Practice Benefits of Universal Composites

Shade matching composite restorations can be challenging for various reasons. First, composite materials are not designed to match standardized VITA shade guides.¹ Clinicians need to either create a custom shade guide for each composite system used within the office or match the shade by placing a small piece of cured composite on the tooth of interest. Another challenge of shade matching composite is that resin composites change color when polymerized.² This can make it difficult for clinicians to ensure that the composite shade selected is correct until it is too late to change it. In addition, the color of the tooth will change once it has desiccated. Most teeth demonstrate a perceptible color change following just 1 minute of desiccation, and even after 15 minutes of rehydration, most teeth do not return to their original color.³ Therefore, clinicians must choose the correct shade at the start of the appointment and prepare the patient that the final color of the restoration may be slightly lower in value (ie, darker) immediately following the procedure. Finally, resin composites can vary in color based on the source of light in the room.⁴ Some clinicians may choose to check shades near a source of natural light, such as from a window, or install color correcting lights, which produce colors that are close to what would be seen under direct sunlight. Due to all of these challenges, shade matching can become a time-consuming process. And this process may be further complicated if several opinions are involved, such as those of the patient or auxiliary.

All dental composites are sold with an expiration date. The shelf life of a composite is dependent on the constituents of the material not separating, evaporating, reacting, or degrading. Chemical and dual-cure composites are more sensitive to storage times due to the instability of the peroxide-based initiators they contain. Light-cure resins are also sensitive to storage time based on the stability of the photoinitiators, the stabilizers, and the polymerization inhibitors.⁵ Typically, the expiration date will reflect when the resin can no longer achieve the desired degree of polymerization. Laboratory tests do not always measure a decrease in the mechanical properties of materials beyond their expiration date⁵; however, this date should be respected. Storage in a refrigerator may help to maximize the shelf life of dental materials.

The universal composites available include both single-shade universal composites, which cover all of the Vita shades with one shade of material, and multi-shade universal composites, which cover multiple Vita shades with one shade of material. For example, some multi-shade universal composite systems include a chart that specifies which Vita shades are represented by each shade of their system, and others offer a "dark shade" that can be used to reproduce all of the low value/high chroma shades.

Most universal composites achieve their color blending effect by leveraging at least some increase in translucency. One innovation utilized in some of these materials is "structural color," which involves the use of filler particles of a certain size (ie, 260 nm) to impart a yellowish hue to the composite instead of using pigments.⁶ The camouflage effect of single-shade universal composites is often demonstrated by placing small restorations into the facial surfaces of all of the teeth in a Vita shade guide. According to the results of a recent laboratory study, a universal composite more closely blended into Class I preparations of denture teeth in Vita shades A1 through D4 than the A2 shades of reference composites.⁷

The increased translucency of universal composites causes them to be more affected by the presence of a dark substructure (eg, sclerotic dentin, staining, discoloration in the preparation). Therefore, the use of an opaque blocker composite may be necessary in these clinical situations. Some manufacturers provide a pink shade composite in their systems because a pink hue is effective at covering discoloration.

Universal composites have applications for both posterior and anterior restorations. Assuming that there is no discoloration in the preparation, universal shade composites can fulfill the esthetic requirements of almost any patient for a posterior restoration. A clinician must also decide how well he or she would like to hide the restoration in the tooth. If the clinician suspects that the restoration may need to be replaced in the future, it may be advantageous to be able to visually differentiate the composite from the natural tooth structure.

One highly successful anterior application for universal shade composites is for cervical Class V restorations. These restorations are usually surrounded by tooth structure on all sides, which helps the material to blend into the tooth. If there is any discoloration in the preparation, a layer of opaque composite should be used first. Another application of universal shade composites is to restore the incisal wear of anterior composites. Although a universal composite will not produce the incisal "halo effect" that can be achieved through composite layering, these composites can produce acceptable results at incisal edges. Universal composites are faced with technical challenges for Class IV restorations. If there is no tooth structure behind the restoration, the material does not have anything to blend with. In addition, the darkness in the back of the mouth can show through a translucent restoration.

In summary, universal composites can offer an efficient option for the placement of both posterior and anterior composite restorations. The efficiencies realized by reducing the inventory of shades that a practice must manage and by limiting or eliminating the time required for shade selection, as well as the cost savings realized by reducing the amount of waste associated with expired products, can all translate into an improved bottom line for practices.

Nathaniel Lawson, DMD, PhD, is the director of the Division of Biomaterials at the University of Alabama at Birmingham School of Dentistry in Birmingham, Alabama.