It is important to know that dental fillings can last many years, however, eventually all fillings do need to be replaced. Normal wear and tear from eating and drinking as well as clenching and grinding contribute to the deterioration of fillings. Fillings that are worn, chipped, cracked or fallen out leave gaps/holes in teeth providing entry points for bacteria. Bacteria can penetrate into these crevices which are not easily reachable with a toothbrush or dental floss. Decay that is not treated may progress to infect the the pulp or nerve, leading to a root canal, a procedure in which the nerve is removed to alleviate pain.
Amalgam fillings can be replaced at your discretion, after consulting with your dentist. These fillings are perfectly stable adequate restorations, but if you are concerned with the esthetics or mercury content, then we would be able to replace them with an acrylic resin-based material called a composite. As stated above, replacing "silver" fillings purely for cosmetic reasons is not recommended. However, replacement of damaged or decayed fillings regardless if they are "silver" or "white" fillings ARE recommended.
When fillings are replaced, typically the old filling is replaced along with any recurrent decay or defect which in turn makes the new filling larger. Replacing fillings numerous times may severely weaken the tooth, so consult with the dentist to ensure that a replacement filling is the best treatment for you.
If your metal dental fillings are defective or show decay, it's important to replace them. Untreated decay may eventually lead to an infection (abscess). In some cases, replacing a metal dental filling may benefit the long-term health of your tooth.
Generally, replacing metal dental fillings for cosmetic reasons should only be done after careful consideration and if your dentist feels it won't compromise the long-term health of your teeth. Likewise, there's no need to replace metal dental fillings because of concerns about mercury in your fillings.
Most metal dental fillings are dental amalgam — a stable alloy made with mercury, silver, tin, copper and possibly other metals. Although concerns have been raised over the years about the safety of mercury in dental amalgam, there is no conclusive evidence to support that you're better off having amalgam fillings replaced with alternative materials. The American Dental Association supports the use of dental amalgam as a safe, reliable and effective treatment for dental decay.