The science of color, light and shade
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The science of color, light and shade
- 1. The Science of Color, Light and Shade Selection Presented by Lisa Fedor James D.D.S.
- 2. Outline • Light and Color – Description of Light • Quality of light – Description of Color • Hue, Chroma, Value • Munsell Color System – Factors influencing perception • The eye (rods and cones) • Deceptive color perception • Color Blindness • Shade selection – Techniques for determining shade / Shade guides – Shade mapping
- 3. Visible electromagnetic energy whose wavelength is measured in nanometers (nm)
- 4. Without Light Color Does Not ExistWithout Light Color Does Not Exist A yellow object absorbs all lightwaves of all colors, but reflects yellow
- 5. Color Influenced by three main factors 1. Physical properties of the object 2. Assessment of the observer 3. Nature of incident light – Relationship to other colored objects
- 6. Light •Part of the electromagnetic spectrum •The eye is only sensitive to the visible portion of the spectrum (380 – 750nm) •Different wavelengths constitute the different colors we perceive
- 7. • Relatively equal quantities of electromagnetic energy over the VLS • When passed through a prism we see component colors of white light • Shorter wavelengths bend more than longer wavelengths Pure White Light 380nm 750nm + + + + + + =
- 8. Quality of Light / 3 Types 1.Incandescent Light 2.Fluorescent Light 3.Natural Daylight Most dental offices are outfitted with incandescent and fluorescent lights
- 9. 1. Incandescent Light • Emits high concentration of yellow waves • Not suitable for shade matching • Low Color Rendering Index (CRI)
- 10. 2. Fluorescent Light • Emits high concentration of blue waves • Not suitable for shade matching • CRI =(50-80)
- 11. 3. Natural Daylight • Northern daylight considered the best • Closest to emitting the full spectrum of white light • Used as the standard by which to judge other light sources • CRI close to 100
- 12. Color Rendering Index • CRI = (0-100) • Indicates how well a light source renders color as compared to a standard source (N. Daylight) • Northern daylight (hence CRI) can be affected by – Time of day – Cloud cover – Humidity – Pollution
- 13. CRI and Time of Day • Morning and evening – Shorter wavelengths scatter before penetrating atmosphere – Daylight rich in yellow/orange, lacks blue/green • Mid-day – Hours around noon = ideal – Incident daylight is most balanced within VLS – Full spectrum of colors visible
- 14. Color Temperature • Another light source reference standard • Related to the color standard black body when heated • Reported in degrees Kelvin (°K) – 1000K – red – 2000K – yellow – 5555K – white – 6500K – northern daylight – 8000K – pale blue • Dependent on four factors which influence CRI
- 15. Color The quality of an object or substance with respect to light reflected by the object, usually determined visually by measurement of hue, chroma and value
- 16. Color Influenced by three main factors 1. Physical properties of the object 2. Assessment of the observer 3. Nature of incident light – Relationship to other colored objects
- 17. Subtractive Color • These are the colors associated with the subtraction of light • Used in pigments for making paints, inks, fabrics etc. • The primary subtractive colors are Red, Yellow, and Blue • The secondary subtractive colors are Green, Purple and Orange • When subtractive primary colors are combined they produce black
- 18. Additive Color • These are the color obtained by emitted light • Associated with television and computer displays • The primary additive colors are Red, Blue and Green • The secondary colors are Cyan, Yellow and Magenta • When additive primary colors are combined they produce white
- 20. Three Attributes of Color 1. Hue 2. Chroma 3. Value
- 21. Hue • Variety of color (red, green, yellow, etc.) • Determined by wavelength of observed light within the VLS • Reflected wavelength determines hue
- 22. The intensity or saturation of a hue Low Chroma High Chroma Chroma
- 23. Value • The relative darkness or lightness of a color, or brightness of an object – Range = 0-10 (0=black, 10 = white) • Amount of light energy an object reflects or transmits • Objects of different hues / chroma can be identical value • Restorations too high in value are easily detected Low Value High Value
- 24. Objects of different chroma / hue can be identical value
- 25. - Equal in Chroma / Variation in Value - Variation in Chroma / Equal in Value Chroma Value Objects of different chroma can be identical value
- 26. Objects of different chroma / hue can be identical value
- 28. Color Perception • Rods – Scotopic (gray scale) vision, interpret brightness – Interpret brightness, not color – Highest concentration on peripheral retina • Cones – Photopic (color) vision – Interpret color – More active under high light – Highest concentration on central retina (macula), most color perceptive area of eye
- 29. Color Adaptation • Color vision decreases rapidly as object is observed • Color viewed dulls, while its compliment increases in intensity – Fatigue • Viewing a pale blue or gray surface between shade matching will restore color vision
- 32. Metamerism Two colors that appear to be a match under a given lighting condition but have different spectral reflectance = metamers, the phenomenon is metamerism. Light Source #1 Single Light Source Light Source #2 Light Source #3
- 33. Metamerism
- 34. Color Blindness • Defect in color vision – 8% males – 0.5% females • Several variations exist – Achromatism – complete lack of hue sensitivity – Dichromatism – sensitivity to two primary hues – Anomalous Trichromatism – sensitivity to all three hues, with abnormality in retinal cones affecting one of primary pigments Dentists should have their color vision evaluated. If any deficiency is detected, a dentist should seek assistance when selecting tooth shades.
