Removing grass stains from teeth??? (autistic son)?!

my son has taken to eating grass, he is 12 years old with Autism, Mental Retardation, OCD, and bi-polar!. The docs have said it won't hurt him because he eats mainly clovers which I've researched and found that some people pick them in early spring for salads and indians used them for medicinal purposes!. I've researched all that, but what I can't find is how to remove the grass stain from his front tooth!!! LOL!.!.!.i know it sounds crazy, but life with autism can be!!! He has alot of tactile defensiveness, and i'm worried if I use baking soda or peroxide that he will freak out and never let me brush his teeth again!!! I've used my toothpaste that has both in it and it didn't do much just lightened it a little!. The dentist is able to get it off, but #1 I can't run to the dentist every time this happens and #2 he hates the dentist, its a major ordeal!. I know this is a strange question and I appreciate any suggestions!!!!!!!Www@Answer-Health@Com

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