Humans have four types of teeth: incisors, canines, premolars, and molars. Adults have 32 permanent teeth in total (28 if wisdom teeth are excluded), while children have 20 primary (baby) teeth. Each type has a distinct shape designed for a specific stage of breaking down food.
Incisors: Your Front Cutting Teeth
Incisors are the eight teeth at the very front of your mouth, four on top and four on the bottom. Each incisor has a single narrow edge, almost like a chisel, that cuts into food when you bite. These are the teeth you use when you bite into an apple or slice through a sandwich. They’re also the most visible teeth when you smile.
Incisors are the first permanent teeth most children get, typically replacing baby incisors between ages 6 and 8.
Canines: Your Tearing Teeth
Sitting just next to the incisors are four canine teeth, one in each corner of your mouth. They’re pointier than any other type of tooth, with a single sharp cusp that helps you tear into tougher foods like meat and crunchy vegetables. Canines have the longest roots of any tooth, which gives them extra stability for gripping and pulling.
If you’ve ever noticed that you instinctively use the corner of your mouth to rip off a piece of jerky or tear open a packet, your canines are doing the work.
Premolars: The Transitional Grinders
Behind the canines sit eight premolars (also called bicuspids), four on top and four on the bottom. These teeth are a hybrid between the pointed canines and the broad, flat molars. Most premolars have two cusps, the raised bumps on the biting surface, though some lower premolars can have three. Their job is to crush and grind food into smaller pieces before it moves further back in the mouth.
Premolars only exist in the permanent set. Children don’t have them. The baby molars in a child’s mouth are eventually replaced by adult premolars, usually between ages 10 and 12.
Molars: Your Heavy-Duty Grinders
Molars are the largest, broadest teeth in your mouth. Adults have 12 in total: three on each side of the upper and lower jaws. Their wide, flat surfaces are covered with multiple cusps, anywhere from four to five depending on the specific molar. Upper molars typically have four cusps, while the first lower molars have five. All that surface area makes them ideal for grinding food down into a consistency you can swallow.
The first permanent molars arrive around ages 6 to 7, often before any baby teeth have fallen out. They erupt behind the existing baby teeth, which is why parents sometimes don’t notice them. The second molars follow around age 12 or 13. By age 13, most children have 28 of their 32 permanent teeth in place.
Wisdom Teeth
The final four molars, called third molars or wisdom teeth, are the last to arrive, typically pushing through between ages 17 and 21. They were useful to early human ancestors who ate tough, uncooked foods that gradually wore down their other teeth. An extra set of molars arriving in early adulthood helped compensate for that wear.
Modern humans cook and process food, so our jaws have gotten smaller over evolutionary time. The result: there’s often enough room for wisdom teeth to form inside the jawbone but not enough room for them to fully emerge through the gums. That’s why impaction and crowding are so common, and why many people have their wisdom teeth removed.
How They’re Arranged
Your teeth follow a symmetrical pattern. If you split your mouth into four quadrants (upper left, upper right, lower left, lower right), each quadrant in an adult contains the same lineup: two incisors, one canine, two premolars, and three molars. That’s 8 teeth per quadrant, 32 total.
Children’s baby teeth follow a simpler version. Each quadrant has two incisors, one canine, and two molars, with no premolars and no third molars. That gives 5 per quadrant, 20 total. The baby molars hold space in the jaw for the premolars that will replace them later.
What Every Tooth Is Made Of
Regardless of type, all teeth share the same basic layered structure. The outermost layer is enamel, the hardest substance in the human body. It protects the tooth from the constant pressure of chewing and from temperature changes. Beneath the enamel sits dentin, a slightly softer layer that forms the bulk of the tooth. Dentin is yellowish, which is why teeth with thinner enamel can look less white.
At the core of each tooth is the pulp, a soft tissue packed with nerves and blood vessels. This is what makes a deep cavity painful: once decay reaches the pulp, the nerve is exposed. Below the gum line, a thin layer called cementum covers the root and anchors the tooth to the jawbone through tiny ligaments.
Why the Mix Matters
The four tooth types work as a system. Your incisors slice, your canines tear, and your premolars and molars crush and grind. This division of labor reflects an omnivorous diet. Pure herbivores tend to have mostly flat grinding teeth, while pure carnivores have more pointed, blade-like teeth. Humans have both because we evolved eating a wide range of plant and animal foods. Losing or damaging any one type shifts extra work onto the remaining teeth, which is one reason dental restoration focuses on preserving or replacing teeth that match the original shape and function.