Thor has really bad teeth too.
I brush every night, and I can still see plaque forming.
What else can you do to keep a dog's teeth good? I give Thor flossies, but he won't chew them unless they are really soft, so they are not very "scrape-y". I feed him kibble for the potential teeth benefits, though I know a lot of people think it doesn't a difference.
I've heard to stuff you can put in their water, but it seemed like you had to measure it really carefully and I'm always refilling his bowls, so I wasnt' sure I'd be able to do it right.