12 - Shade Selection

the eye

perception is the ability to detect and interpret light

• rods → black/white (brightness/value)

  • 120 million rods in retina

• cones → color (hue)

  • 6 million cones in retina

primary / secondary colors vs complementary colors

primary → red, yellow, blue; secondary → green, orange, purple

• complementary colors:

  • yellow + purple

  • red + green

  • blue + orange

• complement colors neutralize each other and form grey

  • complement of grey is pink

• additive mixing → applies to color produced by light and creates white

• subtractive mixing → combinations of all three primary colors creates black

light terminology

• hue — color

  • divided into red, yellow, green, blue, purple

• chroma — intensity, related to saturation

  • low chroma → “washed out”

  • high chroma → “saturated”

  • saturation changes

• value — lightness

  • value 0 → black; value 10 → white

  • low value = dark colors; high value = light colors

  • luminosity or lightness changes

• translucency — gradient between transparent and opaque

  • represented by change in value in teeth

  • high translucency → lower value

  • low translucency → high value

VITA Classical shade guide

• letter → hue

  • A = reddish-brown

  • B = reddish-yellow

  • C = grey

  • D = reddish-grey

• number → chroma

chroma and value relationship

chroma and value are inverse of each other

• A1 → low chroma, high value

• A4 → high chroma, low value

rearrangment

eyes are most sensitive to value

• B1 → highest value, lowest chroma

• C4 → lowest value, highest chroma

VITA 3D Master shade guide

• 1 → value determination (1-5)

  • 1 = lightest (high value); 5 = darkest (low value)

• 2 → chroma determination (1-3)

  • 1 = least chromatic; 3 = more chromatic

• 3 → hue determination

  • L = yellow; M = standard; R = red

variables affecting color perception

• light source — low to high temperature light

  • incandescent → 2856K; fluorescent → 4000K; color corrected → 5500K

• luminous intensity

  • 1 footcandle = 1 lumen/ft²

  • 200 footcandles ideal for dental

factors affecting illumination

• metamerism — phenomenon in which same object will vary in appearance under different lighting conditions

• contrast effects — value contrast, hue contrast

• viewer-associated effects — age/sex, color blindness, diet, emotions/psychological status, fatigue, medication, occular differences between L/R eyes

• effects of chemicals —

  • alcohol → lighter R/O/Y, darker B/G/P

  • caffeine → darker R/O/Y, lighter B/G/P

guidelines for shade selection

evaluate tooth prior to restorative

• tooth condition → take shade at beginning of appointment with plaque/stains removed

• selection time:

  • larger cases → take multiple times starting at diagnostic appointment

  • avoid eye fatigue → take shade at beginning of appointment

    • short glances of 5 seconds with periods of rest between prolonged staring

    • look at blue/grey between glances to neutralize

• patient position — seated upright

  • teeth are operator’s eye level

  • not supine

• selection distance → best to be 12-18 inches away from patient

  • 3-6 ft away for better evaluation of value

• lab communication → reference photographs of shade system suggested shades including full smile photos and photos of surrounding dentition

  • shots from different angles and lighting conditions

  • 18% grey card to eliminate color distractions

  • shade tab next to tooth if adjacent site is edentulous, otherwise above or below teeth

Omnichroma by Tokuyama

one shade for all, not including use of blocker

• uniformly sized 260nm spherical fillers

• size/shape of filler generates red-to-yellow color as ambient light passes through the composite, without need of added pigments or dyes

• red-to-yellow generated by spherical fillers combines with reflected color of patient’s surrounding dentition

• procedure:

  • prep and apply bevel to help eliminate margin visibility and aid in shade matching

  • apply blocker as lingual layer and light cure

  • apply omnichroma as secondary layer and light cure, finish, and polish

Universal Restorative Filtek by 3M

• nanosized uniformly sized 100nm fillers

• 19 Vita shades using 8 composite carpules

• utilize pink opaquer to “block” dark stain