Robert,

I can't speak for gum printing but I have used Kodak XOMAT x-ray duplicating film for duplicating x-rays for over forty years and for enlarging negatives or platinum/palladium printing for many years. I develop it with Kodak GBX developer and fixer with a water stop in between. It gives superb results. The GBX chemistry dev and fix to make a gallon of working solution costs about $23 together and should last about a month in covered containers. As you know it is a reversal film and in my hands tends to be slightly more contrasty than my original negatives which is fine for pt/pd. If you go that route you should test what exposure and development time will work for you. The film is slow and rather grain free. You might have to get the chemistry from a dental/medical supply or through your dentist.

http://www.jeffreyglasser.com/