color science, esthetics, & shade selection-4th year lecture
TRANSCRIPT
Color Science & Shade Selection
Wael Al-Omari
Light & Color
Without light, color does not exist Factors influence an object’s color:1. Physical properties of the object.2. The nature of incident light.3. Relationship to the colored objects4. Subjective assessment of the
observer
Light & Color Light is a visible
electromagnetic energy
Reflected light wavelength determines the particular color of an object
Description of Light: 380-750 nm
Light & Color Sources of light in dental
office:(1) Incandescent: yellow light waves(2) Fluorescent: blue waves
(3) Northern daylight. Ideal light, Northern Ideal light, Northern
daylight around the noon daylight around the noon hour on a bright dayhour on a bright day
Never select shades in direct sun light
Light & Color
Color Rendering Index (CRI) 100 Color Temperature: color of
standard black body when heated Use a color corrected fluorescent
light (CRI > 90)
Description of Color Three color attributes:(1) Hue: Particular variety of a color(2) Chroma: Saturation or intensity of a hue(3) Value: Relative lightness and darkness of
a color or brightness of an object
Munsell Color Order System
Hue: 10 gradations, most natural teeth in a range between yellow and yellow-red.
O’Brien et al (1997): average Hue for anteriors; ging. 1/3 = 1.2Y middle 1/3 = 1.3 Y, incisal 1/3 = 1.4Y
Chroma: Natural teeth 0.5 to 4.
Value: Value from 5.5 to8.5
CIELAB Color System
CIELAB: L*, a* & b* L* = Value
Color-Measuring Instruments Spectrophotomete
r and colorimeter
Perception of Color Retina (rods+cones) Optical
Centre in the brain Scotopic Vision: under low
lightning conditions. Rods used. Brightness interpretation
Photopic Vision: under higher lighting. Cones used. Color vision
Central field of vision is more color perceptive.
Perception of Color Color Adaptation: Color vision decreases as
an object is observed, and intensity of complementary color appears greater. Pale gray-blue object should therefore be glanced during shade matching.
Deceptive Color Perception: influenced by surrounding colors, like brightly colored clothing and lipstick
Metamerism: Two matching colors differ by changing the light source. Select shade and confirm it under different lighting conditions.
Perception of Color Fluorescence: Reemitting absorbed
radiant energy in visible color of lower frequency. In practice, not significant in color matching of dental restorations
Opalescence: Light scattering effect, Bluish-white scattering similar to opal-gem. Incisal edges
Color Blindness: Achromatism, Dichromatism, or Trichromatism. Affect males more than females
Esthetics Defined as the study of beauty. Anatomy of a smile1. Influenced by culture2. Extensive smile showing anteriors and
teeth posterior to first molar is perceived as attractive and youthful
3. Incisal edges parallel to lower lip
Esthetics Proportion: Based on what is found in nature. Golden proportion: Ration between
succeeding terms converge on approximately 1.618 or 1.
Golden Ration (1.618): A Wonder of God's Creation
Pleasing proportion: central incisors width to length
ration of 75% to 80%
Esthetics Balance: Balance arrangement
implies stability and permanence. Symmetry around the midline
Midline: Coincidence between facial and dental midline.
Minimal lack of coincidence between maxillary midline and central incisor midline is aesthetically acceptable
Shade Selection
Shade matching is subjective, thus consistency is difficult to achieve
Restoration should blend with the teeth to produce a lifelike appearance.
Shade Selection Principles:1. View the patient
at the eyelevel.2. Shade comparison
under different light levels
3. Teeth to be matched should be clean
4. Compare at the beginning of the visit
5. Operatory not bright, bright colors & lipstick removed
6. Quick comparison, with samples under lip level
7. Rest eyes on gray-blue surface
8. Select higher value (lighter) if in doubt
9. Select surface luster
Shade SelectionCommercial Shade Guide: Pickup the shade tap most natural Chose the nearest hue first, then chroma and value Region of highest chroma should be used Value is best chosen with the aid of another commercial shade guide, hold it away, squinting the eyes to reduce light effect on the Retinal cones.
Vita Lumina: A=reddish brown, B=reddish yellow, C=grey, D=reddish grey
Selecting value using classical
guide
Selecting chroma using classical
guide
Shade Selection
Vitapan 3D Master Shade Guide: Shade taps are arranged in 6 groups according to their value Recommended to Chose the lightness level first, then chroma and finally the hue
Shade Selection
Extended Range Shade Guides: Dentin Shade Guide: Custom Shade Guide:
Shade Selection
Shade Distribution Chart: