Just wondering about all of you doggie folks: my Coal's teeth look a bit....ah.....like he'd been chewing on something he shouldn't. Mr. Chev....his teeth look pretty good. Chev is about 3 years old, and Coal will be 9 in September. Do the dingy teeth just happen with age, or....do you all actually brush your dog's teeth ???? Here's a pic of Coal with the "not so white" teeth.