My silver filling is cracked, or there may be decay under it: does it need to be replaced?

Why "leave intact fillings alone" does not apply to a failing one

The FDA's advice on silver (amalgam) fillings is specific: a filling that is in good condition, with no decay beneath it, is usually best left in place, because removing it sacrifices healthy tooth structure and briefly raises exposure to mercury vapor. That advice assumes the filling is intact. Once a filling has cracked, broken, developed a gap at its edge or has decay growing beneath it, it is no longer doing its job of sealing the tooth, and the question changes from "should I remove a sound filling?" to "how should a failing one be repaired?"

Two things make this worth acting on. Decay under a filling keeps progressing out of sight, and untreated decay can reach the pulp (the nerve and blood supply inside the tooth), where it may cause pain and infection. And a cracked filling can be a sign that the tooth around it has cracked too; chewing can then move the pieces and irritate the pulp, and an extensive crack may lead to pulp infection. Whether the repair is a new filling or a crown is decided by an examination, not by the symptom alone.

Failing filling or cracked tooth: what the pattern may suggest

No single symptom settles the diagnosis, and a cracked tooth in particular is known for pain that comes and goes and is hard to pin to one tooth. The table below shows what a dentist usually considers when hearing each description.

If facial swelling spreads quickly toward the eye, under the jaw or into the neck, if you have any difficulty breathing or swallowing, if facial swelling comes with fever, or if there is uncontrolled bleeding or severe trauma, go to the nearest emergency department or call 911 first; do not wait for a dental appointment or submit an online request. Our guide on facial swelling with tooth pain explains why.

What the examination checks, and why an X-ray alone can miss it

Silver fillings are radiopaque: they block X-rays and appear bright white on the image. Decay directly beneath the metal can be partly or completely hidden behind that bright area, so a clear X-ray does not rule it out. Cracks are harder still; a crack is often invisible to the eye and to X-rays. That is why the examination usually combines several steps:

• Visual inspection and magnification of the filling's edges, looking for gaps, chips, fractures through the metal, and stained or soft margins.
• Probing the margins with a fine instrument to feel for catches, ledges and softened tooth structure at the junction between filling and tooth.
• X-rays, which still matter: they can show decay at the sides of the filling, decay between teeth and changes around the root tip that suggest the pulp is affected.
• Bite tests on individual cusps, asking you to bite on a small device one cusp at a time; pain on biting or on release of a single cusp points toward a crack in that part of the tooth.
• Transillumination or dye staining, where a bright light or a disclosing dye helps show a crack line that would otherwise be missed.
• Temperature tests that help judge whether the pulp is healthy, reversibly inflamed or beyond recovery, which changes the plan more than almost anything else.

Sometimes the final answer only comes once the old filling is removed and the dentist can see the floor of the cavity directly. Our guide on whether you can have a cavity without tooth pain covers the same silence from the other direction.

What replaces a failing amalgam

Material choice depends on the size and location of the cavity and on how much sound tooth is left once the old filling and any decay are removed. The options below move from least to most coverage.

A direct filling

When enough healthy enamel and dentin remain, the cavity can be refilled directly with a tooth-colored composite bonded to the tooth. Cracked teeth whose pulp is healthy or only reversibly inflamed have shown high rates of pulp and tooth survival when restored with direct or indirect composite restorations. Ask what material is proposed for your tooth and why.

An onlay or overlay

When the walls of the tooth are thin or a cusp has been weakened, a partial-coverage restoration made outside the mouth (an onlay or an overlay) can cover and reinforce the weak parts while leaving the sound parts untouched. Our guide on when a partial-coverage restoration may be discussed instead of a crown explains how that decision is reasoned, and the practice's biomimetic dentistry page describes its general approach to conserving tooth structure.

A crown

When little tooth structure remains, or a crack runs deep enough that the remaining walls cannot be trusted, a crown covers the whole tooth to protect a weak tooth from breaking or to restore one that already has. If the pulp has died or is irreversibly inflamed, root canal treatment may be needed before the crown. Nobody can promise in advance that a crown or a root canal can be avoided; what you can expect is an explanation of why one is or is not recommended. A tooth under a crown still needs care, as our guide on whether a tooth under a crown can still get a cavity explains. The practice lists same-day crowns, onlays and overlays with in-house milling; our walkthrough of a same-day crown appointment covers what that visit usually involves.

Why a large old filling often cannot simply be swapped like-for-like

A silver filling that has been in place for many years may already be large, and each replacement removes a little more tooth. Large restorations are themselves a recognized contributor to cracked teeth, and composite is usually suited to small- and medium-sized cavities. So the honest answer to "can you just put in a new filling?" is often "that depends on what is left once the old one comes out," and a plan may name a filling as the goal with an onlay or crown as the fallback if the remaining tooth turns out to be weaker than hoped.

How urgent is it?

Most failing fillings can be scheduled rather than treated as emergencies; describe your symptoms when you call so the office can judge how soon you should be seen. In the meantime, the ADA's general advice for a cracked or broken tooth is to rinse with warm water, use a cold compress on the face if there is swelling, and see a dentist as soon as possible, and clear trapped food gently with floss rather than anything sharp. It is also sensible to avoid chewing on that side until you are seen. If a broken edge is cutting your tongue or cheek, ask the office whether a temporary cover such as over-the-counter dental wax is reasonable until you are seen.

Call sooner, the same day if possible, for constant or throbbing pain, pain that wakes you, swelling of the gum or face, a loose piece of tooth, or a fever; if any of the emergency signs listed earlier is present, go to emergency care first. Our guide on what information helps your dentist decide urgency lists what to have ready when you call. The office does not publish after-hours or same-day arrangements on this page; ask when you call.

What this practice does and does not claim

Loul Dental Studio lists mercury-free restorations and biomimetic dentistry among its services. It does not claim that replacing a failing silver filling treats or prevents any general health condition, and this guide does not recommend removing fillings that are intact and sealing well; that is consistent with FDA guidance. Replacing intact fillings for reasons of your own is a different conversation with different trade-offs, and the examination still comes first.

The next step

Request a check-up or, if you have symptoms now, call during office hours and say so so the appointment can be arranged promptly. Bring any previous X-rays or notes about when the filling was placed. The examination, bite tests and X-rays described above usually show whether the tooth needs a filling, an onlay or overlay, or a crown, and whether the pulp is involved, and you can ask for a written explanation of what was found and why each option was or was not recommended.