Anatomy of molars

Position in the dental arch and crown surfaces

An adult has 16 teeth in each jaw, 6 of which are molars. They form the basis of the masticatory apparatus. Normally, each molar contacts two teeth of the opposite jaw (the main and additional antagonists). The only exception is the last maxillary molars, which have only one antagonist.

The crown anatomy of any molar includes five surfaces:

• Vestibular (facing outward).
• Lingual (facing the oral cavity).
• Anterior contact.
• Posterior contact.
• Occlusal (masticatory, occluding with antagonist teeth).

Biomechanics and tooth inclination

The stability of molars directly depends on their spatial arrangement.

In the mandible, the crowns of the molars are inclined anteriorly and the roots posteriorly. This configuration blocks the posterior displacement of the dental arch during chewing. At the same time, the dental arch turns out to be narrower than the basal arch (lines along the root apexes).

In the maxilla, biomechanics is less favorable: the crowns are tilted outward and the roots are directed inward (the dental arch is wider than the basal arch). This anatomical disadvantage, which reduces stability, is compensated for by the greater number of roots in the upper posterior teeth.

Topography of maxillary molars

Upper molars traditionally have three roots: one massive palatal root and two buccal roots (mesiobuccal and distobuccal).

1. First molar (6th tooth): The palatal root contains one wide canal. The buccal roots have narrow canals, with the mesiobuccal root containing two canals in more than 50% of cases.
2. Second and third molars (7th and 8th teeth): They repeat the anatomy of the first molar, but their roots are shorter. In the wisdom tooth (8th), the roots are often closely spaced or completely fused. The pulp cavity in these teeth is smaller, and the root canals show high variability.

Topography of mandibular molars

Lower molars have two roots: a mesial (anterior) and a distal (posterior) root.

1. First molar (6th tooth): The flattened mesial root usually conceals two narrow canals (mesiobuccal and mesiolingual). The distal root is more massive and usually has one wide canal (less frequently two).
2. Second and third molars (7th and 8th teeth): The roots are located closer to each other and are prone to partial or complete fusion (especially in the 8th tooth). In such cases, the canals may merge into a single wide slit-like space.

Features of deciduous (milk) molars

The anatomical structure of deciduous teeth (dentes temporali) is basically identical to permanent ones, but has a number of specific differences:

• The overall size of the teeth is smaller, while the width of the crowns prevails over their height.
• The enamel is white with a characteristic bluish tint.
• An enamel bulge is well-defined in the cervical area.
• The sign of crown curvature is more pronounced.
• The roots are shorter, flattened, and diverge significantly wider.
• The pulp cavity is wider, while the hard walls of the crowns and roots are thinner.

Class and exam questions

What else to study on this topic

• Biomechanics of masticatory pressure distribution and the role of interdental contacts
• Structure of the marginal periodontium interdental ligament
• Differences between the dental, alveolar, and basal arches
• Clinical dental formula and WHO tooth numbering system
• Development of senile progenia in tooth loss and jaw atrophy

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.