Lesson 1: Adult Teeth


My first patient today is John, a 55-year-old male, in for a routine checkup and cleaning. He is a nonsmoker, does not take medication, and has no history of periodontal disease.

Dr. Lee to John: "Hi John. Today we will be examining your teeth, and then you will receive a thorough cleaning. I hope you don’t mind me using your mouth to train these future oral health care providers."

Image: Patient opening mouth.
Like everyone, John has had two sets of teeth. His first set of teeth, or primary dentition, contained 20 teeth. These “baby teeth” were replaced by 32 adult teeth, called permanent dentition or secondary dent most adults have 32 teeth; however, some have more and some have less. Permanent teeth erupt around age 6 as the baby teeth (deciduous teeth) are exfoliated.

Dr. Lee to John: "Would you give us a big smile?"

Notice how the teeth are generally arranged in upper and lower semicircles around the mouth.

The upper jaw, or maxilla, forms a semicircle of teeth called the maxillary arch and contains the maxillary teeth. The lower jaw, or mandible, forms a semicircle of teeth called the mandibular arch and contains the mandibular teeth. The occlusion, or bite, is the contact between the upper and lower sets of teeth.

The teeth in the front are the anterior teeth, while the teeth in the back are the posterior teeth.

Image: Maxillary arch and mandibular arch.
Image: Midline.

Each jaw can be divided into two sections giving us four quadrants – two on the upper and two on the lower.

The midline in the mouth is the imaginary medial line in each arch that runs from front to back. The midline serves as a general guide for identifying other surfaces and structures in the mouth.

So that John doesn’t have to keep his jaw open through this lesson, I’ll use a diagram to illustrate and explain oral anatomy.

There are four quadrants of teeth, as shown in this diagram–the upper right, upper left, lower right, and lower left.

To review the adult teeth locations, we will start from the back of the mouth and move forward.

The molars are grinding teeth. There are usually six in each of the two jaws—the mandible and the maxilla.

A bicuspid is a tooth that has two cusps, or rounded parts. It is also known as a premolar. Molars and bicuspids are located in the posterior, or back, of the mouth.

Canines are sharp, pointed, tearing teeth. There are two in each jaw, and they are also known as cuspids or eye teeth.

Image: Quadrants of the mouth.

Incisors are the front cutting teeth. There are four in each jaw: two central incisors (front) and two lateral incisors (side). Canines and incisors are found in the front, or anterior, of the mouth.

John had his wisdom teeth removed in his early 20s, but you can see on the diagram where they normally appear. “Wisdom teeth” is actually the lay term for the third molars. Wisdom teeth are located in the posterior part of the mouth.