Summary: 

Purpose: to investigate the canal system of mandibular 2nd molars and its relationship to the patient's age, race, sex and side of the mouth.

N= 149 mandibular 2nd molars.

Materials/Methods: 

• The pulp was removed, the canal space filled with black ink and the roots demineralized and made transparent.
• The canal system was defined as follows: type 1, type 2-1, type 2, type 1-2 and type 3.

Most highlighted Results: 

1. Lateral canals were positioned most frequently in the apical third (59.4%) followed by the furcation area (22.6 %).

2. Transverse anastomoses were found in 1/3 of roots and were most frequent in the middle and apical thirds.

3. Canal shape was significantly related to race, with more c-shaped canals observed in the teeth from Asians

4. The presence of apical deltas was significantly related to the sex & side of the mouth, male > female, left> right.

5. Mandibular 2nd molars with single roots had a more complex root canal system than two-rooted teeth, more lateral canals and transverse anastomoses were observed, and apical foramen was found at the apex less frequently.

Clinical significance:

Dentists should be careful when treating the single-rooted and mesial root of the two rooted mandibular 2nd molars.