Hello, My Wife Is Suffering From Mouth Ulcers That Have

Hello, My wife is suffering from mouth ulcers that have come up after a scaling process, She has tried many things including swishing with coconut oil, changing her diet, and trying AHCC mushroom supplement. The symptoms seem to get better and then return. Her PCP, and the periodonist that did the scaling say there is nothing she can do, any suggestions/info would be very helpful.