Posterior_Direct_Restorations Salvatore_compressed

FIG 7-30 (a) Regardless of the type of simultaneous technique used, increments are adapted using a moistened microbrush. (b) The adaptation is performed on all increments.

(c) The composite is cured. (d) Cured increments. (e) A cusp is extended by adding an increment to the cusp side. (f) Condensing the increment. (g) The increment wall is formed into a right angle using a pointed instrument, and this is adapted to the cusp side using a microbrush. (h) Once modeled, the cusp extension is cured. (i) An increment is positioned on the other cusp to create a groove. (j) The increment is adapted. (k) Condensing the composite. (l) The compressing action using the condenser and microbrush allows the composite to bulge outward and create a natural groove. (m) As usual, the increment is adapted to the preexisting modeled composite. (n) The ridge may be lost. If this happens, it is reopened using a pointed instrument and closed again, shifting the increment toward the other cusp. This alternation makes it possible to obtain a natural-looking groove. (o) The increment is cured. (p) Completed restoration.

Because the occlusal anatomy can be so variable, an effective modeling technique should guarantee control of increments and allow their reciprocal ratios to be modulated while considering groove definition. Teeth requiring treatment are not always morphologically intact. They are often destroyed by caries or have been treated by

conservative methods involving silver amalgam or composite, which prevents appreciation of the original tooth shape. Once a cavity has been created, the carious tissue and/or old restorative material has been removed, and bonding steps have been performed, anatomical information on the occlusal perimeter can be projected toward the center of the occlusal surface using composite to construct a natural 3D morphologic whole.

Knowledge of dental anatomy is essential. Although this procedure simplifies modeling in posterior teeth, the main aspects of occlusal morphology and possible anatomical variables should be known in advance, starting with the usual position of fossae, grooves, and ridges (ie, triangular, oblique, and marginal) and culminating in proportional ratios between the various teeth.

The preliminary information gathering must take place prior to isolation with rubber dam. It is always preferable to isolate an extensive area so that anatomical information available from adjacent teeth can be checked during the restoration. Observation plays a very important role at the outset. If the teeth to be treated are not structurally impaired or do not contain extensive poorly fitting restorations, practitioners can analyze them to define the position of grooves and fossae as well as the orientation and inclination of ridge sides. SMT is based on building up multiple composite increments that are segmented (ie, not in contact). These are modeled simultaneously to define the initial occlusal anatomy while ensuring that the structure of each individual increment is in proportion to the others. This process is always based on a standard cavity depth of approximately 1.5 to 2 mm (Fig 7-24) after evaluating:

FIG 7-24 (a to c) Assessing initial depth for SMT.

Tooth morphology prior to preparation

Residual morphology after preparation

Morphology of adjacent teeth

Contralateral tooth morphology

The number of increments varies according to the number of ridges making up the tooth’s occlusal surface. There is no finite rule. The number of increments must be enough to allow several cusps to be modeled easily and simultaneously while ensuring that their sizes and mutual proportions are correct (Fig 7-25). Starting with a Class 1 cavity, the rule of thumb is as follows: