What is the Silver Fillings ‘Debate’ all about?

‘Amalgam! You don’t still use that stuff do you?’

We often hear this statement from patients. Dental amalgam has been used successfully for over 100 years and has been researched more than any other material. It is commonly referred to as ‘silver fillings’ by patients.

Its main advantages are its strength, durability and resistance to wear which make it a great long term filling choice and of particular use in the molar teeth which take a lot of pressure and wear in chewing. The average life expectancy of an amalgam filling is about 11 years but it is not uncommon to see amalgams that have lasted over 20 years, even 40 years! From a dental perspective, it is very easy to use, cost effective and its benefits are still widely commended in dental schools throughout the world. Despite these facts composite fillings are becoming more popular.

The silver colour is perhaps the biggest issue for patients, because it can often be seen when you laugh and speak- especially if the filling is nearer to the front of the mouth.

Amalgam is also held in by mechanical retention; which means slightly more tooth has to be removed in order to place it properly. By ensuring undercuts in the cavity (the tooth being wider at the base of the cavity than the top) and having locks and dovetails, amalgam ensures that once pushed into the tooth the filling will be prevented from coming out in any direction.

In recent times there has also been some concern over the mercury content of dental amalgam. This has received over enthusiastic media coverage and created much concern. Dental amalgam is actually a mixture of metals (mainly silver, tin and copper) and a little mercury- a known toxic substance on its own. However, during the setting reaction of the amalgam, the mercury combines with the other metals to form a very stable material that is safe in your teeth and in your body- it doesn’t get released over time.

Millions and millions of you are walking round happily with amalgam fillings in your mouth with no effect. The only real concern may be a true allergic reaction which is incredibly rare- only a few cases have ever been recorded. There is no evidence I have seen to suggest that dental amalgam is harmful.

If you are pregnant, because of the ability of mercury to cross the placenta, it is recommended by various government bodies, that you avoid having amalgam fillings placed or removed as a precaution. If you are pregnant, it is preferable wherever possible to defer any dental care until after the birth but if absolutely necessary, dentists can use some of the other materials discussed in this section to restore the tooth.

A diet high in seafood will contain more mercury than that released by a mouthful of amalgam fillings. I have heard it discussed in dental circles, that there is more mercury released into your body from eating a single mackerel (that oily fish which is so good for you!) than having an amalgam filling. I personally find this rather re- assuring. Toxic effects only occur if the amount of a substance- in this case mercury- exceeds the amount that your body is able to eliminate and this isn’t going to happen from the quantity released by dental amalgam fillings- even if every single one of your teeth was amalgam.

Perhaps a greater health issue is the environmental effect of dental amalgam. Whilst most dental surgeries are fitted with specialist separators which are devices to prevent this from getting into the public sewers, dental amalgam still contributes about 1/3 of mercury waste. Unfortunately, USA law does require surgeries to have these amalgam separators fitted. To my mind, this is the real issue that dental amalgam presents- at an environmental and community level, not the fact you may have an amalgam filling in your mouth.

Studies into the safety of dental amalgam are extensive and the results somewhat varied. Unfortunately with statistics, case selection and by directing focus, you can almost prove or disprove anything you wish to. The perfect scientific study is almost an impossibility- there are so many variables to consider that it is extremely difficult to draw any firm conclusions. Have a read of some of the articles from the U.S. National Library of Medicine and you will get more of a flavour for this ongoing debate.

Some of the World’s leading international scientific and health bodies such as the National Institute of Health, The Food and Drug Administration and the World Health Organization have all backed the conclusion that ‘dental amalgam is a safe and effective filling material’.

The Australian dental association takes what I believe to be the correct approach on amalgam fillings, stating on available research that ‘the use of dental amalgam produces no harmful effects’.

Should I get my Amalgam Fillings Removed?

Once Amalgam is set (24 hours after being placed) very little mercury is ever released- it has been used up in the reaction with the other metals. Most is released on placement or on removal and it is for this reason I would suggest only replacing amalgam fillings if they are excessively worn, broken or present a significant aesthetic problem to you. For those of you who are desperate to have them replaced from a cosmetic point of view (as this is the only benefit from the procedure), this is best done where possible under rubber dam though the high speed suction dentists use is very effective. But please consider that every time a filling is replaced, more natural tooth ends up being taken away in the process. Therefore a little less remains for strength and bonding.

