What is the composition of amalgam?
- 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
Why do we use amalgam?
- inexpensive
- ease of use
- proven track record >100 years of use
- familiarity
- resin free - less allergies than composite
What types of amalgam are there?
- lathe-cut alloys: small condensers, high force
- spherical alloys: large condensers, less sensitive to force
- admixture alloys: intermediate handling
Why would you bond amalgam?
- 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
What is the technique of bonded amalgam?
- acid etch margins
- apply prime and bond
- place rely-x-arc or smartcem and leave uncured (chemical cure)
- condense amalgam, carve, etc
What are the side effects of amalgam?
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
What are some safety precautions when handling amalgam?
- 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
What are some symptoms of mercury poisoning?
- headaches, GI upset, dyspepsia, tremors, salivation/xerostomia, severe gingivitis, fatigue, irritability, oedema of face and ankles, character changes
There is NO cure!
What is the Minimata Treaty?
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
