The 40ug/dl is blood levels. If you work around lead and your blood levels get above that you're supposed to get moved to some less contaminated environment until they drop below that.
As far as the other question goes, I guess it might be possible (lots of "ifs" there), but if this person suspected they'd gotten lead poisoning from their dental work I'd think they'd go get the bloodwork done to verify it, and we'd be reading about it in the article.
Cheers!