- 35. Shade Selection • Subjective evaluation with considerable variation • Subtle variations can exist without causing disharmony in smile – Restoration contour – Value of restoration • Process improved by applying principles of light and color
- 36. Principles of Shade Selection 1. Teeth to be matched must be clean 2. Remove bright colors from field of view - makeup / tinted eye glasses - bright gloves - neutral operatory walls 3. View patient at eye level 4. Evaluate shade under multiple light sources 5. Make shade comparisons at beginning of appointment 6. Shade comparisons should be made quickly to avoid eye fatigue
- 37. Commercial Shade Guides • Most convenient and common method of making shade selections • Guides consist of shade tabs – Metal backing – Opaque porcelain – Neck, body, and incisal color • Select tab with the most natural intraoral appearance
- 38. Commercial Shade Guides • Vita Classic • Vitapan 3D –Master • Extended Range Shade Guides
- 39. Vita Classic Shade Guide A B C D • Very popular shade guide • Tabs of similar hue are clustered into letter groups – A (red-yellow) – B (yellow) – C (grey) – D (red-yellow-gray) • Chroma is designated with numerical values • A3 = hue of red-yellow, chroma of 3
- 41. Vita Classic Shade Guide Manufacturer recommended sequence for shade matching 1. Hue Selection 2. Chroma Selection 3. Value Selection 4. Final Check / Revision
- 42. Vita Classic – Step 1 (Hue Selection) • Four categories representing hue – A, yellow-red – B, yellow – C, gray – D, red-yellow-gray • Operator should select hue closest to that of natural tooth • Use area of tooth highest in chroma for hue selection – Difficult to select hue for teeth low in chroma
- 43. Vita Classic – Step 2 (Chroma Selection) • Hue selection has been made (B) • Chroma is selected from gradations within the B tabs – B1, B2, B3, B4 • Several comparisons should be made – Avoid retinal fatigue – Rest eyes between comparisons (blue-gray)
- 44. Vita Classic – Step 3 (Value Selection) • Use of second, value ordered shade guide is recommended • Value oriented shade guide – B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4, C4, • Value best determined by squinting with comparisons made at arms length – Decreases light – Diminishes cone sensitivity, increases rod sensitivity – Tooth fading first has a lower value
- 45. Vita Classic – Step 4 (Final Check / Revision) • Potential Problem – Following value selection, tabs selected for hue and chroma may not coincide with shade tab selected for value
- 46. Vita Classic – Step 4 (Final Check / Revision) • Possible Findings / Solutions – Value of shade tab < natural teeth • Select new shade tab with higher value • Cannot increase value of restoration with extrinsic staining • Will only increase opacity, light transmisison – Value of shade tab > natural teeth • Select new shade tab with lower value (or) • Bridge difference with intrinsic or extrinsic staining
- 48. Vita-3D – Step 1 • Determine the lightness level (value) • Hold shade guide to patient’s mouth at arms length • Start with darkest group moving right to left • Select Value group 1, 2, 3, 4, or 5
- 49. Vita-3D – Step 2 • Select the chroma • From your selected Value group, remove the middle tab (M) and spread the samples out like a fan • Select one of the three shade samples to determine chroma
- 50. Vita-3D – Step 3 • Determine the hue • Check whether the natural tooth is more yellowish or more reddish than the shade sample selected
- 51. Vita-3D – Step 4 • For more precise shade, intermediate levels for hue, value, and chroma can be given – 2.5M2 = value between 2M2 and 3m2 – 3M1.5 = chroma between 3M1 and 3M2 – 3M2 / 3L2.5 = hue between 3M2 and 3L2.5
- 52. Vita-3D – Value Modification • For more precise shade, intermediate levels for value, chroma, and hue can be given – 2.5M2 = value between 2M2 and 3M2
- 53. Vita-3D – Chroma Modification • For more precise shade, intermediate levels for value, chroma and hue can be given – 3M1.5 = chroma between 3M1 and 3M2
- 54. Vita-3D – Hue Modification • For more precise shade, intermediate levels for value, chroma and hue can be given – 3M2 / 3L2.5 = hue between 3M2 and 3L2.5 2.5 Intermediate values should be noted on the laboratory communication form
