Is dental amalgam safe when it rests against another metal (e.g. braces) in the mouth?
It should be noted that Health Canada has taken the position that “new amalgam fillings should not be placed in contact with existing metal devices in the mouth, such as braces.” Health Canada’s concern is related to galvanic effect, which occurs when two different metals are in close proximity and create the potential for electric current to be generated.
Dentists are aware of the possibility of abutting metals creating a galvanic effect. It is also recognized that galvanic effect, through corrosion of metallic dental materials, may increase the release of mercury and other elements or compounds. Some recent evidence suggests that galvanic effect may also slightly increase the release of mercury vapour from amalgam.
For all these reasons, it is prudent for dentists, in suggesting a restorative material, to avoid creating a galvanic effect whenever patient care will not be compromised. It is also inadvisable to remove existing fillings unless the patient complains of symptoms which may be attributed to galvanic effect.
At the same time, the placement of orthodontic braces on patients with amalgam is often necessary and desirable, and has not been shown to be associated with ill effects. It may also be necessary, for the purpose of adequate restorative treatment, to place restorations in close proximity and to create the potential for galvanic effect.
CDA’s Committee on Clinical and Scientific Affairs notes, however, that when amalgam has been in the mouth for a small a period of time, oxidation (corrosion), through a complex process, contributes to the reduction of electrical flow. Galvanic effect, apart from its potential to contribute to heavy metal body burden, has not been demonstrated to be harmful, and concerns about galvanic effect must be considered in the context of the patient’s overall oral health care needs.
CDA has asked Health Canada for an annotated scientific bibliography supporting its unconditional recommendation on galvanic effect. If this information is received, it will be reviewed immediately and, if necessary, further advisories will be sent out to the profession and made available to patients.