I bought them thinking they were a great idea. Mine have chlorhexidine (or whatever that disinfectant is). I actually found them really hard to use well. I'll sometimes swipe a bit at the dog's teeth with them, but I'm not sure I'm really doing anything.
Anyway, since I switched Meg to raw, I haven't pulled any of her teeth-cleaning stuff out. I let the bones do the hard work, and that bit of yellow tarter around the tops of her teeth is gone.