I've gone through the last book via search on the word teeth, and in the entire book, not once does Jim mention that amalgams will interfere with using MMS for cleaning your teeth. As long as you're not mixing it in a metal cup, and as long as you've got it there just long enough to brush and rinse, etc., it should not be a problem. Otherwise, very few people could take MMS, period, since so many of us have amalgams.
I'm using the new CDS - put about an ounce of cold water in a shot glass, then using a 3mL syringe (without the needle), I pull up 2mL or 2ccs of the CDS, drop it into my cold water and brush with that. Once I've brushed, I rinse my mouth out with first the mixture in the shot glass, then fresh water from the tap. So far, my teeth have the same feeling they had with the traditional MMS treatment - very clean. No biofilm, which I always had after traditional toothpaste.
Bishop Jim discusses teeth several times in his book, and I strongly recommend it - or look on his webpage - jimhumble.biz and find the tooth protocol.
Good luck!