Human Anatomy - Maxillary first premolar - Maxillary second premolar - Mandibular first premolar - Mandibular second premolar - Premolar teeth are permanent teeth distal to the canines, preceded by deciduous molars.

Morphology - Premolars have one large buccal cusp, especially in the mandibular first premolar. - The lower second premolar usually has two lingual cusps. - The lower premolars and the upper second premolar usually have one root. - The upper first premolar usually has two roots, but can have just one or three roots. - Premolars are referred to as bicuspid, with a buccal and a palatal/lingual cusp separated by a mesiodistal occlusal fissure.

Maxillary Premolars - Maxillary First Premolar: - Crown appears ovoid, wider buccally than palatally. - Similar to adjacent canine from a buccal view. - Roots: Two roots buccal and palatal, sometimes only one root. - Maxillary Second Premolar: - Similar to maxillary first premolar, but with rounder mesio-buccal and disto-buccal corners. - Two cusps are smaller and more equal in size. - Shorter occlusal fissure. - Usually one root.

Mandibular Premolars - Mandibular First Premolar: - Smallest premolar out of all four. - Dominant buccal cusp and a very small lingual cusp. - Two-thirds of the buccal surface can be seen from the occlusal aspect. - Single conical root with an oval/round cross-section, grooved longitudinally mesially and distally.

Orthodontics and Other Mammals - Orthodontics: - Four first premolars are the most commonly removed teeth in orthodontic treatment. - Removal of only the maxillary first premolars is the second likeliest option. - Premolar extraction therapy was initially contested in the orthodontic field. - Patient reports of health consequences due to extraction/retraction have sparked debate. - More orthodontists are now avoiding extraction therapy, with a current official rate of 25%. - Other Mammals: - Primitive placental mammals have four premolars per quadrant, but the most mesial two have been lost in catarrhines. - Paleontologists refer to human premolars as Pm3 and Pm4. - Weiss and Mann (1985) and Warwick and Williams (1973) provide further information on premolars in mammals. - Standring (2015) discusses the anatomical basis of premolars in humans. - Kimura et al. (2009) identify a genetic determinant of shovel-shaped incisors in humans.