|Year : 2013 | Volume
| Issue : 1 | Page : 26-31
RS Basavanna, Chitra Gohil, Vasundhara Shivanna
Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere, Karnataka, India
|Date of Web Publication||26-Nov-2013|
R S Basavanna
Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere - 577 004, Karnataka
Source of Support: None, Conflict of Interest: None
Recent advances in color matching have been driven by the market demand for high-quality esthetic restorations. Improved shade guides, availability of shade-taking devices and research in the area of human color vision have improved the potential of clinicians to achieve excellent color-matched restorations. A thorough understanding of appearance attributes of natural teeth is required along with these new tools to maximize shade-matching results.
Keywords: Color, electronic devices, shade guides, shade matching
|How to cite this article:|
Basavanna R S, Gohil C, Shivanna V. Shade selection. Int J Oral Health Sci 2013;3:26-31
| Introduction|| |
Shade selection is an important procedure to provide patients with an esthetic restoration that harmoniously blends to the patient's existing dentition. Due to the great variety of natural tooth color, achieving a close shade match of an artificial restoration with the natural dentition is a complex process. Practitioner requires an understanding of color, light and related characteristic of porcelain and resin as well as the ability to clearly communicate instruction with the lab technicians in order to obtain natural looking restoration, there are two crucial steps in shade selection: Selection of color through shade guide and consequently the correct reproduction of this color in the prosthesis or restoration. ,
| Color and Science|| |
Sir Isaac Newton's experiments during 18 th century showed that white light passing through a prism divided into a pattern of colors termed as spectrum and he proved that without light color does not exist. The color of an object can change depending on the type of illuminant. There are three main illuminant such as Incandescent, Fluorescent, and Natural light. Incandescent emits more of red/yellow light and its color temperature is about 2856 K. Fluorescent emits more of blue light and its color temperature is 4000 K, were as natural light is extremely variable. Mid-day light is said to be best for shade selection because at this time light is most balanced. There are special lights that are color corrected light, which emits light with more uniform distribution of color. Its color temperature is 5500 K. 
| Dimensions of Color|| |
At the beginning of 20 th century Prof. Albert D. Munsell gave a color wheel which includes the dimension of Hue, Value and Chroma  [Figure 1]
(The greater the total amount of light reflected the higher the value). The scale ranges from low of 0 (i.e., pure black) to high of 10 for pure white. Chroma has been found to increase with age in both enamel and dentin, while hue and value do not based on in vitro testing. 
- Hue determines the color tone or pigment of the tooth (for, e.g., red, orange or yellow)
- Chroma determines the saturation or purity of color tone (for, e.g., more the wavelength of a particular color reflected more pure color will be obtained)
- Value determines the relative darkness/lightness of hue.
| Elements Affecting Color Perception|| |
Shade selection involves the perception of color, which depends on three entities:
According to (Commission International De l' Eclairage in 1931 categorized illuminant based on their effect on color perception, in that D50 and D65 illuminant which has a color temperature of 5000 and 6500 K respectively are most commonly used as a standard illuminant. Clinically while performing shade matching, clinician should use D50 illuminant.
- The environment
- The viewer.
However, shade selection should always be done under different lights to avoid metamerism (The phenomenon that occurs when shade appear to match under one lighting condition and not another). 
| Recommended Protocols For Shade Selection|| |
- Remove bright color from the working field. If the patient is wearing bright clothing, it is prudent to cover the patient with neutral color bib (grey). Any dark color lipstick should be removed, because it could affect shade matching
- Always clean the tooth by using prophylaxis paste prior to shade selection
- Its important not to view the shade comparision for more than 7 s to avoid eye fatigness
- Clinician should be at a distance of 28-33 cm from the patient during shade selection
- Always determine shade when the teeth are most hydrated, because enamel dehydration reduces its translucency by 82%, misleading the clinician
- Shade comparision should always be done in between 10 am and 2 pm, because at this time color tempreature is around 5500 K and then under color corrected light to ensure the accuracy of the match
- During the shade comparision always place shade tabs either above or below the tooth to be match, never place shade tab adjacent to the tooth to avoid binocular effect
- Always, value is analyzed first, followed by chroma and then hue
- Shade selection should not be done immediately after bleaching, patient should be recalled after 2-3 weeks for shade comparision
- Always during shade selection teeth should be divided in 3 regions. Gingival area (gives accurate determination of dentinal chroma), Body area and Incisal area (enamel is thickest here and varies from translucent to transparent).
In addition to hue, chroma and value, more subtle optical properties are also included they are translucency, opacity, opalescence, surface gloss, surface texture and fluorescence. These secondary optical properties contribute natural appearance of restoration. Translucency and opacity have been viewed as the most important of these secondary properties, since they are an indication of the quality and quantity of light reflection.  Translucency of the restoration depends on the value and the thickness of composite resin. As high value composite resin are more translucent than low value composite and translucency of the restoration decreases as the thickness of the specimen increases.  Opalescence is the ability of translucent material to appear blue in reflected light and red-orange in transmitted light. This feature is primarily observed in an enamel. Fluorescence is an important physical property of natural teeth (more specifically dentin), because they emit blue visible light when exposed to uv light. Surface gloss affects the appearance and vitality of teeth. It has been described as the optical property that produces a lustrous appearance.  Surface texture influences esthetics by determining the amount and direction of light reflected off the facial surface. Young teeth may have a lot of characterisation with stippling, ridges, striations and lobes. 
