The Science of Color, Light and Shade Selection

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 Exist Without Light Color Does Not Exist A yellow object absorbs all lightwaves of all colors, but reflects yellow

5. Color Influenced by three main factors • Physical properties of the object • Assessment of the observer • 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. Pure White Light • 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 + + + + + + = 380nm 750nm

8. Quality of Light / 3 Types • Incandescent Light • Fluorescent Light • 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

19. Complimentary Colors

20. Three Attributes of Color • Hue • Chroma • Value

21. Hue • Variety of color (red, green, yellow, etc.) • Determined by wavelength of observed light within the VLS • Reflected wavelength determines hue

22. Chroma The intensity or saturation of a hue Low Chroma High 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. Value Objects of different chroma can be identical value Chroma - Equal in Chroma / Variation in Value - Variation in Chroma / Equal in Value

26. Objects of different chroma / hue can be identical value

27. Perception of Color

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. Single Light Source Light Source #1 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 • Teeth to be matched must be clean • Remove bright colors from field of view - makeup / tinted eye glasses - bright gloves - neutral operatory walls • View patient at eye level • Evaluate shade under multiple light sources • Make shade comparisons at beginning of appointment • 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. A B C D Vita Classic Shade Guide • 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

40. Grey Red/Yellow Red/Yellow Yellow Grey

41. Vita Classic Shade Guide Manufacturer recommended sequence for shade matching • Hue Selection • Chroma Selection • Value Selection • 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

47. VITAPAN 3D-MASTER Shade Guide

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