- 55. Extended Range Shade Guides • Most shade guides do not cover all the colors in the natural dentition • Some porcelain systems extend the typical range • Bleached shades • Dentin shades • Custom shade guides
- 56. Shade Mapping • Recommended even when good custom shade match exists • Tooth is divided into – Three regions – Nine segments • Each region is matched independently • Further characterizations are sketched on diagram, may include… – Craze lines – Hypocalcifications – Proximal discolorations – Translucency
- 57. Summary • An understanding of the science of color and color perception is crucial to the success in the ever expanding field of esthetic restorative dentistry. • Although limitations in materials and techniques may make a perfect color match impossible, a harmonious color match impossible, a harmonious restoration can almost be achieved. • Shade selection should be approached in a methodical and organized manner. • This will enable the practitioner to make the best choice and communicate it accurately to the laboratory.
- 58. Thank You
Editor's Notes
- I. LIGHT AND COLORWithout light color does not exist. An object we perceive as red absorbs all light waves (light waves of all colors) and reflects only the waves we interpret as red. (EXAMPLE) THE apparent color of an object is influenced by three factors.. the physical properties of the object the nature of the incident light to which the object is exposed the relationship to other colored objects (blue goves) the subjective assessment of the observer Variations in these factors can make a single tooth look very different among various observers. There is no standard for lighting in dentistry
- THE apparent color of an object is influenced by three factors.. the physical properties of the object the nature of the incident light to which the object is exposed the relationship to other colored objects (blue goves) the subjective assessment of the observer Variations in these factors can make a single tooth look very different among various observers. There is no standard for lighting in dentistry
- Pure white light consists of relatively equal quantities of electromagnetic energy over the VLR. When passed through a prism we see its component colors because the longer wavelengths are bent refracted) less than the shorter ones.
- Quality of Light Most common lights in dental offices are incandescent and fluorescent lights. Incandescent bulbs –emit higher concentrations of yellow light waves Fluorescent bulbs – give off higher concentrations of blue waves. Common fl bulbs (CRI= 50-80) therefore not suitable for shade matching Natural daylight (northern) is closest to emitting the full spectrum white light and is often used as the standard for judging light from other sources. CRI close to 100
- Trying to find the ideal time location for shade matching may point towards the use of an artificial light. In these cases a color corrected fluorescent light is recommended. You want to have a CRI no less than 90, but hopefully more.
- Although daylight is often used as the standard against which other light sources are compared, never use direct sunlight to take shade. Its CRI is influenced by Time of day *Morning and evening incident daylight shorted blue and green waves are scattered and only the longer waves penetrate the atmosphere. Therefore daylight at dawn and dusk is rich in yellow and orange but is lacking in blues and greens. *Northern daylight around the noon hour on a bright day is considered ideal, because the incident daylight is most balanced within the VLS&gt; Humidity Cloud Cover Pollution
- *Morning and evening incident daylight shorted blue and green waves are scattered and only the longer waves penetrate the atmosphere. Therefore daylight at dawn and dusk is rich in yellow and orange but is lacking in blues and greens. *Northern daylight around the noon hour on a bright day is considered ideal, because the incident daylight is most balanced within the VLS&gt; Trying to find the ideal time location for shade matching may point towards the use of an artificial light. In these cases a color corrected fluorescent light is recommended. You want to have a CRI no less than 90, but hopefully more.
