Tooth-coloured composite resin fillings — now often presented as the safer, mercury-free alternative to amalgam — are manufactured from bis-GMA (bisphenol A glycidyl dimethacrylate) or bis-DMA (bisphenol A dimethacrylate) monomers. Both bis-GMA and bis-DMA are synthesised from bisphenol A and retain the BPA structure within their polymer backbone. Residual unreacted BPA and bis-DMA leach from dental composites for hours to days following placement — saliva collected immediately after composite filling placement contains detectable BPA. Bis-DMA is additionally hydrolysed in the oral environment to release free BPA over time. While total BPA release from dental composites is modest compared to dietary sources, it is direct oral mucosal exposure — the most bioavailable route — and it occurs repeatedly throughout the filling's 5–15 year lifespan.
Where it's found
Tooth-coloured composite resin fillings placed in posterior (molar and premolar) and anterior (front) teeth. Composite resin dental bonding agents and dental veneers. Dental sealants applied to children's molar fissures to prevent decay — these are perhaps the most concerning application because they cover large tooth surfaces, are applied to children's teeth, and the BPA release has been measured in children's saliva immediately after sealant application. Orthodontic adhesives used to bond braces brackets. Some glass ionomer cements contain resin components.
Routes of exposure
Oral mucosal absorption of BPA and bis-DMA directly from the filling surface — saliva acts as the solvent for unreacted monomer extraction. BPA is rapidly absorbed across oral mucosal tissue, bypassing first-pass hepatic metabolism that reduces the bioavailability of dietary BPA. Salivary BPA from freshly placed composites and sealants is the highest-concentration oral exposure event. Ongoing low-level leaching from the filling surface throughout its lifespan provides chronic low-level oral mucosal exposure. Inhalation of bis-DMA aerosol during composite polishing and drilling — relevant to both patients and dental practitioners.
Health concerns
Bisphenol A is an oestrogenic endocrine disruptor — it binds oestrogen receptors ERα and ERβ, activates membrane-associated oestrogen signalling, and interferes with thyroid hormone receptor binding. BPA from dietary sources is associated with increased odds of cardiovascular disease, obesity, insulin resistance, and fertility impacts in epidemiological studies. The dental composite route delivers BPA via the oral mucosa with higher bioavailability than gut-absorbed dietary BPA. Children receiving dental sealants have measurably elevated urinary BPA in the hours following application. Dental practitioners are occupationally exposed during composite placement and polishing.
Evidence
BPA oestrogenic activity is established. BPA release from dental composites and sealants is analytically documented. Elevated urinary BPA in children within 24 hours of dental sealant placement is demonstrated in controlled studies. The health significance of composite-derived BPA specifically, relative to background dietary BPA exposure, is difficult to quantify — dental BPA is one source among many. Regulatory assessment of dental composite BPA by the EU Scientific Committee on Consumer Safety (SCCS) has been ongoing. The EU restriction of BPA in food contact materials (2022) does not cover dental materials, which fall under the Medical Devices Regulation.
Who's most at risk
Children receiving dental sealants on multiple teeth — peak BPA exposure in children's oral environment. Patients receiving multiple composite restorations placed in a single appointment. Dental hygienists and dentists who routinely polish and drill composite restorations. Patients with many existing composite fillings who are undergoing routine maintenance polishing. Pregnant women at dental appointments where composite work is performed.
Regulatory status
RegulationDental composites and sealants are classified as medical devices under the UK Medical Devices Regulations 2002 and the EU Medical Devices Regulation (2017/745) — they are not regulated as food contact materials or cosmetics, and BPA-specific limits do not directly apply. The ISO 4049 standard for resin-based restorative materials does not set BPA leaching limits. Individual BPA-free composite formulations (using urethane dimethacrylate, UDMA, rather than bis-GMA) are available and increasingly used by forward-thinking dental practices.
How to reduce your exposure
Ask your dentist whether BPA-free or low-BPA composite formulations are available for your treatment. BPA-free composites using UDMA monomer are available at most modern dental suppliers — the performance is equivalent. After any composite or sealant placement, polishing the restoration surface to remove the oxygen-inhibited surface layer substantially reduces initial BPA release. Rinsing with water immediately after placement and polishing removes residual surface BPA before oral mucosal absorption. For children's fissure sealants, discuss glass ionomer cement alternatives with your dentist — these do not contain BPA-based monomers.
The nutrition connection
BPA is an oestrogenic endocrine disruptor that also affects thyroid hormone binding — adequate iodine and selenium nutrition is relevant to thyroid resilience. Cruciferous vegetables support BPA metabolism via CYP1A1 induction and phase II conjugation. Urinary BPA excretion depends on glucuronidation — a process requiring adequate UDP-glucuronic acid synthesis from glucose and B-vitamin cofactors. Fermented foods may support the gut microbiome's BPA deglucuronidation regulation, which is relevant to the enterohepatic recirculation of BPA. Sulforaphane from broccoli sprouts has been shown to enhance BPA clearance in animal studies.