concept of Color in prosthodontics / cosmetic dentistry training

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concept of Color in prosthodontics / cosmetic dentistry training

  1. 1. Concept ofConcept of Color inColor in ProsthodonticsProsthodontics INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  2. 2. INTRODUCTIONINTRODUCTION Esthetics is the science of sensitiveEsthetics is the science of sensitive perception; in a narrower sense: the science ofperception; in a narrower sense: the science of beauty.According to Microsoft "Encarta 97"beauty.According to Microsoft "Encarta 97" encyclopedia (1997) esthetics is a branch ofencyclopedia (1997) esthetics is a branch of philosophy concerned with the essence andphilosophy concerned with the essence and perception of beauty and ugliness. A Germanperception of beauty and ugliness. A German philosopher Baumgarten introduced the termphilosopher Baumgarten introduced the term esthetics in 1753, but the study of the nature ofesthetics in 1753, but the study of the nature of beauty had been pursued for centuries.beauty had been pursued for centuries. Albert Einstein is reported to have said, "IfAlbert Einstein is reported to have said, "If you cannot explain it simply, then you do notyou cannot explain it simply, then you do not understand it well enough." This appears to beunderstand it well enough." This appears to be the problem regarding color matching. In athe problem regarding color matching. In a time of growing interest in cosmetic dentistry,time of growing interest in cosmetic dentistry, there is a need for adequate training andthere is a need for adequate training and communication for better and more life likecommunication for better and more life like results.results. www.indiandentalacademy.comwww.indiandentalacademy.com
  3. 3. The first signs of man’s interest in the facial beautyThe first signs of man’s interest in the facial beauty were recorded more than 4000 years ago. Facial maskswere recorded more than 4000 years ago. Facial masks of "ideal" shape and proportions used to be theof "ideal" shape and proportions used to be the hallmark of royalty even in the ancient Egypt as far ashallmark of royalty even in the ancient Egypt as far as from 2600 to 2000 BC (Mack, 1996). Shape andfrom 2600 to 2000 BC (Mack, 1996). Shape and proportion, however, are not self-sufficient and theyproportion, however, are not self-sufficient and they are not the only parameters of beauty. Modernare not the only parameters of beauty. Modern concepts of esthetics in dentistry analyze this issueconcepts of esthetics in dentistry analyze this issue using a much wider approach. Dento-facial estheticsusing a much wider approach. Dento-facial esthetics and various factors of patients’ perception andand various factors of patients’ perception and expectations have become a very important part of theexpectations have become a very important part of the prosthodontic treatment (Goldstein and Lancaster,prosthodontic treatment (Goldstein and Lancaster, 1984;; Bishop and Priestley, 1996. The results of an1984;; Bishop and Priestley, 1996. The results of an examination of Albino et al. (1984) point out thatexamination of Albino et al. (1984) point out that esthetics is the first demand of patients: 42% of theesthetics is the first demand of patients: 42% of the patients indicated that appearance "very strongly"patients indicated that appearance "very strongly" influenced their decision to obtain treatment; 19% putinfluenced their decision to obtain treatment; 19% put forward functional problems as the major reason, whileforward functional problems as the major reason, while in 14% of cases the reason was pain. When asked toin 14% of cases the reason was pain. When asked to list 14 characteristics of a denture ranking them bylist 14 characteristics of a denture ranking them by importance, the patients ranked its lifelike appearanceimportance, the patients ranked its lifelike appearance as number one.as number one. www.indiandentalacademy.comwww.indiandentalacademy.com
  4. 4.  Lombardi (1973) described principles of visualLombardi (1973) described principles of visual perception and their clinical application to dentureperception and their clinical application to denture esthetics. When the term "esthetic"or "unaesthetic" isesthetics. When the term "esthetic"or "unaesthetic" is used it usually means that something is perceived asused it usually means that something is perceived as pleasant or unpleasant. The observer’s response to apleasant or unpleasant. The observer’s response to a physical stimuli is, in fact, his/her psychological andphysical stimuli is, in fact, his/her psychological and physiological interpretation of that what he/shephysiological interpretation of that what he/she perceived. The stimulus, i.e. the observed object onperceived. The stimulus, i.e. the observed object on one hand and the response to that stimulus on theone hand and the response to that stimulus on the other are the elements of the science of visualother are the elements of the science of visual perception.perception.  Tooth shape, size, position and color are classicalTooth shape, size, position and color are classical determinants of esthetics in prosthodontics, and color isdeterminants of esthetics in prosthodontics, and color is probably most important. A number of experts pointprobably most important. A number of experts point out the outstanding need for a systematic andout the outstanding need for a systematic and scientifically based approach to color science in dentalscientifically based approach to color science in dental (especially prosthodontic) education, and its application(especially prosthodontic) education, and its application in clinical practice.in clinical practice. www.indiandentalacademy.comwww.indiandentalacademy.com
  5. 5. Prosthodontics is more concerned withProsthodontics is more concerned with color than other dental branches, so it iscolor than other dental branches, so it is logical to expect that a dentist who haslogical to expect that a dentist who has been trained in prosthodontics should bebeen trained in prosthodontics should be better in shade matching. It can also bebetter in shade matching. It can also be expected that working experience exertsexpected that working experience exerts positive impact on the shade matchingpositive impact on the shade matching quality.quality. www.indiandentalacademy.comwww.indiandentalacademy.com
  6. 6. According to Sproull (1974): "TheAccording to Sproull (1974): "The technology of color is not a simple mattertechnology of color is not a simple matter that can be learned without study neitherthat can be learned without study neither is it a complicated matter beyond theis it a complicated matter beyond the comprehension of dentists". Manycomprehension of dentists". Many authors think that certain improvementsauthors think that certain improvements in color practice are an objective need ofin color practice are an objective need of dentistry (Hayashi, 1967; Sproull, 1973dentistry (Hayashi, 1967; Sproull, 1973 b; Sorensen and Tores, 1987; Sorensenb; Sorensen and Tores, 1987; Sorensen and Tores, 1988 a; Sorensen and Tores,and Tores, 1988 a; Sorensen and Tores, 1988 b).most of the authors think that1988 b).most of the authors think that color science study should be included incolor science study should be included in the undergraduate and postgraduatethe undergraduate and postgraduate curriculum and/or in the prosthodonticscurriculum and/or in the prosthodontics training program.training program.www.indiandentalacademy.comwww.indiandentalacademy.com
  7. 7. There is a lot of perplexity and confusionThere is a lot of perplexity and confusion just as there are numerous insufficientlyjust as there are numerous insufficiently explained questions in shade matching andexplained questions in shade matching and reproduction procedures. However, it is neitherreproduction procedures. However, it is neither easy nor simple to answer these questions. Ineasy nor simple to answer these questions. In spite of objective and subjective inadequaciesspite of objective and subjective inadequacies of the shade matching and reproductionof the shade matching and reproduction method itself, dental material manufacturersmethod itself, dental material manufacturers could be blamed for certain problems in thiscould be blamed for certain problems in this area. . The problem is that the majority ofarea. . The problem is that the majority of dental color standards lack a logical sampledental color standards lack a logical sample arrangement order and adequate colorarrangement order and adequate color distribution; moreover, they do not matchdistribution; moreover, they do not match natural teeth color range. Since natural toothnatural teeth color range. Since natural tooth color is not uniform, harmonization of shadecolor is not uniform, harmonization of shade guide samples, dental materials andguide samples, dental materials and prefabricated artificial teeth color compositionprefabricated artificial teeth color composition with the color composition of natural teethwith the color composition of natural teeth emerges as a yet unresolved issue.emerges as a yet unresolved issue.www.indiandentalacademy.comwww.indiandentalacademy.com
  8. 8. Color disharmony was found in someColor disharmony was found in some manufacturers ceramic masses intended formanufacturers ceramic masses intended for certain ceramic layers (especially betweencertain ceramic layers (especially between opaque and dentin ceramic powders). Also, itopaque and dentin ceramic powders). Also, it cannot be positively asserted whether (and tocannot be positively asserted whether (and to what extent) manufacturers manage towhat extent) manufacturers manage to standardize color in different batches of dentalstandardize color in different batches of dental materials and whether particle size differencesmaterials and whether particle size differences influence color. Color reproduction forinfluence color. Color reproduction for porcelain-fused-to-metal (PFM) restorations isporcelain-fused-to-metal (PFM) restorations is also a source of many questions, such as: toalso a source of many questions, such as: to what extent the final color of restoration iswhat extent the final color of restoration is influenced by the type of substrate, theinfluenced by the type of substrate, the application method, the thickness of ceramicapplication method, the thickness of ceramic layers, the number of firings and the firinglayers, the number of firings and the firing temperature.temperature. www.indiandentalacademy.comwww.indiandentalacademy.com
  9. 9.  Color matching can be performed using visualColor matching can be performed using visual and/or instrumental methods. Visual colorand/or instrumental methods. Visual color matching methods are subjective, whilematching methods are subjective, while instrumental methods are objective, but stillinstrumental methods are objective, but still not widespread in dental practice. Precise andnot widespread in dental practice. Precise and objective answers to most of the questionsobjective answers to most of the questions mentioned could be obtained only by usingmentioned could be obtained only by using instrumental color matching techniques,instrumental color matching techniques, because they allow numerical expression ofbecause they allow numerical expression of results. A correct interpretation of colorimetricresults. A correct interpretation of colorimetric results requires knowledge of the basicresults requires knowledge of the basic elements of the color science.elements of the color science.  Def: “ Color is light,modified by an object asDef: “ Color is light,modified by an object as percieved by an eye”.percieved by an eye”.www.indiandentalacademy.comwww.indiandentalacademy.com
