Hi D,
I wouldn't mess with the teeth. If they didn't take them out prior to treatment I would leave them there but be meticulous in their care. In fact, you may not be able to find a dentist that would extract them for you now. The problem is called radiation osteonecrosis. Basically it is the death of bone caused by the radiation treatment. There are little "cells" (for lack of a better word) that rebuild bone and teeth when they are damaged, as in tooth extraction. The radiation kills those "cells" which means the bone (jaw and teeth) will not rebuild and heal. Then you have major problems. My dentist says he doesn't even want to talk to me about the possibilities but he says they would be "dire".
I really don't think that removing body parts will reduce the chance of SCC coming back. Since you have squamous cells all over the place you can't eliminate all of them. Even if you had your tonsils removed a cancer can start in the place where the tonsils used to be or anywhere else in your mouth. Same with the molars. You just have to be vigilant with your self-examinations and doctor appointments and try not to let anything slip passed the goalie.
Good Luck,
Joe