T.B.
There is a non-acidic form of vitamin c called calcium ascorbate. Buy it as a powder and spread 1/2 teaspoon on gum surfaces. Hold it for ten minutes, then rinse. Do this daily. Also in conjunction with that you could try a comfrey root tea. You can either use it as a mouthwash, or drink a cup every day or two.
Check out "Doctor Yourself" by Andrew Saul, PhD - this is in there!