Dental occlusion is the relation between surfaces of the mandibular and maxillary teeth at rest and while in function. In other words, it is the contact between teeth. The term "occlusion" actually derives from the Latin proverb occludere. It means "to close up".

Every person has their unique body characteristics, and one of them is the face with its own individual set of teeth and jawbones, giving a more aesthetical look to the face. The normal occlusion not only gives a more pleasing appearance, but it also provides an efficient mastication process and, therefore, improves digestion.

During the lifetime, the occlusal relationship of a person can change multiple times, and it is crucial to detect the changes in order to prevent its caused consequences and provide normal functions. If a proper alignment is present, the teeth have strong contact with their neighbour and opposing teeth, but over the years, gradually, the spacing between teeth changes, causing the teeth to become looser and resulting in occlusal relationship changes. These changes are not only associated with age but also with various pathologies.

In the maintenance of correct occlusion, more structures than just teeth are involved, and contacts between teeth cannot be looked at in isolation as the masticatory system also involves the periodontium, as well as skeletal components such as the temporomandibular joint and muscles of mastication.

In order to know if the dental treatment needs to be preventive or already restorative, it is crucial to understand the basics of dental anatomy and physiology, especially dental relationships and occlusion.