgams have good compressive strength

Tensile strength

  • Amalgam cannot withstand high tensile or bending stresses
  • The cavity design should be such that the restoration will receive compression forces and minimize tension or shear forces in service
  • The tensile strengthis 48-70 MPa

4.Creep

  • Creep is defined as a time dependent plastic deformation

5.Retention of amalgam

Retention form
  • Amalgam does not adhere to tooth structure
  • Rather retention of the amalgam filling is obtained through mechanical locking.This is achieved through proper cavity design

6.Tarnish & Corrosion

  • Amalgam restorations often tarnish & corrode in the mouth
Tarnish & Corrosion

MDS ENTRANCE QUESTIONS

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1.Which among the following is a surface phenomenon ?

A.Tarnish

B.Corrosion

C.Both A and B

D.None of the above

2.Does amalgam adhere to tooth structure ?

A.Yes, it forms bonding with the tooth

B.Do not adhere to tooth structure, even on cavity proper cavity design

C.May or may not adhere to tooth structure, depending on the type of amalgam

D.Adheres to tooth, only on proper cavity design

3.The tensile strength of amalgam is ?

A.56-82 MPa

B.64-94 MPa

C.48-70 MPa

D.30-76 MPa

4.Zinc containing amalgam, consist zinc

A.>0.01%

B.>0.1%

C.>0.04%

D.None of the above

1.A 2.D 3.C 4.A

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