According to Vanini, the tooth color is composed of five dimensions  [Figure 2]:
|Figure 2: Vanini's classification of enamel effects. Three categories: Intensive, opalescent and characterization. Understanding this categorization will provide the clinician a simple road map to color matching|
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- Chromaticity - it is the hue and Chroma of the dentin
- Value/luminosity - (it is strictly related to enamel)
- Intensive - it occurs more frequently in young tooth and represents hypo mineralized area of enamel
- Opalescent - it is confined to the incisal third
- Characterization - it affect both enamel and dentin.
Tooth shade matching is most frequently performed visually using dental shade guide. The first shade guide was introduced in 1956 by Vita Zahnfabrik. The most popular shade guide is - VITA Classical, Chroma scope, Vitapan 3D-Master shade guide.
VITA classical shade guide - It consist of 16 tabs, arranged into four groups based on the hue and within the group according to increasing Chroma. Hue is categorized by letter i.e., A = Orange, B = Yellow, C = Yellow/Gray and D = Orange/Gray. Chroma and Value are categorized by numbers i.e., 1 = least chromatic and highest value, 4 = most chromatic and lowest value [Figure 3]. , Another popular shade guide is the chromascope. It uses only numbering system to identify the shade.
Chromascope is arranged in groups based on the hue (100 = white, 200 = yellow, 300 = orange, 400 = gray, 500 = brown) and and within the groups according to increasing chroma from 10 to 40. Vitapan 3D-Master [Figure 4] - it has 11 sets of teeth, which consist of 26 sample ranging from lightest to darkest value, from lowest to highest intensity and from yellow to red. Samples are arranged in groups of 2 or 3 that form 5 sets (number 1-5).
Each set shows a single value, 1 being the lightest (high value) and 5 being darkest (low value). In each of the groups, Chroma increases from top to bottom (1 being least chromatic and 3 being most chromatic). All the group except 1 and 5; have 3 letters: L, M, R which allow hue to be chosen (L is yellow hue; M is yellow-red and R is red hue). ,
Recently, Vitapan 3D-Master was modified with the introduction of 6 groups in it. No. 0 for the shade matching of bleached teeth [Figure 5]. One of the other advantages of VITA 3D-Master is repeatability of shade selection with the system. It was concluded that use of this system compared with classic guide improved intra-rater repeatability among practitioners. 
A further development is the introduction of new shade guide, i.e., VITA Linear guide 3d-Master which enables the quick determination of precise tooth shades and uses same principles found in VITA 3D-Master guide, only difference is, it is sleeker, linear design [Figure 6].
More over these techniques were hard to understand as they do not explain clinical use of specific opaque material. Hence, layering technique may be better classified as follow. ,
| Shade Taking Devices: Electronic AID|| |
There are three basic types of devices used for shade selection: 
Colorimeter device is designed to measure color (hue, Chroma and value) as perceived by the human eye. The spectrophotometer is more sophisticated instrument, built to measure hue, value, Chroma and translucency. Significant advantages with spectrophotometric measurements include the ability to analyze the principal components of a series of spectra and its ability to convert spectrophotometric measures to various color measures. 
- Spectrophotometry, e.g. Vita easy shade [Figure 7] and [Figure 8]
|Figure 8: Improved version of VITA easy shade smaller, wireless, easy to handle|
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- Colorimeter, e.g. shade vision
- Digital camera and RGB devices, e.g. shade scan.
Recent advances in electronic have resulted in more accurate determination of color and to the very latest development in which digital images are combined with colorimeter or spectrophotometer [Figure 9] and [Figure 10].
|Figure 9: Spectro shade micro medical high technologies (digital imaging + spectrophotometer)|
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| Sopro 717 Shade Matching Tool|| |
A dental camera combines video assisted tooth shade selection with all the advantages of a modern high-performance camera. It has four Sopro Shade tips, which make it easier for the practitioner to undertake a differentiated diagnosis of the varying tooth shapes and color shades and the intra oral camera SOPRO 717 high quality intra-oral and macroscopic views. The Sopro shade concept of the Sopro 717 intraoral camera is a reliable assistance to visual color assessment compared with conventional visual methods [Figure 11]. 
According to Kuzmanoviæ and Lyons Study found no significant difference in the accuracy of shade selection when using either a conventional visual assessment technique or a colorimetric instrument. There was, however, some discrepancy when the two shade selection techniques were compared for shade selection of the same tooth. 
Colorimeters are significantly less reliable than spectrophotometers and digital cameras. Combination of visual color determination (Vitapan 3D-Master shade guide and Linear guide) with digital cameras and electronic devices (spectrophotometers) increase chances for successful shade matching. 
The VITA easy shade had the best combination of accuracy and reliability. Reliability percentages were 99.0, for shade vision, 96.9, for Spectro Shade, 96.4 for VITA Easyshade and 87.4 for Shade Scan. Accuracy percentages were 92.6 (highest) for the VITA Easyshade. 
| Conclusion|| |
Each individual perceive color differently here the knowledge and skill of each practitioner always play a significant role. There are several factors that can influence the clinician color assessment. So only using traditional shade matching technique is not enough to get accurate shade. Technology based system provides an accurate shade selection and natural looking restoration.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]