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How to Improve Shade Matching in the Dental Operatory
A S S O C IA T IO N
REPORTS
How to improve shade matching in the dental operatory Council on Dental Materials, Instruments, and Equipment
T
A oday’s dental patient is becoming increasingly aware and much more critical of modern restorative services. Considerable emphasis is now placed on the esthetic appearance as well as the function of restorations. As a re sult, shade matching is a challenge in both the dental operatory and dental laboratory. This report gives some basic guidelines for matching dental prostheses with tooth color. Color is the effect of a source of light as it is reflected by an object to the eye of the observer.1,2An understanding of how each of these variables (light source, object, and observer) can affect color or shade is necessary for proper color matching. Color can be described in three qualities: the hue (color); the value (lightness or darkness); and the chroma (saturation or intensity of color). This method of color designa tion, known as the Munsell system, has been applied to matching tooth colors. The dentist should also be a w a r e o f p r o b l e m s s u c h as metamerism, in which two materials appear to have an identical color under one light source, but are an obvious mismatch under another. Shade m atching is, therefore, a complex problem. This article focuses on how shade matching can be im proved by understanding the variables presented by the light source, the teeth and surrounding environment, and the observer.
currently available emphasize slight changes in hue3; others use a limited number of hues and introduce small steps in chroma to test for color dis crimination.4Some knowledge of light and color notation5'8 is desirable to transmit data from the dental opera tory to the laboratory—dental shade guides provide the most com m on standard.9 During color matching, eye fatigue can be avoided by looking at neutral (gray) surfaces occasionally, or gazing at colors complementary to those pre valent in tooth shades, such as blue, for short periods. The qualified observer should have no gross deficiencies in color discrimination, such as any form of color blindness, either congenital or temporarily induced by medication. All types of color blindness can be de tected by relatively simple vision tests.10-11
THE OBSERVER. The ability to distin guish colors is not uniform among ob servers, although it is usually possible to improve color discrimination by conscious effort. In addition, the ob server can be trained in color dis crimination by the repeated use of standard color tests. Some of the tests
LIGHTING. Lighting in the dental op eratory is a most important factor in proper shade matching. The ideal light source would have its energy evenly distributed across the entire visible spectrum. This is unattainable in prac tice; however, color-corrected light sources approach this condition.12It is
OBJECT. Objects m o d ify l i gh t by transmission, absorption, reflection, and scattering. The human tooth is both translucent and transparent and, as such, presents a complex material for color matching. Manufacturers have developed shade guides to help in selection of the proper shade, but the dentist should realize that these guides can only approximate natural tooth color and must be used properly even to approach an accurate color match.
recommended that a dental light with a color temperature (a measure of the energy distribution of the light) of 5,500 K be used, and that the colorrendering index (a measure of the de gree the light source corresponds to natural daylight) of the light be above 90.13If possible, the shade should also be checked under a different light source, as the patient w ill not always be seen under color-corrected lighting. A light source that approaches an in candescent light, such as a warm white fluorescent light, is a good choice. The intensity of light is also an im portant factor. Improper lighting in tensity can result in severe adaptation fatigue; in particular, the differential color sensitivity of the eye decreases as the level of intraoral illumination de viates from an optimum level. The ideal ratio of intraoral to extraoral il lumination is considered to be 3:1; however, ratios as high as 10:1 are ac ceptable. It is recommended that the extraoral light intensity be in the range of 200 to 300 footcandles at a distance of 30 inch (76 cm) above floor level. This can be attained by the use of 12 4-ft fluorescent tubes in a 10- x 10-ft room with an 8-ft ceiling.13,14 An allluminous ceiling is also desirable for good visibility with fewer shadows. Acrylic diffusers that have at least 90% light transmission and do not alter the spectral characteristics of the light source are recommended because they tend to scatter the l i g h t evenly throughout the operatory and reduce glare. The color environment of the dental operatory is another critical factor in shade matching. To reduce the spe cific absorption and reflection of inci dent light, which will modify the per ception of color, a neutral, light-gray background color (Munsell Value ~ 8) JADA, Vol. 102, February 1981 ■ 209
A S S O C IA T IO N
REPORTS
should be present in the room. The counter tops should have a nonglare surface with a Munsell Value of 7 or higher, and the floor should be neutral, if possible, with a Munsell Value of 6 or higher.
