Written by : Dr. Urusa I Inamdar

It is the portion of the pulp cavity from the canal orifice to the apical foramen.

It is divided into 3 sections :

• Coronal
• Middle
• Apical

1. Accessory canals or lateral canals : lateral branching of the main root canal generally occurring in the apical third or furcation area of a root.
2. Lateral canal : accessory canal that branches to the lateral surface of the root and may be visible on a radiograph.
3. Apical foramen : aperture at or near the apex of a root through which the blood vessels and nerves of the pulp enter or leave the pulp cavity.
4. Accessory foramina : openings of the accessory and lateral canals in the root surface.

A straight root canal extending the entire length of the root is uncommon. Either a constriction is present before the apex is reached or , as is often the case , a curvature is present.

The curvature may be :

• A straight canal extending with minimal apical curvature.
• A gradual curvature of the canal with a straight apical ending.
• A gradual curvature of the entire canal.
• A sharp curvature of the canal near the apex.

A curvature of about 20° in a narrow root canal may be difficult or even impossible to negotiate with endodontic instruments, whereas a curvature of even 30° may be negotiated if the root canal is wide.

Success in negotiating a narrow , curved canal depends on following :

• Degree of curvature.
• Size and constriction of the root canal.
• Size and flexibility of the endodontic instrument blade.
• Skill of the operator.

The various classification proposed are as follows :

• Vertucci’s Classification:

1. Type I : Single canal extends from the pulp chamber to the apex (1)
2. Type II : Two separate canals leave the pulp chamber and join short of the apex to form one canal (2-1)
3. Type III : One canal leaves the pulp chamber and divides into two in the root , the two then merge to exit as one canal (1-2-1)
4. Type IV : Two separate distinct canals extend from the pulp chamber to the apex (2)
5. Type V : One canal leaves the pulp chamber and divides short of the apex into two separate distinct canals with separate apical foramina (1-2)
6. Type VI : Two separate canals leaves the pulp chamber , merge in the body of the root , and redivide short of the apex to exit as two distinct canals (2-1-2)
7. Type VII : One canal leaves the pulp chamber, divides and then rejoins in the body of the root , and finally redivides into two distinct canals short of the apex (1-2-1-2)
8. Type VIII : Three separate distinct canals extend from the pulp chamber to the apex (3)

• Weine’s classification :

1. Type I : Single canal from pulp chamber to apex
2. Type II : Two canals leaving from the chamber and merging to form a single canal short of the apex
3. Type III : Two separate and distinct canals from chamber to apex
4. Type IV : One canal leaving the chamber and dividing into two separate and distinct canals

• Classification based on canal cross – section:

1. Round (circular)
2. Oval
3. Long oval
4. Flattened (flat/ribbon)
5. Irregular

References:

• Dental notes
• Grossman’s Endodontic Practice (13th edition)