Metal fillings typically last between 10 and 15 years in everyday clinical practice, though many survive far longer. A large longitudinal study put the median survival time at about 12.8 years, while some research has documented amalgam fillings lasting 20 years or more when conditions are favorable. The range is wide because durability depends on where the filling sits in your mouth, how large it is, and how well it was placed.
What the Survival Numbers Actually Show
Study results on amalgam longevity vary quite a bit depending on the setting. Surveys of private dental offices report a median lifespan of roughly 6 to 15 years. Academic dental centers, where placements tend to follow strict protocols, have recorded median survival times ranging from 11.4 years to well beyond 20. One widely cited study calculated a median of 22.5 years.
A useful way to think about it: roughly 85% of amalgam fillings are still intact after five years, and about 80% make it past the ten-year mark. Annual failure rates across studies range from near zero to about 7%, depending on the patient population and the size of the restoration. So while “10 to 15 years” is a reasonable midpoint expectation, it’s entirely normal for a well-placed metal filling to last two decades or longer without needing attention.
Filling Location and Size Matter
Fillings on molars, the large teeth at the back of your mouth, take a beating every time you chew. They consistently show shorter lifespans than fillings on premolars, the slightly smaller teeth just in front of them. In one study, premolar restorations had a five-year survival rate of about 77%, compared to roughly 65% for molars. The force difference is significant: your back molars generate the most bite pressure in your entire jaw.
The number of tooth surfaces a filling covers also plays a role, though not always in the direction you’d expect. Small, single-surface fillings can perform well, but larger restorations that wrap around multiple sides of a tooth sometimes hold up even longer because of how the filling locks into the tooth structure. The cavity design your dentist uses, specifically how the walls and edges are shaped, influences whether the filling stays put or develops cracks over time.
How Metal Fillings Compare to Other Options
Amalgam has historically been considered the most durable direct filling material, meaning a material your dentist places and shapes in a single visit. Tooth-colored composite fillings have improved significantly over the past two decades, but systematic reviews still show amalgam edging them out on raw longevity, particularly in larger restorations on back teeth.
Gold restorations occupy a different category entirely. Cast gold inlays and onlays, which are custom-made in a lab rather than packed directly into the tooth, have documented survival rates of about 94% after 40 years in some studies, and roughly 74% at the 30-year mark. Gold is the most durable material available for filling a tooth, but the higher cost and multiple appointments needed for placement mean it’s far less common today.
Signs a Metal Filling Needs Replacing
A metal filling doesn’t suddenly stop working one day. It deteriorates gradually, and dentists look for specific warning signs during checkups. The most common reasons for replacement include:
- New decay at the edges. Bacteria can work their way into the gap between the filling and the tooth over time. This secondary decay often isn’t visible to you until a cavity has already formed along the margin.
- Cracking. Either the filling itself or the surrounding tooth structure can fracture, especially if the original cavity design left thin walls of tooth enamel.
- Marginal ditching. A visible gap or ditch forms where the filling meets the tooth. The edge may look dark or bluish-gray from corrosion buildup. Ditching alone doesn’t always mean the filling is failing, but it creates a spot where decay can start.
- Pain or sensitivity. Ongoing discomfort around an old filling can signal decay underneath, a crack, or irritation of the nerve. Some cases resolve with a minor bite adjustment, while others point to deeper problems that need treatment.
- Cosmetic concerns. This is actually the most frequently reported reason people choose to replace amalgam fillings. Many opt for tooth-colored alternatives, particularly on teeth that show when they smile.
If none of these issues are present, there’s no clinical reason to replace a metal filling just because it’s old. The FDA’s position is clear on this point: if the filling is in good condition and there’s no decay beneath it, removal is unnecessary and can actually remove healthy tooth structure in the process.
Should You Proactively Replace Old Amalgam?
Amalgam contains mercury, which is the main reason some people consider having their metal fillings swapped out preemptively. The FDA recommends that certain groups avoid amalgam when possible: children under six, pregnant or nursing women, people with kidney problems or neurological conditions, and anyone with a known sensitivity to mercury or the other metals in the alloy (silver, copper, tin, zinc).
For everyone else, the FDA’s guidance is straightforward: leave a stable filling alone. Drilling out an intact amalgam filling exposes you to a brief spike in mercury vapor during removal and sacrifices tooth structure that can’t grow back. Each time a tooth is re-drilled, the cavity gets slightly larger, and the replacement filling has a bit less tooth to grip onto. Over a lifetime, that cycle of replacement can eventually push a tooth toward needing a crown or even extraction.
The practical takeaway is that a metal filling’s useful life isn’t defined by a calendar. It ends when your dentist finds a specific problem: decay, a crack, a failing margin. Until then, regular checkups and X-rays are the best way to monitor an aging filling and catch trouble before it becomes a bigger repair.