Humans develop two sets of teeth over a lifetime. Children grow 20 primary (baby) teeth, while adults have up to 32 permanent teeth. Those 32 teeth fall into four distinct types: incisors, canines, premolars, and molars. Each type has a different shape tailored to a specific job in 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. They have flat, thin edges that work like a blade, letting you bite into food and slice it into smaller pieces. Think of biting into an apple: your incisors do that initial work.
These are split into two subtypes. The central incisors sit right in the middle of your smile, and the lateral incisors flank them on each side. In children, the lower central incisors are typically the first teeth to appear and the first to fall out. In the permanent set, incisors erupt between ages 6 and 8, making them among the earliest adult teeth to come in.
Canines: The Pointed Tearing Teeth
You have four canines, one in each corner of your mouth where the incisors end. They’re easy to spot because of their single pointed tip, sometimes called a cusp. That sharp shape is built for gripping and tearing tougher foods like meat or fibrous vegetables.
Canines also play a role in guiding your jaw when you chew from side to side. They have the longest roots of any tooth, which anchors them firmly and makes them especially durable. Permanent canines arrive relatively late, typically between ages 10 and 13.
Premolars: The Transitional Grinders
Premolars (also called bicuspids) sit just behind the canines. Adults have eight of them, two in each quadrant of the mouth. Their flat chewing surface has two raised points, which makes them a hybrid between the sharp canines in front and the broad molars in back. Premolars crush and grind food into smaller pieces before it moves further back in the mouth.
Children don’t have premolars at all. The primary teeth in that position are baby molars, and premolars replace them when they fall out. Permanent premolars typically erupt between ages 9 and 12.
Molars: The Heavy-Duty Grinders
Molars are the large, flat teeth at the back of your mouth. Adults have 12 in total: four first molars, four second molars, and four third molars (wisdom teeth). Their broad surfaces with multiple cusps are designed to do most of the heavy grinding, mashing food into a consistency you can swallow.
First molars are actually the earliest permanent teeth to arrive, erupting between ages 5 and 7, often before a child loses any baby teeth. Second molars follow between ages 11 and 13. Children also have a set of primary molars that serve as placeholders, though these are smaller and eventually give way to the premolars and molars of the adult set.
Wisdom Teeth
Wisdom teeth are the third and final set of molars. They erupt much later than the rest, typically between ages 17 and 25. Many people’s jaws simply don’t have enough room for them. When there isn’t enough space, wisdom teeth can become impacted, meaning they get stuck below the gumline or push in at an angle against neighboring teeth.
Impacted wisdom teeth can lead to pain, infection, cavities, and gum disease. They’re also harder to clean because of their position at the very back of the mouth, which makes them more prone to decay even when they do come in fully. Removal is recommended when impacted wisdom teeth cause pain, infection, or damage to surrounding teeth. Some people grow all four, others develop fewer, and a small percentage never develop wisdom teeth at all.
Baby Teeth vs. Adult Teeth
Children grow 20 primary teeth: eight incisors, four canines, and eight molars. Notice the missing category: there are no premolars in a child’s mouth. The baby molars occupy the space where premolars and some permanent molars will eventually sit.
Baby teeth typically fall out in roughly the same order they appeared. The lower central incisors go first, followed by the upper central incisors, then the lateral incisors, first molars, canines, and second molars. This process usually starts around age 6 and continues into the early teen years, gradually replaced by the full set of 32 permanent teeth.
What Every Tooth Is Made Of
Regardless of type, every tooth shares the same four-layer structure. The outermost layer is enamel, the hardest substance in the human body. It acts as a shield against bacteria that cause cavities. Beneath the enamel sits dentin, a softer layer that becomes vulnerable to decay when enamel wears away or chips.
The root of each tooth is covered by cementum, a thin layer that works with the surrounding tissues to anchor the tooth into the jawbone. At the very center is the pulp, a soft tissue containing nerves and blood vessels. The pulp is what makes a tooth sensitive to temperature and pain, and it’s the tissue that becomes infected during a root canal situation.
How Many Teeth You Should Have
A full adult mouth contains 32 teeth: 8 incisors, 4 canines, 8 premolars, and 12 molars. In practice, many adults end up with 28 after wisdom tooth removal. Some people are also born missing one or more teeth, a condition called congenitally missing teeth, which most commonly affects the wisdom teeth, upper lateral incisors, or second premolars.
Your teeth are distributed evenly across four quadrants: upper right, upper left, lower left, and lower right. Each quadrant holds the same lineup: two incisors, one canine, two premolars, and three molars. Dentists number the teeth 1 through 32 starting from the upper right third molar, sweeping across the top, then dropping to the lower left third molar and sweeping back to the right.