Posterior_Direct_Restorations Salvatore_compressed

The oblique ridge is characterized by a slight depression (groove) in the center. Figure 2-21 shows anatomical references whose specificities and variants should be considered when modeling. Figure 2-22 provides additional views of the occlusal surfaces of maxillary first molars, highlighting the variations that occur naturally.

FIG 2-21 Maxillary left first molar. (a) The central fossa is approximately centered in the occlusal surface. M, mesial. (b) The pit of the central fossa can be approximately positioned by drawing a line joining the mesiobuccal and distobuccal cusp tips and extending a perpendicular line starting from the intercuspal groove. (c) The occlusomesial and occlusobuccal grooves run from the central fossa (generally perpendicular to one another). The distal fossa is located approximately at the buccopalatal midpoint and 1.5 to 2 mm from the distal margin. (d) The distopalatal groove extends from the distal fossa in a mesiopalatal direction. This oblique groove generally runs parallel to the distal portion of the mesiopalatal cusp crest. (e) The mesial marginal ridge invades the occlusal surface to a greater or lesser extent, determining the length of the mesial groove. (f) The oblique ridge is defined by two opposing cusp crests. The mesial slopes of the ridge are broader and shallower than the distal slopes. (g) The supplemental grooves can be more or less pronounced. (h) Sometimes the mesial marginal ridge is clearly interposed between the mesiopalatal and mesiobuccal cusps, almost reaching the central fossa. (i) The mesial marginal ridge can be a single ridge or sometimes has breaks that divide it into several segments invading the occlusal surface. (j) Sometimes, as with the first premolar, the break in the mesial marginal