Fillings: Composite vs. Amalgam

The dentist asks whether you want the white filling or the silver one. Most people say "the white one" because it sounds better, then spend the drive home wondering if they picked right. Or the opposite: you have silver fillings from childhood, read something alarming about mercury, and now wonder whether to have them out.

The short version: both are considered safe and effective for most adults. Amalgam has a longevity edge in back teeth, though the evidence is weaker than the confident numbers floating around suggest. Composite looks like a tooth and generally preserves more of it. And amalgam is being phased out worldwide for environmental reasons, which increasingly shapes what's offered.

What's actually in each one

Amalgam, the "silver" filling, is liquid elemental mercury — roughly 42 to 50 percent by weight — mixed with a powdered alloy of silver, tin, and copper. It's been in use more than 150 years, so we know how it behaves over decades.

Composite is a tooth-colored resin filled with glass or ceramic particles, placed soft and hardened with a curing light. It bonds to the tooth rather than being wedged into an undercut shape, so the dentist often needn't cut retention grooves into sound enamel — the quiet argument for composite.

Which one lasts longer?

Amalgam, probably — but the evidence base is narrower than it looks.

A Cochrane Oral Health review, updated in 2021, found composite fillings in permanent back teeth were close to twice as likely to fail as amalgam, driven mainly by new decay at the edge. No clear difference in fracture showed up, though that estimate was too imprecise to rule one out. Cochrane rated the evidence low to very low certainty, with two caveats that matter: the main analysis rested on trials in children aged six to twelve, and composite materials have likely improved since — likely, not demonstrably, since nobody has repeated the comparison with modern materials. A 2025 review in Cureus points the same way, highlighting a cohort where amalgam's median survival passed 16 years against about 11 for composite, while rating its studies at moderate to high risk of bias.

The direction is consistent, but much of that comparison traces to older trials, so the true gap in a modern adult mouth is uncertain — and these are averages, not predictions about your tooth.

Is the mercury in amalgam dangerous?

For most people, the major health bodies say no — with specific exceptions.

The FDA has not banned amalgam and advises against removing fillings that are intact with no decay underneath, since taking out a sound amalgam exposes you to more mercury vapor than leaving it alone. In 2020 it did recommend certain groups avoid new amalgam whenever possible and appropriate: children, especially under six; people pregnant, planning to be, or nursing, and their babies; people with pre-existing neurological disease such as MS, Alzheimer's, or Parkinson's; people with impaired kidney function; and anyone allergic to the metals in it.

The ADA holds that amalgam is safe and that the mercury it releases falls below the EPA's reference dose. The International Association for Dental Research reaffirmed that in June 2025, citing two federally funded trials of 500-plus children each that found no difference in neurological or kidney testing.

The stronger case against amalgam has always been environmental, and it has largely won. In November 2025 the parties to the Minamata Convention agreed to phase dental amalgam out globally by 2034, upgrading an earlier commitment to phase it down. The EU banned it from January 2025, with a narrow exception where a dentist judges it strictly necessary. In the US it remains legal, though in July 2026 CMS urged state Medicaid programs to restrict coverage — a recommendation, not a mandate, but one that may reach what your plan pays. Offices that place or remove amalgam, including ours in Riverside, must run EPA-required separators.

What about BPA in composite?

Some composite resins release trace bisphenol A. The ADA's read: a small, temporary rise can appear in saliva and urine right after placement and returns to baseline within a day or two, and diet — canned food, plastic containers, receipts — dominates BPA exposure by a wide margin. Evidence on long-term, low-dose exposure remains scarce; careful curing and rinsing afterward reduce what little there is.

How we actually decide

Front teeth and anything in your smile line: composite, essentially always. Small and moderate cavities: composite performs well. Very large restorations on molars, especially with a heavy bite or a grinding habit: amalgam still has a durability argument, though at that size a crown or onlay is often the better answer than either filling. Composite also needs a dry field to bond, so a deep cavity near the gum line is harder to restore with it. Cost belongs in the conversation too — amalgam has typically been cheaper, and some plans reimburse composite on back teeth at the amalgam rate only.

When to see your dentist

Book an appointment if you notice a rough or chipped edge on an old filling, feel a catch when you floss around a filled tooth, find a filling sits high when you bite, or see a visible gap at the margin. Those suggest a filling may be failing with decay underneath — much easier to fix early. A dark line alone around a silver filling is usually staining, not decay — worth mentioning at your next visit, not worth worrying about.

Pain that lingers more than a few seconds after something cold is a different signal. That points to the nerve inside the tooth and should be seen promptly, whatever the filling looks like.

And if you're thinking about having intact amalgams removed purely out of mercury concern, talk it through first. Neither the FDA nor the ADA recommends it, and replacing a working filling costs you some tooth.

If you're in Riverside and due for a check-up, or have an old filling you've been quietly worrying about, we'd be glad to take a look and talk it through. Hashimi Dental is at 3701 Market St, Suite E.

This article is general information, not a diagnosis or treatment recommendation for any individual. Please see a dentist about your own situation.

Sources: American Dental Association (Oral Health Topics: Amalgam; Bisphenol A; Amalgam Separators), U.S. Food and Drug Administration (dental amalgam recommendations, 2020), Cochrane Oral Health (CD005620, 2021), International Association for Dental Research (position statement on the safety of dental amalgam, updated June 2025), Cureus systematic review (2025), U.S. Environmental Protection Agency (40 CFR Part 441), U.S. Department of Health and Human Services / CMS (July 2026), Minamata Convention on Mercury (COP-6, November 2025).