Begin teaching your dog to accept having his teeth cleaned when they are a puppy. Small dogs especially are notorious for dental problems, and dirty teeth can cause serious health problems such as heart disease and kidney disease.
Using a rough cloth wrapped around your finger , gently wipe your puppy's teeth. when your dog is bigger you can eventually use a special doggy toothbrush and toothpaste, but never use human toothpaste, as it is not edible.
To brush your pooches teeth position yourself and your dog, so that you can access the dogs teeth comfortably. Lift your dogs upper lips and begin to brush in a circular motion, much like you would brush your own teeth. Be sure to brush where the tooth meets the gum-line. Don't forget to get the very back teeth, since this is where your dog is most likely to develop problems. When you are finished the top, move on to the bottom Sometimes you will notice a small amount of blood when brushing your dog's teeth. Lighten up on the pressure but do not stop the brushing. Your dog's gums and mouth will only continue to get healthier with repeated brushings. Praise your dog often during and after the brushing. ( I always give my pooch Basil a treat afterwards.)
Brushing should be done at least twice a week, and have your dogs teeth checked once a year by your veternarian. If your dogs teeth have significant tarter build up, they need to be cleaned. This usually done with anesthesia. source: Darlene Arden - "Small Dogs big hearts"