Dental Fillings
What is a filling — and how we think about materials
When decay (a cavity) or a small fracture damages a tooth, the dentist removes the damaged part and fills the space with a restorative material. This stops the decay from spreading and restores the tooth’s shape and function.
Our philosophy is simple: wherever a filling does not show — molars, premolars, and the non-visible surfaces of front teeth — durability should decide the material, and metal-based restorations win that comparison. Amalgam is the best all-round choice; gold is the best there is for those who can afford it. Tooth-colored composite is what we recommend for the surfaces you actually see when you smile. This is exactly what we specify in our own collaboration contracts — we practice what we recommend.
Make the right choice: your options
Ranked by durability and long-term value. Where the filling sits — chewing tooth, hidden surface, or visible smile surface — decides the right material.
| Option | Best for | Pros | Cons | Typical lifespan | Relative cost |
|---|---|---|---|---|---|
| Our preferenceAmalgam (silver) | Molars, premolars and non-visible surfaces — the best all-round choice | The most forgiving, proven material in dentistry; tolerates moisture during placement; self-sealing margins over time; unbeatable value | Metallic color — for surfaces that don’t show | 10–15+ years, often 20+ | $ |
| Gold inlay/onlay | The best restoration money can buy — for those who can afford it | The durability benchmark of all dentistry; wears at the same rate as natural enamel; thermal expansion virtually identical to tooth structure, so the seal stays tight with hot and cold; among the most biocompatible materials in medicine; gentle on opposing teeth; protects weakened cusps | Gold color; lab-made (two visits); highest upfront cost — but often the cheapest per year of service | 15–20+ years, often lifelong | $$$$ |
| Composite (tooth-colored resin) | Visible surfaces only | Excellent aesthetics; bonds to the tooth; preserves more tooth substance in small cavities | Shorter lifespan under heavy chewing; shrinkage stress on curing pulls on the tooth walls and can start micro-cracks — a higher risk of the tooth itself cracking later; shrinkage plus a temperature expansion mismatch opens micro-gaps that let bacteria in and promote bacterial growth, so new decay starts under the filling — and reaches the nerve faster, meaning a higher risk of needing root canal treatment; must be placed bone-dry to perform; releases trace BPA-related monomers — hormone-mimicking chemicals that some research suggests may increase the risk of certain cancers (not proven in humans) | 5–10 years (less in big posterior fillings) | $$ |
| Glass ionomer | Baby teeth, root surfaces, temporary repairs | Releases fluoride; bonds chemically; quick | Weakest option; wears fast; not for chewing surfaces long-term | 3–5 years | $ |
Costs are relative and vary a lot by country and clinic. Lifespans are typical ranges from long-term clinical studies — cavity size, bite forces and home care shift them in both directions.
When the cavity is too big for a filling: inlays and onlays
When a cavity gets large, a plain filling stops being sensible: the tooth becomes a thin-walled shell packed with material, and it cracks. The answer is a lab-made restoration cemented into the tooth — an inlay (sitting within the cusps) or an onlay (covering and protecting one or more cusps). It is the step between a filling and a crown, and it keeps far more of your tooth than a crown would.
Here the material choice gets consequential, because you are cementing a rigid object into a weakened tooth. Metal flexes with the tooth and cannot break. Ceramic does not flex — and when it goes, it can take the tooth with it.
