An adult dog carries 42 permanent teeth: 20 in the upper jaw, 22 in the lower. That breaks down as 12 incisors, 4 canines, 16 premolars, and 10 molars. Puppies begin with 28 deciduous teeth and no molars whatsoever. Each tooth type performs a distinct mechanical job — nibbling, gripping, shearing, grinding — and each fails in its own characteristic way.
How Many Teeth, and Where Do They Sit?
The upper and lower jaws are not symmetrical, which surprises most owners. The lower jaw carries two extra teeth, both third molars, which have no counterpart above.
Per half of the mouth, working from the midline backward:
- Upper: 3 incisors, 1 canine, 4 premolars, 2 molars = 10 teeth, doubled to 20
- Lower: 3 incisors, 1 canine, 4 premolars, 3 molars = 11 teeth, doubled to 22
Run your finger along the outside of your dog's cheek and you can feel the transition points. The canine is the obvious landmark. Behind it, the premolars step up in size until you reach the largest tooth in the upper arcade, then the molars flatten out toward the back of the jaw.
What Does Each Tooth Type Actually Do?
Incisors are small and shallow-rooted, which is why they're often the first to wobble when gum disease advances. Canines have the longest roots in the mouth — the root of an upper canine extends roughly twice the visible crown length, curving up alongside the nasal passage. That anatomy explains why a badly infected canine can produce nasal discharge, and why extracting one is a genuine surgical undertaking.
What Is the Triadan Numbering System?
A shorthand veterinarians use so that "the upper right fourth premolar" becomes "108." The mouth divides into four quadrants, each with a leading digit: 1 for upper right, 2 for upper left, 3 for lower left, 4 for lower right. The following two digits number the tooth position from the midline, with 01, 02, 03 being incisors, 04 the canine, 05 through 08 the premolars, and 09 onward the molars.
So tooth 108 is the upper right fourth premolar. Tooth 404 is the lower right canine. Deciduous teeth use 5 through 8 as the quadrant digit instead.
Once you know the pattern, a dental chart stops being cryptic. When your vet says they extracted 209 and 210, you can picture exactly where the gap is.
Which Teeth Are the Carnassials?
The upper fourth premolar and the lower first molar — 108, 208, 309, and 409. These two pass each other like scissor blades, and they're where a dog cracks anything hard.
The upper carnassial is the biggest tooth in the mouth and carries three roots. It's also the single most commonly fractured tooth in dogs, and the most common site of heavy calculus, because the parotid salivary duct empties nearby and saliva supplies the minerals that harden plaque. If you only ever cleaned four teeth, those would be the four to pick.
How Does Puppy Dentition Become Adult Dentition?
Deciduous teeth erupt between three and six weeks: 28 of them, comprising incisors, canines, and premolars but no molars at all. Those teeth are needle-sharp and thin-walled, which anyone who has hosted a twelve-week-old puppy already knows.
The replacement sequence runs roughly like this:
- 12–16 weeks — incisors are replaced
- 16–20 weeks — canines come in behind the deciduous ones
- 16–24 weeks — premolars erupt
- 20–28 weeks — molars erupt for the first time, having no baby predecessor
- By about 7 months — the full adult set of 42 should be present
Retained deciduous teeth are the common hiccup, most often the upper canines. When a baby tooth doesn't shed, the adult tooth erupts alongside it, creating a tight space that traps hair and debris. This usually needs extraction, and it's typically handled during the spay or neuter appointment.
What's Inside a Tooth?
Three layers, plus the supporting structures. Enamel forms the outer shell and is the hardest substance in the body, though in dogs it's strikingly thin — roughly 0.1 to 0.6 mm, compared with 2 mm or more in humans. That thinness is why wear exposes dentin faster in dogs than people expect.
Beneath enamel sits dentin, a living tissue threaded with microscopic tubules that transmit sensation. At the center is the pulp: nerve, blood supply, and the cells that lay down new dentin over the animal's life. Around the root, cementum anchors the periodontal ligament, which suspends the tooth in its bony socket.
That ligament is the structure periodontal disease destroys. The tooth itself often remains sound while its attachment quietly disappears.
Which Teeth Cause the Most Trouble?
Three culprits stand out. The upper fourth premolars, for the fracture and calculus reasons above. The lower first molars, which sit far back where brushes rarely reach and where resorptive lesions turn up. And the mandibular canines and incisors in toy breeds, where crowding and a thin jaw combine badly — severe bone loss around a lower canine in a five-pound dog can weaken the mandible enough to fracture it.
If a tooth looks wrong to you — discolored, chipped, surrounded by red or receding gum — hand that observation to your veterinarian rather than diagnosing from a chart. Much of what determines the answer sits below the gumline where only a radiograph can see it.
For daily care, the practical takeaway from all this anatomy is where to aim. The outer surfaces of the upper premolars and molars accumulate the most and get brushed the least. A Brushless Toothpaste chew works that zone by design, since the chewing action concentrates exactly where the carnassials meet. It's a source of mechanical contact in the hardest-to-reach part of the mouth, alongside whatever brushing you manage up front.
Related reading: the puppy teething timeline and how to read your dog's dental chart. Cornell's College of Veterinary Medicine publishes accessible material on oral anatomy.
FAQ
Why does my dog have fewer teeth than 42?
Missing teeth are common and have several causes: congenital absence, a tooth that never erupted and remains buried in bone, or one lost to disease or trauma before you owned the dog. Some short-muzzled breeds are missing premolars routinely. A radiograph distinguishes a genuinely absent tooth from an unerupted one, which matters because buried teeth can form cysts.
Do dogs get cavities like people do?
Rarely. True caries occur in roughly 5% of dogs, far less than in humans, because canine saliva is more alkaline and the diet contains less fermentable sugar. Dogs instead lose teeth overwhelmingly to periodontal disease and fractures. When cavities do appear, the flat molar surfaces are the usual location.
How can I tell my dog's age from their teeth?
Eruption timing gives a reliable estimate up to about seven months, since the sequence is consistent. After that it becomes guesswork based on wear and calculus, both of which depend heavily on diet and chewing habits. A three-year-old rock chewer can have more worn teeth than a healthy eight-year-old.
What are the little bumps on my puppy's incisors?
Those are cusps, sometimes called the fleur-de-lis pattern, and they're normal on newly erupted incisors. They wear flat over the first few years of adult life. Their disappearance is one of the rough age markers used in shelter medicine, though it's imprecise.
Is it normal for my dog's back teeth to look yellower?
Somewhat, yes. The upper premolars and molars sit adjacent to salivary duct openings, and saliva delivers the calcium and phosphate that turn soft plaque into hardened calculus. That region accumulates faster than the front of the mouth and gets cleaned less. Persistent heavy buildup there still warrants a professional look.