Apical foramen

In young, incompletely developed teeth., the apical foramen is funnel shaped, with the wider portion extending outward. The mouth of the funnel is filled with periodontal tissue that is later replaced by dentin and cementum. As the root develops, the apical foramen becomes narrower. The inner surface of the root apex: becomes lined with cementum, which may even extend for a short distance ( 1 mm or so) into the root canal. The cementodentinal junction (CDJ), therefore, does not necessarily occur at the extreme end of the root, but may occur within the main root canal. Consequently, it is not necessary to clean, shape, or fill root canals to their anatomic apices, but rather to the cementodentinal junction, which usually lies within the canal just short of the apex. The apical foramen is not always the most constricted portion of the root canal. Constrictions can and do occur before the extremity of the root is reached. Apical constrictions are found 0.5-1.0 mm away from the root apex.

The apical foramen is not always located in the center of the root apex. It may exit on the mesial, distal, labial, or lingual surface of the root, usually slightly eccentrically. Anatomic studies have shown that the apical foramen coincides within the anatomic apex in only 17-46% of cases and it is located at an average of 0.4-0.7 mm away from the anatomic apex. In a few cases, the apical foramen has been found as much as 2-3 mm away from the anatomic apex. These studies have led to the recommendation that root canal obturation should end approximately 0.5 mm from the anatomic root apex as seen in the radiograph.

Knowledge of the age at which calcification of the root apex occurs is essential for endodontic practice, particularly when dealing with pulp-involved or pulpless teeth of children and young persons. As a general rule, a root apex is completely formed about 2-3 years after eruption of the tooth. Endodontic treatment of young teeth does not affect the normal eruption.

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