Pierre,

Glands have a much better chance of recuperating post radiation than hair follicles. Dry mouth can be terrible, like sucking on sand all the time. There are many things you can do to help stimulate them to heal but time will be required. There are many products and home remedies that can substitute for saliva (minus the enzymes of course) that will lubricate and protect your mouth and make eating much easier.
Biotene has many such products http://www.oralcancerfoundation.org/products/patients_products.htm and you can get free samples from there web site. Visit your dentist and explain your treatment and what you are currently experiencing. They should be able to offer some help and suggestions. They will also be able to provide topical fluoride and/or home gels and trays to protect your teeth. Saliva is your bodies natural cleansing and first line of defence against mouth ulcers, mucositis, and decay. Decreased saliva flow without topical fluoride can allow decay to destroy otherwise healthy teeth very rapidly. Avoid all products that contain alcohol. Read my post from August 2007, on the General Board entitled "Alcohol", to get some good info.
Drink lots, and I mean lots of water to keep hydrated. Your kidneys will thank you for the effort as well.

Simply adding a few lemon drops to every glass of water will help stimulate saliva flow and is a cheap and readily available product.

Hope this is of some use to you, e-mail me anytime.

Mike