Premolar

Human anatomy

The premolars in humans are the maxillary first premolar, maxillary second premolar, mandibular first premolar, and the mandibular second premolar. Premolar teeth by definition are permanent teeth distal to the canines, preceded by deciduous molars.

Morphology

There is always one large buccal cusp, especially so in the mandibular first premolar. The lower second premolar almost always presents with two lingual cusps.

The lower premolars and the upper second premolar usually have one root. The upper first usually has two roots, but can have just one root, notably in Sinodonts, and can sometimes have three roots.

Premolars are unique to the permanent dentition. Premolars are referred to as bicuspid (has two main cusps), a buccal and a palatal/lingual cusp which are separated by a mesiodistal occlusal fissure.

The maxillary premolars are trapezoidal in shape. Whilst the mandibular premolars are rhomboidal in shape.

Maxillary first premolar[9]

• The crown of the tooth appears ovoid, wider buccally than palatally
• From a buccal view, the first premolar is similar to the adjacent canine
• Roots: Two roots buccal and palatal. Sometimes (40%) there is only one root.

Maxillary second premolar[9]

• Similar to maxillary first premolar but the mesio-buccal and disto-buccal corners are rounder
• The two cusps are smaller and more equal in size
• Shorter occlusal fissure
• Usually one root

Mandibular first premolar[9]

• The smallest premolar out of all four
• Dominant buccal cusp and a very small lingual cusp
• The buccal cusp is broad and the lingual cusp is less than half the size of the buccal cusp.
• Two-thirds of the buccal surface can be seen from the occlusal aspect
• A single conical root with an oval/round cross section. The root is grooved longitudinally both mesially and distally.

Mandibular second premolar[9]

• The crown is larger than the mandibular first premolar
• Lingual cusp is smaller than the buccal cusp but better developed.
• The lingual and buccal cusp is separated by a well defined mesiodistal occlusal fissure
• The lingual cusp is divided into two; the mesiolingual and distolingual cusps with the mesiolingual cusp being higher and wider than the distolingual.
• Root: Single conical root, oval/round in cross section.