  10. 10. COLOR SCIENCECOLOR SCIENCE A need to overcome subjectivity, asA need to overcome subjectivity, as the major disadvantage of the visualthe major disadvantage of the visual shade matching method, induced theshade matching method, induced the evolution of color science. Color scienceevolution of color science. Color science is multidisciplinary and it encompassesis multidisciplinary and it encompasses elements of physics, chemistry,elements of physics, chemistry, physiology and psychology. In order tophysiology and psychology. In order to understand the science of color, oneunderstand the science of color, one should be aware of some physical aspectsshould be aware of some physical aspects of light, as well as of both physiologicalof light, as well as of both physiological and psychological processes that enableand psychological processes that enable color perception.color perception.www.indiandentalacademy.comwww.indiandentalacademy.com
  11. 11.  Webster: "Color is the sensation resulting fromWebster: "Color is the sensation resulting from stimulation of the retina of the eye by light waves ofstimulation of the retina of the eye by light waves of certain lengths".certain lengths".  Billmeyer and Saltzman: "Color is the result of theBillmeyer and Saltzman: "Color is the result of the physical modification of light by colorants asphysical modification of light by colorants as observed by the human eye and interpreted by theobserved by the human eye and interpreted by the brain".brain".  Color is a special type of psychophysical sensationColor is a special type of psychophysical sensation provoked in the eye by the influence of the visibleprovoked in the eye by the influence of the visible light .That incident light, or so-called coloredlight .That incident light, or so-called colored stimulus, provokes the stimulation of high sensitivestimulus, provokes the stimulation of high sensitive eye receptors, producing the nerve impulse, which iseye receptors, producing the nerve impulse, which is transported to the brain. The brain is the interpretertransported to the brain. The brain is the interpreter that recognizes those nerve impulses as a certainthat recognizes those nerve impulses as a certain color.color.  To work with color, it is necessary to be acquaintedTo work with color, it is necessary to be acquainted with the physical, physiological and psychologicalwith the physical, physiological and psychological aspects of light as well as with the basic principles ofaspects of light as well as with the basic principles of colorimetry.colorimetry. www.indiandentalacademy.comwww.indiandentalacademy.com
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  13. 13. Physical, physiological and psychologicalPhysical, physiological and psychological aspects of lightaspects of light Psychophysics is a scientific disciplinePsychophysics is a scientific discipline dealing with mathematical relations betweendealing with mathematical relations between physical stimuli and the sensations theyphysical stimuli and the sensations they cause. Electromagnetic radiation that cancause. Electromagnetic radiation that can provoke a sensation of color is calledprovoke a sensation of color is called stimulus. Stimulus is, speaking in terms ofstimulus. Stimulus is, speaking in terms of physics, determined by the total flux ofphysics, determined by the total flux of radiation, i.e. by the quantity of energyradiation, i.e. by the quantity of energy transported to the retina in the function oftransported to the retina in the function of time and distributed onto differenttime and distributed onto different wavelengths (Lemiere and Burk, 1975; Prat,wavelengths (Lemiere and Burk, 1975; Prat, 1978; Birren, 1979; Billmeyer and1978; Birren, 1979; Billmeyer and Saltzman, 1981).Saltzman, 1981).www.indiandentalacademy.comwww.indiandentalacademy.com
  14. 14. The entire process starts with the light source,The entire process starts with the light source, which justifies the saying: "Color is light"which justifies the saying: "Color is light" (Saleski, 1972). What one recognizes as natural(Saleski, 1972). What one recognizes as natural white light is daylight (not direct sunlight,white light is daylight (not direct sunlight, which is yellow, but sunlight reflected backwhich is yellow, but sunlight reflected back from the sky). The visible part of the spectrumfrom the sky). The visible part of the spectrum comprises electromagnetic radiation fallingcomprises electromagnetic radiation falling between wavelengths from 380 to 780 nm. Thebetween wavelengths from 380 to 780 nm. The visible spectra range, is called monochromaticvisible spectra range, is called monochromatic light. White light can be separated intolight. White light can be separated into monochromatic components if it passes throughmonochromatic components if it passes through prism or diffraction bars . If the wavelength ofprism or diffraction bars . If the wavelength of the electromagnetic radiation is less than 380the electromagnetic radiation is less than 380 nm, it is called ultraviolet radiation and if itnm, it is called ultraviolet radiation and if it exceeds 780 nm, it is called infrared radiationexceeds 780 nm, it is called infrared radiation www.indiandentalacademy.comwww.indiandentalacademy.com
  15. 15. www.indiandentalacademy.comwww.indiandentalacademy.com
  16. 16.  Light sourceLight source.. Light source is any area or bodyLight source is any area or body emitting radiation in the visible spectra range.emitting radiation in the visible spectra range. According to one classification, light sources can beAccording to one classification, light sources can be primary (emitting their own radiation) and secondaryprimary (emitting their own radiation) and secondary (reflecting a part of the radiation from some other(reflecting a part of the radiation from some other light source), and according to another one, they arelight source), and according to another one, they are divided into natural and artificial light sources. Thedivided into natural and artificial light sources. The Sun is the most important natural light source.Sun is the most important natural light source.  The objectThe object.. One seldom looks directly at the lightOne seldom looks directly at the light source. The radiation flux that reaches the eye issource. The radiation flux that reaches the eye is almost all the time reflected from some object, whichalmost all the time reflected from some object, which indicates that observed object influences colorindicates that observed object influences color perception. The structure of the object (type ofperception. The structure of the object (type of material, texture) influences its optical properties.material, texture) influences its optical properties.  The eyeThe eye.. Color, as well as all other visual sensations,Color, as well as all other visual sensations, is brought to the brain through the eye. Visualis brought to the brain through the eye. Visual perception occurs owing to the optical system in theperception occurs owing to the optical system in the anterior and the retina in the posterior part of theanterior and the retina in the posterior part of the eye .eye . www.indiandentalacademy.comwww.indiandentalacademy.com
  17. 17. The light reflected from the object is brought to theThe light reflected from the object is brought to the observer’s eye. Light enters through the optical systemobserver’s eye. Light enters through the optical system and the image is focused onto the retina. The retina isand the image is focused onto the retina. The retina is a complex mosaic of millions of nerve endingsa complex mosaic of millions of nerve endings containing a chemical substance which transforms thecontaining a chemical substance which transforms the light stimulation into a nerve signal that is furtherlight stimulation into a nerve signal that is further transported to the brain. There are two types of nervetransported to the brain. There are two types of nerve endings, rods and cones. Rods only record light, i.e.endings, rods and cones. Rods only record light, i.e. they see in black and white. They are connectedthey see in black and white. They are connected together in bunches before reaching the brain, thetogether in bunches before reaching the brain, the interpretive part of the system, so that they achieveinterpretive part of the system, so that they achieve high sensitivity at the expense of fine resolution. Athigh sensitivity at the expense of fine resolution. At high levels of illumination, they play a small part in thehigh levels of illumination, they play a small part in the vision process. Cones are nerve endings that enablevision process. Cones are nerve endings that enable color vision. Some seven million cones are placed in thecolor vision. Some seven million cones are placed in the centre of the retina, in a small pit called fovea,centre of the retina, in a small pit called fovea, subtending an angle of about 2° in the visual field.subtending an angle of about 2° in the visual field. Here, instead of the bunching found in the rod area,Here, instead of the bunching found in the rod area, there is a "one-to-one" connection with the opticalthere is a "one-to-one" connection with the optical system so that their resolving power is high.system so that their resolving power is high.www.indiandentalacademy.comwww.indiandentalacademy.com
  18. 18. This is the area of visual acuity, lying on theThis is the area of visual acuity, lying on the visual axis of the eye. Cones require a highervisual axis of the eye. Cones require a higher level of illumination to be brought into action.level of illumination to be brought into action. This can be demonstrated by a slow increase ofThis can be demonstrated by a slow increase of illumination from complete darkness, throughillumination from complete darkness, through dim illumination at which stage only shape candim illumination at which stage only shape can be distinguished (rod vision), allowing onlybe distinguished (rod vision), allowing only glimpses of color, up to the stage of fullglimpses of color, up to the stage of full intensity of light when the function of the conesintensity of light when the function of the cones is maximum. This experiment covers threeis maximum. This experiment covers three stages of vision: scotopic, when only rod visionstages of vision: scotopic, when only rod vision is operating; mesopic, when the cones are onlyis operating; mesopic, when the cones are only initially stimulated and rods have not beeninitially stimulated and rods have not been flooded yet; photopic - full light color visionflooded yet; photopic - full light color vision (Chamberlin and Chamberlin, 1980).(Chamberlin and Chamberlin, 1980).www.indiandentalacademy.comwww.indiandentalacademy.com
  19. 19. www.indiandentalacademy.comwww.indiandentalacademy.com
  20. 20. Trichromatic character of visionTrichromatic character of vision.. There areThere are many complicated theories as to how conesmany complicated theories as to how cones function, but the simplest and most commonlyfunction, but the simplest and most commonly accepted is Thomas Young theory, supported byaccepted is Thomas Young theory, supported by Helmholz. It is based on the experimental fact thatHelmholz. It is based on the experimental fact that a suitable mixture of three monochromatica suitable mixture of three monochromatic radiations can match any color. This trichromaticradiations can match any color. This trichromatic theory postulates three different types of cones,theory postulates three different types of cones, which are sensitive to different bands ofwhich are sensitive to different bands of wavelengths. The "blue-sensitive" cones arewavelengths. The "blue-sensitive" cones are brought into action chiefly by light of short visiblebrought into action chiefly by light of short visible wavelengths, the second type responding chiefly towavelengths, the second type responding chiefly to light of wavelengths in the middle of the visiblelight of wavelengths in the middle of the visible spectrum are called "green-sensitive", while thespectrum are called "green-sensitive", while the third type, the "red-sensitive" cones, are mostthird type, the "red-sensitive" cones, are most affected by light of the longer visible wavelengths.affected by light of the longer visible wavelengths. The visible pigments responsible for these variousThe visible pigments responsible for these various functions have not as yet been positively isolated.functions have not as yet been positively isolated.www.indiandentalacademy.comwww.indiandentalacademy.com
