The Pros and Cons of Amalgam and Composite Fillings

In dentistry, there are two different types of fillings: amalgams (silver or metal fillings) and composites (tooth-colored fillings). Dental amalgam is best known as silver fillings because of their color and due to the mixture of mercury, silver, copper, tin, and zinc. Composite fillings are made of a tooth-colored resin. Understanding more about them helps the patient to understand which is an ideal option to treat a cavity as well as why it may or may not be a good idea to have a filling removed and replaced. It is important to understand that both have their place in dentistry.  

Which is the best solution for initially treating a cavity?

While amalgam fillings are more durable and long-lasting, composite fillings are ideal for multiple reasons. Aside from the obvious aesthetic difference, the manner in which the amalgam is affixed to the tooth requires more tooth structure to be removed, making it a less conservative option to begin with. Amalgam fillings also require a corrosive action that happens after placement to form a seal around the edges of the filling. 

With tooth-colored, composite fillings, less tooth structure needs to be removed because this sort of restoration is bonded to the tooth and the resin requires a smaller access preparation. Because composite resin bonds to the tooth, unlike amalgam, there is less leakage. Leakage essentially means that there is an opportunity for bacteria to seep in around the margins of the filling. Once this occurs, the bacteria become trapped under the filling. 

Additionally, amalgam fillings respond differently than composite fillings to changes in temperature that comes with eating, drinking, and breathing. Amalgams are sensitive to thermocycling (expansion and contraction with temperature exposure) which could result in microfractures in the tooth. The metal in silver fillings also leaches into the dentin (the layer of tooth below the enamel) causing the tooth around the filling to turn black.  

When should an amalgam filling be replaced?

Removing amalgams and replacing them with composite fillings for purely cosmetic reasons is discouraged. If your amalgam filling is intact, in good condition, and there is no decay under it, it is not recommended to remove it as it will require unnecessary removal of healthy tooth structure. Removal of the amalgam could cause cracks in the remaining tooth and the risk of nerve damage increases due to the required drilling. 

Amalgams are tried and true and safe to have in the mouth.  If the amalgam filling has failed, then it is time to remove and replace it with a composite filling—if there is enough tooth structure to support a composite filling. Otherwise, the tooth would need to be restored with a dental crown.

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Written by Dr. Christopher King

Dr. King has been leading King Dental since 2000. In the 20-plus years since opening King Dental, his experiences have only strengthened his excitement for his chosen career. Dentistry is Dr. King’s life’s mission.