This is pretty typical according to my dental hygienist. I switched to Biotine toothpaste and if I'm feeling really dry I'll use their gum.
The dehydration suggestion is also a good thing I had to keep an eye on because when I exercise I loose a lot of fluid and then focus on managing my food and BGs and forget to keep the fluid coming in. Great A1c if you are avoiding the lows. Mastering the big D, way to go!
I heard that a while back from my dental hygienist too, but at the time i was like naw thats not me. Whats different about Biotine than regular crest or colgate?