Just thought I would place this here as it was the cause for me. I had an extremely dry mouth, almost over night last year. GP said everything was fine at the time so had no idea what the problem was so did a bit of googling. Cut a long story short I had accidentally purchased a different toothpaste which was the whitening version of what I usually get, so stopped using it and the dry mouth cleared up as quickly as it came. Used the toothpaste again a week later to experiment and the dry mouth came back, so for me at least, on that occasion it was the whitening properties in the toothpaste that created my issue. Just thought I would mention it.