Premolar
Morphology
The canine teeth (dentes premolares) are found only in the permanent dentition between the canine and the first molar. Unlike the canines and incisors, they have five surfaces (oral, vestibular, two approximal and masticatory - facies occlusalis). Their original name was dentes bicuspidati - teeths bicuspid, precisely because of the typical two bumps on the masticatory facies, which face vestibularly and orally.
The marginal bars are found on the masticatory surface in the approximal direction. Their main importance is to support and reinforce the relief of the crown and to reduce the risk of crown breakage. There is also a pronounced groove which runs mesiodistally and divides the surface into oral and buccal parts (more pronounced in the upper premolars than in the lower ones). All premolars are classified as pillars Class II
Upper premolars
The upper premolars have an outline similar to a rectangle or an ellipse, and their vestibular surfaces resemble the labial surface of a canine. The approximal surfaces have a rectangular shape and are convex at the point of contact (on the contrary, they are concave in the cervical direction).
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First upper premolar
Two cusps – the buccal cusp points distally and is higher and sharper than the palatal cusp. As the only one of all premolars, it has the largest percentage of cases (60%)
two roots and 92% two canals. The roots are gracile and twisted - difficult to treat endodontically. Frequent extraction for orthodontic reasons. This is pillar II. class according to Voldřich .
Second upper premolar
It is smaller in volume than the first premolar , to which it is very similar except for a few differences. Unlike the first upper premolar, both cusps are the same height. In 90%, it has only one root, which has a close relationship with the maxillary cavity . Like all premolars, they belong to pillars II. class according to Voldřich .
Lower premolars
A distinctive feature of the lower premolars is the 'inclination of the crown in the lingual direction.
Lower first premolar
It is the smallest premolar in the oral cavity. It belongs to the pillars of class II according to Voldrich.
The cusps are divided by an edge into a shorter, higher mesial part and a longer, higher distal part. The buccal tubercle is very sharp and points in a lingual direction. The lingual bump, on the other hand, is smaller and much lower.
There is only one root, oval or circular in shape.
The root canal is only one in 75 % of the cases and is oval in shape.
The pulp cavity is cylindrical and extends into the two corners of the pulp, the larger buccal and the smaller lingual.
Second lower premolar
It is generally the largest of all premolars. Its masticatory surface differs from the others in that it can exist in several forms (two-pronged, three-pronged and multi-pronged). It is a Voldrich class II pillar.
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References used
- SVOBODA, Otto, et al. Stomatologická propedeutika : Učebnice pro lékařské fakulty. 1. vydání. Avicenum, 1984. 392 s.
