Indications for Use and Hazards of Dental Amalgam

Question 1

History of dental amalgam

Answer 1

7th century paste used in China
1800s in Europe
1830s introduced to North America from France
1970s high-Cu alloys developed

Question 2

Composition of dental amalgam

Answer 2

Hg
Alloy:
-low copper: 70% silver, 25% tin, 4% copper, other traces
-high copper: 50% silver, 25% tin, 30% copper, other traces
These react to form ‘amalgam’

Question 3

Useful properties of amalgam

Answer 3

• good compressive strength
• good balance of working & setting times
• fair resistance to marginal leakage
• minimal dimensional change on setting
• relatively resistant to contamination
• nearly 200 years of scientific development
• low cost

Question 4

Limitations of amalgam

Answer 4

• not adhesive to tooth
• brittle in thin sections
• alloy/ Hg proportions critical
• detectable levels of creep
• corrosion can weaken
• affected by water during setting reaction
• toxic components
• unaesthetic
• not minimally invasive
• costly

Question 5

Indications for use of amalgam

Answer 5

• Posterior teeth
• When too late for prevention
• When adhesive restoration not indicated (occlusal load/ too big/ isolation from moiture)

Question 6

Cavity design for amalgam was created by

Answer 6

Developed from work by G.V Black in 1897

Question 7

How are amalgam restorations retained?

Answer 7

Mechanical ‘lock’ of restoration

• undercuts (can e subtle)
• occlusal lock

Question 8

How do amalgam restorations resist occlusal forces?

Answer 8

• at least 2mm thick
• no feather edges (cavosurface angle)
• consider effects of creep: floor perp. to occlusal forces
• smooth internal angles

Question 9

Hazards of mercury

Answer 9

• Neurotoxic
• Adversely affects renal function
• Cumulative in body & environment

Question 10

Hazards of alloy components

Answer 10

Tin and silver compounds considered hazardous to environment

Question 11

What was the phase-down of amalgam mostly driven by?

Answer 11

Environmental concerns e.g. 1997 use dicouraged in Sweden

Question 12

When is the European phase down of amalgam to be completed by?

Answer 12

2030 (agreed at Minamata Convention in 2013)
2000 amalgam free dental schools in Holland
2008 banned in Sweden, Denmark, Norway

Question 13

Risk management for amalgam

Answer 13

• PPE
• avoid in pregnancy
• Use capsules (< exposure, optimises trituration)
• aspiratory and isolation
• proper disposal

Question 14

Isolating the cavity

Answer 14

Free of debris
Dry but not dessicated
Isolated to maintain dryness througout procedure

Question 15

Triturate amalgam

Answer 15

Capsule
‘Amalgamator’
Use trays

Question 16

Place and condense amalgam

Answer 16

Amalgam carrier (clean & functional)
Condensers/ pluggers (appropriate p and size)
-add layers
-press all parts together
-above cavity margin (remove Hg-rich layer)

Question 17

Burnishing

Answer 17

Pear-ended/ Ladmore burnisher

• Initiates fissures
• Condenses margins

Question 18

Carving

Answer 18

During plastic phase, removes Hg-rich layer

-develops anatomy (occlusion, food shedding, resists corrosion)

Question 19

Finishing

Answer 19

Adjust occlusion & morphology
Reduces corrosion
Aesthetics
Wait 24 hours

Question 20

Stages of amalgam application

Answer 20

Isolate cavity
Triturate amalgam
Place
Condense
Burnish
Carve
Finish

Question 21

Should we use amalgam for majority of restorations?

Answer 21

No, composite