Permanent Mandibular Second Molar

The permanent mandibular second molar helps the first molar in the grinding of food. The mandibular second molar is smaller in dimensions as compared to the first molar. The tooth has four well-developed cusps. The tooth has two roots one mesial and one distal root. The roots are broad buccolingually but narrow mesiodistally. The roots are not widely separated like the mandibular first molar.

Development and Eruption of the Permanent Mandibular Second Molar

Following is the summary of the development and eruption of the permanent mandibular second molar.

• Beginning of calcification of tooth: 2.5 to 3 years
• Completion of Crown: 7 to 8 years
• Eruption of tooth: 11 to 13 years
• Completion of root: 14 to 15 years

Buccal Aspect

• The cervico-occlusal and mesiodistal dimensions of the tooth are slightly less as compared to the first molar.
• In between the mesiobuccal and distobuccal cusps, a buccal developmental groove is present. This is the only developmental groove present on the buccal aspect.
• Both the mesiobuccal and the distobuccal cusps have nearly equal mesiodistal dimensions.
• The mesiobuccal cusp is slightly higher as compared to the distobuccal cusp.
•  The cervical line is nearly straight on the buccal aspect. Sometimes the cervical line sharply points towards the root bifurcation.
• The roots of the mandibular second molar are slightly shorter and less developed as compared to the first molar.
• The roots are not widely separated and in the apical third portions, the roots have a slight distal inclination.

Lingual Aspect

• In the permanent mandibular second molar, the convergence of the crown and the root on the lingual aspect is less as compared to the first molar.
• Due to this less convergence very small part of the mesial and the distal surface of the crown and root are visible from the lingual aspect.
• A lingual developmental groove is present between the mesiolingual and the distolingual cusps.
• The mesiolingual cusp is a little higher as compared to the distolingual cusp.

Mesial Aspect

• The mesiobuccal and the mesiolingual cusps are the only visible cusps from the mesial aspect.
• Both of these cusps are connected with a mesial marginal ridge.
• The overall dimensions buccolingually are slightly less as compared to the first molar.
• The cervical line is straight or has a very little curvature towards the occlusal aspect.
• The root surface has no developmental groove or depression.
• The part of the distal root is sometimes visible from the mesial aspect. The mesial root has a pointed root apex.

Distal Aspect

• Part of the occlusal surface is visible from the distal aspect because of the less cervico-occlusal length of the crown on the distal aspect.
• There is no developmental groove visible on the buccal aspect.
• The cervical line is nearly straight.
• Part of the mesial root is visible from the distal aspect because of the less buccolingual dimensions of the distal root.

Occlusal Aspect

• The general outline of the mandibular second molar from the occlusal surface is rectangular.
• All four cusps are visible from the occlusal surface and they are nearly equal in development.
• The buccal and the lingual developmental grooves meet at the central pit.
• The central developmental groove crosses the occlusal surface at the right angle to the buccal and the lingual developmental grooves.
• These grooves form a cross on the occlusal surface and divide the occlusal surface into four equal halves.
• In addition to the main grooves, several supplementary grooves are radiating from these grooves.
• The mesial and the distal triangular fossae are present adjacent to the marginal ridges.

Video Lecture Explaining the Key Identification features of the Permanent Mandibular Second Molar

Video Demonstration Explaining the Morphology of Permanent Mandibular Second Molar on tooth models