The first mandibular molar tooth is the very first tooth that appears among the permanent teeth. It is also the most significant mandibular molar tooth, and mesiodistally it has the largest crown part.

The first mandibular molar tooth presents with five cusps:

Mesiobuccal
Distobuccal
Distal
Mesiolingual
Distolingual

The lingual cusps usually are sharper than others. As this tooth contains a small distal cusp, it appears pentagonal, and it looks like the distal surface of the tooth has two angled surfaces. The buccolingual length of the distal surface is slightly smaller than the same length of the mesial surface.

Every cusp presents with the cusp apex, which is the highest point, and the triangular ridge that extends downward from the apex towards the center of the occlusal surface.

The mesial marginal ridge is located more occlusally compared to the distal marginal ridge.

The height of contour of the first mandibular molar is as follows:

Buccal - in the cervical third, close to the middle third;
Lingual - in the middle third, close to the occlusal third.

This tooth presents with two roots (mesial and distal). The distal root is more rounded, while the mesial - flatter. The mesial root has two depressions, named the mesial and distal root depressions. The first mandibular molars contain three root canals, from which two are located in the mesial root.

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First mandibular molar (part 1)