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Are Metal Fillings Dangerous?

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Historically, tooth cavities causing people pain would normally be extracted. However without anaesthetic agents, the tooth extraction would be done without anaesthetic! Along came dental amalgams – a solution to fixing those nasty painful holes in people’s teeth and a way to reduce the need for extractions. Amalgams have been around for centuries and were one of the first materials used to fill people’s teeth. Dental amalgams are an alloy, meaning they are a mixture of metals consisting of various quantities of zinc, mercury, tin and copper, which when mixed together, form a very hard, stable and safe material that can withstand the test of the time.

Dental amalgams provide excellent strength, durability, self-sealing properties and antibacterial benefits. For these reasons, they were widely used for the restoration of decayed teeth, and can still be the preferred restorative material of choice in the 21st century. However, due to its metallic colour and ubiquitous concerns regarding health effects and environmental effects, its use in dentistry has vastly decreased.

Mercury and amalgams

Some people may be concerned about the mercury content in amalgams. But, did you know, that mercury is found everywhere in our day to day lives? The air we breathe often contains very small traces of mercury which can be due to environmental or human related activities. Volcanic activity and bushfires release mercury into the atmosphere where it can travel vast distances to settle around the general population. Human activities such as the burning of coal, oil, and wood can release mercury into the air. Power plants that use fossil fuels as energy account for some of the largest sources of mercury emissions. Mercury levels differ depending on which part of the world we reside.

The mercury that travels airborne can settle in bodies of water. Fish and shellfish build up mercury levels over their lifetime. The amount of mercury in a given fish or shellfish is dependent on what they eat (do they eat other fish that contain mercury?), or how long they live (if they live longer, then they are able to ingest more mercury over their lifetime). It is worth mentioning that the levels of mercury in fish have proven to be of low risk with no detrimental effects to the human body. Tuna, a commonly consumed fish in the world contains the largest traces of mercury. This is largely due to the fact that they can grow quite large, and feed off other fish. In fact, the exposure of mercury with dental treatment is less than a can of tuna!

Research has shown that dental amalgams are safe and that there has not been any evidence of impacts to health. Studies have suggested that the leaching of metals into the mouth is exceptionally low and within ranges that are considered safe. However, amalgams can be unsafe when it comes to removal as this can create vapours in small quantities. With the addition of high vacuum suction, found in the dental chair, these vapours can be vastly reduced to a level that is safe. The environmental concerns of amalgam during removal are also important, as to not let such metals enter our waterways. Luckily, dental chairs have amalgam traps which prevent the pollution of amalgam into the water.

In rare circumstances, some people may be allergic to mercury. This is an immune response to very low levels of mercury known as “mercury hypersensitivity”. Patients may experience symptoms to their gums or tissues in the oral cavity. Symptoms include skin rashes around the mouth, itching and swollen lips. Most reactions to amalgams require no treatment and will disappear with time, however in some cases, the amalgam restorations need to be removed and replaced with another restorative substitute. The majority of dental clinics no longer use amalgam as a choice of filling material so patients need not be concerned of such an occurrence happening even if the risk of having a reaction is extremely low.

For the majority of patients that already have amalgam fillings in their teeth, there is very little to no risk to their health. So, the need to rush to the dentist and have all of your amalgam fillings replaced is not necessary for the purpose to reducing mercury levels in the body. Amalgam fillings have been used for over 100 years and have been widely studied in relation to its effect on the human body and their great quality is why they have been the mainstay of dental fillings for the past 100 years.

One of amalgams unique properties is that it has ‘self-sealing’ properties. Through expansion of the amalgam after placement, and corrosion, amalgam fillings can improve their contact with your cavity. Fillings may contain small microleakages when placed in your teeth which acts as a breeding ground for microorganisms causing dental decay. The amalgam’s self-sealing property act to seal this microleakage, thus preventing the recurrence of dental decay. This is one of the best reasons for why amalgam fillings last for a very long time.

Amalgam fillings are extremely durable and can withstand years of wear and tear with the appropriate care. Their strength ensures that you can chew on foods without worrying of pieces of ‘filling’ breaking off. Such durability is evident in many patients that still have their amalgam fillings in their teeth that were placed when they were young.

Why should we replace amalgam fillings?

As much as we would like to think that everything will last forever, amalgam fillings are still susceptible to wear. Because they last for such a long time, wear may not be easily detected. Amalgams do not stick to the tooth so once their margins start to open, they allow for food and bacteria to colonise in the cracks. Over time, the recurrence of decay can eventuate and is often quite difficult to detect, even with X-rays. Careful examinations with your dentist on a regular basis help to monitor the status of your amalgam fillings. Regular X-rays are useful for detecting signs of decay underneath your amalgam. As mentioned previously, it can be quite tricky to determine if there is decay underneath your amalgam filling. The amount of decay detectable underneath amalgam fillings may be quite substantial when it finally appears in the dental X-ray, so it is recommended to attend regularly, not only for your bi-annual cleans, but for thorough assessment of all existing fillings. We also recommend X-rays for patients regularly for the best assessment. The duration of when to take X-rays is dependent on your risk of decay. Those will a higher risk may require more regular X-rays. We recommend bitewing X-rays once every 2 years for the majority of our patients to ensure we are kept up to date with your teeth. If we notice any signs of failure or early signs of decay, we can properly prepare for the replacement of your amalgam whilst conserving as much tooth structure as possible.

Amalgams require bulk to stay in your tooth, and so the cavity designed in your tooth for your amalgam filling to fit in your tooth may often be undermining some of your much needed enamel and dentine. Larger amalgams in teeth, in particular the molar teeth are more prone to fracture. This is an area of concern when conducting a dental examination, and your dentist would generally raise these issues with you and discuss options for ensuring your teeth don’t fail you on the next bite.

Another disadvantage of amalgam fillings is that they can stain the surrounding tooth structure overtime. This may not be aesthetically pleasing for some patients and thus the request for replacement of amalgam fillings. However, replacement of any filling generally leads to a larger filling size and loss of very important tooth structure. One must consider the benefits and risks involved when replacing amalgam fillings. We must also remember that the highest levels of mercury exposure are during amalgam removal. With the appropriate protocols in place at your dentist, removal can still be very safe. Thus, we suggest you discuss with your dentist first whether it is worthwhile to replace your amalgam fillings.

As time and technology advanced, dental amalgams were no longer the preferred choice of material for restoring teeth. Composite fillings and ceramic restorations have become increasingly popular as restorative substitutes due to their aesthetic properties and are now the material of choice for dental restorations. They provide strength, biocompatibility, safety and aesthetics.

So the question is, should I replace my dental amalgams? All fillings have a lifespan and you would be very surprised at how long dental amalgams can last. In some cases, they can outlive the tooth itself! Replacement of dental amalgams should always be assessed carefully and your dentist can help you to determine if it is safe to do so. Because the removal of amalgams may sometimes weaken the tooth and subsequently reduce the lifespan of your tooth, it is best to discuss with your dentist the best options when considering the replacement of amalgam fillings. The team at True Smiles Dental can assist you with these concerns. Contact us at (02) 7228 7272 or book online at