A Review of Color Science in Dentistry: Shade Matching in the Contemporary Dental Practice

This article is the third in a series of review articles discussing the applications of color science to the clinical practice of dentistry. This installment discusses contemporary techniques for shade selection of teeth, as well as, challenges to successful clinical matching of the tooth shade to dental restorative materials. match. This article will discuss the visual and automatic device techniques available for shade selection. It is recommended that the first two articles in this series be reviewed to better understand the concepts of color theory and colorimetry applied to shade matching. Materials and Methods Manual, Visual Shade Selection Techniques The most frequently used technique in the shade matching of teeth to restorative materials is done manually and visually with dental shade guides [14]. Using this method, shade matching is accomplished by visually comparing a tooth with multiple standards, usually represented as shade guide tabs, Figure 1. The shade selection done in this fashion is subjective and is influenced by the ability of the human observer to choose the best matching shade. Factors such as observer color perception, observer bias, ambient lighting, and the acceptance threshold of mismatch have effects on accurate shade matching. Also, not all commercial shade guides cover all the ranges of value, hue, and chroma present in human tooth structure [15]. The aging of these shade guides combined with potential “darkening” of the tabs due to cold sterilization create havoc if undiscovered. The original shade guides represented only about 30 percent of the color range of natural dentition. This range has improved tremendously with the advances in colorimetry and improved shade guides. None of the currently available laboratory restorative material systems are available in more than two shade systems with many available in only one. Quite often this creates the need for “cross-matching” which requires the Introduction This article is the third in a series of articles that will review the fundamentals of color science as applied to the practice of dentistry. The first article discussed the basic human perception of color and reviewed the current accepted theory of human color perception [1]. The second article reviewed the measurement color, color difference calculations, and the principles of colorimetry [2]. This article discusses the contemporary techniques and challenges of clinically determining the color of teeth, as well as, matching tooth shade to dental restorative materials. The common theme for all three of the articles is that an understanding of the principles of color vision, color measurement, and the communication of color parameters will improve the restorative dentist’s abilities to meet patient expectations for biomimetic dental restorations. The restoring of form and function of the dentition for dental patients should be at the forefront of restorative dental care. However, patients generally have high expectations for excellent esthetic results. The incorporation of restorative materials with the teeth resulting in a natural appearance in which the dental restorative materials blend without detection should also be a major goal of the restorative dentist [3]. Restorative dental materials and prostheses matched to patient tooth color using contemporary clinical techniques generally provide results acceptable by most patients [4,5,6,7,8,9,10,11,12,13]. However, visual shade guides with shade tabs are commonly used for shade selection and these techniques are very subjective, and often these techniques depend on numerous ambient factors and the color vision acuity of the clinician. In the contemporary restorative dental practice, colorimetric instrumentation can be used to choose a close color Figure 1: Dental shade Matching Tabs (Vita Classical A1D4®). Page 2 of 5 Citation: Ragain JC (2016) A Review of Color Science in Dentistry: Shade Matching in the Contemporary Dental Practice. J Dent Oral Disord Ther 4(2): 1-5. A Review of Color Science in Dentistry: Shade Matching in the Contemporary Dental Practice Copyright: © 2016 Ragain laboratory technologist to reformulate the material shades to match the particular dentition. This is an extremely subjective process which could lead to unacceptable mismatches. Another problem is the influence of shade designation on the difference in color in various brands of dental restorative materials. Kim and Lee [16] found inconsistency in the color of the same shade designation of composite resin materials by manufacturer brand. This should be taken into consideration when selecting shades of these materials clinically. There are a variety of shade guides available to the practitioner. Three examples are illustrated in Figure 2. Some are universal shade guides in that they could be used for matching ceramic materials and composite resin materials with teeth. However, it is usually beneficial to use a shade guide made of the corresponding restorative material. Examples of resinmade shade guides are Esthet-X® (Densply/Caulk, Milford, DL, USA) Tetric Cream® (Coltene/Whaledent, Cuyahoga Falls, OH, USA), Venus® (Haeraus Kulzer, South Bend, ID, USA), and Vit-lescence ®(Ultradent, South Jordan, UT, USA). The ceramic made shade guides include the Vita line of shade guides (Vita North America, Yorba Linda, CA, USA), Chromoascop® (Ivoclar Vivadent, Amherst, NY), and Vintage Halo® (Shofu Dental, Menlo Park, CA). Many of the manual, visual shade guides have similar design and functionality, so we will concentrate on one line of products to illustrate the manual, visual shade selection technique. The VITA Classical A1-D4®shade guide (Vita North America, Yorba Linda, CA, USA) was introduced to dentistry in 1956, Figure 3. The VITA Classical A1-D4®is composed of sixteen tabs. The tabs are arranged into four groups (A-D) based on hue with increasing chroma within the groups. In this arrangement, Group A is reddish-brown, Group B is reddish-yellow Group C is gray, and Group D is reddish-Gray. As described by Paravina and Powers, the manufacturer also provides an arrangement of shade guide tabs by hue [15]. Many dentists find that matching tooth shades is simplified by this arrangement of tabs, and this array of tabs by degree of brightness has been found to be easier and more reliable to use, Figure 4 [15]. In the 1990’s, Vita North America enhanced their shade guide system and introduced the VITA System 3-D MASTER shade guides®. This system is composed of the VITA Linear guide 3-D MASTER®, the VITA Bleach guide 3-D MASTER®, and the VITA Tooth guide 3D-MASTER®with Bleached Shades, Figure 5. The VITA System 3-D MASTER ® shade guides consist of 26 shade tabs in five groups according to lightness. Within each group, the tabs are arranged vertically according to chroma and horizontally according to hue. The concept of the VITA 3D-MASTER ®system is based on a color classification principle where the values of lightness, chroma, and hue have been positioned an equal distance from each other. Therefore, the shade determination can be easily carried out according to systematic criteria. The VITA Linear guide 3-D MASTER® simplifies tooth shade determination compared to the VITA Classical A1-D4 and the VITA Tooth guide 3D-MASTER® Figure 6 with Bleached Shades. It is organized in terms of lightness, chroma, and hue, and the shade can be determined in two steps. The VITA Bleach guide 3-D MASTER® with Bleached Shades is a one-step process to determine the level of lightness for the tooth whitening process. When comparing the VITA 3-D MASTER® system with the VITA Classical A1-D4 ®shade guide it can be noted that the value range is wider, there are more chromatic tabs, the hue range is extended into the reddish color spectra, there is more uniformity in the shade tab spacing, and the overall tab arrangement is improved over the VITA Classical A1-D-4® [16]. In general, when using shade guides to select a shade, it is recommended that hue selection be made first, followed by chroma and value, in that order. The clinician should always do a final check and revise the shade selection if needed. The following are recommendations for shade selection in the dental operatory: • Teeth to be matched must be clean. • Remove bright colors from the field of view. • Tooth shade should be determined in daylight or under standardized daylight lamps (not operation lamps). • Operatory walls should be neutral in color. Figure 2: Examples Of Three Manual, Visual Shade Guides Used in Dentistry. Figure 3: VITA Classical A1-D4 Shade Guide® (Vita North America, Yorba Linda, CA, USA).