  21. 21. The distribution of rods and cones changes asThe distribution of rods and cones changes as one travels outward from the fovea. The centralone travels outward from the fovea. The central area (2° field), which receives the image fromarea (2° field), which receives the image from an object, is rod free and color differentiation isan object, is rod free and color differentiation is the best in this area. Outwards, to a 4° field,the best in this area. Outwards, to a 4° field, there is a mixture of rods and cones, thethere is a mixture of rods and cones, the composition of which mixture can vary withcomposition of which mixture can vary with individuals. Outside of this area the coneindividuals. Outside of this area the cone population falls off rapidly. The periphery of thepopulation falls off rapidly. The periphery of the eye is not color discriminating, although veryeye is not color discriminating, although very sensitive to light variations, movements etc. Itsensitive to light variations, movements etc. It is because of this varying distribution of rodsis because of this varying distribution of rods and cones between individuals that there arisesand cones between individuals that there arises the slight difference in color discriminationthe slight difference in color discrimination between "color normal" observers, but they arebetween "color normal" observers, but they are surprisingly small among more than 90% ofsurprisingly small among more than 90% of people. Hence the statement: "Although all thepeople. Hence the statement: "Although all the people have not the same sight, the majority ofpeople have not the same sight, the majority of them see very similar"them see very similar"www.indiandentalacademy.comwww.indiandentalacademy.com
  22. 22.  The brainThe brain. Although an image may be. Although an image may be formed on the retina, the observerformed on the retina, the observer cannot be said to "seeunless that imagecannot be said to "seeunless that image is in some way conveyed to hisis in some way conveyed to his consciousness. A number of impulses areconsciousness. A number of impulses are set in motion by the light, and theseset in motion by the light, and these messages have to be conveyed to, andmessages have to be conveyed to, and interpreted by, the brain beforeinterpreted by, the brain before perception occurs.perception occurs. www.indiandentalacademy.comwww.indiandentalacademy.com
  23. 23.  The electrical impulses set up in the rods andThe electrical impulses set up in the rods and cones are programmed and sorted outcones are programmed and sorted out somewhere on the way to the brain, but theresomewhere on the way to the brain, but there is no general agreement as to the mechanismis no general agreement as to the mechanism of sorting. There are different opinions if theof sorting. There are different opinions if the commencement is made with coding in thecommencement is made with coding in the retina itself, or in the tissues and nervesretina itself, or in the tissues and nerves immediately adjacent to it, or at intermediateimmediately adjacent to it, or at intermediate points where the nerve ganglions join to formpoints where the nerve ganglions join to form bundles of pathways. However, some form ofbundles of pathways. However, some form of message is eventually conveyed by the opticmessage is eventually conveyed by the optic nerve to the appropriate part of the brain.nerve to the appropriate part of the brain. The messages from the rods are telling of theThe messages from the rods are telling of the light or no light, while the cone messageslight or no light, while the cone messages convey information that gives rise to theconvey information that gives rise to the sensation of color.sensation of color.www.indiandentalacademy.comwww.indiandentalacademy.com
  24. 24.  On reaching the brain, the messages areOn reaching the brain, the messages are decoded and refereed, as in a computer, to adecoded and refereed, as in a computer, to a bank of stored memories, which will connectbank of stored memories, which will connect the picture presented with somethingthe picture presented with something previously experienced, and finally sensationpreviously experienced, and finally sensation of something "out there in front" materializesof something "out there in front" materializes in consciousness. All this operation is carriedin consciousness. All this operation is carried out at light speed. When one is waking, he isout at light speed. When one is waking, he is presented with an avalanche of messagespresented with an avalanche of messages from the eyes. Fortunately, the brain isfrom the eyes. Fortunately, the brain is selective, ignoring what is not relevant. Oneselective, ignoring what is not relevant. One perceives only the things he is interested in orperceives only the things he is interested in or which the brain automatically brings to hiswhich the brain automatically brings to his notice of the built-in instinct for self-notice of the built-in instinct for self- preservation (Chamberlin and Chamberlin,preservation (Chamberlin and Chamberlin, 1980).1980). www.indiandentalacademy.comwww.indiandentalacademy.com
  25. 25. The most frequent complications in color perceptionThe most frequent complications in color perception are chromatic adaptation, metamerism andare chromatic adaptation, metamerism and dichroism.dichroism.  Chromatic adaptationChromatic adaptation is defined as a coloris defined as a color constancy phenomenon of the perceived color of theconstancy phenomenon of the perceived color of the viewed scene. Going from daylight, into a room litviewed scene. Going from daylight, into a room lit only by incandescent lamps, one is seldom aware ofonly by incandescent lamps, one is seldom aware of the fact that the color of everything has changed,the fact that the color of everything has changed, although reason points out that this must be so.although reason points out that this must be so.  MetamerismMetamerism which occurs when the color of twowhich occurs when the color of two objects looks identical when observed under one lightobjects looks identical when observed under one light source but different under other light conditionssource but different under other light conditions  DichroismDichroism refers to a situation when the color of anrefers to a situation when the color of an object, viewed by transmitted light, may be differentobject, viewed by transmitted light, may be different accordingto the thickness of the sample viewed.accordingto the thickness of the sample viewed. Blood is, for example, yellow if viewed in anBlood is, for example, yellow if viewed in an extremely thin film but is red in greater depth.extremely thin film but is red in greater depth.www.indiandentalacademy.comwww.indiandentalacademy.com
  26. 26. Color defining and/or measuringColor defining and/or measuring Visual comparisonVisual comparison is a comparison withis a comparison with some known physical standard acceptedsome known physical standard accepted as referral. There are numerous systemsas referral. There are numerous systems of visual comparison and description ofof visual comparison and description of color. The easiest way is to produce somecolor. The easiest way is to produce some kind of systematized and preciselykind of systematized and precisely repeatable catalogue. Such cataloguesrepeatable catalogue. Such catalogues are called color atlases or color derivationare called color atlases or color derivation systems. The Munsell Book of Color, thesystems. The Munsell Book of Color, the Ostwald system and DIN (DeutchesOstwald system and DIN (Deutches Institut für Normung) system are theInstitut für Normung) system are the most famous color catalogs.most famous color catalogs.www.indiandentalacademy.comwww.indiandentalacademy.com
  27. 27. No matter what visual method is used, lightNo matter what visual method is used, light source and viewing geometry should besource and viewing geometry should be standardized in order to obtain valid results. Instandardized in order to obtain valid results. In the case of instrument itself, standardization isthe case of instrument itself, standardization is to be done by the manufacturer, but in caseto be done by the manufacturer, but in case when color atlases or some other samples arewhen color atlases or some other samples are used, adequate conditions have to be provided.used, adequate conditions have to be provided. Furthermore, in all cases of visual colorimetryFurthermore, in all cases of visual colorimetry before any real work starts it is necessary tobefore any real work starts it is necessary to test whether the observer is color deficient. Ittest whether the observer is color deficient. It has already been emphasized that there arehas already been emphasized that there are differences among so-called "color normal"differences among so-called "color normal" observers, but training and practice may reduceobservers, but training and practice may reduce these differences to an acceptable level. Ifthese differences to an acceptable level. If some important examination is underway, it issome important examination is underway, it is recommended to use more than one observerrecommended to use more than one observer and take the mean value of their responses asand take the mean value of their responses as a result.a result. www.indiandentalacademy.comwww.indiandentalacademy.com
  28. 28. ColorColor VisionVision TestingTesting Pseudo-Isochromatic PlatesPseudo-Isochromatic Plates frequently arefrequently are used by eye specialists to get an idea ofused by eye specialists to get an idea of one’s color efficiency or deficiency. To aone’s color efficiency or deficiency. To a color-deficient person, all the dots in onecolor-deficient person, all the dots in one or more of the plates will appear similaror more of the plates will appear similar or the same—“isochromatic.” To aor the same—“isochromatic.” To a person without a color deficiency, someperson without a color deficiency, some of the dots will appear dissimilar enoughof the dots will appear dissimilar enough from the other dots to form a distinctfrom the other dots to form a distinct figure (number) on each of the platesfigure (number) on each of the plates —“pseudo-isochromatic.”—“pseudo-isochromatic.”www.indiandentalacademy.comwww.indiandentalacademy.com
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  30. 30. Light and Its Role in Dental CeramicsLight and Its Role in Dental Ceramics Just as a musician must know the scales,Just as a musician must know the scales, dentists and ceramists must know thedentists and ceramists must know the principles of light. Without scales, thereprinciples of light. Without scales, there would be no music; without light, nowould be no music; without light, no colour. To better appreciate thecolour. To better appreciate the importance of light in dental ceramics, weimportance of light in dental ceramics, we must learn some of its basicmust learn some of its basic characteristics and how these, whencharacteristics and how these, when combined with the physical and chemicalcombined with the physical and chemical composition of natural teeth, influencecomposition of natural teeth, influence our visual perception of tooth colour.our visual perception of tooth colour.www.indiandentalacademy.comwww.indiandentalacademy.com
  31. 31. Direct LightDirect Light  When direct light falls upon an object, it isWhen direct light falls upon an object, it is either absorbed, reflected, or transmitted.either absorbed, reflected, or transmitted.  If all of the light is reflected, the object appearsIf all of the light is reflected, the object appears white.white.  If the light is entirely absorbed, the objectIf the light is entirely absorbed, the object appears black.appears black.  The larger the amount of light reflected by anThe larger the amount of light reflected by an object, the brighter the object will appear.object, the brighter the object will appear.  Furthermore, the greater the intensity of theFurthermore, the greater the intensity of the direct light source, the brighter the object willdirect light source, the brighter the object will appear.appear.  The final effect depends greatly on whether theThe final effect depends greatly on whether the object is transparent, translucent or opaque.object is transparent, translucent or opaque.  Teeth and porcelain have all theseTeeth and porcelain have all these characteristics, however the differences in thecharacteristics, however the differences in the chemical and physical properties of teeth andchemical and physical properties of teeth and porcelain require that these characteristics beporcelain require that these characteristics be treated differently.treated differently.www.indiandentalacademy.comwww.indiandentalacademy.com
