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