Dental amalgam fillings are the most versatile dental restorative material. Approximately 75% of restorations are done by dental amalgam worldwide. It is the most economical dental restoration and hence in use for more than 165 years. It is a reliable long-term restoration in load-bearing areas and has low technique sensitivity, self-sealing property, and longevity.
The mercury component in amalgam, however, makes it a concern for patients. People with multiple amalgam fillings can have mercury leeching through saliva, which can easily enter the digestive tract.
The mercury fumes can be inhaled and absorbed by the lungs. FDA has approved the use of amalgam restoration for adults and children above the age of 6. But do weigh the effects of this restoration before getting one (1).
What is dental amalgam?
The composition of the currently used alloy is silver 40–70%, Tin 12–30% and copper 12–24%. It may also include zinc up to 1%, indium 0–4%, palladium 0.5%.
Zinc prevents the oxidation of other metals in the amalgam alloy and also inhibits corrosion. Researchers believe that if zinc containing amalgam is contaminated with moisture, it causes delayed expansion.
Indium containing admixed high-copper amalgam exhibited a reduction in creep and increase in strength. Less mercury is required for mixing amalgam when it contains indium in concentration up to 10%.
The reason for lower mercury emission is that amalgam prepared with indium rapidly forms indium oxide and tin oxide films which reduce mercury release (2). Palladium reduces tarnish and corrosion.
Pros and cons of dental amalgam restoration
Dental amalgam may not be the first preference of dentists. But its cost, durability, and ease of manipulation still make it an essential dental office material.
Where there is a loss of tooth structure, where the restoration must give support to the tooth, extensive restorations of amalgam may be the choice. However, the versatile restoration comes with some pros and cons.
- Good long-term clinical performance
- Least technique sensitive of all restorative materials (3)
- Ease of manipulation by a dentist
- Greater long-term resistance to surface corrosion
- Minimal placement time compared to other materials
- Initially, corrosion products seal the tooth-restoration interface and prevent bacterial leakage
- One appointment placement
- Long lasting if placed under ideal conditions
- Often can be repaired
- Destruction of sound tooth tissue
- Poor esthetic qualities
- Long-term corrosion of the restoration interface may result in ditching leading to replacement
- Galvanic response potential exists
- Local allergic potential
- Concern about possible mercury toxicity
- Marginal breakdown
Potential Risks of amalgam filling
Amalgam contains mercury in elemental form. The low-level, low levels of mercury are released in the form of a vapor which can be inhaled and absorbed by the patient.
Continued exposure to high levels of mercury vapor can have adverse effects on the brain and the kidneys. Dental professionals are thus at a higher risk of mercury toxicity.
FDA has reviewed several scientific evidence to determine whether the low levels of mercury vapor from dental amalgam fillings can cause any health hazard (4). Based on this evidence, FDA considers dental amalgam filling to be safe for adults and children ages 6 and above.
No scientific evidence could establish any association between dental amalgam restoration and adverse health effects in the patients. Clinical studies conducted on adults and children ages 6 and above with dental amalgam restoration could not find a link between any health problems and dental amalgam fillings.
However, the developing neurological systems of young children are more sensitive to any neurotoxic effects of mercury vapor. Insufficient clinical data are available regarding long-term health outcomes in pregnant women and their developing fetuses, and infants who are breastfed (5).
However, the amount of mercury in breast milk attributable to dental amalgam is far too low to have any scientific consideration.
FDA concludes that infants are not at any risk for adverse health effects from the mercury in breast milk from women exposed to mercury vapor from their dental amalgam restoration.
Amalgam tattoo also called localized argyrosis or focal argyrosis. It is a grey, blue or black area of discoloration on the mucous membranes and soft tissues of the mouth (6).
It is typically seen on the gums, cheek and buccal mucosa, though it can occur anywhere in the mouth. It is an iatrogenic lesion, caused by entry of dental amalgam into the soft tissues.
Amalgam tattoo is a common, painless, and benign discoloration, though it can sometimes be mistaken for melanoma. During placement of an amalgam filling, if any pre-existing abrasions on the mucosa are present, the amalgam dust can enter through the abrasion.
Amalgam particles can also contaminate a dental floss and lead to the formation of linear amalgam tattoos in between the teeth. This occurs especially if flossing is carried out immediately after placement of an amalgam filling in the mesial or distal aspect of a tooth surface.
The pressure from high-speed turbine dental drills can force the amalgam particles into the soft tissue if the patient has preexisting gum disease or periodontitis.
When a tooth with an amalgam filling is extracted, the broken bits of an amalgam filling or amalgam dust can fall into an extraction socket and cause discoloration of the gingiva.
Apicectomy is a procedure that requires the use of dental amalgam, to seal the tooth root apex. They are common causes of amalgam tattoo since the amalgam is used as a retrograde filling and comes in direct contact with the alveolus and the soft tissues.
In rare cases, some individuals can have an allergy or sensitivity to mercury or the other components in dental amalgam such as silver, copper, or tin. Dental amalgam may cause these individuals to develop oral lesions or contact reactions.
The ADA, American Dental Association, says that fewer than 100 cases of this type of allergy have ever been reported (7). If you are allergic to any of the metals in dental amalgam, you can discuss other treatment options with your dentist.
Pregnancy and dental amalgam
Research has not shown any effects on pregnancy from amalgam fillings. However, elemental mercury can cross the placenta, and hence dentists advise pregnant women to avoid any unnecessary dental care (8).
As a precautionary measure, women should not get amalgam fillings during pregnancy. If required dentists can suggest other materials for a pregnant woman, who needs a cavity filled.
Candida and dental amalgam
Mercury is a neurotoxin and can affect immune, nervous and endocrine system (9). Mercury toxicity is also linked to lower IQ in children. Mercury is pro-inflammatory, and it increases oxidative stress in the body.
It also destroys the enzyme EPA in the body which is vital for oxygen delivery in the cell. This oxidative stress creates conditions where candida can more easily flourish.
Are there any alternatives to amalgam?
There is now a dental amalgam that contains indium as well as mercury. The indium helps retain the mercury so that less is released into the environment. There are also high-copper amalgams. They contain less mercury and more copper.
Dentists use other materials to restore teeth. These include composite resin, glass ionomer cement, and gold. Amalgam is stronger than composite resin and requires less time for manipulation and is also less technique sensitive.
Composite resin wears faster than amalgam and can’t be used in every situation but are still the most popular alternative to dental amalgam. Glass ionomer cement dissolves and wears faster than composites and have limited clinical application for posterior tooth restorations.
Over to you on dental amalgam fillings
Ask your dentist all the possible options before getting a dental filling. Dental amalgam has high strength and wear resistance but cannot be used in every situation.
Though negligible, do consider and inquire about the effects of dental amalgam before getting them as a restoration. Pregnant women and lactating mothers should precautionary avoid any dental amalgam restoration.
If you are allergic to any element in dental amalgam, inform your dentist beforehand.