Overall I would not be worried based on symptoms of it being MS. The neck could be playing with the nerves in your mouth, but it could be thrush, dry mouth disease, vitamin deficiencies (iron, zinc, vitamin b 1,2,6,9 and or 12)
If you have dentures, allergies, acid reflux, different medications may cause it, grinding your teeth, biting your tongue, over brushing, too strong a toothpaste or mouth was, acid foods, stress.... I mean really an endless list of perfectly innocuous things which could be causing it. And it’s not a normal symptom of MS either so pretty sure you’re in the clear