- Color Temperature – another light source reference standard. Related to the color of a standard black body when heated. Reported in degrees Kelvin (K) 1000K – red 2000K- yellow 5555K – white 8000K – pale blue Northern daylight has an average color temperature of 6500 degrees K, also dependent on the above 4 factors cited for CRI.
- THE apparent color of an object is influenced by three factors.. the physical properties of the object the nature of the incident light to which the object is exposed the relationship to other colored objects (blue goves) the subjective assessment of the observer Variations in these factors can make a single tooth look very different among various observers. There is no standard for lighting in dentistry
- Almost everyone understands the concepts of the primary colors as they pertain to pigments. Red, yellow and blue are the primary pigment colors. Mixing yellow and blue yields green, blue and red yields magenta, etc. Subtractive colors are colors that are used in conjunction with reflected light. In this case the subtractive colors are blue red and yellow, (cyan, magenta and yellow where printing and coatings are concerned). These are the colors we are probably most familiar with the as the primary colors from school. These are the colors that are associated with the subtraction of light and used in pigments for making paints, inks, colored fabrics, and general colored coatings that we see and use every day. All printing processes use subtractive colors in the form of cyan (blue) magenta (red) yellow and black. This is know as CMYK (cyan, magenta, yellow, black) the K stands for black in the printing process. If all three of the subtractive primary colors were combined together, they would produce black. Some examples where subtractive primary colours are used: textiles clothes furnishings printing paints colored coatings
- Light behaves in a similar fashion, though it has a different set of primary colors. Red, green and blue are the primary colors of light. Additive colors are colors that are used in conjunction with emitted light. In this case the additive primary colors are red, green and blue. These are the colors we are probably most familiar with in association with television, and computer displays. These are the colors that are obtained by emitted light. The additive primary colors are red, green and blue. If all three of the additive colors were combined together in the form of light, they would produce white. Some examples where subtractive primary colors are used: television theatrical lighting computer monitors
- complementary colors -- colors that are opposite from one another in their makeup
- Hue – a variety of color, shade or tint (EXAMPLE) red, yellow, green… and is determined by the wavelength of the reflected and or transmitted light observed. Where the wavelength lies in the VLS determines the Hue of the color. The shorter the wavelength the closer the hue is to violet, longer the wavelength the closer the hue is to red. In the Munsell system there are 10 hue gradations. (Don’t REALLY WANT OT GET INTO THIS?)
- Chroma- defined as the intensity of a hue. Another term for chroma is saturation, terms are used interchangeably in the dental literature, both mean strength of hue or concentration of pigment. (GOOD EXAMPLE – take a container of water, add a drop of pigment, the result is a solution of low chroma, add another drop and the chroma intensifies, when solution is almost all ink a solution of high chroma has been reached) In the Munsell system chroma depends on hue and ranges form 10-14 Achromatic shades have chroma near 0. The chroma of natural teeth range form 0.5-4.
