Indications and Limitations of Single-Shade Composite Resins

Due to the polychromatic nature of teeth and their diverse optical properties, emphasis has been placed on manufacturing products with a large range of shades with various hues, chromas, and opacities that mimic those of enamel and dentin in an effort to create restorations that will be imperceptible to the human eye. These materials are referred to as multi-shade composites (eg, 3M^™ Filtek^™ Supreme Ultra, 3M; Estelite Omega^®, Tokuyama; IPS Empress^® Direct, Ivoclar; Evanesce^™, Clinician's Choice). With appropriate shade matching and layering, they can be used to create restorations that satisfy the most critical and demanding patients.^3,4

Although the layering technique has been proven to deliver great results that demonstrate higher esthetic integration, some consider these restorations to be unachievable due to the technical skills needed to place them and the time required for shading, polychromatic layering, and contouring and polishing.² The success of layered restorations is dependent on the clinician's knowledge and ability to integrate the various shades and opacities of the chosen material.^1,2 Beyond being technique sensitive, another potential downside of these restorations is the need to maintain a large inventory of composites in different opacities and shades as well as tints and opaquers.^6-9

In response to these difficulties, dental manufacturers have introduced several composite systems that have a reduced number of shades. Manufacturers claim that the shades in these simplified-shade systems (eg, 3M^™ Filtek^™ Universal Restorative, 3M; Tetric EvoCeram^®, Ivoclar; SimpliShade^™, Kerr Corporation; Estelite Sigma Quick^®, Tokuyama; TPH Spectra^® ST, Dentsply Sirona; G-ænial^® A'CHORD, GC America), which are sometimes referred to as "universal" shades, can be used to replicate and match several shades through a so-called "chameleon effect."^5,7 For the most part, the systems with reduced numbers of shades in this category include shades that are in the VITAPAN^® A range and in a single opacity that is usually between that of enamel and dentin. It is very common for manufacturers to offer composites in multi-shade systems with multiple opacities as well as in simplified-shade systems.

Taking shade simplification even further, some manufacturers have also introduced single-shade composite resins.⁸ These materials are marketed as being able to match all tooth shades.^5,10 They eliminate the process of shade selection and the need for layering techniques entirely because a single variant can mimic the opacity, translucency, and optical characteristics of all teeth.^5,7 Several terms have been used to describe this concept of a single shade matching all shades, including "single-shade," "one-shade," "single-shade universal," "one-shade universal," "smart monochromatic composite," and others.^4,11 Although there are various brands of single-shade composites available on the market (eg, OMNICHROMA^®, Tokuyama; Venus Diamond^® ONE, Kulzer; Venus Pearl^® ONE, Kulzer; CLEARFIL MAJESTY^™ ES-2 Universal, Kuraray Noritake; Vittra APS Unique, FGM), most are recommended for posterior restorations only.

Anecdotally, the opacity of single-shade composites is very enamel-like, and they seem to work better when lighter shades are being matched when compared with darker shades. They also seem to polish fairly easily and maintain their polish over time. In small- to medium-sized restorations, they demonstrate a great blending ability and imperceptibility, especially when fully surrounded by tooth structure. They work well for medium to small diastema closures (Figure 1 and Figure 2), procedures to eliminate black triangles (Figure 3 and Figure 4), thin direct composite veneers (Figure 5 and Figure 6), Class I restorations (Figure 7 and Figure 8), and small Class III and Class V restorations (Figure 9 and Figure 10).

The single-shade composite (OMNICHROMA^®, Tokuyama) that was used in all of these case examples was selected because of its Smart Chromatic Technology, which is based on homogeneously sized spherical-shaped filler particles.¹² It is claimed that these particles generate red to yellow structural color as light passes through the fillers, reflecting the red to yellow range of colors found in all the teeth.¹¹ These colors then combine with the surrounding tooth colors to create a seamless integration that makes restorations nearly invisible.^11,13

Translucency is considered a crucial property when developing single-shade composite resins with the ability to replicate the optical behavior of dentin and enamel.¹ The more translucent the resin gets, the more the blending effect increases.¹⁴ However, this concept doesn't hold up when placing a large Class III or a Class IV restoration due to the lack of surrounding tooth structure and the darkness of the mouth. In these cases, such as this one involving a Class IV restoration (Figure 11 and Figure 12), the manufacturer recommends using a less translucent supplementary material (OMNICHROMA^® Blocker, Tokuyama) to reduce shade-matching interference. More specifically, the "blocker" is placed first as a lingual layer and then the single-shade composite is applied as a second layer.¹²

Because there is no need for shade matching or to have a shade guide, single-shade composites make shade selection obsolete, which reduces not only inventory but also chair time. Clinically, the blending effect of these materials can be further enhanced by incorporating bevels into preparations to permit better color integration. The bevel creates a "shade transition zone" between the restorative material and tooth structure.

In the authors' experience, single-shade composite resin materials are not able to correct color inadequacies or block dark discolorations, and their blending ability is significantly reduced in darker shades and when a greater thickness of material is required. In order to overcome this, a dentin-like material, opaquer, or blocker is necessary. It is also important to consider the impact of superficial staining on the esthetics of restorations because it has been reported as one of the main causes of failures leading to restoration replacement. In-vitro studies have been published in which single-shade composites demonstrated more color change from wine, coffee, and black tea than multi-shade composites, which may limit their clinical use in cases of high esthetic demand.^10,13 In addition, polychromatic, halo, and translucency effects as well as internal characterization cannot be achieved with either "simplified-shade" or "single-shade" resin composites.

Multi-shade, simplified-shade, and single-shade composite resins all offer benefits and drawbacks. It is up to dentists to choose which category of material best fits their needs in each case regarding indications, skill, effort, time, and economics. However, considering the current trend to reduce treatment complexity, single-shade composite resins can help dentists reduce technical difficulty, increase efficiency, and reduce inventory. These materials demonstrate the potential to achieve accuracy and predictability in mimicking the natural dentition and to create restorations that are not only acceptable but also deliver admirable esthetics in many situations. Nonetheless, these materials cannot replace polychromatic multi-shade materials for cases with high esthetic demands. Although single-shade composite resins show promising results, additional clinical studies are necessary to assess their long-term success and acceptability to patients.

Hiromi Saisho, DDS, MS
Clinical Assistant Professor
Department of Family Dentistry College of Dentistry and Dental Clinics
The University of Iowa
Iowa City, Iowa Marcos

Vargas, BDS, DDS, MS
Professor Department of Family Dentistry College of Dentistry and Dental Clinics
The University of Iowa
Iowa City, Iowa