Posterior_Direct_Restorations Salvatore_compressed
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FIG 2-38 Mandibular right second premolar. M, mesial. (a to c) H variant. The central developmental groove (slightly lingually positioned in all mandibular premolars) is horizontal and confers an H-shaped appearance once the supplemental grooves delimiting the marginal ridges have been defined. (d to f) U variant. If the buccal cusp is very pronounced, it extends toward the lingual portion to assume a U shape. (g to i) Y variant. Two lingual cusps are present, giving a Y shape to the central developmental groove.
FIG 2-39 (a to d) Extreme anatomical variability of mandibular premolars.
Conclusion
A study of anatomy is extremely useful in order to grasp anatomical basics. However, it is one thing to talk about anatomical fundamentals and quite another thing to talk about shape and its perception (see chapter 1). Observing a natural tooth from an occlusal viewpoint allows one to check the basic anatomical theories described (Fig 2-40a), but the only way to perceive the anatomical details that will be very useful to clinicians in constructing a natural-looking model is to change the observation perspective (Fig 2-40b). Many of these details, even those imperceptible from a particular observation perspective, are still always present and play a crucial role in shape perception. A shape is a set of details, with each one making an intrinsic contribution to the overall shape; without any particular detail the perceived shape will no longer be the same.
FIG 2-40 (a) Occlusal view of a maxillary first molar. (b) Occlusal view with a slightly palatal angle. Different anatomical features are identified according to the observation point.
Recommended Reading
Fuller J, Denehy GE, Hall SA. Concise Dental Anatomy and Morphology, ed 4. Chicago: Year Book Medical, 1984.
Nelson SJ. Wheeler’s Dental Anatomy, Physiology, and Occlusion, ed 10. St Louis: Elsevier, 2014.
Scheid R, Weiss G. Woelfel’s Dental Anatomy, ed 8. Philadelphia: Lippincott Williams & Wilkins, 2011.