- Value – the relative lightness or darkness of a color or brightness of an object. This is a direct consequence of the amount of light energy the object reflects or transmits. It is the only dimension of color that may exist by itself. Light energy is measured in photons, objects of different hues can reflect equal number of photons and thus have the same value. (EXAMPLE – try to tell the difference between two color sharing the same value in a black and white photograph). This also creates the myth that value is the amount of grayness in an object. Munsell method of describing value = ten gradations. 0 = black and 10 = white. Natural teeth range from 5.5-8.5. A restoration too high in value is easily detected by an observer and a common mistake in metal-ceramic prosthodontics
- Chroma vs. Value
- The Eye – under low light conditions only rods are used (scotopic vision). Rods can interpret brightness but not color of objects. Color vision is dependent on cones, they become active under higher lighting conditions (Photopic vision). Dark adaptation is the change from photopic to scotopic vision, takes about 40 minutes. The area with the most cones is the center of the retina, which is free of rods. Rods increase in concentration and predominate toward the periphery of the retina. Therefore the central field of vision is more color perceptive. There are three types of cones, those sensitive to red, green and blue light. Together these form an image in much the same way as the additive effect of the pixels in a television picture. Color is also influenced by surrounding colors – particularly complementary ones. When blue and yellow are placed side by side, their chroma may appear to be increased. The color of teeth can also look different if the patient is wearing brightly colored clothing or lipstick (LESSON – DRAPE PATIENT IN LIGHT BLUE OR BLUE/GRAY COLOR&lt; REMOVE BRIGHT FACIAL MAKEUP&lt; SWITCH BRIGHTLY COLORED GLOVES FOR LIGHT NEUTRAL COLOR)
- Color Adaptation – Color vision decreases rapidly as and object is observed. The original color appears to become less and les saturated until it appears almost gray. At the same time, the chroma (intensity) of complementary colors appears greater. This phenomenon suggests that operatory walls be painted pale blue (complementary to yellow) or that a pale gray-blue surface should be glanced at periodically while viewing color choices. (LESSON – TAKE GLANCING LOOKS AT SHADE TABS&lt; DON”T STARE AT CHOICES&gt; THEN LOOK AT COMP COLOR TO BRING BACK INTENSITY OF COLOR PERCEPTION MOST OFTEN FOUND IN TEETH ----yellow red).
- (EXAMPLE – 3 objects appear to be an identical shade of purple, but they may in fact absorb and reflect light differently). Normally purple objects will reflect purple light, but some may actually absorb purple light and reflect blue and red. To the observer the blue and red combination may appear purple. But when the lighting changes the 3 objects no longer appear to match. They become metamers. (LESSON – samples that appear to match under the operatory light may not be satisfactory matches in daylight) The problem can be avoided by selecting and confirming shade under different lighting conditions. (i.e.- natural light and daylight)
- (LESSON – samples that appear to match under the operatory light may not be satisfactory matches in daylight) The problem can be avoided by selecting and confirming shade under different lighting conditions. (i.e.- natural light and daylight
- Color Blindness – A defect in color vision affecting 8% of the male population and less of the female population. Several types of color blindness exist, Achromatism – complete lack of hue sensitivity Dichromatism – sensitivity to only two primary hues, usually red or green are not perceived Anomalous trichromatism – sensitivity to all three hues with deficiency or abnormality of one of the three primary pigments in the retinal cones Dentists should have their color vision evaluated. If any deficiency is detected, a dentist should seek assistance when selecting tooth shades.
- SHADE SELECTION Because shade selection is a subjective evaluation, consistency is difficult to achieve. Considerable variation among dentists exist and even dentists selecting a restoration for the same patient on multiple occasions may not be consistent in his/her final shade selection. Fortunately, an inexact shade may not break the balance of the smile. There can be subtle variations without much notice, if tooth contour and value are meticulously recreated. The overall shade must blend well with the contralateral and adjacent teeth. Shade selection can be improved by applying the principles of light and color in dental ceramic techniques.
- General Principles – regardless of which system is used, the principles for shade selection do not change. 1. Teeth to be matched should be cleaned of all debris and stains. If necessary ad prophy should precede tooth shade selection. 2. Brightly color lipstick/makeup should be removed and bright clothing draped. Protective gloves of bright colors should be swapped out for a neutral color. The operatory walls should not be brightly painted. 3. Patient should be viewed at eye level, so the most sensitive part of the retina will be used. 4. Shade comparisons should be made under different lighting conditions. Initial shade may be taken under a color corrected fluorescent light and then reevaluated or confirmed in natural daylight. (taking patient to an operatory window). 5. Shade comparisons should be made at the beginning of a patient’s visit. Teeth increase in value, particularly if a rubber dam is used. (DESSICATION) 6. Shade comparisons should be made quickly (REMEMBER COLOR FATIGE), with shade tabs placed just under the lip and adjacent to the teeth to be matched. This ensures that the background of both the shade tab and the tooth to be matched are the same – essential to shade matching.
