When does a filling need to be replaced?

A filling is a repair in a hostile place: bathed in saliva, attacked by acid several times a day, chewed on with forces that in the back of the mouth run into hundreds of newtons, heated and cooled by everything you drink. Tooth and filling expand and contract at slightly different rates, and over years that flexing works on the join.

So the question is never whether a filling will fail, but when — and how you will know. Service life by material is a topic of its own: How long does a dental filling last? (EN).

New or returning sensitivity to cold or sweetness. One tooth, one spot, a wince that keeps coming back. Sugar drawing fluid through exposed dentine tubules is a classic marker of a leaking margin, and it often appears before anything is visible.

Pain or pressure when you bite, especially a sharp jab as you release. That can mean a crack in the tooth around the filling — a different problem from decay, and one to assess promptly.

Floss that shreds or catches at the same gap every time, or a rough step your tongue keeps finding. Plaque collects on rough surfaces, and plaque at a filling margin is how new decay begins.

Food packing between two teeth. If you fish food out of the same space after every meal, the contact point has been lost, often through wear on the filling.

A dark shadow or grey line at the edge. In tooth-coloured fillings that can be decay showing through; around old silver fillings a grey halo is usually harmless metal staining. Not a distinction to make in a bathroom mirror.

A chip, a missing piece, or a bad taste from one spot. Even a small chip leaves the tooth underneath unprotected, and bacteria under a leaking filling produce that taste.

Nothing at all. The uncomfortable truth: decay under a filling frequently causes no symptoms until it is deep. That is what routine check-ups and X-rays are for.

The commonest failure. The join develops a microscopic gap, bacteria and acids get in, and the seal is lost. Under a microscope or on an X-ray this shows long before you feel anything.

New decay at the edge of an existing filling — one of the most frequent reasons for any dental treatment in adults. It travels along the margin and spreads sideways in the softer dentine, which is why a small dark line can sit above a much larger cavity: Caries under an old filling (EN).

Large old fillings leave thin walls of tooth standing either side. Those walls flex under load and can split — sometimes with a sharp pain on releasing a bite, sometimes with nothing until the cusp breaks off. This is where replacing like for like is the wrong answer and an inlay, partial crown or crown is the right one.

Chewing surfaces wear down, and where a filling meets the neighbouring tooth the contact point can flatten until food packs in, irritating the gum and starting decay from the side. Discolouration is a different matter: composite takes up colour from coffee, tea, red wine, curry and tobacco and does not lighten with whitening — a cosmetic reason to replace a filling, not a medical one.

This is the part patients rarely hear about, and it is where the real decision lies.

Leave alone. A sealed, functional filling with no decay and no crack should stay. Every replacement removes a little more healthy tooth: the cavity widens, the walls thin, and after enough rounds a tooth that once needed a small filling needs a crown. Dentists call this the restorative cycle, and the way to slow it is not to enter it unnecessarily. “It’s old” is not a diagnosis.

Repair. If one corner has chipped or one margin has a defect and the rest is sound, that section can often be cleaned out and rebuilt while the intact part stays put. Repair preserves substance and is less invasive, and German and international dental bodies have moved firmly in this direction. It is not right everywhere: where a filling is failing in several places, or decay has undermined it, the whole thing comes out.

Replace. Decay underneath, a broken or loose filling, a defective margin over a wide area, or a tooth that hurts persistently at that spot.

Escalate. Sometimes a filling is no longer the right restoration at all — little tooth wall left, a fractured cusp, or a tooth after root canal treatment. An inlay, partial crown or crown then protects better than an ever-larger filling: Filling or crown? When each solution makes sense (EN).

This comes up in almost every consultation with patients who have moved to Germany, so let us be precise.

Since 2025 amalgam may no longer be placed in the European Union, apart from narrowly defined medical exceptions. That is a rule about new fillings, and largely an environmental measure driven by mercury in wastewater. It is not an instruction to remove what is already in your mouth.

The position of German dental associations is that an intact, well-sealing amalgam filling is not in itself a reason for removal. Drilling one out releases more mercury vapour in that half hour than leaving it does over years, and it costs healthy tooth substance. Amalgam fillings are replaced for the same reasons as any other: decay underneath, a fracture, a failing margin, or a documented allergy. Non-urgent removal is generally postponed during pregnancy and breastfeeding, and where one has to come out anyway, careful technique — good suction and isolation — is standard. What replaces it today is tooth-coloured composite: White fillings: what they are made of and how they are placed (EN).

1. We look and we listen. Which tooth, which trigger, how long — then a visual and tactile examination, usually under the microscope, which resolves margins the naked eye cannot. 2. X-ray where it is needed. Decay between teeth and under fillings is often invisible from above; a small bitewing X-ray is the standard tool. 3. We tell you what we found and what the options are, including monitoring something small rather than treating it today. 4. Treatment. Local anaesthetic (Betäubung) where the work goes near the nerve, old material and decay removed, the tooth dried, the new filling bonded and layered in, then shaped, the bite checked and the surface polished. Half an hour or so for a single surface, longer for a large rebuild. How we work: Fillings and caries treatment – service page (EN).

What it costs you. In statutory health insurance (gesetzliche Krankenversicherung, GKV) a replacement filling is covered exactly like the first one. Since the amalgam ban, standard care (Regelversorgung) means a tooth-coloured filling in back teeth as well as front teeth, provided as a benefit in kind with nothing to pay at the desk. Extra costs arise only if you opt for something beyond that standard — a laboratory-made ceramic inlay, say — and then only under a written extra-cost agreement (Mehrkostenvereinbarung) signed before treatment, with the fund’s share still counting towards the bill. The bonus booklet (Bonusheft) belongs to the denture system and does not change what a filling costs you. The money side in full: What does a filling cost? (EN).

If you grind your teeth. Bruxism is one of the strongest predictors that fillings and the teeth around them will fracture. If you replace fillings often, the fillings are usually not the problem — the load is, and a night guard (Knirscherschiene) protects the work.

Dry mouth. Many everyday medications reduce saliva flow — some blood pressure drugs, antidepressants, antihistamines — and less saliva means markedly more decay at filling margins. Tell us what you take; it changes how often we want to see you.

Teenagers and young adults. Fillings placed in childhood reach their limit as adult chewing forces arrive — a good age for one careful review rather than a decade of drift.

If you have just moved to Germany. Your fillings were placed under a different system and there is no shared record here. Bring what you have: old X-rays, a treatment summary, even photos on your phone. It saves radiation, time and guesswork. If you would like to discuss all this in English: English-Speaking Dentist in NRW.