Posterior_Direct_Restorations Salvatore_compressed

matrix, axial wall, and the composite placed in the previous step. The height of the ridge summit is adapted, taking as a reference the coronalmost point of the first composite layer, always remembering to accurately assess the ridge references of adjacent teeth. This is one reason that it is recommended to always isolate an extensive operating field, ie, to include all the teeth in a quadrant from the last molar to the central incisor (see Fig 4-20). A modeling spatula is used to spread the composite in a buccal direction. The spatula is tilted to 45 degrees, then rested gently on the composite and moved from one end to the other in close contact with the matrix wall. This joins the first composite increment with the axial wall to shape the cervico-occlusal and buccopalatal curvatures.

A freshly wetted brush can be used to improve composite adaptation (Fig 6-33o). The brush works by interpolating and joining the composite increment in the inner box and along the seal with the residual occlusal perimeter. The uncured increment is ready for definition of the anatomical details (Fig 6-33p).

This process essentially involves drawing in the required secondary grooves (Figs 6-33q to 6-33u). Positioning the instrument tip almost parallel to the occlusal plane allows a preview of the next modeling stage. The instrument tip is dipped gently into the composite, and the course of the groove is slowly defined (see Figs 6-33q, 6-33r, and 6-33u). Secondary grooves may or may not be present on the marginal ridge of a molar or premolar. Sometimes there is only one, but two or three can be present. If another secondary groove is to be modeled, the procedure is carried out again, or a groove is defined by stamping an impression of the instrument tip in the composite by compression and deformation (see Fig 6-33q).

When modeling a groove, the composite deforms to create two sides and two secondary ridge crests (see Fig 6-33u). After the marginal ridge anatomy is correctly configured, the second increment is cured. The separator ring (Fig 6-33v) and the sectional matrix (Fig 6-33w) are removed, but not the wooden wedge, because this maintains hemostasis in the papillary area. Keeping the teeth slightly separated makes for easier access by burs and disks during the subsequent finishing and defining of the final contour, which is performed once the separator ring and sectional matrix have been removed (Fig 6-33x). To manage the

proportions correctly, it is essential to ensure that the peripheral margins of the restoration are well defined and finished before finalizing the occlusal surface. An abrasive disk (Fig 6-33y) is used to define the occlusal contour of the marginal ridge. It is important to work without irrigation to allow a good view of the working area; however, an assistant should cool the area and remove milled material using an air jet. An Arkansas stone flame bur can be used to mark the proximal depressions of secondary grooves (Fig 6-33z). The tip works by creating a hollow external to the secondary ridges. The resulting marginal ridge features secondary ridges that will enhance the future occlusal surface with anatomical details. The Class 2 cavity is now converted to a Class 1 (Fig 6-33aa), simplifying the next occlusal surface modeling stage (Fig 6- 33bb).

Conventional or two-step CBT: Decision-making criteria

When the two techniques are compared (Figs 6-34 and 6-35), building up in steps makes it possible to model a marginal ridge that is structurally stronger with a greater wealth of anatomical details, which simplifies occlusal surface modeling. Conventional CBT makes for easier management of the restoration in small Class 2 cavities because it leaves enough cavity space for occlusal modeling. As a guide, conventional CBT is recommended when Class 2 cavity size amounts to one-third of the mesiodistal distance and up to two-thirds of the buccolingual intercuspal distance; two-step CBT is recommended if the cavity is more extensive (Fig 6-36).

FIG 6-34 (a to e) Main stages of standard CBT.

FIG 6-36 Guidelines on the type of CBT to perform. (a) Cavity size can be gauged best by measuring the mesiodistal (blue arrow) and buccolingual (black arrow) intercuspal distances of the cavity. (b) Cavities suitable for standard CBT. (c) Cavities requiring two-step CBT.

Calculating the height of the marginal ridge and occlusal contact

Given the presence of rubber dam isolation, the marginal ridge and occlusal surface are modeled empirically without checking static and dynamic occlusal interactions while chewing. Reference parameters for constructing a functionally acceptable model are as follows:

Establish the height of the marginal ridge to be constructed in relation to that of the adjacent tooth.

Read anatomical information from the residual occlusal perimeter, carefully assessing the degree of inclination of each individual residual ridge slope.

Read the anatomy of adjacent teeth, assessing the ridge slopes, anatomical regularity of the grooves, and functional wear on ridge slopes and crests.

When replacing old restorations, assess the height and angle of previous restorations before removing them, trying not to exceed occlusal limits during the modeling stage.

If newly formed caries lesions are present, evaluate any well-preserved tooth anatomy before drilling.

Such measures do not permanently rule out the need for occlusal adjustments once the restoration is complete, but they definitely reduce their extent.

Freehand Restoration Technique

If no tooth is present to establish the interproximal contact area, a matrix and wedge are of limited use. A wedgeless matrix method cannot achieve a tight marginal seal and tends to generate a flat cervico-occlusal emergence profile. In such cases, it is advisable to perform a freehand restoration as demonstrated in the following clinical case (Fig 6-37), in which there is a distal caries lesion affecting a maxillary right first premolar. The adjacent tooth is an abutment for a provisional prosthesis, which has been removed to perform the restoration. In cases like this, it

is preferable to perform the restoration freehand and entrust the dental technician with the task of making a prosthetic crown with a tight and reliable contact area.