Selecting shades The following rules should be ob served in shade matching. —The manufacturer’s shade guide for the product should be used. This is true for both porcelain and plastic den ture teeth, as well as for porcelainmetal or plastic-metal restorations. Er rors by the dentist and laboratory may result when shade guides other than those designed for the material specified are used. — Shade matching should be done under lights of similar spectral distri bution and intensity, both in the den tist’s operatory and in the dental tech nician’s laboratory. Ideally, shades in the patient’s dentition should be an equally good match under daylight, fluorescent light, and incandescent light. At the least, restorative materials and natural teeth should match closely under lighting conditions similar to daylight. — Effects of translucency and posi tion should be considered; higher translucency and more distal position in the natural dentition causes a darker gray appearance. The color of the lips,
210 ■ JADA, Vol. 102, February 1981
tongue, palate, and gingiva also affects the color of the teeth. The position of the tooth in contrast to the palatal vault will affect translucency: higher trans lucency against a dark background would be equivalent to a lower M un sell Value in the shade of a semi opaque restoration. — The m a n u f a c t u r e r ’s r e c o m mendations for preparing the surface of the tooth before shade-matching should be followed. Leaving a glossy layer of saliva or removing moisture af fects the proportion of specular (mirror-like) reflection to diffuse re flection.15 Only diffuse reflection is indicative of the true shade. Specular reflection can be misleading, espe cially if high intensity illumination is used. — When shade matching, the indi vidual shade tab should be removed from the guide and held close to the tooth alone. This w ill prevent the socalled “effect of placement” in a series of tabs in which saturation varies. —The surface texture of the restora tion should be matched as closely as possible with that of the remaining dentition. This w ill tend to reproduce the characteristics of light reflection inherent in the remaining natural den tition.
This report was prepared at the request of the Council on Dental Materials, Instruments, and Equipment by Wayne T. Wozniak, PhD, assistant
secretary of the Council, and John B. Moser, PhD, associate professor, department of biological ma terials, Northwestern University School of Den tistry, Chicago. 1. Lemire, P.A., and Burk, A.A. Color in den tistry. Hartford, Conn, J. M. Ney Co., 1975. 2. McPhee, E.R. Light and color in dentistry. Tex Dent J 3:6-13,1979. 3. The Farnsworth-Munsell 100-Hue Test. Munsell Color Co. Inc., Baltimore, Md, 1957. 4. Color Matching Aptitude Test; Federation of Societies for Coatings Technology. Philadelphia, 1978. 5. Sproull, R.C. Color matching in dentistry. The three dimensional nature of color. J Prosthet Dent 29(4):416-424, 1973. 6. Sproull, R.C. Color matching in dentistry. Practical applications of the organization of color. J Prosthet Dent 29(5):556-566,1973. 7. Sproull, R.C. Color matching in dentistry. Color control. J Prosthet Dent 31(2):146-154, 1974. 8. Rainwater, C. Light and color. New York, Golden Press, 1971. 9. Preston, J.D., and Bergen, S.F. Color science and dental art. St. Louis, C. V. Mosby Co., 1980. 10. Dvorine, Pseudo-Isochromatic Plates. New York, Psychological Corp. 11. Standard Pseudo-Isochromatic Plates, (I-H-T-K Plates). New York, Igaku-Shoin Medical Publishers. 12. Bergen, S.F., and McCosland, J. Dental op eratory lighting and tooth color discrimination. JADA 94(1):130-134, 1977. 13. Sellers, R.W.; Young, J.M.; and Powell, J.M. The scientific application of light and color to the dental environment. Aeromed Rev 2:1-20,1978. 14. Preston, J.D.; Ward, L.C.; and Bobrick, M. Light and lighting in the dental office. Dent Clin North A m 22(7):431-451,1978. 15. Burnham, R.W.; Hanes, R.M.; and Bartleson, C.J. Color: a guide to basic facts and concepts. New York, John Wiley and Sons Inc., 1963.
