There are many reasons why a dog or a puppy will chatter its teeth. The most obvious reason is that it's cold. But dogs and puppies often chatter their teeth and sometimes shiver even when the weather is mild or downright hot. This can be due to behavioural or medical reasons.
According to "Dog Owner's Home Veterinary Handbook," sudden, inexplicable, short bouts of teeth chattering could be a sign of focal motor seizures, also called partial seizures. The dog stays conscious and only has one part of the body go into spasms, such as the lower jaw.
Small, thin-skinned dogs like smooth-haired Chihuahuas, Jack Russells and Italian greyhounds will shiver and chatter their teeth when they are nervous. According to veterinarian Mike Richards, it is not known exactly why these small breeds shake and chatter their teeth when nervous or excited. Unless the dog's coordination or vision is affected, the dog does not need to go to the vet.
A neurological disorder called multisytem neuronal degeneration has been discovered in young Cocker Spaniels, although veterinarian Mike Richards claims it can happen to other breeds. White dog breeds such as West Highland white terriers, the Maltese and the Bichon Frise are subject to white dog shaker syndrome. Both of these disorders need veterinary care and possibly anticonvulsant medications.
Even if the dog is chattering its teeth out of habit, exposure to cold or does not seem to be in pain, regularly check the teeth for breaks, cracks, gum disease and cavities. Teeth chattering can put excessive wear and tear on the dog's teeth that could damage them.
Dogs of all sizes and breeds will often chatter their teeth when they are very excited. This could be in anticipation of a happy event. A dog that enjoys riding in the car may chatter her teeth just before getting inside of the car. A male dog may chatter his teeth when scenting a female in heat. Dogs have also been known to chatter their teeth when in pain as perhaps a sign of fear, which is another form of excitement.