7: Direct Restorations in the Anterior

Direct Restorations in the Anterior

At the beginning of our career we are often interested in technical details that distract us from the true challenge of the case we are handling. For instance, it is much more difficult to motivate a patient to adopt a low–caries risk lifestyle than it is to prepare a cavity. After many years of practice, however, one of the technical aspects in the field of restorative dentistry—either direct or indirect—that is still challenging involves reproducing tooth shades, especially when restoring single teeth. Indeed, although reproduction of tooth shade is based on scientific principles, there is also a strong element of personal interpretation.

The principle of cosmetic restoration is still dominated by too many individual parameters, and, despite the many attempts to systematize knowledge, protocols are subject to strong and personal influences. Indeed, one technique is not necessarily better than another, and some may even be used together. In this chapter I will try to propose a rational and standardized protocol for direct restoration in the anterior, with due regard for scientific principles.

Indications for and Limitations of Direct Restorations

The main indications for direct restorations are as follows:

The main advantages are as follows:

The criteria for choosing adhesive restoration are as follows (Figures 7-2 to 7-6):

In summary, it should be noted that:

When Should Direct Adhesive Restorations Be Performed?

Shade and Morphologic Mapping

The shade of the composite material is mainly related to its opacity and color intensity, parameters that vary greatly according to thickness.

In the case of Black Class IV restorations, the most logical way to control the thickness of the material is to prepare a diagnostic wax-up of the missing portion on a plaster cast mounted in the articulator, and then in the dental laboratory fabricate a silicone tray (Shore hardness about 95) that will be used as a template for the palatal side (Figure 7-7). Thickness control on the buccal aspect is achieved through precise shaping without a great deal of excess material.

Shade Parameters

Shade perception is subjective, and psychological and mathematical parameters must be introduced in order to make it objective.

Psychological Parameters

In 1969 Henry Munsell introduced parameters based on visual and cognitive perception that, translated into dental terms, mean hue, chroma, and value; the last of these is the most significant for dental purposes (Figures 7-8 to 7-10).

In dentistry, shade means the basic color of the tooth. In the Vita shade guide the different shades are indicated by the following letters: A, red-brown; B, yellow; C, gray; and D, gray-pink. Given today’s composite market, maintaining this four-color classification makes little sense, because one of the main problems with these materials is excessive transparency compared with the Vita shade guide. Transparency corresponds to grayness. Consequently, gray shades are obtained automatically by using a composite material (C and D masses are unnecessary, and there is little difference between A and B). Currently a shade can be modified toward gray simply by applying a more transparent enamel (the shade is not changed by the dentin mass). We can hope that in the future for each shade there will be specific dentin masses that are sufficiently opaque and colored (already a feature of all ceramic materials).

Value corresponds to brightness—that is, the amount of light that is reflected, refracted, or absorbed by a surface—and it is influenced by the type of surface finish. As shown in Figure 7-8, the interaction between light and a glass object produces dark and clear areas with a low value, alternating with clearer and more reflective high-value zones, depending on the surface finish: smooth, orange peel, or sanded. In short, analysis of a tooth value can be compared with a black-and-white photograph and can be divided into two parts:

Choice of Shade

Anatomic Preconditions

Careful assessment of the value and chroma of natural teeth can help orient the specialist in choosing the shade.

In Figure 7-11 we can see that the inner layers of dentin (close to the pulp) have a high value, whereas in the outer layers (toward the enamel) chroma increases and the value is lower. The inner enamel layer (toward the dentin) has a low value, whereas the outer one has a high one.

The most important parameters in shade reproduction with composite materials are opacity, shape, and shade for the dentin, and opacity, thickness, and surface texture for the enamel (Figures 7-12 to 7-14).

Philosophy of Composite Materials

Most marketed composites have a number of limitations.

In general, transparent composite materials are characterized by a dominant yellow-gray shade owing to the high percentage of vitreous-like filler. On the contrary, white masses lose their transparency almost completely because they are obtained by adding a large amount of white-opaque pigment. Therefore yellow-gray and white-opaque masses are readily available, whereas the white-transparent masses are poorly represented.

Figure 7-15 shows machine-made enamel samples with the same thickness and polishing, although they differ in opacity. We can observe more transparent samples with a low value and others that are more opaque with a high value.

The samples shown in Figure 7-16 were obtained by overlapping cores of dentin (approximately 2.5 mm) on thick enamel shells (approximately 1.5 mm). In Figure 7-16 the left sample is obtained with chroma dentin 7 (very deep shade) and NT enamel (Neutral Transparent with a low value); the sample on the right side is made with chroma dentin 1 (diluted color) and WB enamel (White Opaque with a high value). The shades of the sample teeth obtained with these layerings are logical and consequential, whereas the color of the sample on the left side of Figure 7-16—obtained with chroma dentin 1 and NT enamel—cannot be grasped immediately. Using a low-chroma dentin one would expect a light-colored tooth, but its association with a thick layer of NT enamel lowers the value drastically, overpowering the dentin in the final result. This demonstrates that overlaying completely different enamel composite shades on the same dentin affects value.

Figures 7-17 and 7-18 exemplify the behavior of several composite materials layered over a thick core to reproduce dentin, over which thin vertical columns differing in opacity, chroma, and hue were applied. Given the />

Only gold members can continue reading. Log In or Register to continue

Jan 1, 2015 | Posted by in Dental Materials | Comments Off on 7: Direct Restorations in the Anterior
Premium Wordpress Themes by UFO Themes