I have been using hydrogen peroxide as a mouth wash and for brushing my 
teeth. It's only been a few weeks, but I have no noticeable negative 
effects. I think there is a difference in my breath, but I have only a 
little feedback.

One time, I ate a squash cooked with a huge clove of garlic, and the 
next day even I could still smell some garlic. I brushed and 
mouth-washed with the H2O2 just before riding in a friend's car. When I 
asked for feedback, she said she noticed something but it wasn't strong 
and she could not tell it was garlic. Another time, when I was 
"rehydrating" (i.e., hung over) with awful breath, I'm sure, I did the 
same thing just before meeting a friend at a pub. When asked, he said he 
did not notice anything.

I use food grade H2O2, which is 35% solution, diluted roughly 11 to 1. I 
mouth-wash, then brush, then wash more, and finally rinse with water 
several times.

Wayne Wynn
Burnaby, BC