I'm afraid it's extraordinarily hard to evaluate whether you have a claim on a board like this. I can tell you that if you're having trouble, you should document it by going to see your dentist and gving him/her a careful history of when and how the sensitivity started and what product you used. It's often true that an internet search can give you an idea about whether other people are experiencing the same problems you are with the product. In the end, though, the only way to know for sure if you have a claim to go see a lawyer who specializes in products liabiltiy law. Don't wait-- waiting too long can harm your claim or cause it to be barred altogether.
You'd have to go to dentist and have your claims documented, with the dentist agreeing that the mouth rise caused the problems you claim of, to even have a possible case. If your dentist is willing to do that, then it's possible an attorney might be able to help you, although it sounds like a very difficult case to establish.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.
I agree with my colleagues.
If you can find a dentist who will write you a letter staing it is their belif that the Mouthwash caused your symptoms you MAY have a case.