  32. 32.  In duplicating tooth colour, we mustIn duplicating tooth colour, we must produce a ceramic restoration thatproduce a ceramic restoration that captures all the colour dimensions foundcaptures all the colour dimensions found in the tooth despite the opacity producedin the tooth despite the opacity produced by the gold and opaque layer, rather thanby the gold and opaque layer, rather than in conjunction with it. The opacity foundin conjunction with it. The opacity found in the dentin is a chemical phenomenonin the dentin is a chemical phenomenon rather then the physical one produced byrather then the physical one produced by the metal in a ceramic restoration.the metal in a ceramic restoration.  Light can be transmitted or passedLight can be transmitted or passed through transparent and translucentthrough transparent and translucent substances.substances.  A clear window glass through which anA clear window glass through which an object can be seen distinctly is anobject can be seen distinctly is an example of a transparent medium; itexample of a transparent medium; it permits maximum transmission of light.permits maximum transmission of light. www.indiandentalacademy.comwww.indiandentalacademy.com
  33. 33.  A frosted glass pane, through whichA frosted glass pane, through which light is visible but objects are seenlight is visible but objects are seen indistinctly, is an example of aindistinctly, is an example of a translucent medium; it transmitstranslucent medium; it transmits diffused light.diffused light.  A wooden door or brick wall is anA wooden door or brick wall is an opaque medium and permits no lightopaque medium and permits no light transmissiontransmission  In both natural dentition and fabricatedIn both natural dentition and fabricated restorations, we are concerned withrestorations, we are concerned with translucent and opaque qualities rathertranslucent and opaque qualities rather than transparent ones. Of the three,than transparent ones. Of the three, teeth have the least transparency; in ateeth have the least transparency; in a ceramic restoration, this is undesirableceramic restoration, this is undesirable for it serves no constructive purposefor it serves no constructive purpose www.indiandentalacademy.comwww.indiandentalacademy.com
  34. 34. www.indiandentalacademy.comwww.indiandentalacademy.com
  35. 35. Reflected LightReflected Light  Reflected light describes light rays that areReflected light describes light rays that are bounced back from the surface of the objectbounced back from the surface of the object encountered instead of being transmitted throughencountered instead of being transmitted through or absorbed by it.or absorbed by it.  Light rays that strike the surface of an object areLight rays that strike the surface of an object are called incident (falling upon) rays and their point ofcalled incident (falling upon) rays and their point of contact is termed point of incidence.contact is termed point of incidence.  Reflected light falls into two categories: specularReflected light falls into two categories: specular and diffused.and diffused.  Specular light travels in a single direction. WhenSpecular light travels in a single direction. When the incident light strikes a perfectly smooththe incident light strikes a perfectly smooth surface, it rebounds from the point of impact atsurface, it rebounds from the point of impact at exactly the same angle as the incident ray.exactly the same angle as the incident ray.  Diffused light travels in more than one direction. IfDiffused light travels in more than one direction. If light rays strike an uneven surface, they cannot belight rays strike an uneven surface, they cannot be reflected at an even angle; the incident rays will bereflected at an even angle; the incident rays will be reflected at various angles, making the lightreflected at various angles, making the light diffuseddiffused www.indiandentalacademy.comwww.indiandentalacademy.com
  36. 36. www.indiandentalacademy.comwww.indiandentalacademy.com
  37. 37. Color matching and reproductionColor matching and reproduction Color visionColor vision Color matching is complicated with individualColor matching is complicated with individual differences in color perception and differentdifferences in color perception and different color matching ability. According to Culipeppercolor matching ability. According to Culipepper (1970), there are tooth color matching(1970), there are tooth color matching differences among dentists themselves and itdifferences among dentists themselves and it happens that the same dentist may matchhappens that the same dentist may match different shades for the same tooth in differentdifferent shades for the same tooth in different days. Hence, it turns out to be necessary fordays. Hence, it turns out to be necessary for dental students, dentists and dental techniciansdental students, dentists and dental technicians to undergo a color vision test, particularly into undergo a color vision test, particularly in view of the fact that approximately 8% of menview of the fact that approximately 8% of men and 0.5% of women are color deficient (Barna,and 0.5% of women are color deficient (Barna, 1981; Paravina et al., 1997 a).1981; Paravina et al., 1997 a).www.indiandentalacademy.comwww.indiandentalacademy.com
  38. 38. Color matching conditionsColor matching conditions  Tooth color is in the clinical practice matchedTooth color is in the clinical practice matched under different illuminants. Illumination forunder different illuminants. Illumination for shade matching should be standardized andshade matching should be standardized and harmonized with the laboratory illuminationharmonized with the laboratory illumination (Bergen and Mccasland, 1977; Preston et al.,(Bergen and Mccasland, 1977; Preston et al., 1978;) While performing tooth color matching,1978;) While performing tooth color matching, attention should be attached to the viewingattention should be attached to the viewing distance, viewing angle as well as to the impactdistance, viewing angle as well as to the impact of such factors as background andof such factors as background and environment. The color of the patient’s clothes,environment. The color of the patient’s clothes, the color of the drapes, uniform, equipment,the color of the drapes, uniform, equipment, office furniture, walls and ceiling are of greatoffice furniture, walls and ceiling are of great importance.importance. www.indiandentalacademy.comwww.indiandentalacademy.com
  39. 39. Dental color standardsDental color standards  Hall (1991) wrote: "Shade guides of allHall (1991) wrote: "Shade guides of all dental restorative materials are based ondental restorative materials are based on the long established porcelain shadethe long established porcelain shade guides which evolved to represent theguides which evolved to represent the available shades of porcelain teeth. Theavailable shades of porcelain teeth. The shades developed by a process of popularshades developed by a process of popular selection by which shades perceived to beselection by which shades perceived to be nearer tooth colour were added and thenearer tooth colour were added and the least popular eliminated. This conceptleast popular eliminated. This concept has not changed since the introduction ofhas not changed since the introduction of porcelain over two hundred years ago".porcelain over two hundred years ago". www.indiandentalacademy.comwww.indiandentalacademy.com
  40. 40.  A number of authorities in dental ceramics point atA number of authorities in dental ceramics point at inadequacies of the commercial shade guidesinadequacies of the commercial shade guides (Sproull, 1967; Sorensen and Tores, 1987;(Sproull, 1967; Sorensen and Tores, 1987; Pizzamiglio, 1991). The shades of the samples arePizzamiglio, 1991). The shades of the samples are not logically arranged, they are not equally placednot logically arranged, they are not equally placed in color solid and do not cover the color range ofin color solid and do not cover the color range of the natural teeth (Hayashi, 1967; Sproull, 1973the natural teeth (Hayashi, 1967; Sproull, 1973 b;). The absence of darker shades in the majorityb;). The absence of darker shades in the majority of dental color standards is caused by theof dental color standards is caused by the compromise with the cosmetic demands for thecompromise with the cosmetic demands for the "white" teeth. The samples used for PFM"white" teeth. The samples used for PFM restoration color matching are made of firedrestoration color matching are made of fired ceramics, with no metal substrate and the anterior-ceramics, with no metal substrate and the anterior- posterior size of the ceramics is considerably largerposterior size of the ceramics is considerably larger than the ceramic part of the final PFM restorationthan the ceramic part of the final PFM restoration (Bergen, 1985. The color of the acrylic resin(Bergen, 1985. The color of the acrylic resin samples is changeable if kept in somesamples is changeable if kept in some disinfectants, particularly in chlorine-containingdisinfectants, particularly in chlorine-containing disinfecting solutions (Cernavin, 1996).disinfecting solutions (Cernavin, 1996). www.indiandentalacademy.comwww.indiandentalacademy.com
  41. 41.  The mentioned inadequacies gave rise toThe mentioned inadequacies gave rise to various propositions for the production ofvarious propositions for the production of new shade guides, and for thenew shade guides, and for the improvement of the sample arrangementimprovement of the sample arrangement order in the existing color standards, ororder in the existing color standards, or resulted in the production of differentresulted in the production of different individual (custom) shade guidesindividual (custom) shade guides www.indiandentalacademy.comwww.indiandentalacademy.com
  42. 42. The manufacturers had ignored for decades theThe manufacturers had ignored for decades the legitimate demands for the production of newlegitimate demands for the production of new dental color standards based on the needs ofdental color standards based on the needs of dental practice, color range of the natural teethdental practice, color range of the natural teeth and the principles of the color science. Certainand the principles of the color science. Certain progress in this area, however, was made notprogress in this area, however, was made not so long ago. Vita Zahnfabrik Company (http)so long ago. Vita Zahnfabrik Company (http) presented a new dental color standard,presented a new dental color standard, "Vitapan 3D Master". This shade guide consists"Vitapan 3D Master". This shade guide consists of 26 samples divided into groups according toof 26 samples divided into groups according to lightness and within those groups according tolightness and within those groups according to saturation (vertically) and hue (horizontally).saturation (vertically) and hue (horizontally). Despite the fact that the improvement inDespite the fact that the improvement in relation to the previous color standard of thisrelation to the previous color standard of this manufacturer (Vita "Lumin Vacuum") ismanufacturer (Vita "Lumin Vacuum") is obvious, certain disharmony in the sampleobvious, certain disharmony in the sample arrangement can be noticed in shade guide as aarrangement can be noticed in shade guide as a whole.whole. www.indiandentalacademy.comwww.indiandentalacademy.com
