Because the Chihuahua is small, he also has a very small mouth. This small mouth can cause problems with the mouth being too small for the teeth, which causes overcrowding. Overcrowding of teeth can cause food to be trapped between the teeth, resulting in plaque and tarter buildup, as well as premature tooth-loss. Keeping the teeth clean is essential to keeping the mouth and the rest of the dog healthy. Dogs that have dirty teeth are found to be at much more at risk of heart, liver and kidney damage from the bacteria entering the bloodstream.
You can help keep the mouth clean by offering dental biscuits, dental chew toys, including edible dental chew toys (i.e. greenies, dentabones, etc.), feeding dry food instead of semi-moist or canned food, brushing your dog’s teeth (but don’t use human toothpaste…it has fluoride…there are doggie toothpastes available at most pet shops), using the available edible water additives for dental hygiene, as well as taking your dog to the veterinarian for a dental cleaning, etc. As the Chihuahua gets older, it is almost inevitable that he will need at least one dental cleaning by the veterinarian, quite often more.
Another issue, although less serious and easily corrected, is retained puppy teeth. Toy breeds are more prone to this problem, and it is caused by the adult tooth growing beside the puppy tooth, instead of the puppy tooth falling out. I usually recommend that if there are any retained puppy teeth (the usual teeth to be retained are the long canines and the small incisors in the front), that the puppy teeth be removed at the time of spay/neuter. This way the dog is only under anesthetic once, and for the rest of his life food can’t get trapped between the puppy and adult teeth