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68 Cards in this Set
- Front
- Back
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minimal refraction scatter absorption. transparent? |
transparent= high transmission. capable of transmitting light so efficiently that objects or images can be seen as if there were no intervening material. light coming through clear glass like camera filter or window is an example of transmission. |
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translucent? |
translucent materials scatter, refract, transmit and absorb light. some light gets through! |
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opaque |
opaque materials reflet, scatter, and absorb: however they do not transmit light. |
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white vs black vs orange? |
white- reflects all wavelengths of light. black-absorbs all wavelengths of light. no light is reflected. orange- absorbs all wavelengths of light except orange which is reflected. |
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electromagnetic spectrum |
radio, microwave, infrared, visible-roygbv, ultraviolet, xray, gamma rays. red 650-800. orange 590-640. yellow 550-580. green 490-530. blue 460-480. indigo 440-450. violet 390-430. |
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white light? |
dispersion of light through a prism breaks the light up into its component colored frequencies which are called wavelengths. |
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additive primaries? |
Used for transmitting light! Bringing in new color components adds to the final color. mixing the additive primaries red, green, and blue together will create white light and all colors in between. |
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subtractive primaries? |
used for reflective light! bringing in new color components subtracts from the final color. useful for paints, printers, or pigments. the primary colors used are cyan, magenta, and yellow (cmyk). K represents a separate black pigment because combining paints or pigments is expensive and typically results in a muddy form of black. |
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describing the phenomenon of color (3D color) |
munsell- early 1900s, specifies color in 3 dimensions:hue, value, and chroma. Has outlasted contemporary approaches and is still in wide use today. cielab 1976- Commission Internationale d Eclairage (CIE)- specifies color in 3 dimensions: relative lightness (L), dimension of red/green (A), dimension of yellow/blue (B). |
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hues of munsell color system? |
at different values for maximal chroma. munsell's color wheel in 3 dimensions |
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Value? |
the only dimension of color that may exist by itself. munsell value range = 0-10 0= black, 10=white. Natural human teeth have a value range 5.5-8.5. Objects of different hues/chroma can be identical value. Restorations too high or too low in value are easily detected and a common error in restorative dentistry. |
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which factor do you believe is the most important to successful shade selection? |
value |
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spectral curve? |
=fingerprint. % reflectance and recorded per 10nm. hue= location of the curves rise relative to wavelength. chroma= the purity of the curve or distinctness of shape. value= the amplitude or height of the curve's waves. |
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CIELAB? |
is based on discoveries in the mid 1960-s that somewhere between the optical nerve and brain, retinal color stimuli are translated into distinctions between light and dark red and green and blue and yellow. CIELAB indicates these values with three axes L, a, and b. |
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the optical triad: |
factors that affect color perception. translucency, fluorescence, opalescence. |
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translucence? |
sometimes referred to as the 4th dimension of tooth color. as important to dentistry as hue, value, chroma. result: even if all other factors are perfect, when the translucency for the restoration is off it will not appear to match the tooth! |
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fluorescence: definition? |
is the emission of visible light from a substance when it is irradiated by uv light (black light) which the eye cannot see. uv light- uv spectrum- below 380 nm. uv light cannot be seen by the human eye, but the bee can readily detect it! dentin> enamel porcelains. composite resins |
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opalescence |
blue red opal. natural opal glass. definition: a material that is capable of transmitting or dispersing amber, red and yellow light but reflects bluish light. cause: whenever small particles are distributed throughout a translucent matrix which are smaller than the wavelengths of incident light and which have a different RI than the matrix material. HA crystals act as tiny prisms which scatter the blue light. enamel acts like a filter. most of the short wave light is reflected-bluish. most of the longer wave light is transmitted- reddish. enamel shells. light source= from where the very white comes from. |
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color perception (the viewer) |
light source. color context. after images. metamerism. ocular fatigue. color blindness. drug side effects. rods and cones |
