The two, most frequently used materials to restore teeth affected by caries are, silver(amalgam) and composites.

Silver Fillings (Amalgams)-which consists of mercury mixed with silver, tin, zinc, and copper)

Advantages of silver fillings:

• Durability – silver fillings usually outlasts composite fillings. They can last 10-15 years.
• Strength – can withstand chewing forces
• Easy to place
• Relatively cheap

Disadvantages of silver fillings:

• Poor aesthetics — silver fillings don’t match the colour of natural teeth.
• Destruction of more tooth structure — healthy parts of the tooth must often be removed for 2 specific reasons:
  • Silver fillings are strong when placed in bulk ( anything less than about 2mm in depth or width is likely to fracture)
  • Silver fillings rely solely on mechanical retention therefore the cavity has to be retentive
• Discoloration — amalgam fillings can create a greyish hue to the surrounding tooth structure.
• Cracks and fractures — although all teeth expand and contract in the presence of hot and cold liquids, which ultimately can cause the tooth to crack or fracture, amalgam material — in comparison with other filling materials — may experience a wider degree of expansion and contraction and lead to a higher incidence of cracks and fractures.
• Allergic reactions — a small percentage of people, approximately 1%, are allergic to the mercury present in amalgam restorations.

Tooth-coloured Composites – which consists of resin and fillers such as quartz, fused silica, aluminosilicate, borosilicate or zirconia and silane coupling agent  

Advantages of composites:

• Aesthetics — the shade/colour of the composite fillings can be closely matched to the colour of existing teeth. Composites are particularly well suited for use in front teeth or visible parts of teeth.
• Bonding to tooth structure — composite fillings actually chemically bond to tooth structure, providing further support.
• Versatility — in addition to use as a filling material for decay, composite fillings can also be used to repair chipped, broken, or worn teeth.
• Conservative preparation — sometimes less tooth structure needs to be removed compared with amalgam fillings when removing decay and preparing for the filling.

Disadvantages of composites:

• Durability — composite fillings wear out sooner than amalgam fillings; in addition, they may not last as long as amalgam fillings under the pressure of chewing and particularly if used for large cavities however they can still last 6 to 12 years.
• Increased chair time — because of the process to apply the composite material, these fillings can take up to 30 minutes longer than amalgam fillings to place.
• Additional visits — if composites are used for inlays or onlays, more than one office visit may be required.
• Expense — composite fillings can cost significantly more than amalgam fillings.

Are amalgam fillings safe?

Over the past several years, concerns have been raised about amalgam fillings. Because these fillings contain the toxic substance mercury, some people think they are responsible for causing a number of diseases, including autism, Alzheimer’s disease, and multiple sclerosis.

The American Dental Association (ADA), the Food and Drug Administration (FDA), and numerous public health agencies say there’s no proof that dental fillings cause harm to consumers. The causes of autism, Alzheimer’s disease, and multiple sclerosis remain unknown. Additionally, there is no solid, scientific evidence to back up the claim that if a person has amalgam fillings removed, he or she will be cured of these or any other diseases.

Although amalgams do contain mercury, when they are mixed with other metals, such as silver, copper, tin, and zinc, they form a stable alloy that dentists have used for more than 100 years to fill and preserve hundreds of millions of decayed teeth.

Can dental amalgam “leak” Mercury?

Yes. There can be a very slight release of mercury from amalgam fillings. A study conducted by measuring the Mercury vapor levels inside the mouth over a 24-hour period in patients with at least nine amalgam restorations showed the average daily dose of inhaled mercury vapor was 1.7 µg (micrograms), which is approximately only 1% of the threshold limit value of 300 to 500 µg/day established by the World Health Organization. So there is Mercury released from fillings, but it’s a very tiny amount.

In June 2008, the FDA said, “Dental amalgams contain mercury, which may have neurotoxic effects on the nervous systems of developing children and fetuses.”

They also said, “Pregnant women and persons who may have a health condition that makes them more sensitive to mercury exposure, including individuals with existing high levels of mercury bioburden, should not avoid seeking dental care, but should discuss options with their health practitioner,” according to the FDA.

The changes come in response to a lawsuit filed by consumer groups and individuals concerned about mercury exposure. To settle the suit, the FDA agreed to update its web site.

Another aspect to consider is the environmental impact:

It is condemned as a risk for “secondary poisoning” by a European Commission scientific advisory body because of its impact on air, land and water, getting into fish that people eat.

Also, when amalgam’s impact on the environment is factored in, the argument that it’s a cheap  material doesn’t stand up.  According to one NGO the cost of an amalgam filling far exceeds the cost of a filling made of composite.

So why do we still place amalgam fillings?

In February 2008 British Dental Association (BDA) produced a paper based on studies conducted by:

• EU Commission’s Scientific Committee
• Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)
• Medicines and Healthcare Regulatory Agency (MHRA)
• Department of Health’s Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT)
• World Dental Federation (FDI)
• World Health Organisation (WHO)
• American Dental Association (ADA)
• Food and Drug Administration (FDA)

They concluded with the following statements:

• no increased risks of adverse systemic effects exist and amalgam is not therefore considered to pose a risk of systemic disease
• there is no available evidence to indicate that the placement or removal of dental amalgam fillings during pregnancy is harmful. BDA is of the opinion, however, that the toxicological and epidemiological data are inadequate to assess fully the likelihood of harm occurring in such circumstances. Until appropriate data are available they concur with the view that it may be prudent to avoid, where clinically reasonable, the placement or removal of amalgam fillings during pregnancy
• it remains the Department’s advice that dentists should continue to avoid or delay any dental intervention or medication during pregnancy; however a dental emergency where treatment with dental amalgam is required can outweigh any, as yet, theoretical risk of systemic toxicity.

NHS Choices offers the following statement when it comes to Fillings and Materials used:

‘’Fillings are used to repair a cavity in your tooth caused by decay. The most common type of filling is dental amalgam, made from a mixture of mercury and different metals. Dental amalgam fillings are often used on your back teeth as they are hard-wearing.

Your dentist will offer you the type of filling most appropriate for your clinical (medical) needs. This may include a tooth-coloured (white) filling. For example, if you need a filling for one of your front teeth, your dentist may suggest a tooth-coloured filling, but the use of tooth-coloured fillings on back teeth is considered purely cosmetic.

Fillings on the NHS can be made of:

• amalgam (silver-coloured) – a mixture of metals including mercury, silver, tin, and copper
• composite (tooth-coloured) – powdered glass and ceramic added to a resin base; they’re not as hard-wearing as amalgam fillings
• glass ionomer (tooth-coloured) – powdered glass, which reacts chemically with your tooth and bonds to it, but it is weak so is only used on baby (first) teeth or around the sides of teeth’’

This blog has the purpose to give you the ability to take an informed decision when it comes to material used for your fillings.

I will conclude with my personal views on this topic.

Dental amalgam has saved countless teeth over the more than 100 years it’s been in use. And, for a while, it will continue to have a place in NHS dentistry. It’s strong and relatively cheap, but it’s ugly.

There are options that require the removal of less tooth structure that can be used as well. They look more like teeth and they are actually bonded to the tooth structure. They are much more difficult to place well. They require much drier conditions and take a lot longer to place correctly. Bonded fillings are by far, my favourite restoration to place! When done with care they are beautiful and quite durable.

By Marius Ilea