after reading these posts of Cutler I think that there is no problem to take selenium with amalgams, because Selenium is not a chelator (do not eliminate mercury from the body), but it binds to mercury to form a compound less toxic than mercury for a while.
In this thread, Newport gives 3 reasons to explain why selenium can be harmfull if one takes it with mercury in the body. If someone has more information about this I would really appreciate the sharing.
Therefore: it is harmfull or not, to take selenium while one has amalgams? is selenium yeast (for example SelenoExcell) safe?