The short answer
A filling usually needs replacing when it has cracked, chipped, worn down, pulled away from the tooth so the edge leaks, or when new decay has formed beneath or beside it. Age by itself is not a reason: the ADA advises against replacing fillings just because they are old, and the FDA does not recommend removing amalgam fillings that are in good condition. Your dentist checks each filling at your exam and on X-rays.
General information, not a diagnosis. Your dentist will examine your mouth before recommending treatment.
Why fillings do not last forever
A filling is a repair, and like any repair it carries load every day. The ADA's review of direct restorative materials reports that fracture is now the most common reason composite fillings fail, and that secondary caries, meaning new decay forming at the edge of an existing filling, remains a major cause of failure for back-tooth restorations. Composite can also shrink slightly as it sets, which the ADA notes may lead to small gaps at the margin where bacteria can collect.
The same review found limited evidence of a significant difference in longevity among the main filling materials, and reports that patient habits are the most significant factor in how long a composite lasts. In plain terms: how you chew, whether you grind, and how well the edges are kept clean matter more than the material.
Signs an old filling has failed
Many failing fillings cause no symptoms at all, which is why they are usually found at a checkup rather than by the patient. When there are symptoms, they tend to be these:
- Sensitivity to cold, heat or sweets around one tooth. The ADA lists worn fillings, tooth decay and fractured teeth among the causes of sensitive teeth.
- Pain when biting or when releasing a bite, which can point to a crack in the filling or in the tooth.
- A rough, chipped or missing piece that your tongue keeps finding, or floss that shreds in the same spot.
- Food packing in one place after every meal, a sign the contact with the next tooth has opened.
- A dark line or shadow at the edge of the filling, or a gray cast through the enamel of a tooth with a silver filling.
- A filling that falls out. Keep the area clean and call; the post on a lost filling or crown covers what to do until you are seen.
How a dentist decides
At an exam the dentist runs an instrument along the edge of each filling to feel for gaps, looks for chips and wear, and checks whether the tooth around the filling has changed color. Bitewing X-rays show decay between the teeth and under fillings that cannot be seen by eye; MedlinePlus notes that dental X-rays may show some cavities before they can be seen just by looking at the teeth.
Pain that comes and goes, or that is hard to pin to one tooth, is also how the American Association of Endodontists describes a cracked tooth. That is one reason a dentist will test the tooth itself rather than assume the filling is the whole story.
A filling that is intact, sealed and free of decay is usually left alone and rechecked at the next visit. The ADA's Choosing Wisely recommendations say not to replace fillings just because they are old, and note that removing a filling can weaken the tooth. A filling that is leaking, cracked or sitting over new decay is replaced, and the decision about what replaces it waits until the old material and decay are out and the dentist can see how much tooth remains.
| What you notice | What it may mean | What usually happens next |
|---|---|---|
| Nothing, but the dentist finds a gap at the edge | The seal has opened; decay can start underneath | Replace before decay spreads; X-ray to check beneath |
| Cold or sweet sensitivity at one tooth | Worn filling, new decay, or a crack | Exam and X-ray; test the tooth for cracks |
| Pain when biting or releasing | A cracked filling or a cracked tooth | Crack check; a crown is often needed, sometimes a root canal |
| A chip or rough edge, floss shreds | The filling has fractured | Repair or replace; the size decides filling, onlay or crown |
| Dark line at the margin | Stain or decay at the edge | Check on X-ray; replace if there is decay |
| Filling fell out | The seal is lost and the tooth is exposed | Call; keep the area clean; same-day appointment when possible |
Old silver (amalgam) fillings
Amalgam is the silver-colored metal filling material; the FDA states it is about half elemental mercury by weight, combined with silver, tin and copper. Infinite Dental Wellness is a mercury-free practice and places tooth-colored composite, so any filling placed or replaced here is composite. That is a choice about materials, not a claim that your existing amalgam fillings are harming you.
Here is the official position. The FDA says the available evidence does not show that mercury exposure from dental amalgam leads to adverse health effects in the general population, and that it does not recommend anyone remove or replace existing amalgam fillings in good condition unless a health care professional considers it medically necessary. The FDA does recommend that certain higher-risk groups, including pregnant women and children younger than six, avoid new amalgam when possible and appropriate. The ADA's patient site states that existing amalgam fillings are safe and do not need to be removed as long as they are in good condition.
So an amalgam filling is replaced for the same reasons any filling is: it has cracked, worn, leaks or has decay beneath it. If you simply prefer a tooth-colored result, that is a reasonable conversation to have at a routine exam. The post on tooth-colored fillings vs. silver fillings compares the two materials, and the practice's composite fillings page explains how a replacement is done here.
When a replacement is bigger than a filling
Every time a filling is replaced, a little more tooth is removed. After a second or third round on the same tooth, or when decay has spread under a cusp, there may not be enough sound wall left to hold another filling. MedlinePlus notes that crowns are used when decay is extensive and there is limited tooth structure. An onlay, which covers one or more cusps without surrounding the whole tooth, is the middle option.
If your dentist proposes an onlay or a crown in place of a worn filling, that is usually why. The crown vs. filling vs. onlay guide explains how the choice is made, and what is an onlay describes the middle option. MedlinePlus adds that a root canal is recommended if the pulp is exposed to bacteria or the nerve dies from decay, so a tooth where decay has reached the nerve may need a root canal before it is rebuilt.
When to call, and when it is an emergency
A chipped or lost filling without pain can usually wait for a regular appointment, though it should not be left for long: the practice's restorations page describes a filling as sealing the tooth against further decay, and that seal is gone. Pain on biting, sensitivity that lingers, or swelling of the gum next to the tooth are reasons to call now; the practice offers same-day appointments when possible.
Swelling of the face or jaw with fever, trouble breathing or swallowing, or bleeding that will not stop is no longer a filling problem. Go to an emergency room or call 911 first. MedlinePlus lists a swollen area of the upper or lower jaw as a very serious symptom of a tooth abscess and warns that an untreated abscess can lead to life-threatening complications.