| Option | Best for | Pros | Cons | Typical lifespan | Relative cost |
|---|---|---|---|---|---|
| Our preferenceGold inlay / onlay | Large cavities in molars and premolars — the best restoration money can buy | It cannot crack, chip or shatter — the failure mode that ends ceramic restorations does not exist for gold. Wears at the same rate as natural enamel and expands with temperature like natural tooth, so the seal stays tight for decades. Among the most biocompatible materials in medicine — inert, no resin chemistry. Needs the least healthy tooth removed, and an onlay actively protects weakened cusps rather than wedging them apart. | Gold color, so it is for teeth nobody sees; two visits; highest upfront cost — though usually the cheapest per year of service | 15–20+ years, often lifelong | $$$$ |
| Other metal alloy inlay / onlay | Back teeth, on a smaller budget | Near-gold durability and the same fracture-proof behaviour; minimal tooth removal | Metal color | 15–20 years | $$$ |
| E-max (lithium disilicate) inlay / onlay | When appearance is the priority and the tooth shows | The most natural-looking of the ceramics | Brittle: it can fracture outright under chewing load, and the tooth beneath can crack with it. Harder than enamel, so it wears and can crack opposing teeth. Requires more healthy tooth to be cut away than metal, because ceramic needs bulk to survive. Must be bonded with resin cement — the same monomer chemistry, including BPA-related compounds, that we warn about in white fillings, and the bond can fail, letting bacteria in underneath. | 8–12 years | $$$ |
| Porcelain inlay / onlay | Rarely the right choice today | Good aesthetics; resists wear itself | The most brittle of the group — chips and fractures readily, and being far harder than enamel it aggressively abrades and can crack the teeth it bites against. Same resin-bonding chemistry; same demand for extra tooth removal. | 5–10 years | $$$ |
| Zirconia inlay / onlay | When metal is declined outright | The strongest ceramic; hard to fracture in bulk | Extremely hard — far harder than your enamel. It grinds down the opposing tooth and can crack it or existing dental work, and polishing reduces but does not remove this. When it does fail it fails suddenly and the tooth often fractures with it. Resin-bonded, so the same chemistry concerns; and because it is one solid block, chips and margin problems are hard to repair. | 10–15 years | $$$ |
| Composite (resin) inlay | Almost never worth it | Cheaper than ceramic; repairable | All the drawbacks of a white filling — wear, shrinkage stress, secondary decay, resin chemistry — but with the added cost and two visits of a lab-made restoration. You pay more for something that behaves like the material we already advise against. | 5–8 years | $$ |
The three problems every white inlay or onlay shares. 1. They are brittle. Ceramic has no give: it survives until it does not, and the fracture often runs into the tooth underneath — sometimes below the gum, where the tooth cannot be saved. 2. They are harder than your teeth. Every bite grinds them against natural enamel, wearing and sometimes cracking the teeth opposite. Gold is close to enamel in hardness and simply does not do this. 3. They must be resin-bonded. A ceramic inlay is not pure ceramic in your mouth — it is glued in with the same resin chemistry, including BPA-related compounds, that we warn about in white fillings. And if that bond fails at any point around the margin, bacteria get underneath a restoration you cannot see behind.
There is a fourth, quieter cost: ceramic needs bulk to survive, so more healthy tooth has to be cut away to make room for it than a metal restoration would ever require. You lose more tooth to get something that lasts less time.
Follow the money: why you are almost always offered white
Let us be clear about something first: most dentists are honest people trying to do a good job. Very few are sitting there scheming. But the defaults of a profession are shaped by its incentives, and the incentives around white fillings all point the same way — and none of them point at how long your tooth lasts.
- A white filling bills higher than a silver one. In almost every fee schedule in the world, composite is priced above amalgam for the same cavity. The dentist earns more for the same tooth, on the same day.
- A ceramic inlay or crown bills far higher still. Cosmetic dentistry is the most profitable work in the building, and it is what practice-management courses, lab reps and material manufacturers push hardest.
- A restoration that fails sooner brings you back sooner. Nobody has to intend this for it to be true: a material with a 7-year life generates roughly twice the lifetime revenue of one with a 15-year life — and each redo is bigger, and billed higher, than the last.
- Patients ask for it. Decades of marketing have taught people that white = modern = healthy and metal = old = bad. Dentists who suggest amalgam are often argued with. The path of least resistance is to give people what they ask for.
- Regulation removed the choice in some places. The EU restricted amalgam from 2025 on environmental grounds — mercury in dental waste water — not because it harms patients. Many dentists have simply stopped offering it, and a generation of graduates was never properly trained to place it.
None of that makes white fillings a fraud. It makes them the default — chosen for reasons that have very little to do with how many years your tooth stays in your head.
