also, feeding a high-quality kibble can help to keep teeth in better shape (thinking about prin's dogs, for example, neither are big chewers yet have white teethies at six years old). Genetics also play a big role, not all teeth and gums are created equal. some dogs get plaque and tooth decay alot easier than others no matter what.
but yes, give your dog a bone to chew on, a raw turkey neck or a knucklebone, or a scrubby-toy like a nylabone or a kong (no rawhides please!), no need to guilt yourself into brushing their teeth every day, let THEM do it themselves. as kibble is a man-made invention, so are the doggy toothbrushes and toothpastes put on the market to combat one of the ensuing problems of such an artificial diet. and so goes the Ka-Ching of the cash machine for vets, eh?