Learning objective: to study the peculiarities of the anatomical structure of mandibular molars, to learn to identify the distinctive features of the first and second molars, the distinctive signs of the rightand left-side teeth.
FIRST LOWER MOLAR
This is the largest molar. Vowed from the vestibular surface, there are 3 cusps: anterior buccal, posterior buccal, and distal separated by two grooves: vestibular and distovestibular (fig. 15.1).
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On the oral side there are two cusps: anterior lingual and posterior lingual, which are divided by the lingual groove (fig. 15.2).
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The proximal surfaces include the medial surface with 2 cusps (buccal and lingual), buccal and lingual parts of the medial ridge. The distal surface has 3 cusps (disto-buccal, distal, disto-lingual), an an additional distal tubercle, as well as distal depression of the distal tubercle.
There are five cusps on the occlusal surface: mesiobuccal, distobuccal, distal, mesio-lingual, disto-lingual. There are five grooves between the cusps: lingual, distovestibular, vestibular, mesial, and distal (fig. 15.3).
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The grooves intersect in three fossas: mesial triangular, central, and distal triangular.
The cavity is of cuboid shape with five horns oriented in the direction of the masticatory cusps.
The tooth has two roots, mesial and distal. They are flattened, their width is greater in the buccal lingual direction. The posterior root is large and straight. The anterior one is flattened in the anterior-posterior direction. There are longitudinal grooves on the surface of the roots.
► Crown height 6-8 mm.
► Medio-distal diameter of the neck 10-13 mm.
► The bucco-lingual diameter of the neck 9-12 mm.
► The length of the root is 13-16 mm.
SECOND LOWER MOLAR