Microplastics and BPA in fillings: what the research actually shows.
The white filling is one of dentistry's quiet triumphs — and it is, chemically, a plastic. Resin composites are polymer materials, and researchers have started asking what they release into the mouth over years of chewing. Here's what the studies genuinely show, what they don't, and what it means for you. Spoiler: it is not "rip out your fillings."
What a white filling is
Composite fillings are resin polymers — commonly built on bis-GMA, a chemical derived from bisphenol-A (BPA) — packed with glass or ceramic filler. They bond to the tooth, look natural, and have largely replaced metal amalgam. They are also, by any material definition, plastic: which means the questions now asked of food packaging and water bottles are being asked of the material chewed on thousands of times a day.
What the research shows
Three findings recur across the literature. First, trace BPA release is real but concentrated in the first days: saliva studies consistently detect small amounts of BPA in the 24–48 hours after a composite is placed, declining sharply afterwards — one measurement approach found tens of nanograms per millilitre immediately after placement, much of it removable by thorough rinsing. A 2022 laboratory study tracking release over 260 days found conventional bis-GMA composites released the most BPA, resin-modified glass ionomers less, and "BPA-free" formulations the least — with release in all cases highest on day one and falling over time.
Second, wear generates particles. A 2025 review in the Journal of Hazardous Materials concluded that micro- and nanoplastics are released in dental settings from resin composites, clear aligners and prosthetic materials through degradation, wear and handling — chewing slowly abrades a composite surface, and those abraded particles are swallowed.
Third, and this matters: the measured amounts in modern studies sit below established toxicity thresholds. A pilot study of newer UDMA-based (BPA-derivative-free) composites found no BPA release at all, and every concentration measured across materials fell below reported cytotoxic levels. Meanwhile a 2025 narrative review in Materials was frank about the field's limits: laboratory release is measurable, but real-world exposure data remain sparse and methods inconsistent. The honest position is "small, mostly transient, incompletely studied" — not "harmless," and not "alarming."
What you should actually do
Nothing drastic. No evidence supports removing sound fillings — drilling out an intact composite exposes you to far more material dust in ten minutes than years of quiet wear, and dentists rightly advise against it. What the research does support: asking what material is going in before your next filling. BPA-derivative-free composites (UDMA-based and newer chemistries) exist, perform well, and released no BPA in testing. If it matters to you, it's a one-sentence question to your dentist: "is this composite bis-GMA based, and is there a BPA-free alternative?"
Where bio. fits
Restorative material is the next frontier of our range — bio.bond, a plastic-conscious approach to bonding and repair, is in development and will be held to the same rule as everything we make: independent testing, results published at the bio. Standard. Until then, the same principle applies to fillings as to retainers: you're allowed to ask what's in your mouth, and good providers answer.
Related reading: Plastic-free dentistry: an honest guide · What are dental retainers made of?
Choose devices that are tested in the open.
bio.bond is coming for restorative work. Today, our retainers and aligners are made from bio-derived, plant-based materials instead of petroleum plastic — every lot independently tested, every result published.