Impact unknown! Meanwhile many American dentists install mercury amalgam (about 50% Hg) in tooth cavities inches from the brain where it will sit for years on end. How can anyone support this with a straight face. The response is something like &#x27;yes,we know mercury is a devastating neurotoxin but it&#x27;s tightly bound in the amalgam and there is no proven statistical relationship to say it&#x27;s dangerous&#x27;.