Lesson 13. Special teeth anatomy. Upper premolars

Learning objective: to stdy the peculiarities of the anatomical structure of maxillary premolars, to learn to identify the distinctive features of the first and second premolar, the difference between right and left maxillary premolars.

FIRST UPPER PREMOLAR

The crown shape is rounded rectangular. The vestibular surface is greater than surface flattened in the vestibule-oral direction (fig. 13.1-13.3).

Two cusps are on the occlusal surface: buccal and palatal. The buccal cusp is a little larger, the cusps are divided by the central groove (fig. 13.4).

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

The cavity of the crown is large, narrowed in the medio-distal direction, it has two protuberances corresponding to the occlusal surface.

Fig. 13.3

Fig. 13.4

The root is flattened, there are deep longitudinal grooves on the lateral surfaces. The root often bifurcates into the buccal and palatal parts. The following signs are well pronounced.

► Crown height on buccal surface 7.5-9 mm.

► Crown height on palatal surface 6-8 mm.

► Width 6.5-7 mm.

► Medio-distal diameter of the neck 4.8-5,5 mm.

► Bucco-palatal diameter of the neck 8.5-9.5 mm.

► Root length 12-16 mm.

SECOND UPPER PREMOLAR

This one differs little from the first, but is somewhat smaller in size, its cusps have the same length.

There are six ridges on the occlusal surface: central vestibular, central palatine, mesial vestibular, distal vestibular, mesial palatal, and distal palatine; the central groove has 2 branches. medial and distal. Each branch forms a triangular fossa (fig. 13.5-13.8).