- Commercial Shade Guides – The most convenient method for selecting shade is with a commercially available shade guide. Each shade tab has a metal backing coated with an opaque porcelain backing, color , neck color, body color and incisal color. Shade selection consists of selecting the tabs that looks most natural in the mouth. It is reproduced by using the techniques and materials recommended by the manufacturer to replicate the colors seen in the tab. Common shade guide are grouped into categories of the same hue (A, B, C, D). To increase the color possibilities In the past shade guide were created to meet the demand for denture teeth. More recently, shade guides have covered the color space occupied by natural teeth (VITA-PAN MASTER 3D).
- Commercial Shade Guides – The most convenient method for selecting shade is with a commercially available shade guide. Each shade tab has a metal backing coated with an opaque porcelain backing, color , neck color, body color and incisal color. Shade selection consists of selecting the tabs that looks most natural in the mouth. It is reproduced by using the techniques and materials recommended by the manufacturer to replicate the colors seen in the tab. Common shade guide are grouped into categories of the same hue (A, B, C, D). To increase the color possibilities In the past shade guide were created to meet the demand for denture teeth. More recently, shade guides have covered the color space occupied by natural teeth (VITA-PAN MASTER 3D).
- Common shade guide are grouped into categories of the same hue (A, B, C, D). To increase the color possibilities In the past shade guide were created to meet the demand for denture teeth. More recently, shade guides have covered the color space occupied by natural teeth (VITA-PAN MASTER 3D).
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- Hue Selection – In the popular Vita Lumin shade guide there are four hue categories. A1,A2, A3. A3.5, A4 are similar in hue, while the B shade are similar in hue. The same holds true for the C and D tabs. An operator may chose the nearest hue and then go on to select the appropriate chroma. If the intensity of chroma is low, it will be more difficult to select the proper hue. If this is the case, on should use the region of the tooth with the most intense chroma to select hue.
- Chroma Selection- Once hue is selected, chroma match is chosen. For example, if a B hue is selected as the best color variety, hue is selected from the four gradations within the B tabs: B1, B2, B3, and B4. Several comparison s are usually necessary to determine the most appropriate hue and corresponding chroma. Between comparisons, glancing and a light blue object will rest the operator’s eye and help avoid retinal fatigue. Hue consistency among shade guides has not been proven and remains on of the main difficulties in maintaining a consistent shade from the shade taking appointment to placement of the final restoration.
- Value Selection – Final value is selected by using a second shade guide whose samples are arranged in order of increasing lightness. The dentist can then determine if the value of the tooth is within the shade guide’s range (HIT BLEACH SHADES) Attention is then focused on the range of the shade guide that best represents the value of the tooth that relates the hue and chroma. Value is most easily determined by observing the guide and teeth to be matched at a distance, standing slightly away from the chair and squinting. ( COLOR VISION IN THE DARK) Squinting reduces the amount of light that reaches the retina. Therefore stimulation of the cones is reduced while rods become more sensitive to the increasingly achromatic conditions. The dentist should concentrate on which disappears first - the tooth of the shade tab. The one the fades first has the lower value.
