REDM 102

Dental Amalgam

Amalgam is a safe, affordable, and durable material used predominantly to restore premolars and molars.

Although amalgam has been used in restorative dentistry for many years, you may see fewer amalgam restorations placed as a result of esthetic concerns of patients and the ongoing controversy about the safety of amalgam use for both the patient and staff.  

Even if you see a minimal number of amalgam restorations being newly placed, you will surely see numerous existing amalgam restorations that remain in good condition for many years after placement.

Example of a class II amalgam restoration.

This figure shows a lower right posterior arch isolated by means of a rubber dam (blue), a rubber dam clamp (metal ring), and rubber dam retainer (yellow plastic).

A class II restoration is one that includes both the necessary portion of the occlusal surface and the proximal surface abutting the adjacent tooth, in this case the mesial. 

 Ideally all teeth to be restored should be isolated with the use of a rubber dam in this manner. In reality, clinical circumstances do not always allow this.

Indications for using Amalgam

• In individuals of all ages 
• In stress-bearing areas of the mouth 
• When there is severe destruction of
  tooth structure 
• As a foundation for a crown
• When personal oral hygiene is poor 
• When moisture control is problematic 
• When cost is an overriding patient concern 

The most convincing indication for amalgam placement continues to be when restoring an area where blood and saliva contamination is extremely difficult, beneath the gingiva, or both or in a poorly accessible, nonaesthetic region of the mouth where composites are contraindicated.

Indications for not using Amalgam

• Esthetics is important.
• Patient has a history of allergy to mercury or other amalgam components.
• The cost of other restorative materials or treatment options is not a factor.

 A patient who present with an amalgam allergy should be questioned about the specific reaction and how the allergy was diagnosed.

 It is important to ask patients which type of restoration they prefer if choice is an option.

 If the patient opts for an unfavorable choice, the discussion should be documented. 

 Once a restoration has been placed in the mouth, the materials used and methods followed must be documented in the patient’s chart.

Composition of Amalgam

• Mercury (43%-54%)
• Alloy powder (57%-46%)
  • Silver, which gives the amalgam strength
  • Tin, for its workability and strength
  • Copper, for its strength and corrosion resistance
  • Zinc, to suppress oxidation     

The widely used Eames technique specifies a 1:1 ratio of mercury to alloy.  

 If you have the opportunity to work with amalgam, you may eventually be able to distinguish between brands because of how they feel when properly triturated and how workable they are during condensation and carving.

The mercury and alloy powder are in their purest form before trituration.
(From Hatrick CD, Eakle WS, Bird WF: Dental materials: clinical applications
for dental assistants and dental hygienists, St Louis, 2003, Saunders.)

This photo displays the mercury liquid and alloy powder, separated on the left, and at various stages of mixing to produce a final amalgam for placement.  

 It is important to ensure that trituration is complete before amalgam is placed in a carrier for placement in the preparation. Different manufacturers call for different trituration times, depending on the components of their products.

 Other variables to keep in mind: Triturating machines sometimes malfunction, and stocked amalgam capsules may reach their expiration dates before being used. 

Issues Concerning Amalgam

• Harm to patients: essentially harmless  
  • The exception is patients who
    have many amalgam restorations or
    a high sensitivity to metals. 
• Harm to dental personnel: health concerns with high exposure to mercury, not amalgam
  • Tremors
  • Kidney dysfunction 
  • Depression
  • Nervous system disorders 

It is important to stress to patients that once amalgam is set, the mercury content is inactive.

Until the amalgam is set, though, components of the composite are toxic to tissues. The public is not aware of this because the irritating components are not commonly used words. 

It may be more detrimental to remove more tooth by replacing a sound amalgam restoration than to leave it alone. The oral environment may be reexposed with removal.

Amalgam Hygiene Guidelines

• Do not allow mercury to come into contact with your skin. 
• Protect against spillage during trituration. 
• Keep the lid closed during trituration. 
• Do not discard scrap amalgam in waste containers. 
• Collect all scrap amalgam and store it under water or a photographic fixer solution in a closed container. 

It is very important to follow these guidelines for safe usage.

 Discard undermixed amalgam materials.

 The scrap-amalgam container should be disposed of properly, too.

Preparation of Amalgam

• Capsules 
  • 600 mg of alloy: for small or single-surface restorations
  • 800 mg of alloy: for larger restorations
• Activator: used to break the separating membrane in the capsule
• Trituration: the process by which the mercury and alloy are mixed together
  to form the mass of amalgam

Amalgam capsules come in different doses, so you should try to estimate what you need.

 Avoid triturating another dose of amalgam until the dentist is ready for it.

Direct Application of Amalgam

1. Mixed amalgam is placed in an amalgam well.
2. The amalgam is carried to the prepared tooth. 
3. The amalgam is placed in increments in the prepared tooth.
4. Each increment is condensed immediately.
5. Carvers are used to carve anatomy into
   the amalgam.
6. A burnisher is used to smooth the amalgam.
7. The new restoration’s occlusion is checked.

 If the restoration involves a proximal surface, a matrix band and wedge must be placed to reform the contour as necessary. The burnisher is used at this step to burnish the metal where contact will be reestablished with the adjacent tooth.

 Polishing of amalgams, if desired, is is done during a subsequent appointment with the use of a polishing cup and a slow-speed handpiece.