Premolar


The premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered transitional teeth during chewing, or mastication. They have properties of both the canines, that lay anterior and molars that lay posterior, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars.

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.

Orthodontics

The four first premolars are the most commonly removed teeth, in 48.8% of cases, when teeth are removed for orthodontic treatment. The removal of only the maxillary first premolars is the second likeliest option, in 14.5% of cases.

Other mammals

In primitive placental mammals there are four premolars per quadrant, but the most mesial two have been lost in catarrhines. Paleontologists therefore refer to human premolars as Pm3 and Pm4.

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