Hylander LD, Lindvall A, Uhrberg R, Gahnberg L, Lindh U. Mercury recovery in situ of four different dental amalgam separators. Science of the Total Environment. 2006 Jul 31;366(1):320-336.
Lab stickers on amalgam separators often claim 95–99% mercury capture under ISO 11143. Swedish researchers asked a tougher question: what happens in real clinics—with real vacuum lines, peak flows, and particle mixes—when three commercial sedimentary separators (and one improved prototype) are measured on the job?
What the study found
The team compared three market separators, each marketed at roughly 99% efficiency under Danish/ISO protocols, plus an investigational low-emission prototype, during in situ clinic operation.
Results for the commercial units were sobering:
- Real-world Hg reduction was only 79–91%—far below manufacturer claims.
- Average mercury remaining in outgoing wastewater was about 1.5 mg/L.
The prototype separator retained 99.9% of wastewater mercury emissions, leaving an average of only 0.004 mg/L Hg in the outgoing stream. The authors argue that physical limits of pure sedimentation miss the finest (and often most problematic) mercury fractions—fractions the ISO test protocol does not fully represent—so the standard itself needs revision. Their long-term prescription: abolish dental amalgam use and clean tubing systems; until then, deploy low-emission separators (alone or stacked with sedimentary units) whenever amalgam is still placed, polished, or removed.
[Paywall note: Elsevier full text may require institutional access. Efficiency ranges, outgoing concentrations, and conclusions above are from the PubMed abstract (PMID 16182343); clinic-by-clinic tables were not re-verified page-by-page.]
Why it matters for SMART
SMART protects people in the chair; separators protect the sewer and the watershed. Hylander’s in-clinic data show why “we have a certified separator” is not enough—maintenance, technology type, and real hydraulic conditions decide whether mercury actually leaves the building. Pairing SMART chairside technique with a high-performing, well-maintained separator (and eventual mercury-free materials) closes both the human and environmental sides of safer dentistry.
Practical takeaways
- Do not trust the brochure alone — Field efficiency can lag ISO lab claims by a wide margin.
- Maintain and replace on schedule — Tubing sludge and worn units sabotage capture.
- Ask what technology you have — Sedimentation-only designs may miss fine/soluble fractions.
- Consider dual/low-emission systems — The prototype’s 99.9% result shows better hardware is possible.
- Plan the phase-down — Ending new amalgam use is the durable emissions fix.
Bottom line: Hylander and colleagues showed three commercial sedimentary separators recovered only 79–91% of mercury in clinic use—versus 99.9% for an improved prototype—evidence that SMART practices need proven wastewater controls, not just a certification sticker.