  43. 43. Color matching methodColor matching method  It is more than obvious that it is not simple to provideIt is more than obvious that it is not simple to provide adequate shade matching conditions. As for the shadeadequate shade matching conditions. As for the shade matching method, there have been significantmatching method, there have been significant improvements in this area, especially in the last tenimprovements in this area, especially in the last ten years.years.  Shade matching should be performed at the beginningShade matching should be performed at the beginning of the appointment (Sorensen and Tores, 1988;of the appointment (Sorensen and Tores, 1988; Pizzamiglio, 1991) and the patient’s mouth should be atPizzamiglio, 1991) and the patient’s mouth should be at the level of the dentist’s eye. A shade guide samplethe level of the dentist’s eye. A shade guide sample should be applied parallel with the tooth whose shade isshould be applied parallel with the tooth whose shade is being matched, not in front of it, for it will appearbeing matched, not in front of it, for it will appear lighter, not behind it because it will appear darker.lighter, not behind it because it will appear darker. Some authors suggest that the cervical part of samplesSome authors suggest that the cervical part of samples should be removed because they are more saturated,should be removed because they are more saturated, which could have a negative effect on the shadewhich could have a negative effect on the shade matching (Miller, 1993). Spencer (http) suggestsmatching (Miller, 1993). Spencer (http) suggests removal of the mesial and the distal third of theremoval of the mesial and the distal third of the samples in order to enable application of two shadesamples in order to enable application of two shade guide samples next to the tooth whose color is beingguide samples next to the tooth whose color is being matched.matched. www.indiandentalacademy.comwww.indiandentalacademy.com
  44. 44. If the sample and the tooth whose color is beingIf the sample and the tooth whose color is being matched have different surface texture, both should bematched have different surface texture, both should be wet, in order to neutralize this difference. Tooth shouldwet, in order to neutralize this difference. Tooth should not be observed for more than five seconds at a time,not be observed for more than five seconds at a time, and, in the meantime, it is desirable to observe someand, in the meantime, it is desirable to observe some blue surface for one minute (Pizzamiglio, 1991) in orderblue surface for one minute (Pizzamiglio, 1991) in order to increase the ability to differentiate yellow color (theto increase the ability to differentiate yellow color (the dominant color of the teeth). Owing to possibledominant color of the teeth). Owing to possible occurrence of metamerism, the choice should beoccurrence of metamerism, the choice should be verified under different illuminants. Some authors’verified under different illuminants. Some authors’ attitude (Seluk and LaLonde, 1985, Swepston andattitude (Seluk and LaLonde, 1985, Swepston and Miller, 1985) that esthetics can be improved if theMiller, 1985) that esthetics can be improved if the dentist and the dental technician use shade guides anddentist and the dental technician use shade guides and relative porcelains of several manufacturers is logicalrelative porcelains of several manufacturers is logical and acceptable. It is also suggested that extendedand acceptable. It is also suggested that extended shade guides should be used (containing the samples ofshade guides should be used (containing the samples of all ceramic masses used for the production of PFMall ceramic masses used for the production of PFM restorations), such as Vita "VMK - Shade Indicator"restorations), such as Vita "VMK - Shade Indicator" (Pizzamiglio, 1991; Miller, 1993).(Pizzamiglio, 1991; Miller, 1993). www.indiandentalacademy.comwww.indiandentalacademy.com
  45. 45. Munsell color order systemMunsell color order system Many color order systems are available, butMany color order systems are available, but for a variety of reasons, including worldwidefor a variety of reasons, including worldwide recognition, consistency, flexibility, andrecognition, consistency, flexibility, and simplicity, the Munsell Color Order System issimplicity, the Munsell Color Order System is the system of choice for color matching inthe system of choice for color matching in dentistry. The attempt to achieve equaldentistry. The attempt to achieve equal visual (Perceptual) spacing in this systemvisual (Perceptual) spacing in this system further recommends it. The color tree (Platefurther recommends it. The color tree (Plate I) is a representation of the tridimensionalI) is a representation of the tridimensional organization of the colors within the Munsellorganization of the colors within the Munsell System. The Munsell color solid can beSystem. The Munsell color solid can be likened to a sphere or to a cylinder, as it is anlikened to a sphere or to a cylinder, as it is an irregular three dimensional figure that hasirregular three dimensional figure that has characteristics of both.characteristics of both.www.indiandentalacademy.comwww.indiandentalacademy.com
  46. 46. Although usually described as a sphereAlthough usually described as a sphere (Munshell’s original concept), for the(Munshell’s original concept), for the purpose of this article, it will be treated apurpose of this article, it will be treated a a cylinder. The relationship of one color ta cylinder. The relationship of one color t another becomes apparent when theanother becomes apparent when the organization of the colors within the threeorganization of the colors within the three dimensional solid is understood. Adimensional solid is understood. A colorless or achromatic axis extendscolorless or achromatic axis extends through the center of the cylinder, purethrough the center of the cylinder, pure white at the top, pure black at the bottomwhite at the top, pure black at the bottom A series of grays, progressing from blackA series of grays, progressing from black to white in equal visual steps, connectsto white in equal visual steps, connects these extremities.these extremities.www.indiandentalacademy.comwww.indiandentalacademy.com
  47. 47. Colors (Hues) are arranged around thisColors (Hues) are arranged around this axis, and within each Hue, the colors areaxis, and within each Hue, the colors are arranged in scales according to theirarranged in scales according to their lightness/darkness (Value) and their puritylightness/darkness (Value) and their purity or strength (Chroma). (In the Munsellor strength (Chroma). (In the Munsell System, Hue Value, and Chroma areSystem, Hue Value, and Chroma are capitalized). Light colors are toward thecapitalized). Light colors are toward the top of the cylinder; dark colors are towardtop of the cylinder; dark colors are toward the bottom. The colors are purest on thethe bottom. The colors are purest on the outer skin of the cylinder and they becomeouter skin of the cylinder and they become progressively grayer as they approach theprogressively grayer as they approach the gray Value axis. Within each of these scalesgray Value axis. Within each of these scales of Hue, Value, and Chroma, the intervalsof Hue, Value, and Chroma, the intervals were chosen to represent equal visualwere chosen to represent equal visual spacing under a standard light source.spacing under a standard light source. www.indiandentalacademy.comwww.indiandentalacademy.com
  48. 48. The cylinder may be considered as a series ofThe cylinder may be considered as a series of wheels stacked one upon the other, each wheel ofwheels stacked one upon the other, each wheel of ascending lightness as we progress to the tope ofascending lightness as we progress to the tope of the cylinder. The hub of each wheel represents thethe cylinder. The hub of each wheel represents the Value axis. The Hues are arranged sequentiallyValue axis. The Hues are arranged sequentially around the rim. The spokes represent thearound the rim. The spokes represent the gradations of Chroma from the color less axis togradations of Chroma from the color less axis to the purest Hues at the rim. In actually, as can bethe purest Hues at the rim. In actually, as can be seen by examining plate I, the Hues projectseen by examining plate I, the Hues project unevenly beyond the surface of the solid, but thisunevenly beyond the surface of the solid, but this is one of the advantages of the system. Asis one of the advantages of the system. As technology permits the creation of purer colors,technology permits the creation of purer colors, they can easily to added to the periphery. Thesethey can easily to added to the periphery. These unequal extensions of the Chroma spokesunequal extensions of the Chroma spokes obviously make some of the wheels flat orobviously make some of the wheels flat or lopsided, but basically we have a cylinder, even if itlopsided, but basically we have a cylinder, even if it is bent out of shape.is bent out of shape. www.indiandentalacademy.comwww.indiandentalacademy.com
  49. 49. value scale www.indiandentalacademy.comwww.indiandentalacademy.com
  50. 50. www.indiandentalacademy.comwww.indiandentalacademy.com
  51. 51. Dimensions of Color.Dimensions of Color. Hue, Value and Chroma, the dimensions of color, areHue, Value and Chroma, the dimensions of color, are just as descriptive in describing color as length, width,just as descriptive in describing color as length, width, and breadth are in describing form, once the languageand breadth are in describing form, once the language is understood by those using it. Since it is so importantis understood by those using it. Since it is so important in working with color to understand thoroughly thein working with color to understand thoroughly the three dimensional concept of color, a more explicitthree dimensional concept of color, a more explicit description of each is presented.description of each is presented. Hue, Hue: the first dimension, is the easiest toHue, Hue: the first dimension, is the easiest to understand, and in Munsell’s words, “it is that qualityunderstand, and in Munsell’s words, “it is that quality by which we distinguish one color family from another,by which we distinguish one color family from another, as red from yellow, green from blue or purple.” Theas red from yellow, green from blue or purple.” The color wheel is a familiar form of this dimension andcolor wheel is a familiar form of this dimension and consists of the Hues that are arranged sequentiallyconsists of the Hues that are arranged sequentially around the central axis of the Munsell color Solid (Platearound the central axis of the Munsell color Solid (Plate II, C). The refer to a Hue in the Munsell system, theII, C). The refer to a Hue in the Munsell system, the initials are used; R for red, YR for yellow red, Y forinitials are used; R for red, YR for yellow red, Y for yellow, and so on. Each Hue is subdivided into tenyellow, and so on. Each Hue is subdivided into ten segments, equally spaced visually (by psychologicsegments, equally spaced visually (by psychologic criteria) from each other. The color wheel cut andcriteria) from each other. The color wheel cut and placed in a horizontal strip.placed in a horizontal strip. www.indiandentalacademy.comwww.indiandentalacademy.com
  52. 52. www.indiandentalacademy.comwww.indiandentalacademy.com
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  54. 54. Value and Chroma are more difficult to understandValue and Chroma are more difficult to understand and are often confused with one another. Specialand are often confused with one another. Special attention must be focused on these dimensions.attention must be focused on these dimensions. Value: Value “is that quality by which weValue: Value “is that quality by which we distinguish a light color from a dark color”, and thisdistinguish a light color from a dark color”, and this is related to the achromatic (colorless) polar axisis related to the achromatic (colorless) polar axis going through the Munsell color solid. The valuegoing through the Munsell color solid. The value of a color is determined by which gray on the Valueof a color is determined by which gray on the Value scale it matches in lightness/darkness. The blackscale it matches in lightness/darkness. The black of the Value scale is assigned a Value of zero, theof the Value scale is assigned a Value of zero, the white a Value of 10. An infinite number ofwhite a Value of 10. An infinite number of gradations of gray is possible as we go from blackgradations of gray is possible as we go from black to white, but only nine Value (gray) steps are usedto white, but only nine Value (gray) steps are used in the Munsell system. Pure white (10) and purein the Munsell system. Pure white (10) and pure black (0) are unattainable. Fractional numbers areblack (0) are unattainable. Fractional numbers are used when a finer evaluation is needed. “Low”used when a finer evaluation is needed. “Low” values refer to dark colors : “high” values to lightvalues refer to dark colors : “high” values to light colors.colors. www.indiandentalacademy.comwww.indiandentalacademy.com
