How our teeth and jaws work together

Our teeth and jaws allow us to soften solid foods by chewing them, and also to take a bite out of harder foods like apples and then cut them down to size in our mouths. To help the teeth do this, the interactions between the bones of the jaw and the chewing muscles are important too.

The structure of our set of teeth

Our teeth are made of a hard, bone-like substance. They are held by small sockets in our upper and lower jawbones called dental . Strong fibers anchor them in place. The upper and lower sets of teeth form two arches. When you close your mouth and bite, these two arches typically fit together with a slight overlap.

A full set of adult teeth includes 16 upper teeth and 16 lower teeth at the most. Each row has:

  • 4 incisors in the middle
  • 2 canine teeth next to the incisors; 1 to the left and 1 to the right
  • 10 molars (back teeth); 5 on each side
Illustration: Upper and lower rows of teeth, including wisdom teeth

What are the different kinds of teeth?

The incisors have narrow edges, and the canine teeth are sharp at the tip. When we close our mouth to bite, the lower incisors are pushed up just behind the upper incisors. This helps the front teeth to tear off bite-sized pieces of food, for instance from a carrot or a sandwich.

The molars look different: They have wide chewing surfaces with raised cusps and small grooves. When we bite down, the cusps of the upper molars fit into the grooves of the lower teeth. That way, they can grind food when we chew.

How are our teeth replaced?

Each tooth develops from a small bud that is anchored in the jawbone. When a tooth pushes through our gums and can be seen, we say that it has come in, or that it has “erupted.”

Baby teeth start coming in when a child is about five months old. This process is called “teething.” It can be painful and may sometimes cause a fever. The child’s first set of 20 baby teeth is usually complete by the age of two years.

At that point, toddler’s skulls have not yet reached their full size. Because the baby teeth don’t get any bigger, they are gradually replaced by 32 larger teeth, starting when the child is about six years old. This way, adults have teeth that are the right size for their mouths. The process is usually completed by the time we reach 18 years of age, when the third molars (the wisdom teeth) come in. But not everyone has wisdom teeth in their jaw. And if they do, only some of these teeth may erupt or none at all.

Illustration: Children have only 20 baby teeth

What role do the bones and muscles play?

The skull is made up of several plate-like bones. These include the upper jawbone (maxilla) and the lower jawbone (mandible). Our teeth are embedded in these bones.

The upper jawbone is rigidly fixed to the other bones of the skull, but the lower jawbone is not: A bit like a swing, it is attached to the temporal bones at the two joints of the jaw, allowing it to move.

Illustration: Detailed view of the jaw

Several muscles run between the lower jawbone and the skull. When these muscles are tensed (tightened), the lower jaw can be pulled up tightly against the upper jaw. This helps us to take a powerful bite. When the muscles are relaxed, our mouth opens. Some of the muscle fibers can actively help to open the mouth as well. Through the interactions of the various muscle groups, the lower jaw can also be moved slightly sideways and forward or backward. That makes it easier to grind food between our molars.

Illustration: The joint connecting the lower jawbone to the skull

Lippert H. Lehrbuch Anatomie. München: Urban und Fischer; 2020.

Menche N. Biologie Anatomie Physiologie. München: Urban und Fischer; 2020.

Pschyrembel Online. 2022.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

Comment on this page

What would you like to share with us?

We welcome any feedback and ideas - either via our form or by We will review, but not publish, your ratings and comments. Your information will of course be treated confidentially. Fields marked with an asterisk (*) are required fields.

Please note that we do not provide individual advice on matters of health. You can read about where to find help and support in Germany in our information “How can I find self-help groups and information centers?

Über diese Seite

Updated on February 13, 2023

Next planned update: 2026


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

How we keep you informed

Follow us on Twitter or subscribe to our newsletter or newsfeed. You can find all of our films online on YouTube.