All teeth are arranged into two arches. When both arches come closer together, contact between the opposing teeth is present. 

The upper arch is a fixated arch named the maxillary arch. The lower arch is a movable arch formed by the mandible, and it is called the mandibular arch. The mandibular arch operates against the maxillary arch and provides that the upper and lower teeth actually meet. 

The term occlusion is used when the upper and lower teeth are in actual contact. It is also known as the occlusal relationship. The occlusion is also referred to as the whole state of interarch teeth contact but not as a single contact between specific teeth. 

When the misalignment or incorrect relation between the teeth of the upper and lower arches is present, it is known as malocclusion. The teeth that are out of contact are known as being in disclusion. Malocclusion can have an impact on the formation of dental diseases, chewing, speech and aesthetical look of a person. 

Depending on the movements, the occlusion can be either static or dynamic:

• Static occlusion is the contact between mandibular and maxillary teeth when the lower jaw is not moving. 
• In contrast, dynamic occlusion is the contact that teeth form during the movements at the temporomandibular joint.

In a static occlusion, contacts of the teeth are described with points, while dynamic occlusion uses lines.