  55. 55. We perceive Value differences when we watch aWe perceive Value differences when we watch a black and white television picture. The actualblack and white television picture. The actual scene is full of color, but only thescene is full of color, but only the lightness/darkness (Value) of a color islightness/darkness (Value) of a color is transmitted, a blue, red or yellow could all betransmitted, a blue, red or yellow could all be transmitted as the same indistinguishable graytransmitted as the same indistinguishable gray if they are of the same Value (a part of theif they are of the same Value (a part of the same Value “wheel’). Colors of high Valuesame Value “wheel’). Colors of high Value would be transmitted as light grays, and thosewould be transmitted as light grays, and those of low Value as dark grays, regardless of theof low Value as dark grays, regardless of the Hue or chroma. It could be said that the ValueHue or chroma. It could be said that the Value of a color is the gray it would match if it wereof a color is the gray it would match if it were seen on a black and white television screen.seen on a black and white television screen. Tab c in Plate II, B, and all the tabs directly toTab c in Plate II, B, and all the tabs directly to its left have the same Value and would,its left have the same Value and would, therefore, transmit as the sametherefore, transmit as the same indistinguishable gray.indistinguishable gray.www.indiandentalacademy.comwww.indiandentalacademy.com
  56. 56. Chroma :Chroma : Chroma, the remaining dimension,Chroma, the remaining dimension, “is that quality by which we distinguish a strong“is that quality by which we distinguish a strong color from a weak one; the departure of a colorcolor from a weak one; the departure of a color sensation from that of white or gray; thesensation from that of white or gray; the intensity of a distinctive Hue; color intensity.intensity of a distinctive Hue; color intensity. Chroma describes the amount of Hue in a color.Chroma describes the amount of Hue in a color. The gradations of Chroma were referred to asThe gradations of Chroma were referred to as the spokes of our wheels. The concept ofthe spokes of our wheels. The concept of painting a box will help to clarify thispainting a box will help to clarify this dimension. Suppose it is desired to paint onedimension. Suppose it is desired to paint one side of box pure red. If an amount of grayside of box pure red. If an amount of gray paint is added to the bucket before the secondpaint is added to the bucket before the second side is painted, the red on the second side willside is painted, the red on the second side will be perceived as less than a pure red; thebe perceived as less than a pure red; the Chroma will be reduced. If additional grayChroma will be reduced. If additional gray paint is added to the bucket before eachpaint is added to the bucket before each additional side is painted, the paint will comeadditional side is painted, the paint will come closer and closer to being perceived as a gray.closer and closer to being perceived as a gray. www.indiandentalacademy.comwww.indiandentalacademy.com
  57. 57. Plate II, B, is from the Munsell Book ofPlate II, B, is from the Munsell Book of Color, and studying this illustration will aidColor, and studying this illustration will aid in the understanding of these points. Ifin the understanding of these points. If the red to the extreme right at Value levelthe red to the extreme right at Value level 4 (tab c) is considered as the original color4 (tab c) is considered as the original color of the paint, the red to the left of thisof the paint, the red to the left of this would represent the paints of reducedwould represent the paints of reduced Chroma. Adding a gray always reducesChroma. Adding a gray always reduces the Chroma and theoretically will not affectthe Chroma and theoretically will not affect the Hue. The change in Value of thethe Hue. The change in Value of the original color depends upon the Value oforiginal color depends upon the Value of the gray added to it. If a gray of higherthe gray added to it. If a gray of higher Value than that of the original color isValue than that of the original color is used, the resulting color will be of theused, the resulting color will be of the same Hue, lessened Chroma, and highersame Hue, lessened Chroma, and higher value (tab a could represent such a result).value (tab a could represent such a result). www.indiandentalacademy.comwww.indiandentalacademy.com
  58. 58. If a gray of the same Value is used, only theIf a gray of the same Value is used, only the Chroma will be affected (lessened). (e.g.,Chroma will be affected (lessened). (e.g., tab d). If a gray of a lower Value is used,tab d). If a gray of a lower Value is used, only the Chroma will be lessened, and theonly the Chroma will be lessened, and the Value will be lowered (e.g. tab b).Value will be lowered (e.g. tab b). Emphasis is placed on this point in order toEmphasis is placed on this point in order to dispel the confusing statements seen indispel the confusing statements seen in some dental literature to the effect thatsome dental literature to the effect that Value depends upon the relative amount ofValue depends upon the relative amount of gray in a Hue and that adding gray alwaysgray in a Hue and that adding gray always lowers the Value.lowers the Value. The need to refer to gray in describing bothThe need to refer to gray in describing both Value and Chroma is a major factor in theValue and Chroma is a major factor in the confusion concerning these two dimensions.confusion concerning these two dimensions. To think of Value in relation to the televisionTo think of Value in relation to the television picture and Chroma in relation to thepicture and Chroma in relation to the painting of the box will provide a simple,painting of the box will provide a simple, easily recalled memory aid.easily recalled memory aid. www.indiandentalacademy.comwww.indiandentalacademy.com
  59. 59. www.indiandentalacademy.comwww.indiandentalacademy.com
  60. 60. SURFACE TEXTURESURFACE TEXTURE Matching the surface texture and outline form is anMatching the surface texture and outline form is an important as matching the shade of a tooth. Thisimportant as matching the shade of a tooth. This statement does not diminish the importance of thestatement does not diminish the importance of the shade but emphasizes the importance of reproducingshade but emphasizes the importance of reproducing surface texture and outline form in establishing estheticsurface texture and outline form in establishing esthetic harmony of a ceramic restoration.harmony of a ceramic restoration. Regardless of whether a tooth is flat or irregular, theRegardless of whether a tooth is flat or irregular, the surface is viewed as being rough or smooth. A smoothsurface is viewed as being rough or smooth. A smooth surface will reflect most of the incident light back to thesurface will reflect most of the incident light back to the observer. A roughened surface randomly scatters theobserver. A roughened surface randomly scatters the reflection of light in many different directions. In thereflection of light in many different directions. In the process of determining the character of light reflection,process of determining the character of light reflection, the surface texture of a crown must be designed tothe surface texture of a crown must be designed to simulate the reflectance pattern of adjacent teeth.simulate the reflectance pattern of adjacent teeth. Properly blending the effects of light reflection andProperly blending the effects of light reflection and absorption in a crown creates a natural appearance thatabsorption in a crown creates a natural appearance that hides slight color differences.hides slight color differences.www.indiandentalacademy.comwww.indiandentalacademy.com
  61. 61. Many dentists have discussed the manipulationMany dentists have discussed the manipulation of surface texture to conceal color differences inof surface texture to conceal color differences in ceramic restorations. Obregon et al, found thatceramic restorations. Obregon et al, found that increased roughness of porcelain samplesincreased roughness of porcelain samples decreased the Value level. Burk, in a pilotdecreased the Value level. Burk, in a pilot study, observed that modifying surface texturestudy, observed that modifying surface texture altered the appearance of porcelain in terms ofaltered the appearance of porcelain in terms of Hue, Value, and Chroma, and even affected theHue, Value, and Chroma, and even affected the degree of translucency.degree of translucency. On eruption, teeth have their roughest surfaceOn eruption, teeth have their roughest surface texture. Undulating vertical ridges are formedtexture. Undulating vertical ridges are formed by the fusion of developmental lobesby the fusion of developmental lobes transversed by fine horizontal lines.transversed by fine horizontal lines. These numerous small transverse lines on theThese numerous small transverse lines on the surface of enamel are perikymata producedsurface of enamel are perikymata produced during the incremental formation of enamel. Induring the incremental formation of enamel. In general, with advancing age these surfacegeneral, with advancing age these surface features are gradually obliterated throughfeatures are gradually obliterated through attrition from tooth brushing or occlusal wear.attrition from tooth brushing or occlusal wear. www.indiandentalacademy.comwww.indiandentalacademy.com
  62. 62. This process of progressive enamel wearThis process of progressive enamel wear corresponding with advancing age can becorresponding with advancing age can be characterized. Through many years ofcharacterized. Through many years of brushing and the process of naturalbrushing and the process of natural abrasion, the lines become less definedabrasion, the lines become less defined and the tooth surface acquires moreand the tooth surface acquires more stippled appearance. As the wearstippled appearance. As the wear process continues into the later years ofprocess continues into the later years of life, all signs of the perikymata are lostlife, all signs of the perikymata are lost and only the gentle undulations of theand only the gentle undulations of the developmental lobes are observed.developmental lobes are observed. Finally, the definition of theFinally, the definition of the developmental lobes is obliterated anddevelopmental lobes is obliterated and the tooth appears smooth with a highlythe tooth appears smooth with a highly reflecting glassy surface.reflecting glassy surface.www.indiandentalacademy.comwww.indiandentalacademy.com
  63. 63. The teeth with a highly reflectively glassyThe teeth with a highly reflectively glassy surface. The teeth of a youngersurface. The teeth of a younger individual will most likely have theindividual will most likely have the perikymata and developmental lobesperikymata and developmental lobes intact. Emulating the surfaceintact. Emulating the surface characteristic for a particular age groupcharacteristic for a particular age group facilitates achievement of a life likefacilitates achievement of a life like restoration. Failure to reproduce surfacerestoration. Failure to reproduce surface detail accurately will result in lightdetail accurately will result in light reflection different from that of the contrareflection different from that of the contra lateral teeth. This result will suggestlateral teeth. This result will suggest artificially, despite correct color andartificially, despite correct color and contour matching.contour matching.www.indiandentalacademy.comwww.indiandentalacademy.com
