Amalgam

Question 1

What is the composition of amalgam?

Answer 1

• mercury, silver, tin, copper, zinc
  High copper alloy eliminates gamma 2 phase (SnHg) - weakest, resulting in lower creep values so amalgam less prone to ditching

Question 2

Why do we use amalgam?

Answer 2

• inexpensive
• ease of use
• proven track record >100 years of use
• familiarity
• resin free - less allergies than composite

Question 3

What types of amalgam are there?

Answer 3

• lathe-cut alloys: small condensers, high force
• spherical alloys: large condensers, less sensitive to force
• admixture alloys: intermediate handling

Question 4

Why would you bond amalgam?

Answer 4

• when there is not enough tooth substance to allow for the retention of the amalgam
• to achieve a complete marginal seal - prevents ingress of bacteria, protecting the pulp
• reduced need for retentive features
• no need to use pins
• reduced marginal leakage and postoperative sensitivity
• reinforcement of tooth structure

Question 5

What is the technique of bonded amalgam?

Answer 5

• acid etch margins
• apply prime and bond
• place rely-x-arc or smartcem and leave uncured (chemical cure)
• condense amalgam, carve, etc

Question 6

What are the side effects of amalgam?

Answer 6

Toxicity: mainly from mercury (Hg)
Allergy: to any component - amalgam allergy may result in contact dermatitis, oral lichen planus etc
Theoretical risk of foetal damage as Hg can cross the placenta

Question 7

What are some safety precautions when handling amalgam?

Answer 7

• all amalgam must be encapsulated (Minimata July 2018)
• appropriate storage of waste amalgam
• waste collected by approved contractor
• well ventilated surgery
• aspiration, venting externally with Hg removal filter

Question 8

What are some symptoms of mercury poisoning?

Answer 8

• headaches, GI upset, dyspepsia, tremors, salivation/xerostomia, severe gingivitis, fatigue, irritability, oedema of face and ankles, character changes
  There is NO cure!

Question 9

What is the Minimata Treaty?

Answer 9

July 2018 - to reduce environmental pollution of mercury from amalgam - not to reduce risk to patients or dental staff
- no longer use amalgam in pregnant or breastfeeding women
- no longer used in primary teeth
- no longer used on children under 15 years
Only exceptions are when clinicians deems amalgam the only appropriate material