Many states have a Dental board that will mediate complaints like this between a patient and their dentist at low or no cost avoiding court. They look at all the facts including the documentation of what the dentist did or didn't do and if they find the care is substandard they order that the patient be compensated.
Check and see if your state has such a board. It will be faster, easier, and cheaper than a med/mal suit.
"That's just my opinion, then again I might be wrong." Dennis Miller