Types of Teeth: Incisors, Canines, Premolars and Molars Explained

Teeth are named by shape, and shape follows job. The front teeth cut, the corner teeth tear, and the back teeth crush and grind. Counting wisdom teeth, an adult has 32 permanent teeth, 16 in the upper jaw and 16 in the lower, split evenly between the right and left sides.

A child's first set, the milk or primary teeth, is smaller: 20 teeth in all, 10 above and 10 below. The set has no premolars. The milk molars at the back are later replaced by premolars, which is one of the details people most often get wrong. Our guide on primary teeth covers the milk set in full.

The incisors are the four upper and four lower front teeth. Each has a thin, straight cutting edge. The two in the middle are the central incisors and the ones beside them are the lateral incisors. In permanent teeth they come through at roughly 6 to 9 years of age, and they carry most of what people see when they smile.

Canines sit at the corners of the arch. A canine has one pointed tip and one of the longest roots in the mouth, which makes it a strong anchor for gripping and tearing, and an important guide for how the upper and lower teeth meet. Permanent canines arrive at around 9 to 12 years. Because they have to travel a long way to reach the arch, they are the teeth most often found stuck behind the gum, as our guide on impacted teeth explains.

Premolars, also called bicuspids, sit between the canines and the molars. There are eight in an adult, two in each quarter of the mouth, and they come through at around 10 to 12 years in the places where the milk molars were. Most have two cusps (points) on the chewing surface. Read more in our guide on premolar teeth.

Molars are the largest teeth, with wide, grooved surfaces and, usually, two or three roots to hold them against chewing force. An adult has twelve: first, second and third molars in each quarter. The third molars are the wisdom teeth, and many people have fewer than four or none that come through. Our full guide on molar teeth covers each one, and the guide on wisdom teeth covers the last four.

A teeth diagram in words: look at one quarter of the mouth from the middle outward. You meet central incisor, lateral incisor, canine, first premolar, second premolar, first molar, second molar and third molar (wisdom tooth). That is eight teeth, and four such quarters make 32. Dentists give each of the 32 a two-digit number, explained in our guide to the tooth numbering system.

Whatever the type, every tooth is built in layers. The visible crown is covered by enamel, the hard outer shell. Beneath it lies dentin, a softer layer that forms most of the tooth, and at the centre is the pulp, which holds the nerves and blood vessels. The root is anchored in the jaw bone.

Knowing the types matters in practice because each is treated differently. A front tooth is a question of appearance and bite, a premolar is often involved in braces planning, and a molar's grooves make it the type most prone to decay.