A worn filling is a dental filling that has degraded over time, losing its smooth shape and tight seal against the surrounding tooth. Every filling eventually wears down from years of chewing, temperature changes, and exposure to acids in food and drink. When that happens, gaps can form between the filling and the tooth, creating spaces where bacteria settle and new decay begins.
How Long Fillings Typically Last
No filling is permanent, but the timeline varies widely depending on the material, the size of the filling, and how much stress it endures. Silver amalgam fillings last a median of about 12 to 22 years in most studies, while tooth-colored composite resin fillings tend to last somewhat less, with median survival times closer to 8 to 17 years. Smaller, single-surface fillings outlast larger ones significantly. A large filling spanning multiple surfaces of a tooth may fail in half the time of a small one.
Survival rates tell a practical story. Roughly 80 to 90% of both amalgam and composite fillings are still functional after five years. By the ten-year mark, that drops to around 75 to 82% for composites and 79 to 85% for amalgam. A 12-year retrospective study of composite fillings placed in back teeth found a 78% success rate, with an annual failure rate of about 2%. So while most fillings hold up well for years, a small percentage fail each year, and over a decade or two the odds of needing a replacement become substantial.
What Causes a Filling to Wear Down
The inside of your mouth is a surprisingly harsh environment. Fillings face constant mechanical stress from chewing, temperature swings from hot coffee to ice water, and chemical exposure from acidic foods and drinks. Over time, these forces fatigue the bond between the filling material and your tooth, creating microscopic gaps at the margins.
Teeth grinding (bruxism) is one of the biggest accelerators. The repeated, forceful contact between upper and lower teeth wears down both natural enamel and filling material far faster than normal chewing. When grinding combines with acid exposure, from frequent soda consumption, citrus, or conditions like acid reflux, the damage compounds. Acid softens the surface, and mechanical friction strips it away more easily. Smoking and tobacco use also contribute to faster breakdown.
The filling material itself plays a role. Composite resin is softer than amalgam and wears more quickly under heavy bite forces, especially on back teeth. But amalgam fillings, while harder, don’t bond chemically to tooth structure the way composites do, so they can develop marginal gaps through a different mechanism as the metal expands and contracts with temperature changes.
Signs Your Filling Is Wearing Out
A filling in good condition has smooth edges that blend seamlessly with the tooth surface. As it degrades, you may notice roughness or a sharp edge when you run your tongue over it. That’s one of the earliest and most noticeable signs. You might also feel a slight catch when flossing around the tooth.
Discoloration is another indicator. Yellowish staining around a filling often comes from plaque buildup in tiny surface irregularities. Brown or black discoloration is more concerning, as it can signal decay forming underneath or around the filling’s edges.
Sensitivity is the symptom that sends most people to the dentist. When a filling loses its seal, the underlying tooth becomes exposed to temperature, pressure, and sugar. You might notice a sharp jolt when drinking something cold, a dull ache when biting down, or discomfort when eating sweet or acidic foods. This sensitivity tends to come on gradually and worsen over time, unlike the temporary sensitivity that’s normal right after a filling is placed.
What Happens If You Ignore It
A worn filling with compromised margins acts like an open door for bacteria. They migrate into the gap between the filling and the tooth, where they’re impossible to reach with a toothbrush or floss. This leads to recurrent decay, which is new cavity formation underneath or around an existing filling. Recurrent decay is one of the most common reasons fillings need replacement, accounting for a significant share of all filling failures.
Left long enough, the decay can reach the inner pulp of the tooth, causing infection, abscess, or the kind of deep pain that requires root canal treatment. In severe cases, so much tooth structure is lost that the tooth can’t support a new filling at all and needs a crown or extraction. The longer you wait, the more involved and expensive the treatment becomes.
How Your Dentist Detects Wear
During a routine exam, your dentist uses a thin metal instrument called an explorer to feel along the edges of each filling. A filling in good shape will feel smooth and flush with the tooth. A worn filling will catch the explorer, revealing gaps, rough margins, or soft spots that suggest decay.
X-rays, particularly bitewing images taken of your back teeth, reveal what’s happening beneath the surface. They can show gaps between the filling and tooth, dark shadows indicating decay underneath, or changes in the filling’s shape. Some offices also use small intraoral cameras that magnify the tooth surface on a screen, making cracks and marginal breakdown easier to see and easier to show you.
Repair, Replacement, or Crown
Not every worn filling needs to come out entirely. If the wear is limited to the edges of the filling and there’s no decay underneath, your dentist may be able to repair it by adding new material to the damaged margin. This is a more conservative approach that preserves more of your natural tooth structure.
Replacement becomes necessary when the signs point to decay beneath the filling. Key factors that push the decision toward full replacement include visible secondary decay, cracks along the filling margin, pain when pressure is applied, and the filling’s age. Multi-surface amalgam fillings get extra scrutiny because their size means more tooth is at risk. Once the old filling is removed, your dentist will clean out any decay and place a new restoration.
If the tooth has lost a significant amount of structure, either from the original cavity, the new decay, or both, a filling alone may not be strong enough. In that case, a crown covers and reinforces the entire visible portion of the tooth. This is more involved than a filling but protects what remains of the tooth from fracture.
How to Make Your Fillings Last Longer
The same habits that prevent cavities also protect your fillings. Brush twice daily with fluoride toothpaste and floss every day, paying attention to the areas around existing restorations. Limit sugary and sticky snacks, and rinse your mouth with water after consuming acidic drinks like soda, juice, or coffee.
If you grind your teeth, a night guard is one of the most effective things you can do. Bruxism dramatically accelerates wear on both fillings and natural teeth, and a custom-fitted guard absorbs that force. Avoid chewing ice, biting pen caps, or using your teeth to open packaging. These habits create the kind of sudden, concentrated force that can crack a filling in a single moment.
Regular dental visits, at least once a year, catch early signs of wear before they become problems. Your dentist can monitor marginal integrity over time and intervene while a simple repair is still an option, rather than waiting until the filling fails completely and decay has spread.