  64. 64. To create the surface texture of a young individual, theTo create the surface texture of a young individual, the developmental lobes and vertical undulations are firstdevelopmental lobes and vertical undulations are first defined with a cone shaped diamond bur. Next, adefined with a cone shaped diamond bur. Next, a rotating football shaped diamond bur movedrotating football shaped diamond bur moved mesiodistally defines perikymata. The crown is fired tomesiodistally defines perikymata. The crown is fired to a light autoglaze to hear surface flaws. Finally,a light autoglaze to hear surface flaws. Finally, diamond polishing paste on a 1 inch felt wheel createsdiamond polishing paste on a 1 inch felt wheel creates the desired surface shine.the desired surface shine. The smooth surface of an older tooth resulting fromThe smooth surface of an older tooth resulting from heavy abrasion, is first prepared by defining anyheavy abrasion, is first prepared by defining any developmental lobes. Ridges and heights of contour aredevelopmental lobes. Ridges and heights of contour are polished with a rubber wheel. The crown is held atpolished with a rubber wheel. The crown is held at glazing temperature for a longer period to achieve aglazing temperature for a longer period to achieve a smoother autoglaze. The final finish is accomplished bysmoother autoglaze. The final finish is accomplished by polishing with Brasso cleaner (French Householdpolishing with Brasso cleaner (French Household products, Rochester, N.Y.) and pumice on a high speedproducts, Rochester, N.Y.) and pumice on a high speed lathe with a large felt wheel to the desired smoothness.lathe with a large felt wheel to the desired smoothness. Wear facets can be created by further selectiveWear facets can be created by further selective polishing with a rubber wheel.polishing with a rubber wheel. www.indiandentalacademy.comwww.indiandentalacademy.com
  65. 65. Although study casts are helpful in demonstratingAlthough study casts are helpful in demonstrating major features such as developmental ridges, surfacemajor features such as developmental ridges, surface texture is inadequately reproduced by a stone cast.texture is inadequately reproduced by a stone cast. The use of a resin replica has been suggested for betterThe use of a resin replica has been suggested for better reproduction of surface detail.reproduction of surface detail. A tooth tab actually demonstrating surface textureA tooth tab actually demonstrating surface texture provides much more detail than a written prescriptionprovides much more detail than a written prescription or a study cast. We have developed a system of usingor a study cast. We have developed a system of using extracted teeth with varying degrees of surface texture.extracted teeth with varying degrees of surface texture. The teeth are sterilized, numbered for easyThe teeth are sterilized, numbered for easy identification, and retained on a ring. By havingidentification, and retained on a ring. By having several sets of surface texture tabs available, theseveral sets of surface texture tabs available, the dentist match and record the appropriate surfacedentist match and record the appropriate surface texture tab and include the tab with the preparationtexture tab and include the tab with the preparation dies. Preparation of various surface texture on porcelaindies. Preparation of various surface texture on porcelain tabs is an alternative to the use of extracted teeth.tabs is an alternative to the use of extracted teeth. The identification tab, which will be discussed, can alsoThe identification tab, which will be discussed, can also be textured for communication with the ceramist. Thebe textured for communication with the ceramist. The identification tabs can be prepared with a range ofidentification tabs can be prepared with a range of surface texture and degrees of luster.surface texture and degrees of luster. www.indiandentalacademy.comwww.indiandentalacademy.com
  66. 66. Although final chairsideAlthough final chairside adjustment is alwaysadjustment is always necessary, the ceramicnecessary, the ceramic restoration produced byrestoration produced by the ceramist will requirethe ceramist will require less adjustment and beless adjustment and be closer to the desiredcloser to the desired finished result. Becausefinished result. Because the surface texture of thethe surface texture of the crown is similar to thatcrown is similar to that the natural teeth to bethe natural teeth to be matched, it allows rapidmatched, it allows rapid evaluation of suitability ofevaluation of suitability of color match.color match. www.indiandentalacademy.comwww.indiandentalacademy.com
  67. 67. SHADE SELECTION PROCEDURE:SHADE SELECTION PROCEDURE: CLARK SAID, "Color, like form, has three dimensions,CLARK SAID, "Color, like form, has three dimensions, but they are not in general use. Many of us have notbut they are not in general use. Many of us have not been taught neither names, nor the scales of theirbeen taught neither names, nor the scales of their measurement. In other words, we as dentists are notmeasurement. In other words, we as dentists are not educationally equipped to approach a color problem."educationally equipped to approach a color problem." This statement is, unfortunately, still true. DentistsThis statement is, unfortunately, still true. Dentists have had little or no training in vision physiology orhave had little or no training in vision physiology or color science. A 1967 survey revealed that 23 out ofcolor science. A 1967 survey revealed that 23 out of 112 dental schools had some sort of color education in112 dental schools had some sort of color education in their curriculum. A survey conducted the followingtheir curriculum. A survey conducted the following year, reported that 3 of 115 dental schools taught ayear, reported that 3 of 115 dental schools taught a formal course in color. Thirty years later,formal course in color. Thirty years later, comprehensive color training continues to be a missingcomprehensive color training continues to be a missing part in the dental school curriculum. If any training atpart in the dental school curriculum. If any training at all is given in dental school, it is cursory or simplisticall is given in dental school, it is cursory or simplistic and usually consists of presenting an incompleteand usually consists of presenting an incomplete explanation of three abstract concepts of the Munsellexplanation of three abstract concepts of the Munsell Notation:4 hue, value and chroma.Notation:4 hue, value and chroma.www.indiandentalacademy.comwww.indiandentalacademy.com
  68. 68. The increase in newer types of ceramicThe increase in newer types of ceramic restorations and the improving quality ofrestorations and the improving quality of esthetics means the dentist of the 21st centuryesthetics means the dentist of the 21st century must be trained to detect differences in colormust be trained to detect differences in color and shades in individual teeth, select a shadeand shades in individual teeth, select a shade that reflects the color and exact shade,that reflects the color and exact shade, transmit this information to a dental technician,transmit this information to a dental technician, and then be able to make any necessaryand then be able to make any necessary adjustments to the restoration. However, thereadjustments to the restoration. However, there are a number of factors that stand in the wayare a number of factors that stand in the way of properly selecting a color match. Subjectiveof properly selecting a color match. Subjective faults range from differences in color perceptionfaults range from differences in color perception to ocular fatigue and lack of educationto ocular fatigue and lack of education regarding the basic principles of color.regarding the basic principles of color. Metamerism may occur if proper lighting is notMetamerism may occur if proper lighting is not used during shade selection in the dental officeused during shade selection in the dental office and laboratory Finally, existing shade guidesand laboratory Finally, existing shade guides are limited and require a more extensive rangeare limited and require a more extensive range of shades.of shades. www.indiandentalacademy.comwww.indiandentalacademy.com
  69. 69. Therefore, it is no surprise that color matching for crownsTherefore, it is no surprise that color matching for crowns and dentures can be a frustrating and discouragingand dentures can be a frustrating and discouraging experience for the dentist, technician and patient. Theexperience for the dentist, technician and patient. The breakdown in communication over matters ranging frombreakdown in communication over matters ranging from shade guide to laboratory prescriptions must beshade guide to laboratory prescriptions must be addressed. This study will review the problems of coloraddressed. This study will review the problems of color matching and will attempt to guide the reader towardmatching and will attempt to guide the reader toward enhancing his or her techniques regarding shade selectionenhancing his or her techniques regarding shade selection and communication with the ceramist.and communication with the ceramist. Tooth vs. PorcelainTooth vs. Porcelain Prior to shade matching, the dentist must have anPrior to shade matching, the dentist must have an understanding that the human tooth and dental porcelainunderstanding that the human tooth and dental porcelain transmit light waves differently It is their physicaltransmit light waves differently It is their physical composition that determines the differences in light-wavecomposition that determines the differences in light-wave transmission, absorption, reflection, refraction, scatteringtransmission, absorption, reflection, refraction, scattering and surface gloss. The manner in which light strikes anand surface gloss. The manner in which light strikes an object determines the total appearance of the material.object determines the total appearance of the material. Transparent materials allow for the passage of light withTransparent materials allow for the passage of light with little change. Translucent materials scatter, transmit andlittle change. Translucent materials scatter, transmit and absorb light. Opaque materials reflect and absorb;absorb light. Opaque materials reflect and absorb; however they do not transmit. Surface characteristics,however they do not transmit. Surface characteristics, such as gloss, curvature and texture, will affect thesuch as gloss, curvature and texture, will affect the degree of light diffusion when striking thedegree of light diffusion when striking the particular object.particular object. www.indiandentalacademy.comwww.indiandentalacademy.com
  70. 70. A vital tooth is both naturally translucent andA vital tooth is both naturally translucent and transparent. Enamel rods are transparent and thereforetransparent. Enamel rods are transparent and therefore refract and reflect light. Light that strikes the incisalrefract and reflect light. Light that strikes the incisal edges of an anterior tooth passes through withedges of an anterior tooth passes through with maximum transmission because of a high degree ofmaximum transmission because of a high degree of translucency.translucency. Porcelain, however, is a heterogeneous material. ItPorcelain, however, is a heterogeneous material. It contains transparent properties and metallic oxides thatcontains transparent properties and metallic oxides that act as opacifiers. These porcelains modify light byact as opacifiers. These porcelains modify light by absorption, transmission and reflection. Absorption isabsorption, transmission and reflection. Absorption is largely responsible for color. It occurs when lightlargely responsible for color. It occurs when light passes through the layers of the porcelain. Scatteringpasses through the layers of the porcelain. Scattering occurs when light encounters interfaces between theoccurs when light encounters interfaces between the materials (i.e., pigments and glass). The smaller thematerials (i.e., pigments and glass). The smaller the pigment size, the less light that is absorbed, resultingpigment size, the less light that is absorbed, resulting in less detectable color. The larger the pigment size,in less detectable color. The larger the pigment size, the more reflection that occurs as light scatters at thethe more reflection that occurs as light scatters at the particle surfaces. Scattering light is necessary in dentalparticle surfaces. Scattering light is necessary in dental porcelains to simulate the prismatic effect of enamel.porcelains to simulate the prismatic effect of enamel. Yet, one must keep in mind that too much dispersedYet, one must keep in mind that too much dispersed reflection through internal scattering will create anreflection through internal scattering will create an unnatural looking prosthesis.unnatural looking prosthesis.www.indiandentalacademy.comwww.indiandentalacademy.com
