Figure 4-32. Mandibular right second bicuspid.
e. Occlusal Surface. The outline form of the occlusal surface varies with the
number of lingual cusps. In the case of a single lingual cusp, the outline form is similar
to that of the first bicuspid. In the case of two lingual cusps, the outline form is broader
and more rectangular toward the lingual. In the case of a two-cusp tooth, the occlusal
surface resembles that of a maxillary bicuspid. In the case of a three-cusp tooth, a
prominent lingual groove passes from the occlusal surface, between the lingual cusps,
onto the lingual surface.
f. Root. The root is longer and larger than the root of the first bicuspid. A cross
section at the cervix is ovoid in form. Most of the taper is confined to the apical third.
4-23. MANDIBULAR FIRST MOLAR
The mandibular first molar is the largest tooth in the mandible (see figure 4-33).
It has five functional cusps, each of which develops from a separate lobe. The maxillary
and mandibular first molars are often called "six-year" molars because of the age at
which they erupt. Eruption of the mandibular teeth usually precedes that of the
maxillary teeth by several months. This tooth plays a vital role in the establishment and
maintenance of occlusion. It is called "the key to occlusion."