Sometimes there may be a weak wall holding the tooth together that during the removal of the filling fractures off. If this occurs, placing a simple composite restoration may no longer be the ideal treatment and it may be better (advisable) to have a more expensive inlays/onlay or a crown.

Often the old saying, ‘if it isn’t broken then don’t fix it’ can be quite appropriate.

Whilst there is nearly always something that can be done, you can in certain circumstances cause more problems than it is worth. When I am replacing amalgams, I will always have this discussion with my patients. I will educate them on dental amalgam and discuss why they want them replaced, before looking at each individual tooth and the potential problems or additional treatment that may be needed.

For example, I may say:

“Yes, this can be replaced- no problem- there is a lot of tooth left for bonding and you only have two amalgams in your whole mouth”.

“This is a very large amalgam that is not suitable for a composite white filling – I probably couldn’t achieve good contacts in-between the teeth, so you may get some food packing and the size of the amalgam means shrinkage and leakage may be a problem. Therefore if you would like this to be white (and to last any decent amount of time) then it would be advisable to have an inlay/onlay or a crown. Or the tooth can be left as it is until the time at which it actually needs replacement”.

“This amalgam is very deep under the gum and it would be difficult to get a quality seal with the white filling that may lead to further problems. In addition, the weak wall may break and make this more suitable for something made in the laboratory like a inlay or a crown- you just need to be aware of the potential problems before we go ahead”.

If a patient was adamant that they wanted a white filling to replace the silver filling but couldn’t afford a crown and I thought that this would be detrimental to the tooth, I may refuse to tamper with the tooth that has been functioning well for many years. Some dentists would go straight ahead- each to their own but I refuse to create more problems than I solve- I think it’s a good motto “to always leave the patient’s mouth better than you found it” and this refers not just to how it looks- but how it functions today and in the future.

Is it Better to have Silver or White Fillings?

Generally circumstances will dictate, whether it is better to place a silver filling or a white filling and your dentist will advise you accordingly. There has been a general shift in private practice from placing amalgam as standard and composite when situations permit, to composite as standard and reserving amalgam for certain occasions.

Some practices choose to no-longer place silver amalgam; that doesn’t make them better or more advanced, it is simply a choice they have made. If this is the case, obviously the choice of silver or white has been made for you.

As for myself in general private practice, I place white fillings as standard, and silver amalgam when I am concerned about the success of a white filling.

Such circumstances would be:

• Very large fillings. The larger the white filling the more likely the shrinkage will be a problem- the more likely the filling will fail. If the look of the silver filling is a particular problem for you, then a tooth coloured inlay/onlay or crown would need to be considered instead.

• Difficulty in controlling moisture. If it is difficult to isolate the tooth from blood and saliva, the chance of contamination is high, poor bonding will result and the filling will fail and need to be replaced.

• Deep sub gingival fillings . Cavities that go deep under the gum are often more easily and effectively filled with silver amalgam.

• Difficult access. Sometimes a tooth may be out of position or very far back in the mouth (e.g. a wisdom tooth), or you have a tiny mouth that makes placing an effective white filling in small increments almost impossible. As silver amalgam is just pushed and compacted into the cavity the need to see exactly what you are doing is less and the outcome is likely to be more successful.

Most of the time the dentist will have a preference for which would be best in your particular situation. Should you have any questions or wish one type of filling over another, discuss this with the dentist before they make a start- not at the end!

All things being equal, the choice comes down to the importance you place on the following factors:

• Cost?

It is generally cheaper (but not always) to have a silver filling because it can be completed more quickly and easily than a white filling. In the UK, on the NHS, white fillings for back teeth are regarded as private treatment and cost considerably more than the silver fillings that are available under the public system.

• How long it will last?

Silver fillings last longer- many scientific studies have been performed that conclude dental amalgam fillings last longer than white composite fillings in back teeth. The bigger the filling the greater this difference appears to be. Silver amalgam being more successful in larger restorations where the filling extends onto three or more surfaces of the tooth. However, the ‘effectiveness’ gap is reducing… composite fillings are lasting longer as bonding technology and techniques improve.

• How it looks?

There is no dispute here- white fillings look considerably more natural and often almost invisible in social encounters when compared to silver fillings. Dental amalgam only comes in the one colour- silver but composite is available in many shades to match the colour of your tooth.

• Your concerns over safety – see our discussion regarding the safety of dental amalgam. On the current available evidence I do not perceive this to be an issue.