Adegbembo AO, Watson PA, Lugowski SJ. The weight of wastes generated by removal of dental amalgam restorations and the concentration of mercury in dental wastewater. Journal of the Canadian Dental Association. 2002 Oct;68(9):553-558.
When an old amalgam comes out under a high-speed bur, where does the debris go—chair trap, pump trap, or straight into the wastewater? University of Toronto researchers weighed the waste stream and then measured mercury in the discharge with and without an ISO-certified amalgam separator.
What the study found
Amalgam restorations were removed from anatomic replica teeth and natural teeth with a tungsten carbide bur, high-speed handpiece, and conventional suction. Investigators weighed particles caught in the primary and secondary solids separators, filtered remaining wastewater through 15-µm paper, and measured total mercury by cold-vapour atomic absorption on instantaneous flow-through samples.
Mass split of removed amalgam:
- About 60% by weight reached the effluent
- About one-third stayed in the primary solids separator
- Less than 10% stayed in the secondary solids separator
With an ISO-compliant separator in line, mercury in instantaneous discharge fell 99.4%, from 31.2973 mg/L to 0.1800 mg/L. The authors conclude that conventional solids collectors miss most removal waste—and that a certified particle separator effectively cleans what they miss.
[Full-text note: The historical JCDA PDF/HTML hosts now return 404; quantitative results above are from the PubMed abstract (PMID 12366886) and contemporaneous JCDA abstract text preserved in citation databases.]
Why it matters for SMART
Every SMART removal appointment generates a dense slurry of amalgam particles. Adegbembo’s weighing study shows most of that mass bypasses ordinary chair and pump traps—exactly why IAOMT-aligned offices emphasize ISO-capable separators and proper hazardous-waste handling alongside dams, HVE, and water. Protecting the patient in the chair is incomplete if the same mercury simply relocates to the municipal plant. Weighing studies like this also help offices explain to staff why separator cartridges and trap filters are hazardous waste—not ordinary trash.
Practical takeaways
- Expect ~60% of removal mass in wastewater — Ordinary traps are not the whole story.
- Install an ISO-certified separator — This trial cut discharge Hg by 99.4%.
- Service primary/secondary collectors — They still capture meaningful fractions that must be recycled.
- Never rinse amalgam into the sink — Chairside scrap belongs in sealed mercury waste containers.
- Combine with SMART technique — Separators manage the drain; SMART manages the breathing zone.
Bottom line: Adegbembo and colleagues found about 60% of amalgam removal waste escaped conventional solids collectors into wastewater, while an ISO-certified separator cut instantaneous mercury discharge by 99.4%—a clear environmental counterpart to SMART chairside protection.