Posterior_Direct_Restorations Salvatore_compressed

FIG 1-8 Tooth surfaces and representation of transition areas.

FIG 1-9 (a and b) Graphic representations of a tooth showing that it is made up of a set of edges and transition areas, where the number of variables is infinite, and every small detail is important.

To see how the occlusal surface of a molar is constructed, its structural components must be broken down. For example, if a mesiobuccal cusp of a maxillary molar is broken down, we can see that it is made up of:

Occlusal perimeter

Cusp slope

Cusp crest

Triangular ridge

Close examination of the triangular ridge (Fig 1-10) reveals that it is defined by:

FIG 1-10 Triangular ridge broken down into the cusp crest, mesial and distal slopes, and grooves.

Occlusal perimeter

Cusp crest

Mesial and distal ridge slopes ending in two supplemental grooves

It therefore follows that:

Each triangular ridge is delimited by the cusp crest, by the ridge slopes (mesial and distal) that define its lateral limit, and by the grooves in which the ridge slopes terminate.

Each ridge slope is contained between a cusp crest and a groove, and each groove is contained between two ridge slopes and can communicate with other grooves.10

The interrelationship defined between the parts of the observed object is reflected in the expressive force of the perceived image: the triangular ridge is perceived because slopes and grooves are present; one slope of the triangular ridge is perceived because this is delimited by a cusp crest

and a groove; and a groove is perceived because this is contained between two slopes. Everything depends on what is being examined and the perspective of observation.

Rudolf Arnheim states that, “Perceptual shape is the outcome of an interplay between the physical object, the medium of light acting as the transmitter of information, and the conditions prevailing in the nervous system of the viewer. The shape of an object we see does not, however, depend solely on its retinal projection at a given moment. Strictly speaking, the image is determined by the totality of the visual experiences we have had with that object, or with that kind of object, during our lifetime.”11 With reference to the observation of things in general, Arnheim stresses that “detail is everything” and overall shape is nothing more than a set of details that define it: without detail there is no shape.

The take-home message is that a tooth is anatomically made up of a set of details that interact with one another to define the perceived overall shape.

References

1.Levitin DJ (ed). Foundations of Cognitive Psychology: Core Readings. Cambridge: MIT, 2002.

2.Ginger S. Gestalt Therapy: The Art of Contact. New York: Routledge, 2007.

3.Spagnuolo Lobb M. The Now-for-Next in Psychotherapy. Gestalt Therapy Recounted in Post-modern Society. Milan: Franco Angeli, 2013.

4.Edwards B. Drawing on the Right Side of the Brain, ed 4. New York: Penguin Group, 2012.

5.Colwyn T, Sperry RW. Brain Circuits and Functions of the Mind: Essays in Honor of Roger W. Sperry. Cambridge: Cambridge University, 2008.

6.Bergland R. The Fabric of the Mind. New York: Viking, 1985.

7.Pind JL. Edgar Rubin and Psychology in Denmark: Figure and Ground. Cham, Switzerland: Springer, 2014.

8.Brogi C, Brogi G. L’Opera di Corrado Brogi—Volume IV: La geometria descrittiva, la trigonometria sferica, solidi geometrici e la cristallografia. Scotts Valley, CA: Createspace, 2014.

9.Miceli GP. Mimesis: Imitation and interpretation of a natural tooth through shape & colour: Part I. Spectrum Dialogue 2006;5(6).

10.Scolavino S, Paolone G, Orsini G, Devoto W, Putignano A. The simultaneous modeling technique: Closing gaps in posteriors. Int J Esthet Dent 2016;11:58–81.

11.Arnheim R. Art and Visual Perception, ed 2. Berkeley: UC Press, 2004.

(PHOTOGRAPH COURTESY OF STANISLAV GERANIN, POLTAVA, UKRAINE.)

2

Anatomical Knowledge for Modeling

Adirect bonded composite restoration must blend into the tooth structure in terms of morphology and color. Just as no two teeth are identical, one model should never be the same as another. It is essential to study dental anatomy to know how teeth are made. This allows a faithful reproduction to be constructed that fulfills two fundamental objectives: blending in with remaining healthy tooth tissue and ensuring proper function during chewing movements.

This chapter describes the anatomical principles behind modeling, paving the way for relating the model to the residual tooth anatomy through interpolation of missing parts.

Anatomical Elements

The clinical anatomy of posterior teeth is characterized by certain welldefined elements explained in the following definitions and in Figs 2-1 to 2-5.

FIG 2-1 Main anatomical elements of the occlusal surface of a molar: cusp ridge (A), supplemental groove (B), central fossa (C), central developmental groove (D), marginal ridge (E), and the occlusal perimeter is A and E together.

FIG 2-2 Ridge slope (F) and cusp crest (G).

FIG 2-3 Cusp tip (blue), cusp slope (orange) cusp ridge (red), and cusp crest (purple).