This spring, the Medical Marijuana Caregivers of Maine joined the usual coalition of anti-pot forces that includes active law-enforcement groups, social conservatives and public health advocates to oppose a state bill that would legalize possession of small quantities of the drug.
And it's not a good idea to use it as mouthwash. Hydrogen peroxide (in dilute form) is used as a tooth whitener (check the active ingredients on those gel-based tooth whiteners, they usually use H2O2). It also has the side effect of turning your gums pale temporarily, though it wears off in a few hours.
Another idea for getting peroxide in to your gums: Put hydrogen peroxide into a Water Pik and then spray the peroxide at your gums, as you usually would do with a Water Pik. I think the people I've heard of doing this have used a mixture of half water and half 3% peroxide.