HI ohfor07, The screws will be made out of 1 of 2 types of stainless steel. Austentic which has nickel in it or ferritic which is the one recommended for cooking with.
I only mention this as it might have a bearing on chelation.
Also depends on the location and blood supply to that area i would imagine.
couple of questions:
Are the screws permanent or will you be able to have them removed at some stage?
Where are the screws located?
Does the need for chelation outweight the risk of chelating with screws intact?
I could also post this question on the cutler yahoo group to see what answer is gleaned if it would be helpful.
edit - that is just erring on the side of caution though - generally if people have a gold crown in their mouth and know that there is no mercury beneath go ahead and chelate with dmsa!