In anatomy the apical foramen is the opening at the apex of the root

Cementum

Cementum is a specialized calcified substance covering the root of a tooth. Cementum is excreted by cells called cementoblasts within the root of the tooth and is thickest at the root apex. These cementoblasts develop from undifferentiated mesenchymal cells in the connective tissue of the dental...

 of a tooth

Tooth

Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...

, through which the nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

 and blood vessels that supply the dental pulp pass. Thus it represents the junction of the pulp and the periodontal tissue.

It is a point of interest in endodontics

Endodontics

Endodontics is one of the dental specialties recognized by the American Dental Association, Royal College of Dentists of Canada, and Royal Australasian College of Dental Surgeons, and deals with the tooth pulp and the tissues surrounding the root of a tooth...

, as it is considered necessary to thoroughly chemomechanically debride the pulp space to remove all necrotic tissue and minimise bacterial load in the pulp space. Ideally this debridement would terminate exactly at the apical foramen. In reality determining the exact position of the apical foramen is problematic, requiring radiography

Radiography

Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....

 and/or use of an electronic apex locator

Electronic apex locator

See also apex locationAn electronic apex locator is an electronic device used in endodontics determine the position of the apical foramen and thus determine the length of the root canal space...

 to produce a refined estimate. A tooth may have multiple small accessory canals in the root apex area forming an apical delta

Apical delta

Apical delta refers to the branching pattern of small accessory canals and minor foraminae seen at the tip or apex of some tooth roots.The pattern is said to be reminiscent of a river delta when sectioned and viewed using a microscope. Because the anatomy of this area is very small and complex with...

 which can complicate the endodontic problem.

An apical constriction

Apical constriction

Apical constriction describes the process in which contraction of the apical side of a cell causes the cell to take on a wedged shape. Generally, this shape change is coordinated across many cells of an epithelial layer, generating forces that can bend or fold the cell sheet .-Morphogenetic...

 is often present. In immature teeth the root is not fully formed leading to an open apex. This is also seen in some pathological teeth.