Human teeth fall into four main types: incisors, canines, premolars, and molars. Adults have 32 permanent teeth in a full set, while children have 20 primary (baby) teeth. Each type has a specific shape and job, and dentists use several naming systems to identify individual teeth by number, letter, or surface.
The Four Types of Teeth
Incisors are the eight flat-edged teeth at the front of your mouth, four on top and four on the bottom. They’re built for biting into food and cutting it into smaller pieces. These are the teeth you use when you bite into an apple.
Canines are the four pointed teeth sitting just next to your incisors, one on each side of both arches. You may hear a dentist call them cuspids. Their sharp, slightly fang-like shape is designed for gripping and tearing tougher foods like meat. Canines are also the longest-rooted teeth in your mouth, which gives them extra stability.
Premolars sit behind the canines, with eight total in adults (two on each side, top and bottom). They’re also called bicuspids because they have two pointed ridges on their chewing surface. Premolars serve a transitional role: they start the crushing and grinding process before food reaches the back teeth. Children don’t have premolars. These teeth only appear in the permanent set, replacing the baby molars.
Molars are the large, broad teeth at the back of your mouth. Adults have up to 12, including the third molars (wisdom teeth). Their wide, flat surfaces are designed for heavy grinding, breaking food down enough to swallow. First molars typically come in around age 6, second molars around age 12, and wisdom teeth between ages 17 and 25, if they come in at all.
Wisdom Teeth: The Third Molars
Wisdom teeth are simply your third and final set of molars. They erupt behind the second molars at the very back of each arch. Many people don’t have enough room in their jaw for these teeth, which is why they frequently become impacted (stuck beneath the gum or bone) or come in at awkward angles. Some people never develop wisdom teeth at all. When all four are present, they bring the adult tooth count from 28 to 32.
Baby Teeth vs. Adult Teeth
Children develop 20 primary teeth, sometimes called deciduous teeth. This set includes incisors, canines, and molars, but no premolars. Primary teeth typically start appearing around 6 months of age and are usually all in place by age 3. They begin falling out around age 6 as permanent teeth push through underneath.
The full adult set of 32 permanent teeth includes 8 incisors, 4 canines, 8 premolars, and 12 molars. Most permanent teeth are in place by the early teen years, with wisdom teeth being the last to arrive in the late teens or early twenties.
How Dentists Number Your Teeth
When your dentist says something like “tooth number 19 has a cavity,” they’re using the Universal Numbering System developed by the American Dental Association. Permanent teeth are numbered 1 through 32. The count starts at the upper right wisdom tooth (1), moves along the upper arch to the upper left wisdom tooth (16), drops down to the lower left wisdom tooth (17), and continues along the bottom to the lower right wisdom tooth (32).
Primary teeth follow a similar pattern but use letters instead of numbers: A through T. The sequence starts at the upper right second molar (A), sweeps across the upper arch to J, then drops to the lower left second molar (K) and continues to the lower right second molar (T). This lettering system makes it easy for dental offices to distinguish between baby teeth and adult teeth in a child’s chart.
Names for Tooth Surfaces
Dentists also have specific names for each face of a tooth, which is how they pinpoint exactly where a cavity or crack is located. The main surfaces are:
- Facial (buccal or labial): the side facing your cheeks or lips
- Lingual: the side facing your tongue
- Mesial: the side closest to the center of your mouth
- Distal: the side farthest from the center of your mouth
- Occlusal: the chewing surface of premolars and molars
- Incisal: the biting edge of incisors and canines
So if your dentist notes a “mesial-occlusal cavity on tooth 19,” they mean there’s decay on the chewing surface and the front-facing side of your lower left first molar. Knowing these terms can help you follow along during appointments.
What Each Tooth Is Made Of
Regardless of type, every tooth shares the same four-layer structure. The outermost layer is enamel, a mineralized shell that protects against bacteria and decay. Enamel is the hardest substance in the human body, harder than bone.
Beneath the enamel sits dentin, a yellowish tissue that makes up most of the tooth’s bulk. Dentin is softer than enamel, which is why cavities can spread quickly once they get past that outer shell. Below the gumline, a thin layer called cementum covers the root and helps anchor the tooth into the jawbone through surrounding tissues. At the very center of the tooth is the pulp, a soft core containing nerves, blood vessels, and connective tissue. The pulp is what makes a tooth “alive” and is the reason deep cavities or cracks can cause sharp pain.