Proper for familizing with Dental Amalgam. Proper for Dental Students/GPs. Based on Chapter 10 of Craig's restorative materials reference. Provided in Shiraz University of Medical Sciences, Shiraz, Iran.

1. DENTAL AMALGAM
School of Dentistry, Shiraz university of Medical Sciences, Shiraz, Iran
Chapter 10, 13th edition, Craig’s Restorative Materials
Kazeroonizadeh M
Keshavarz MR
Zarei S
Ansarifar S
Rajabi F
Amirkhani N
Rahmanian H

2. TERMINOLOGY AND COMPOSITION
Amalgam
Dental Amalgam
Liquid Mercury + Amalgam alloy
Amalgam Alloy
Must contain Ag & Sn
Rather More Cu
Rather Less Zn, Au, Pt, Pd, In, Hg
The Important Point !

3. COMMONLY USED
Direct, Permanent, Posterior Restorations
Large Foundation Restorations
As core

4. AMALGAM PLASTICITY
To be packed/condensed
To be carved
Hardens after a while

5. ADVANTAGES
Easy to insert/Not technique sensitive
Anatomical form
Fracture Resistant
No Marginal Leakage
Stress-bearing areas !
Long service life

6. DISADVANTAGES
Silver color and aesthetic
Corrosion/Galvanic reaction
Brittle
Marginal Fracture
Doesn’t keep retaining weakened tooth structure
Environmental concerns

7. THUS
Cost benefit and successful restorative material BUT
Cast gold & resin based composites & ceramics are
good competitors

8. CLASSIFICATION
Based on Zinc:
Zinc Containing Alloys :Zn > 0.01%
Zin non-containing alloys : Zn < 0.01%
small amount of zinc in high-copper reduces brittleness
Based on Copper:
Low copper : Cu < 5%
High copper: Cu 6-30%
high early strength, low creep, good corrosion resistance,
marginal fracture resistance

9. CLASSIFICATION
Based on Particles’ Shape:
Irregular(Lathe-cut)
Spherical
Admixed

10. CHARACTERISTIC
Alloy composition
Particle Size & Shape & Distribution

11. AMALGAMATION
(TRITURATION)
Low copper:
One-step:
Y(Ag3 Sn) + Hg -> Y1(Ag2 Hg3) + Y2 (Sn7-8 Hg)+ unreacted Y(Ag3 Sn)
High copper:
Multi-step:
Y(Ag3 Sn) + Ag-Cu(eutectic) + Hg -> Y1(Ag2 Hg3) +Y2(Sn7-8Hg)+unreacted Y(Ag3
Sn)+unreacted Ag-Cu(eutectic)
Y2(Sn7-8Hg) + Ag-Cu (eutectic) -> (Cu65n5) + Y1(Ag2Hg3)+unreacted Ag-Cu (eutectic)

12. MERCURY REACTION
During Trituration
In every mg of Copper, 1 mg of Hg dissolves
In every mg of Silver, 10 mg of Hg dissolves
In every mg of Tin, 170mg of Hg Dissolves

13. SOME MISSED POINTS
Amalgam manipulation: Mercury 43-54% (almost 1:1)
90% of current dental amalgams are high copper
More spherical and admixed Types, Less Irregular ones

14. A MINUTE
‫واژه‬ ‫دروازه‬
‫ها‬

15. AMALGAM PROPERTIES
Compressive Strength
After 1h:80MPa After 24h: 300MPa
Dimensional Change
Less than -15 to 20µm/cm
Creep
Must be less than1% in first 4hours
Corrosion Resistance

16. AMALGAM PROPERTIES
Compressive Strength
Dimensional Change
Creep
Corrosion Resistance

17. COMPRESSIVE STRENGTH
Good @ Compressive Strength
Weak @ Tensile, Shear Strength
THUS cavity design : Maximize compression & Minimize Tensile, Shear
ATTENTION : Rapid application of stress makes visco-elastics such as
amalgam function as a brittle material : Fracture

18. AMALGAM PROPERTIES
Compressive Strength
Dimensional Change
Creep
Corrosion Resistance

19. DIMENSIONAL CHANGE(DC)
First 20 mins : expansion, remaining for 8 hours
Final Values after 24 hours
Lowest : High copper admixed alloys -1.9µm/cm
Largest DC: Low copper lathe-cut alloys -19.7µm/cm
Post operative sensitivity
Disadvantages Amalgam doesn’t adhere to tooth
Negative DC ->pulpal fluid -> pressure sense change
Spherical high copper admixed

20. AMALGAM PROPERTIES
Compressive Strength
Dimensional Change
Creep
Corrosion Resistance

21. CREEP
Permanent change in length in 1-4 first hours
Lowest value : High copper Spherical 0.09%
Highest value : Low copper Lathe-out 6.3%
Reminder: Spherical Advantage= creep
Spherical Disadvantage= Sensitivity
Y2 Amalgams = more creep = prone to marginal fracture

22. AMALGAM PROPERTIES
Compressive Strength
Dimensional Change
Creep
Corrosion Resistance

23. CORROSION
Electrochemical Destruction of metal near the environment
Disadvantages: increase porosity, Loss of strength, Metal release
Y2 (Sn7-8 Hg) is the most corrodible, Y1(Ag2 Hg3) has the highest resistance

24. AMALGAM PROPERTIES
Compressive Strength
Dimensional Change
Creep
Corrosion Resistance

25. AMALGAM MIXING
(TRITURATION)
Low Copper requires Low speed (3200-3400 cycles/min @ Amalgamator)
High Copper requires High Speed (4000-4400 cycles/min @ Amalgamator)
According to the manufacturers recommendation(Instructions attached to the
products)
Normal mixed: Shiny & Single mass
Undermixed: Dull & Crumbly
Overmixed: Soupy & Sticky

26. OVERTRITURATION
Soupy & Sticky & Hot mass
Working Time decreases
Creep increases
Compressive/Tensile Strength of Irregular ones Increases
Compressive/Tensile Strength of Spherical/Admixed ones decreases

27. UNDERTRITURATION
Dull & Crumbly
Working Time Increases
Decrease Creep
Decrease Strength
Poor Corrosion Resistance

28. AMALGAMATOR MACHINE

29. AMALGAM MERCURY LIQUID IN MARKET OF IRAN

30. DENTAL AMALGAM ALLOYS IN MARKET OF IRAN

31. THANK YOU FOR YOU ATTENTION
Any Question ?