REPORTS
How to improve shade matching in the dental operatory Council on Dental Materials, Instruments, and Equipment
T
A oday’s dental patient is becoming increasingly aware and much more critical of modern restorative services. Considerable emphasis is now placed on the esthetic appearance as well as the function of restorations. As a re sult, shade matching is a challenge in both the dental operatory and dental laboratory. This report gives some basic guidelines for matching dental prostheses with tooth color. Color is the effect of a source of light as it is reflected by an object to the eye of the observer.1,2An understanding of how each of these variables (light source, object, and observer) can affect color or shade is necessary for proper color matching. Color can be described in three qualities: the hue (color); the value (lightness or darkness); and the chroma (saturation or intensity of color). This method of color designa tion, known as the Munsell system, has been applied to matching tooth colors. The dentist should also be a w a r e o f p r o b l e m s s u c h as metamerism, in which two materials appear to have an identical color under one light source, but are an obvious mismatch under another. Shade m atching is, therefore, a complex problem. This article focuses on how shade matching can be im proved by understanding the variables presented by the light source, the teeth and surrounding environment, and the observer.
currently available emphasize slight changes in hue3; others use a limited number of hues and introduce small steps in chroma to test for color dis crimination.4Some knowledge of light and color notation5'8 is desirable to transmit data from the dental opera tory to the laboratory—dental shade guides provide the most com m on standard.9 During color matching, eye fatigue can be avoided by looking at neutral (gray) surfaces occasionally, or gazing at colors complementary to those pre valent in tooth shades, such as blue, for short periods. The qualified observer should have no gross deficiencies in color discrimination, such as any form of color blindness, either congenital or temporarily induced by medication. All types of color blindness can be de tected by relatively simple vision tests.10-11
THE OBSERVER. The ability to distin guish colors is not uniform among ob servers, although it is usually possible to improve color discrimination by conscious effort. In addition, the ob server can be trained in color dis crimination by the repeated use of standard color tests. Some of the tests
LIGHTING. Lighting in the dental op eratory is a most important factor in proper shade matching. The ideal light source would have its energy evenly distributed across the entire visible spectrum. This is unattainable in prac tice; however, color-corrected light sources approach this condition.12It is
OBJECT. Objects m o d ify l i gh t by transmission, absorption, reflection, and scattering. The human tooth is both translucent and transparent and, as such, presents a complex material for color matching. Manufacturers have developed shade guides to help in selection of the proper shade, but the dentist should realize that these guides can only approximate natural tooth color and must be used properly even to approach an accurate color match.
recommended that a dental light with a color temperature (a measure of the energy distribution of the light) of 5,500 K be used, and that the colorrendering index (a measure of the de gree the light source corresponds to natural daylight) of the light be above 90.13If possible, the shade should also be checked under a different light source, as the patient w ill not always be seen under color-corrected lighting. A light source that approaches an in candescent light, such as a warm white fluorescent light, is a good choice. The intensity of light is also an im portant factor. Improper lighting in tensity can result in severe adaptation fatigue; in particular, the differential color sensitivity of the eye decreases as the level of intraoral illumination de viates from an optimum level. The ideal ratio of intraoral to extraoral il lumination is considered to be 3:1; however, ratios as high as 10:1 are ac ceptable. It is recommended that the extraoral light intensity be in the range of 200 to 300 footcandles at a distance of 30 inch (76 cm) above floor level. This can be attained by the use of 12 4-ft fluorescent tubes in a 10- x 10-ft room with an 8-ft ceiling.13,14 An allluminous ceiling is also desirable for good visibility with fewer shadows. Acrylic diffusers that have at least 90% light transmission and do not alter the spectral characteristics of the light source are recommended because they tend to scatter the l i g h t evenly throughout the operatory and reduce glare. The color environment of the dental operatory is another critical factor in shade matching. To reduce the spe cific absorption and reflection of inci dent light, which will modify the per ception of color, a neutral, light-gray background color (Munsell Value ~ 8) JADA, Vol. 102, February 1981 ■ 209
A S S O C IA T IO N
REPORTS
should be present in the room. The counter tops should have a nonglare surface with a Munsell Value of 7 or higher, and the floor should be neutral, if possible, with a Munsell Value of 6 or higher.
