Posterior_Direct_Restorations Salvatore_compressed

ridge is pronounced enough to mark a distinct separation from the mesiopalatal cusp.

The maxillary second molar is not as bulky as the first molar (Fig 2-23). The normal geometry of this tooth is somewhat more diamond-shaped than the first molar, which is much squarer. Sometimes this tooth also has an oblique ridge, almost always divided by a relatively pronounced groove. Figures 2-24 and 2-25 shows anatomical diagrams of both the fourand three-cusp variants. Sometimes, it is more triangular than square due to the absence of a distopalatal cusp.

FIG 2-23 Maxillary right second molar.

FIG 2-24 (a and b) Clinical photograph and illustration of the occlusal surface of a four-cusp variant of a maxillary left second molar. M, mesial.

FIG 2-25 (a and b) Clinical photograph and illustration of the occlusal surface of a threecusp variant of a maxillary left second molar. M, mesial.

Mandibular Molars

Mandibular molars (Fig 2-26) differ from maxillary molars because their mesiodistal diameter is greater than their buccopalatal diameter. The first molar has five cusps, and the second has four. The occlusal anatomy of the second molar is defined by grooves that form a cross that separates

the four cusps in a relatively equally proportioned manner.

FIG 2-26 Mandibular right first (left) and second molars.

Mandibular first molar

The occlusal surface of the mandibular first molar (Fig 2-27) consists of five cusps—three buccal and two lingual. In order of magnitude they are as follows: mesiolingual, distolingual, mesiobuccal, centrobuccal, and distobuccal. The latter is absent in the four-cusp variant. Because an occlusal view of the tooth shows a large amount of the tooth’s buccal surface, the occlusal surface looks as though it has shifted lingually. Figure 2-28 shows anatomical references whose specificities and variants should be considered when modeling. Figure 2-29 provides an additional occlusal view.