10-13 Color & Shade Selection

pure white light...

... consists of relatively equal quantities over visible light range

what is color render index and what does it mean to be at the highest index? (2)

1) a number from 1 - 100 given to a light source to indicate its relative equivalence to pure white light 2) closer the number is to 100 = resembles pure white in which different color lights have equal energy

value (2)

1. MOST important in dentistry 2. lightness dimension (achromatic)

what are the 8 steps to clinical shade selection?

1. appropriate timing for shade selection 2. ensure balanced and adequate lighting 3. prepare target and shade guide 4. ensure right position 5. compare/select shade guides 6. verification with 2nd person 7. verification with digital pictures with 3 closest shade guides in place 8. shade communication

step 6: verification with 2nd person

1. ask someone else for their opinion

step 2: ensure balanced and adequate lighting (2)

1. balanced lighting source with CRI > 90 2. control surrounding color

hue (3)

1. basic color 2. attribute color by means of which color is perceived to be red, yellow, green, blue, purple, etc 3. white, black and gray processes NO hue

step 5: compare/select shade guides (5)

1. begin by selecting color group (HUE) 2. canine cervical part usually has most clear hue 3. after hue, narrow selection for chroma and value 4. short duration glances (5 seconds) with periods of rest instead of prolonged staring or focus on gray card 5. squint eyes to increase sensitivity of value

what are the 3 aspects of Munsell's color system?

1. chroma 2. hue 3. value

what are the types of light sources? (3)

1. day light 2. incandescent source 3. fluorescent (high blue waves CRI 50-80)

what is Vita 3D master and how is it organized? (3)

1. design to provide systemic coverage of entire tooth color 2. values of lightest, chroma, hue have been positioned an equal distance from each other 3. prioritize value (rather than hue from VitaPan)

step 7: verification with digital pictures with 3 closest shade guides in place (3)

1. document the case 2. provides more information for the technician 3. digital professional cameras helpful with ring guide flash

what is metamerism and how does it influence dentition? (3)

1. metamerism: restoration match is one light but display different color in other light conditions 2. mimic layers of tooth employing materials with same optical properties 3. matching tooth shade under different light source to minimize metamerism (use multiple color sources to test for best shade)

what is opalescence and how does it influence dentition? (3)

1. optical property of material due to scattered light 2. gives material bluish appearance under reflecting light 3. enamel of natural teeth has opalescent effects = brighten tooth and give it optical depth and vitality

step 3: prepare target and shade guide (3)

1. plaque and stain removal 2. moisture retained in teeth: do NOT overdry tooth 3. moist shade tab to match intraoral moist condition

chroma (2)

1. purity of color (departure from white or gray) 2. strength or saturation of hue (color)

step 4: ensure right position (4)

1. seat UPRIGHT with teeth at EYE LEVEL of dentist 2. not in supine position 3. stay in CLOSE PROXIMITY to teeth 4. 3 - 6 feet from oral cavity: esp. important for determining value

step 1: appropriate timing for shade selection (2)

1. start color matching at diagnostic appointment and repeat in next appointments 2. select shade before beginning tooth preparation (eye fatigue, color changes due to moisture)

what are 3 factors that influence natural appearing teeth?

1. translucency 2. opalescence 3. metamerism

step 8: shade communication (3)

1. write shade number 2. draw diagram 3. submit picture

what is the visible light spectrum

380nm - 750nm

what source of shade selection and color matching have as a color temperature?

5500K

what distance should shade selection be made? what other factors should be accounted for? (2)

> 3 - 6 feet from oral cavity > eye level to dentist > upright position

what biological cell only detects value? what can be done to improve perception of value and why?

> rods; capable of responding to very low light levels > squinting helps reduce interference of color perception to more important value perception

why is value most important in dentistry?

> value differences are more easily detected at varying distances > differences in hue and chroma become more difficult to quantify as viewing distances increase

explain the Vitapan system

A: orange B: yellow C: yellow/gray D: orange/gray (brown) > from A --> D >> increase saturation (stronger color) >> decrease value (darker)

in terms of Vitapan, what is the brightest value? what is the darkest value?

B1= brightest value C4 = darkest value

what is the minimum color render index (CRI) required for accurate shade matching?

CRI > 90

what group of Vitapan do most people fall under?

Group A (orange) and Group D (orange/gray)

what is required to determine hue and chroma?

adequate amount of light

after image and fatigue

after light removed from retina, receptors continue for short time to be active & send signal to brain > after image: if comparing 2 colors (hue) and value of 2 objects for too long = eyes blend differences

light source (2)

an object that emits radiant energy to which human eye is sensitive > emission of a light source can be described by relative amount of energy emitted at each wavelength in visible spectrium

what is the best part of oral cavity to determine shade guide? and why?

cervical part of canine = clearest hue

what does blue sky light do as a spectral reflection ?

emits more blue

what does tungsten do as a spectral reflection ?

emits more red

what causes after image? how to resolve (2)?

fatigue of cone receptors 1. give eyes a break with neutral GRAY backgrounds 2. select color/shade before tooth preparation

what is important about color dictation of dentition? and why?

important to decide within seconds when holding shade guide close to tooth > two will soon begin to appear more alike

what is an ideal background for color matching

light gray

what is the % of males & females with color vision confusion (CVC)?

males: 8% females: 2%

spectrophotometers

measure amount of light energy reflecting from object at 1-25nm intervals along visible spectrum

colorimeters

measure values and filter light in red, green and blue areas of visible spectrum

what might interfere color dictation in a dental clinic?

surrounding colors: interferes with optimal light source

color temperature

temperature in degrees Kelvin (273+C) of a totally absorbing or black body (object) that produces colors as temperature changes > range is from dull red to yellow to white to blue