Posterior_Direct_Restorations Salvatore_compressed

FIG 2-32 (a and b) Two mandibular second molars in which two opposing cusp crests meet to create two central fossae separated by a groove.

Mandibular Premolars

Unlike their maxillary counterparts, the mandibular premolars are very

different from one another (Fig 2-33). They have one feature in common: The lingual cusps are much lower than the buccal cusps (particularly on the first premolar), causing the center of the occlusal surface to be highly lingualized from an occlusal viewpoint. The mandibular second premolar shows great occlusal anatomical variability.

FIG 2-33 Mandibular first (right) and second premolars.

Mandibular first premolar

The mandibular first premolar is mainly composed of its buccal cusp; the lingual cusp is reduced in both volume and height (Fig 2-34). There is one developmental groove, and the occlusal surface is lingually displaced (Fig 2-35). Figure 2-36 shows anatomical references whose specificities should be considered when modeling.

FIG 2-34 (a and b) Illustration and clinical photograph of the occlusal surface of a mandibular right premolar.

FIG 2-35 Premolar comparison. The occlusal plane of the first premolar (left) is very angled compared with that of the second premolar.

FIG 2-36 Mandibular right first premolar. (a and b) The central developmental groove is positioned lingually, creating a buccal portion that is two-thirds or three-quarters of the occlusal surface. The surface may be concave, convex, or straight. The central developmental groove often continues to cut into the marginal ridge (both mesially and distally). M, mesial. (c) Supplemental grooves originating from the developmental groove delimit the occlusal extensions of the marginal ridges.

Mandibular second premolar

The lingual portion of the mandibular second premolar is more pronounced than that of the first premolar and may consist of one or two cusps. This variability is the result of differences in the central developmental groove, giving this tooth an H, U, or Y configuration (Fig 2-37). Figure 2-38 shows anatomical references whose specificities and variants should be considered when modeling. Figure 2-39 provides additional views of the occlusal surfaces of mandibular premolars, highlighting the variations that occur naturally.