No worries, my fillings are made of a plutonium - osmium alloy.
They glow in the dark and if I ever get lost they can find me with a geiger counter.
Though I do agree that mercury is poisonous, to say that it is the second most poisonous substance is quite an exaggeration... I'm sure I can mention 100 more poisonous substances. Just google neurotoxins and you'll find plenty.
Here the world substance should be read as element of the periodic table. Whether or not mercury is the second most toxic element of the periodic table is debatable, mercury shouldn't be used in dentistry.
I understand the point you want to make, and you're right. I believe that they have already switched to composite fillings. (though mine are all amalgam)
To me, when I read a post like this that starts with such a highly debatable statement, the post loses the chance to make the impact it deserves. ;)
I agree and many of them come straight from animals... https://sciencebasedlife.wordpress.com/2011/04/12/the-most-poisonousvenomous-animals-in-the-world/