![]() When evaluating enamel translucency, the observer will often focus on the opalescent blue areas ( Figure 2). Areas within a tooth or a restoration with higher translucency will have a lower value because light transilluminates through and away from the viewer. Enamel and dentin have varying degrees of translucency. In the dental context, translucency can be described as the gradient between transparent and opaque. Choosing porcelains with higher opalescence, 5 optical density, and fluorescence will manifest brighter qualities. As tooth bleaching becomes even more popular, dentistry will continue to search for porcelain that is both bright and translucent. The characteristics of brightness and translucency work counter to each other. Using porcelain with less chroma and less translucency can increase a dental restoration’s brightness. Lowering value means diminished light returns from the illuminated object thus, more light is absorbed, scattered elsewhere, or transmitted through and away from the object. Value is the sum total amount of light that is returned from an illuminated object. The words value and brightness are synonymous. Increasing opacity of the enamel, as seen with dehydration and bleaching, can exaggerate the chroma gradient. ![]() 4 When the enamel is thin at the gingival third but thick incisally, a chroma gradient is created. The chroma of a natural tooth comes mainly from the dentin, and the thickness and opacity of the overlying enamel determines how much chromatic influence the dentin has. As chroma increases, the value decreases they are inversely related. As the powder becomes more saturated with brown pigment, the mixture appears darker, so the increase in chroma has a corresponding change in value. Each time more brown pigment is added, the strength or saturation (chroma) of the brown color increases but the mixture is still the same brown hue. 2 When brown pigment is placed into white powdered porcelain, the mixture takes on a brown hue. 2 In this age of highly bleached teeth, where little color exists, it is becoming less important to document the hue.Ĭhroma is the measure of how much color is present. 1 The lower the intensity of the hue, the harder it is to distinguish. Because hue is a biologic and psychological interpretation of the combination of the wavelengths reflected back from an object to the observer, the exact wavelength of the perceived color may not even be present. Hue is specified as the dominant range of wavelengths in the visible spectrum that yields a perceived color ( Figure 1). Synonyms for hue are color, cast, shade, tint, or tone. This article should give the reader a better understanding of how light interacts with a natural tooth, and to give the dentist/technician team the nomenclature to best describe it. It is difficult to duplicate nature in ceramics if the clinician cannot describe or fully illustrate what he or she sees in the shade-matching process. The capability to appraise and fully share the appropriate information from the operatory to a distant laboratory can be greatly enhanced by learning the language of color and the optical characteristics specific to teeth. Matching one or two artificial restorations to a highly characterized natural dentition can be a challenging procedure for the dentist/technician team. Understanding the properties of light and color will help communicate shade prescriptions to the laboratory for optimal results. The Optical Characteristics of Natural Teeth
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