  71. 71. Light SourcesLight Sources One of the questions asked whenOne of the questions asked when selecting a shade is, what light sourceselecting a shade is, what light source should be used? Shade determinationshould be used? Shade determination should be performed under colorshould be performed under color corrected fluorescent lighting, whichcorrected fluorescent lighting, which contains a balance of the entire visiblecontains a balance of the entire visible spectrum. The operatory should be litspectrum. The operatory should be lit using a luminous ceiling with translucentusing a luminous ceiling with translucent diffusing panels that are simple todiffusing panels that are simple to maintain. Clean watt saver lamps havingmaintain. Clean watt saver lamps having a color temperature of 4200K or higher isa color temperature of 4200K or higher is advocated. Shade selection should not beadvocated. Shade selection should not be made using daylight, because daylight ismade using daylight, because daylight is subject to constant changes.subject to constant changes. www.indiandentalacademy.comwww.indiandentalacademy.com
  72. 72. One must also be concerned with the phenomenon ofOne must also be concerned with the phenomenon of metamerism, which occurs when the color of twometamerism, which occurs when the color of two objects looks identical when observed under one lightobjects looks identical when observed under one light source but different under other lightsource but different under other light conditions.Metamerism occurs only when two objectsconditions.Metamerism occurs only when two objects have different wavelength distribution and thereforehave different wavelength distribution and therefore reflect different spectra.reflect different spectra. The color of the operatory can also affect shadeThe color of the operatory can also affect shade selection. Colors should be kept at a low saturationselection. Colors should be kept at a low saturation level. Walls and cabinets should be glossy enough tolevel. Walls and cabinets should be glossy enough to maintain brightness without causing a glare. It ismaintain brightness without causing a glare. It is recommended that the color of the walls and ceiling berecommended that the color of the walls and ceiling be white or off-white.white or off-white. The dentist should be concerned with "blue fatigue:'The dentist should be concerned with "blue fatigue:' this occurs when the eye is unable to differentiatethis occurs when the eye is unable to differentiate between the various shades of blue. However, bluebetween the various shades of blue. However, blue fatigue increases sensitivity to yellow therefore, tofatigue increases sensitivity to yellow therefore, to improve shade selection in the yellow range, theimprove shade selection in the yellow range, the operator should stare at a blue card or patient napkinoperator should stare at a blue card or patient napkin between shade comparisons.between shade comparisons. www.indiandentalacademy.comwww.indiandentalacademy.com
  73. 73. It has been suggested that dentists useIt has been suggested that dentists use natural north daylight for shadenatural north daylight for shade matching. Many dental offices have beenmatching. Many dental offices have been designed to face the north to enhance thedesigned to face the north to enhance the selection process. However, daylight isselection process. However, daylight is not at a constant throughout the day andnot at a constant throughout the day and therefore must not be used as the onlytherefore must not be used as the only light source for shade matching.light source for shade matching. www.indiandentalacademy.comwww.indiandentalacademy.com
  74. 74. The Problem with Shade GuidesThe Problem with Shade Guides Shade guides have become the standard for selectingShade guides have become the standard for selecting shade, yet there have been many errors associatedshade, yet there have been many errors associated with the use of commercial shade guides. Problems thatwith the use of commercial shade guides. Problems that may arise include the following:may arise include the following: 1. Porcelains do not match the shade guides that they1. Porcelains do not match the shade guides that they are being compared to.are being compared to. 2. Shade variations occur between different die lots of2. Shade variations occur between different die lots of porcelain from the same manufacturer.porcelain from the same manufacturer. 3. Shade guide tabs are 4-5 mm thick compared to the3. Shade guide tabs are 4-5 mm thick compared to the thin 1.5 mm piece of porcelain used for the restoration.thin 1.5 mm piece of porcelain used for the restoration. 4. Shade guides are not always made with fluorescent4. Shade guides are not always made with fluorescent porcelain, which causes inconsistencies in colorporcelain, which causes inconsistencies in color matching.matching. 5. It is difficult to predict the final shade after the5. It is difficult to predict the final shade after the layering of opaque, dentin and enamel.layering of opaque, dentin and enamel. 6. Guide tabs lack a metal backing when using6. Guide tabs lack a metal backing when using porcelain-fused to-metal restorations.porcelain-fused to-metal restorations. 7. Shade tabs are condensed differently than porcelain7. Shade tabs are condensed differently than porcelain used for final restorations.used for final restorations.www.indiandentalacademy.comwww.indiandentalacademy.com
  75. 75. Now that the reader understands theNow that the reader understands the potential problems that arise whenpotential problems that arise when selecting shade, it is imperative that theselecting shade, it is imperative that the dentist have a proper education in color.dentist have a proper education in color. However, we must assume that not everyHowever, we must assume that not every dentist will seek out the proper courses.dentist will seek out the proper courses. The latter portion of this article will be aThe latter portion of this article will be a review of numerous methods forreview of numerous methods for enhancing laboratory communicationenhancing laboratory communication between the dentist and the dentalbetween the dentist and the dental technician, to assure the success oftechnician, to assure the success of proper shade matching. The dentist mustproper shade matching. The dentist must then decide for himself or herself howthen decide for himself or herself how much information is enough to guaranteemuch information is enough to guarantee the replication of the restored teeth.the replication of the restored teeth.www.indiandentalacademy.comwww.indiandentalacademy.com
  76. 76. Shade Selection GuidelinesShade Selection Guidelines The dentist must have a working knowledge ofThe dentist must have a working knowledge of the basic principles of color. This allows forthe basic principles of color. This allows for accurate shade selection. Munsell described theaccurate shade selection. Munsell described the three dimensions of color as hue, value andthree dimensions of color as hue, value and chroma.chroma. Hue is the property of color that is determinedHue is the property of color that is determined by wavelength, which distinguishes one colorby wavelength, which distinguishes one color from another. Value is a quantity of brightness.from another. Value is a quantity of brightness. It is a qualitative term related to lightness orIt is a qualitative term related to lightness or blackness of color and not the quantity of theblackness of color and not the quantity of the color gray Chroma is the saturation of color.color gray Chroma is the saturation of color. Matching the proper shade is not carried outMatching the proper shade is not carried out just by holding up a guide tab to the tooth injust by holding up a guide tab to the tooth in question. There are a number of methods thatquestion. There are a number of methods that can be employed to intensify the shadecan be employed to intensify the shade selection. They are as follows:selection. They are as follows: www.indiandentalacademy.comwww.indiandentalacademy.com
  77. 77. 1. If patient is wearing bright clothing, drape him or her1. If patient is wearing bright clothing, drape him or her with a neutral colored cover.with a neutral colored cover. 2. Have patient remove lipstick or other make-up.2. Have patient remove lipstick or other make-up. 3. Clean the teeth and remove all stains and debris.3. Clean the teeth and remove all stains and debris. 4. Have patient's mouth at dentist's eye level.4. Have patient's mouth at dentist's eye level. 5. Determine shade at the beginning of the appointment5. Determine shade at the beginning of the appointment to avoid ocular fatigue.to avoid ocular fatigue. 6. Shade comparisons should be performed at five-second6. Shade comparisons should be performed at five-second intervals so as not to fatigue the cone cells of theintervals so as not to fatigue the cone cells of the retina.retina. 7. Obtain value levels by squinting.7. Obtain value levels by squinting. 8. Compare shade under varying conditions (i.e., wet vs.8. Compare shade under varying conditions (i.e., wet vs. dry lips; retracted lip vs. pulled down lip).dry lips; retracted lip vs. pulled down lip). 9. Use the canine as a reference for shade because of the9. Use the canine as a reference for shade because of the highest chroma of the dominant hue of the teeth."highest chroma of the dominant hue of the teeth." 10. If unable to precisely match shade, select a shade of10. If unable to precisely match shade, select a shade of lower chroma and higher value.lower chroma and higher value. 11. Grind off the necks of the shade tabs because they11. Grind off the necks of the shade tabs because they tend to be darker than the rest of the shade tab.tend to be darker than the rest of the shade tab.www.indiandentalacademy.comwww.indiandentalacademy.com
  78. 78. Custom Shade GuidesCustom Shade Guides To properly start the shade matching processTo properly start the shade matching process the dentist should acquire a custom shadethe dentist should acquire a custom shade guide. This guide is the beginning of improvingguide. This guide is the beginning of improving communication with the laboratory Eachcommunication with the laboratory Each custom shade guide should include thecustom shade guide should include the ceramists metal, porcelain, staining kits,ceramists metal, porcelain, staining kits, equipment and techniques. It should alsoequipment and techniques. It should also contain pointers as to what to look for whencontain pointers as to what to look for when selecting a shade. The technician needs to sendselecting a shade. The technician needs to send a chart along with the guide for jotting downa chart along with the guide for jotting down any additional information that will allow for aany additional information that will allow for a better understanding of the particular shade.better understanding of the particular shade. The dentist may choose to create a luster tabThe dentist may choose to create a luster tab and send it to the laboratory with theand send it to the laboratory with the prescription. The technician will then have aprescription. The technician will then have a visual aid for what he must fabricate.visual aid for what he must fabricate. Numerous techniques regarding custom shadeNumerous techniques regarding custom shade guides have been noted in the literature.guides have been noted in the literature.www.indiandentalacademy.comwww.indiandentalacademy.com

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