Histological Considerations

The pulp and the periodontium have a common embryological development, and their ways of communication are the same: lateral canals, dentin tubules, and apical foraminas. Therefore their anatomical-functional interrelationships are going to be very close, in good health as well as in physiopathological disease.

Lateral canal

This relationship can be tracked from early embryological development. During its development, the radicular epithelial sheath of Hertwig captures mesoderm in its inner part that will become pulp, and the mesoderm that is kept in the outer part will become periodontium.

However, in some areas there will be discontinuities of this sheath, or sometimes this sheath will run across blood vessels, giving birth to lateral canals.

Lateral canals are more frequent in the apical third and furca. They are very difficult to identify radiolog-ically and clinically, but they can be indentified in one of the following circumstances:

• when a lateroradicular lesion of a tooth without pulp has enlarged enough to be seen radiologically.
• when sealant and/or gutta-percha are forced through the lateral canal.

There are times when the canals will not be visible, but their consequences can be tracked.

Dentin tubules

Their number and size decrease from the pulp space to the periodontium and from cervical to apical. Their number also decreases with age, and so does their size due to the continuous deposition of peritubular dentin. The cement layer that covers the radicular periphery works as a barrier that prevents micro-organisms passing from the pulp to the periodontium.

Apical foraminas

With different numbers, sizes and distances from the apex, they are the most significant ways of communication between pulp and periodontium. When pulp necroses, the lesions produced in the periodontium are mainly localized around the apex; and a periodontium lesion can necrose pulp only when it affects the apical foraminas.