Mandibular First Molar Anatomy

Mandibular First Molar

• The lingual cusps are pointed and separated by the lingual groove.
• The mesiolingual cusp is the widest mesiodistally, with its cusp tip higher than the distolingual cusp.
• The cervical line lingually is irregular.
• The roots are about 1 mm longer lingually than buccally.

Mesial Aspect

• Two cusps and one root are visible from the mesial aspect.
• The buccolingual measurement is greater at the mesial portion than at the distal portion.
• The contact area is located at the occlusal third and is almost centered buccolingually.
• The buccal outline of the crown is convex above the cervical line.
• The lingual outline is straight in the lingual direction above the cervical line to the middle third and then becomes convex.

Distal Aspect

• The distal contact area is placed just below the distal cusp ridge and is slightly higher than the mesial contact area.
• The cervical line distally usually extends straight across buccolingually and may be irregular.

Occlusal Aspect

• The mandibular first molar is hexagonal in shape from the occlusal aspect.
• The crown measurement is 1 mm or greater mesiodistally than buccolingually.
• The buccolingual measurement of the crown is greater on the mesial than on the distal.
• The crown converges lingually from the contact areas.
• There is a major fossa (central fossa) and two minor fossae (mesial triangular fossa and distal triangular fossa).

Mandibular Second Molars

• The second molar is smaller than the first molar by a fraction of a millimeter in all dimensions.
• The roots are not as broad as those of the first molar, nor are they as widely separated.
• There is only one developmental groove buccally (buccal groove).
• There are four well-developed cusps of nearly equal size, with no fifth cusp or distal cusp.
• The DB developmental groove is absent.
• The crown and root converge lingually to a lesser degree than the first molar.
• The cervical ridge buccally is less pronounced than the first molar.
• The B and L developmental grooves meet the central developmental groove at right angles at the CP, forming a cross that divides the occlusal surface into four nearly equal parts.

Mandibular Third Molars

• The mandibular third molar varies considerably in different individuals and presents many anomalies in form and position.
• It supplements the second molar in function, but is seldom as well developed as the second molar.
• The crown portion or roots may be irregularly developed, with 5 or more cusps, or undersized roots that are more or less malformed.
• The roots are generally two in number, shorter in length, and tend to be fused together.
• The roots may show a distinct distal curve.
• Mandibular third molars are most likely to be impacted, partially or completely within the jaw due to insufficient space for eruption.
• They may be horizontally directed and sometimes congenitally absent.

This quiz covers the anatomy of the mandibular first molar, including its cusps, roots, and measurements.