Chihuahuas have bad teeth primarily because their teeth are too big for their jaws. Through generations of breeding for smaller bodies, their jawbones shrank faster than their teeth did, creating a mouth where 42 adult teeth are packed into a space that can’t comfortably hold them. This overcrowding sets off a chain reaction of dental problems that most chihuahua owners will encounter by the time their dog is a few years old.
Too Many Teeth, Not Enough Jaw
All dogs have the same number of adult teeth regardless of breed. A Great Dane and a chihuahua both get 42 permanent teeth. The difference is that a chihuahua’s jaw may be a fraction of the size, while the teeth themselves haven’t scaled down proportionally. Veterinary dentists describe this as a large tooth-to-bone ratio: the jawbone decreased in size much more than the teeth did, resulting in crowding and rotation.
When teeth are jammed together and twisted out of alignment, the tiny gaps between them become traps for food particles and bacteria. In a larger dog, saliva can wash between normally spaced teeth and carry debris away. In a chihuahua’s crowded mouth, plaque builds up in spots that are nearly impossible to reach, even with brushing. That plaque hardens into tartar within days, and tartar below the gumline triggers inflammation and, eventually, periodontal disease.
Baby Teeth That Never Fall Out
Chihuahuas are especially prone to retained baby teeth, a condition where the deciduous (puppy) teeth don’t fall out when the permanent teeth come in. When a baby tooth stays in place, it blocks the adult tooth from erupting in its correct position. The permanent tooth is forced to grow in at an odd angle, worsening the crowding that’s already a problem in a tiny jaw.
This creates two issues at once. First, the doubled-up teeth (baby tooth sitting right next to its adult replacement) form a narrow channel that collects food and bacteria far more readily than a single tooth would. That buildup accelerates tartar deposits, gum inflammation, and ultimately the breakdown of the structures holding teeth in place. Second, mispositioned teeth can press into the gums, the roof of the mouth, or other teeth, causing pain, abnormal wear, and sometimes fractures. If retained baby teeth aren’t extracted early, the damage compounds quickly.
Dog Saliva Promotes Tartar Buildup
Dogs rarely get cavities, and the reason is their saliva. Canine saliva has a pH between 8.5 and 8.65, making it significantly more alkaline than human saliva (which sits between 6.5 and 7.5). That alkalinity protects tooth enamel from the acid-driven decay that causes cavities in people. But it comes with a tradeoff: the high pH and elevated calcium levels in dog saliva cause calcium salts to precipitate out and harden onto teeth, forming calculus (tartar) much faster than it forms in a human mouth.
Research has not found significant differences in salivary pH between small and large breeds, so chihuahuas don’t produce uniquely problematic saliva. The issue is that tartar formation happens at the same rate in all dogs, but chihuahuas have far less room for error. In a mouth where teeth are already crowded and rotated, even normal tartar accumulation hits harder because it concentrates in tight spaces where it’s difficult to remove.
How Diet Plays a Role
What a chihuahua eats can either slow down or speed up dental problems. Dry kibble provides some mechanical scraping action as the dog chews, helping to break plaque off the tooth surface before it mineralizes into tartar. Soft or wet food, on the other hand, tends to stick to teeth and fills the gaps between crowded teeth more easily, promoting faster plaque and calculus formation.
Many chihuahua owners feed soft food because their dogs are picky eaters or have already lost teeth that make chewing kibble difficult. This creates a cycle: tooth loss leads to softer diets, which accelerate plaque buildup on the remaining teeth. Dental-specific diets formulated with larger kibble pieces or textured surfaces can help, though they’re not a substitute for regular tooth brushing or professional cleanings.
Why Dental Disease Matters Beyond the Mouth
Periodontal disease in chihuahuas isn’t just a cosmetic or comfort issue. When gum tissue breaks down, bacteria from the mouth enter the bloodstream directly through damaged tissue. In many dogs, periodontal disease goes untreated for years, allowing chronic, low-grade infections to seed bacteria into the blood on a recurring basis.
Research shows strong correlations between chronic periodontal inflammation and increased bacterial counts in the heart and kidneys. The mechanism works like this: bacteria and their toxic byproducts travel through the circulatory system and settle in distant organs. Over time, the immune system’s response to these bacterial antigens can cause inflammatory damage to heart valves, kidney tissue, and joints. Chihuahuas are already predisposed to heart conditions like mitral valve disease, so the added burden of dental-related bacteria circulating through the bloodstream is a genuine health risk, not a theoretical one.
What Helps Prevent the Worst Outcomes
The single most effective thing you can do is brush your chihuahua’s teeth daily, or as close to daily as you can manage. A finger brush or a small, soft-bristled brush designed for toy breeds fits their mouth better than a standard dog toothbrush. Focus on the gumline, where plaque accumulates fastest.
Have your vet check for retained baby teeth by the time your chihuahua is six to eight months old. If any baby teeth haven’t fallen out by then, early extraction prevents the cascading problems of crowding, misalignment, and trapped debris. Most vets recommend removing retained teeth during spay or neuter surgery, since the dog is already under anesthesia.
Professional dental cleanings under anesthesia are the only way to remove tartar that’s already formed below the gumline. How often your chihuahua needs a cleaning depends on how quickly tartar builds up, but many small-breed dogs benefit from annual cleanings starting as early as age two. Between cleanings, dental chews and water additives designed to slow plaque formation can help, though they work best as supplements to brushing rather than replacements for it.