The real price: what a white filling costs over twenty years
The cheap-looking choice is rarely the cheap one. Dentistry has a name for what follows a first white filling in a heavily loaded back tooth: the restoration cycle — each repair removing a little more tooth, each one bigger and more expensive than the last, until there is not enough tooth left to repair.
| What happens | Amalgam / gold in a back tooth | White composite in the same tooth |
|---|---|---|
| The first restoration | One filling. Amalgam is the cheapest material there is; a gold onlay costs more upfront. | One filling — typically charged at a higher fee than amalgam, because it takes longer to place and is sold as the premium option. |
| 5–10 years later | Still there. Amalgam margins tend to seal themselves as they age; gold is barely worn. | Wear, marginal gaps, or decay underneath. Replacement filling — and each replacement removes a little more healthy tooth. |
| 10–15 years | Often still the original restoration. | Second or third replacement. The cavity is bigger now, the walls thinner. Talk turns to an inlay, onlay or crown. |
| 15–20 years | Amalgam frequently still in service. A gold onlay may well outlive you. | The tooth is mostly restoration. A crack, or decay reaching the nerve, brings a root canal — then a crown on top of it. |
| The end of the road | The tooth is intact and functioning, having cost you one restoration. | A heavily rebuilt, root-treated tooth — or an extraction and implant, the most expensive outcome in dentistry. |
Add it up. Over twenty years, a white filling in a molar can plausibly cost you: the original filling, two or three replacements, an onlay or crown, and — if a crack or decay reaches the nerve — a root canal and another crown. That is five to seven appointments and a substantial bill, to end up with a weakened, root-treated tooth. The amalgam or gold alternative, in many cases, costs you one appointment and still has your tooth intact and alive at the end of it.
And every step of that cycle removes healthy tooth that never grows back. The most expensive thing in dentistry is not gold. It is a tooth you cannot save.
How the treatment works
- Diagnosis
The dentist examines the tooth, often with an X-ray, to see how deep the decay goes. - Numbing
Local anesthetic makes the area completely numb. Small, shallow cavities sometimes need no anesthetic at all. - Removing the decay
The soft, decayed part of the tooth is removed. This usually takes just a few minutes. - Filling the tooth
Amalgam is packed firmly into the cavity and carved to shape. Composite is placed in layers, hardened with a blue light, then shaped and polished. Gold inlays/onlays are made in a lab and cemented at a second visit. - Bite check
You bite on marking paper so the dentist can adjust the filling until it feels natural.
Aftercare
- Numbness lasts 1–3 hours — be careful not to bite your cheek or lip.
- Composite hardens immediately; with fresh amalgam, avoid chewing hard food on it for 24 hours while it reaches full strength.
- Mild sensitivity to cold or pressure for a few days is normal.
- If your bite feels “high” or uneven after a few days, ask for a small adjustment — it takes two minutes.
- Brush twice a day with fluoride toothpaste and clean between teeth — the tooth around the filling can still get new decay.
Frequently asked questions
Longevity and reliability. Large clinical studies consistently show amalgam outlasting composite in load-bearing teeth, and it is far more forgiving of real-world conditions like moisture during placement. Gold goes even further — it is the most durable restoration in all of dentistry, it wears at the same rate as your own enamel, and it expands with temperature like natural tooth, so the seal stays tight for decades. In places nobody sees, trouble-free chewing beats invisible aesthetics. Amalgam is the best all-round choice; gold is the upgrade for those who can afford it.
Four honest reasons. Lifespan: under heavy chewing, composite wears and fails years earlier than metal. New decay: composite shrinks slightly while curing and expands/contracts with hot and cold more than your tooth does — over time this can open micro-gaps that collect bacteria, and studies show more secondary decay around composite than amalgam. Technique: composite only performs well when placed absolutely dry, which is hard to guarantee deep in the mouth. Chemistry: composite resins release small amounts of monomers that are toxic to cells in laboratory studies, including compounds related to BPA — a hormone-mimicking (endocrine-disrupting) chemical that some studies suggest may increase the risk of certain hormone-related cancers. Regulators take this chemistry seriously: the EU banned BPA in food-contact materials from January 2025 (Regulation (EU) 2024/3190), after the European Food Safety Authority slashed its safe-intake limit by a factor of 20,000. It is a fair question why a chemical considered too risky for the lining of a food tin is acceptable bonded to your tooth, in your mouth, 24 hours a day for years. To be clear: harm from fillings has not been proven in humans at these exposure levels, and we say so plainly. But with proven mechanical drawbacks and unresolved chemical questions, we see no reason to place composite where nobody sees the tooth and metal simply performs better.
For an inlay or onlay, our answer is the same for every tooth it could possibly go in: choose metal. Gold if you can afford it, another metal alloy if you cannot.
