The premolars, also called 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 lie anterior and molars that lie 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.
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.
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.
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.
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
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.
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A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the outermost embryonic germ layer, the ectoderm.
Incisors (from Latin incidere, "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, whereas armadillos have none. Adult humans normally have eight incisors, two of each type.
Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as occurs during chewing or at rest. Static occlusion refers to contact between teeth when the jaw is closed and stationary, while dynamic occlusion refers to occlusal contacts made when the jaw is moving.
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