The tray is a soft insert set to hold the fluoride on your teeth for the time required -- I found that removal after treatment was nauseating me, so I just manually applied the paste with a brush and held it in my mouth for much longer than the time alloted while I read a book or watched TV or messed with computer.

What you want to do during treatment is be aware of trismus, and how to avoid it, and also try to swallow as much as you can during the treatments so you don't lose that ability.

I recommend a PEG; if you don't need it, you don't have to use it (except to flush it with water to keep it cleaned out), but if you need it, it will be there.

One final note: A lady of my acquaintance had her treatments (IMRT in her case) at MD Anderson in TX. Her dental oncologist made some sort of "stent" to protect both her teeth and saliva glands and she came out of the treatments with lots of saliva intact; I don't know if that was appropriate for the XRT that I underwent, but I wish I could have known enough at the time to investigate the possibility.