Selecting shades The following rules should be ob served in shade matching. —The manufacturer’s shade guide for the product should be used. This is true for both porcelain and plastic den ture teeth, as well as for porcelainmetal or plastic-metal restorations. Er rors by the dentist and laboratory may result when shade guides other than those designed for the material specified are used. — Shade matching should be done under lights of similar spectral distri bution and intensity, both in the den tist’s operatory and in the dental tech nician’s laboratory. Ideally, shades in the patient’s dentition should be an equally good match under daylight, fluorescent light, and incandescent light. At the least, restorative materials and natural teeth should match closely under lighting conditions similar to daylight. — Effects of translucency and posi tion should be considered; higher translucency and more distal position in the natural dentition causes a darker gray appearance. The color of the lips,
210 ■ JADA, Vol. 102, February 1981
tongue, palate, and gingiva also affects the color of the teeth. The position of the tooth in contrast to the palatal vault will affect translucency: higher trans lucency against a dark background would be equivalent to a lower M un sell Value in the shade of a semi opaque restoration. — The m a n u f a c t u r e r ’s r e c o m mendations for preparing the surface of the tooth before shade-matching should be followed. Leaving a glossy layer of saliva or removing moisture af fects the proportion of specular (mirror-like) reflection to diffuse re flection.15 Only diffuse reflection is indicative of the true shade. Specular reflection can be misleading, espe cially if high intensity illumination is used. — When shade matching, the indi vidual shade tab should be removed from the guide and held close to the tooth alone. This w ill prevent the socalled “effect of placement” in a series of tabs in which saturation varies. —The surface texture of the restora tion should be matched as closely as possible with that of the remaining dentition. This w ill tend to reproduce the characteristics of light reflection inherent in the remaining natural den tition.
This report was prepared at the request of the Council on Dental Materials, Instruments, and Equipment by Wayne T. Wozniak, PhD, assistant
secretary of the Council, and John B. Moser, PhD, associate professor, department of biological ma terials, Northwestern University School of Den tistry, Chicago. 1. Lemire, P.A., and Burk, A.A. Color in den tistry. Hartford, Conn, J. M. Ney Co., 1975. 2. McPhee, E.R. Light and color in dentistry. Tex Dent J 3:6-13,1979. 3. The Farnsworth-Munsell 100-Hue Test. Munsell Color Co. Inc., Baltimore, Md, 1957. 4. Color Matching Aptitude Test; Federation of Societies for Coatings Technology. Philadelphia, 1978. 5. Sproull, R.C. Color matching in dentistry. The three dimensional nature of color. J Prosthet Dent 29(4):416-424, 1973. 6. Sproull, R.C. Color matching in dentistry. Practical applications of the organization of color. J Prosthet Dent 29(5):556-566,1973. 7. Sproull, R.C. Color matching in dentistry. Color control. J Prosthet Dent 31(2):146-154, 1974. 8. Rainwater, C. Light and color. New York, Golden Press, 1971. 9. Preston, J.D., and Bergen, S.F. Color science and dental art. St. Louis, C. V. Mosby Co., 1980. 10. Dvorine, Pseudo-Isochromatic Plates. New York, Psychological Corp. 11. Standard Pseudo-Isochromatic Plates, (I-H-T-K Plates). New York, Igaku-Shoin Medical Publishers. 12. Bergen, S.F., and McCosland, J. Dental op eratory lighting and tooth color discrimination. JADA 94(1):130-134, 1977. 13. Sellers, R.W.; Young, J.M.; and Powell, J.M. The scientific application of light and color to the dental environment. Aeromed Rev 2:1-20,1978. 14. Preston, J.D.; Ward, L.C.; and Bobrick, M. Light and lighting in the dental office. Dent Clin North A m 22(7):431-451,1978. 15. Burnham, R.W.; Hanes, R.M.; and Bartleson, C.J. Color: a guide to basic facts and concepts. New York, John Wiley and Sons Inc., 1963.