Cut it first, but do not use the dremmel, wire cutters work good for this, cut on thew live tissue area maybe 1/8" above the dead area, then do a LIGHT solution with your salt water and like ten drops of the iodine in a small cup largw enough to hold the frag, leave it there for no more than 2 minutes, if you plan to mount this frag, this will be the time to do it, get a drop of gel superglue on the plug and bring your frag on top of the drop, press lightly but firm no movement until it sets approx 20 seconds, good luck