- After value selection has been made it is more likely that the previously selected hue and chroma will not be found in the shade tab of the value selected. One must then consider whether to revise previously selected shade sample. (SHOW BLEACH SHADE GUIDES) If the value of the shade tab is lower (darker) than that of the natural teeth, a change is usually necessary (WHY?) Because increasing the value of a restoration is not possible by means of staining. An increase in opacity will result with inadequate end result for shade. If the value of the shade tab is higher than the natural teeth on must decide whether to decrease the value by selecting a new shade tab or if the difference can be bridged the addition of intrinsic (internal) or extrinsic (external) staining. (HOW LONG DOES EXTRINSIC STAINING LAST?) Value oriented shade guide B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4, C4,
- After value selection has been made it is more likely that the previously selected hue and chroma will not be found in the shade tab of the value selected. One must then consider whether to revise previously selected shade sample. (SHOW BLEACH SHADE GUIDES) If the value of the shade tab is lower (darker) than that of the natural teeth, a change is usually necessary (WHY?) Because increasing the value of a restoration is not possible by means of staining. An increase in opacity will result with inadequate end result for shade. If the value of the shade tab is higher than the natural teeth on must decide whether to decrease the value by selecting a new shade tab or if the difference can be bridged the addition of intrinsic (internal) or extrinsic (external) staining. (HOW LONG DOES EXTRINSIC STAINING LAST?) Value oriented shade guide B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4, C4,
- VITAPAN 3D-MASTER SHADE GUIDE Manufacturer claims this guide covers the entire tooth color space. Shade samples are grouped in 6 lightness levels, each of which has hue and chroma variations in evenly spaced steps of 4 CIELAB units of lightness. Dimension and 2 CIELAB units of hue and chroma.. Because the tabs are evenly spaces intermediate shades can bee predictably formulated by combining porcelain powders. Manufacturer recommends selection value, hue and chroma in that order. (MAY NEED TO ELABORATE)
- In the past shade guide were created to meet the demand for denture teeth. More recently, shade guides have covered the color space occupied by natural teeth (VITA-PAN MASTER 3D). Al shade samples belonging to one lightness level (1- 5) have the same value (see black and white photograph). Differences within one lightness level are only with regard to the chroma and hue. These are determined in stage 2 and 3. In step 1 we are only concerned with determining the correct value (lightness level), i.e. not a single shade sample tooth (1 out of 26), but a group of shades with the same value (1 out of 5). Al shade samples of an M-group feature the same hue and lightness. They only differ in the chroma. Tips for
- Intermediate values should be noted on the laboratory communication form
- Most shade guides cover a more limited range of colors than is found in the natural, and altered dentition. Some porcelain systems are available which extend this range. Using two shade guides is a practical way to extend the range of the traditional commercial shade guides. (EXAMPLE – BLEACH SHADES) Dentin Shade Guides (STUMP GUIDE) When using translucent all-ceramic system for a crown or veneer (FEDLSPATHIC PORCELAIN OR IPS EMPRESS), communicating the shade of the prepared dentin is very helpful to the laboratory. One system provides specifically colored die materials that match the dentin shade guide and enable the technician to better judge restoration esthetics. Custom Shade Guide Unfortunately, some teeth can be impossible to match to commercial shade guides. It can also be difficult to exactly match the final restoration with the shade tab. The extensive use of extrinsic surface staining has severe drawbacks, Stains increase surface reflections Prevent light from being transmitted through the porcelain One approach to this dilemma is to extend the concept of a commercial shade guide with the creation of a custom shade guide. An infinite number of samples can be made by using different combinations of porcelain powders in varying distributions. This is a very time consuming procedure and typically limited to specialty practices.
- Shade Distribution Chart (SHADE MAPPING) A shade distribution chart is a practical approach to accurate shade selection. IT is recommended even when a fairly good shade match is available from the custom shade guide. Method - The tooth is divided into 9 segments ( three regions: cervical, middle and incisal) Each region is matched independently, either to the corresponding area of a shade tab or to a single color porcelain chip (SAY WITH A CUSTOM SHADE GUIDE) Because only a single color is matched, intermediate shades can usually be estimated rather easily and duplicated by mixing porcelain powders. The junctions between these areas are normally distinct and can be communicated to the lab in the form of a diagram. The shade distribution and thickness of the enamel porcelain are particularly important. Individual characteristics are marked on such a sketch and will allow the ceramist to mimic details like hairline fractures, hypocalcifications, and proximal discolorations.
- SUMMARY An understanding of the science of color and color perception is crucial to the success in the ever expanding field of esthetic restorative dentistry. Although limitations in materials and techniques may make a perfect color match impossible, a harmonious color match impossible, a harmonious restoration can almost be achieved. Shade selection should be approached in a methodical and organized manner. This will enable the practitioner to make the best choice and communicate it accurately to the laboratory. Newly developed shade systems and instruments may help the practitioner achieve a reliable restoration match.
- An understanding of the science of color and color perception is crucial to the success in the ever expanding field of esthetic restorative dentistry. Although limitations in materials and techniques may make a perfect color match impossible, a harmonious color match impossible, a harmonious restoration can almost be achieved. Shade selection should be approached in a methodical and organized manner. This will enable the practitioner to make the best choice and communicate it accurately to the laboratory. Newly developed shade systems and instruments may help the practitioner achieve a reliable restoration match.