Shortly after I was diagnosed with Sjogren's I developed an allergy to SLS - sodium lauryl sulfate - an ingredient in most toothpastes. It looks like an extreme version of Sjogren's dry mouth. Once I started using toothpaste without SLS my Sjogren's mouth symptoms became much more manageable. Sensodyne's Fresh Mint doesn't have it and I think Tom's is SLS free.
You might try changing your toothpaste. My dentist is the person who suggested this remedy. Hope this helps.