Here is why this one is not a close call. An inlay or onlay is only ever placed in a molar or a premolar — those are the teeth with the chewing surfaces and the cusps that need protecting. And it sits on the chewing surface, not on the front of the tooth. Even in a premolar, that surface is barely visible: someone would have to be looking into your open mouth, from above, at the right angle, to see it at all. You are being asked to accept a materially worse restoration in exchange for an aesthetic benefit that, in practice, almost nobody will ever notice.
And “materially worse” is not a figure of speech. Compared with a gold inlay in the same tooth, an e-max or zirconia inlay:
- can crack, and take the tooth with it — ceramic is brittle, it fails suddenly, and the fracture often runs into the tooth beneath, sometimes below the gum where nothing can be done;
- is far harder than enamel, so it grinds down and can crack the teeth it bites against, polished or not;
- needs more of your healthy tooth cut away, because ceramic requires bulk to survive where gold can be paper-thin at the margins;
- must be glued in with resin cement — the same BPA-related chemistry we warn about in white fillings — and if that bond fails anywhere, bacteria get in underneath;
- lasts years less.
Gold, by contrast, cannot crack, chip or shatter; it wears at the same rate as your own enamel; it expands and contracts with hot and cold like natural tooth, so the seal stays tight for decades; and it is one of the most biologically inert materials in medicine.
So the question to ask is not “is this tooth visible?” — for an inlay, it effectively never is. The question is: why am I being offered the weaker material for a tooth nobody sees?
The honest exception: if a cavity extends onto the visible front-facing surface of a premolar — high in your smile line, where it genuinely shows when you talk — then appearance is a legitimate factor and the trade-off becomes a real conversation. That situation is uncommon, and it is not what most ceramic inlays are sold for.
Both risks are real, and both come from the same root cause: composite shrinks as it hardens.
Cracked teeth. That shrinkage does not happen in mid-air — the material is bonded to your tooth, so as it contracts it pulls the walls of the tooth inward. In a large filling this shrinkage stress can flex the cusps and seed micro-cracks in the remaining tooth structure. Years of chewing then work on those cracks. Metal fillings do not shrink as they set, so they do not load the tooth this way — and an inlay, onlay or crown in metal actively protects weakened cusps instead of pulling on them.
Root canals. Where shrinkage wins against the bond, it leaves a micro-gap at the margin. Bacteria enter that gap easily, and composite’s surface tends to accumulate more plaque bacteria than amalgam does. Decay then travels along the underside of the filling — close to the nerve, and hidden from view, so it is often found late. Several long-term studies have found more secondary decay and more subsequent root canal treatment on teeth restored with composite than with amalgam. Amalgam behaves in the opposite way: corrosion products gradually seal its margins, so it tends to get tighter with age, not leakier.
This is why, for a molar or premolar, we would rather give you a filling nobody can see than a white one that quietly puts the tooth at risk.
Yes — the WHO, FDI and major national dental associations consider amalgam safe for the general population; the mercury in it is bound in a stable alloy. The EU restricted amalgam use from 2025 primarily for environmental reasons (mercury waste), not patient safety, and it remains a standard, approved material in most of the world. People with a documented mercury allergy (rare) should choose alternatives.
Yes. Fillings wear out over the years and can be replaced, often several times, before a tooth needs a crown. Each replacement removes a little more tooth — another argument for choosing the longest-lasting material the first time.
No — and we would rather you did not read it that way. The overwhelming majority of dentists are decent clinicians who want your teeth to last. Very few of them are cynics.
What we are saying is that the incentives in dentistry are not aligned with the longevity of your teeth, and defaults drift in the direction of the incentives. White bills higher than silver. Ceramic bills higher than white. Work that fails sooner brings the patient back sooner. Patients ask for white and argue when offered metal. Regulators removed amalgam for environmental reasons and dental schools quietly stopped teaching it. Put all of that together and you get a profession whose default answer is a material that, in a back tooth, is measurably worse for you — without anyone in the chain having to act in bad faith.
So do not accuse your dentist. Just ask them the questions a good one will happily answer: How long would you expect this to last? What would you put in your own molar? If this fails, what is the next step — and the one after that? Is amalgam or a gold onlay an option here, and if not, why not?
A dentist who welcomes those questions is one worth keeping. One who gets defensive has told you something too.
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