Hahn LJ, Kloiber R, Vimy MJ, Takahashi Y, Lorscheider FL. Dental “silver” tooth fillings: a source of mercury exposure revealed by whole-body image scan and tissue analysis. The FASEB Journal. 1989;3(14):2641-2646.
Are amalgam fillings sealed tombs—or slow-release sources? Hahn and colleagues used radioactive mercury in animal amalgam restorations and whole-body imaging to visualize where released mercury goes.
What the study found
Mercury (Hg) vapor is released from dental “silver” tooth fillings into human mouth air after chewing, but its possible uptake routes and distribution among body tissues are unknown. This investigation demonstrates that when radioactive 203Hg is mixed with dental Hg/silver fillings (amalgam) and placed in teeth of adult sheep, the isotope will appear in various organs and tissues within 29 days. Evidence of Hg uptake, as determined by whole-body scanning and measurement of isotope in specific tissues, revealed three uptake sites: lung, gastrointestinal, and jaw tissue absorption. Once absorbed, high concentrations of dental amalgam Hg rapidly localize in kidneys and liver. Results are discussed in view of potential health consequences from long-term exposure to Hg from this dental material.
Why it matters for SMART
Whole-body distribution evidence undercuts the folk claim that amalgam mercury “stays in the tooth.” Hahn’s sheep model showed uptake through lung, gut, and jaw tissue within weeks, with kidneys and liver as major depots—so vapor and swallowed debris are both clinically relevant. For SMART audiences, that supports both avoiding unnecessary disruption of amalgam and maximizing capture when removal is indicated—because released mercury does not remain a local dental curiosity. It also reinforces why chairside water spray, high-volume evacuation, rubber dam, and patient alternate-air delivery are treated as a system, not optional extras.
Practical takeaways
- Communicate clearly: “silver” fillings contain ~50% mercury that can redistribute.
- Do not polish or grind amalgam casually.
- When removing, assume systemic relevance — use full SMART barriers.
- Prefer mercury-free alternatives for new restorations.
- Pair patient education with occupational protections for the team doing the work.
Bottom line: Hahn et al.’s classic FASEB imaging study showed mercury from amalgam fillings can distribute into body tissues—foundational evidence behind SMART’s cautious removal philosophy.
For patients and clinics evaluating safe amalgam removal, the practical lesson is consistency: apply the full SMART checklist—barriers, dam, alternate air, water and high-volume evacuation, chunking technique, mercury-rated respiratory protection, air filtration, and maintained separators—rather than relying on any single study in isolation. Educational use of this reference on thesmartchoice.com should link back to the IAOMT SMART protocol page for the complete procedure set.
