Lesson 14. Special teeth anatomy. Lower premolars

Learning objective: to study the peculiarities of the anatomical structure of mandibular premolars, to learn to identify the distinctive features of the first and second premolars, the difference between the teeth on the right and left side.

FIRST LOWER PREMOLAR

The shape of its crown is rounded; the vestibular and oral surfaces are similar to that of the lower canine (fig. 14.1, 14.2).

There are 2 cusps on occlusal surface: buccal and lingual, the buccal surface is much larger.

There are six ridges on the occlusal surface: central vestibular, central lingual, mesial vestibular, distal vestibular, mesial lingual, distal palatine. The central groove has 2 branches, medial and distal. Each branch forms a triangular fossa (fig. 14.3).

There is one root: straight, of oval shape, slightly flattened laterally. Shallow grooves pass along the anterior and posterior surfaces (fig. 14.4).

► The height of the crown on the buccal surface is 7.5-11 mm.

► The height of the crown on the lingual surface is 5-6 mm.

► Width 6-8 mm.

► Medio-distal diameter of the neck of the tooth is 8.2-8.6 mm.

► The bucco-lingual diameter of the neck is 5.4-5.8 mm.

► The length of the root is 13-16 mm.

SECOND LOWER PREMOLAR

This is a very variable tooth within its class, which is shown by a varying ratio between the vestibular and lingual parts of the crown and by the number of cusps.

The vestibular surface is smooth with 3 ridges, the lingual surface is smaller.

The occlusal surface can have 2, 3 or more cusps. There are 3 cusps in most cases: vestibular, mesio-lingual and disto-lingual. The vestibular cusp is distinctly larger (fig. 14.5-14.8).

There is one root: straight, of oval shape, slightly flattened laterally. Shallow grooves pass on the anterior and posterior surfaces.