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cones |
the three types l-long, m-medium, s-short wavelengths. each type has light sensitive pigments that respond best to light of different wavelengths. |
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rods= vs cones= |
rods= value. cones= hue and chroma. rods>cones. value> hue, chroma. |
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some factors that influence color perception and confound accurate shade selection... |
temperature of the light source. |
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color context: simultaneous contrast |
two colors side by side, interact with one another and change our perception accordingly. Since we rarely see colors in isolation, simultaneous contrast affects our sense of the color that we see. red appears more brilliant against black background and somewhat duller against white background. in contrast with orange, the red appears lifeless, in contrast with blue-green, it exhibits brilliance. |
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simulataneous contrast: |
the small purple rectangle on the left appears to have a red purple tinge when compared to the small purple rectangle on the right. They are both the same. |
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value contrast effect: |
a ceramic tooth appears lighter against a dark background than it does against a lighter background. |
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hue contrast effect: |
when viewed against different background colors, the teeth appear to take on the hue of background's complimentary color |
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chroma contrast effect: |
note that the tooth is less visible against an orange background similar in chroma. the tooth is even less visible against a yellow background that very closely approximates its chroma. |
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spatial contrast: |
an object closer to the observer will appear larger and lighter, whereas an object more recessed will appear to be smaller in size and darker. teeth that are rotated/recessed relative to adjacent teeth appear darker. |
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contrast effects: |
value= a darker environment will tend to make a tooth appear lighter and vice versa. hue= the complimentary color of the surrounding background or environment is more apparent in the tooth. Chroma= a less chromatic background will make the tooth color appear more intense and vice versa. Also, a background with a hue and chroma similar to the tooth will make it more difficult to discern the tooth shade. Areal= larger teeth tend to appear lighter and lighter teeth appear larger in size. Smaller teeth appear darker and darker teeth appear smaller. Spatial= recessed teeth appear darker. Darker teeth appear more recessed. Protrusive teeth appear lighter and lighter teeth appear more protrusive. Successive= when one color is viewed immediately following another an afterimage often will appear and affects perception of the second color. |
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color blindness |
defect in color vision: 8%m, 0.5% f. the gene that allows humans to perceive red on X, may exchange genetic material with an adjacent gene responsible for green-> variant red color gene. x variant= enhanced red vision. x var x var= color defect y,x variant=color defect |
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achromatism? dichromatism? anomalous trichromatism? |
achromatism= complete lack of sensitivity. dichromatism= sensitivity to two primary hues. anomalous trichromatism- sensitivity to all three hues, with an abnormality in retinal cones affecting one of primary pigments. |
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Farnsworth- Munsell 100 Hue Color Vision Test |
one of the most famous color vision tests available. belongs to the group of hue discrimination (arrangement tests). 88 plates arranged in 4 batches of 22 differently colored plates. People with normal color vision make few errors. Lower score indicates more perfect color vision. |
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f-m 100 hue test results? |
because the % of color deficiency is lower in women, traditional opinion has it that women are better at taking dental shades. However, the shade matching abilities for color normal males and females are equal. Therefore it is the results of the color vision testing and not gender that should be the criterion for who selects the shade in a dental practice. |
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drug SE |
antiarrythmia drugs, such as amiodarone and digoxin are used to tx abnormal heart rhythms and may cause visual disturbances such as blurred vision, yellow vision or blue-green halos around objects. phenothiazine drugs, like chloropromazine and thioridazine, are used to tx schizophrenia and other psychological conditions. These drugs may lead to blurred vision, changes in color vision and difficulty seeing at night. |
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drug SE |
viagra, cialis, levitra- less serious SE such as temporary changes in color vision-such as trouble telling the difference between blue/green or having blue colors with a tinge to them- eyes being more sensitive to light or blurred vision. commercial airline pilots refrain from viagra 12 hrs and cialis 36hr prior to flight . oral contraceptives- r/g, b/y defects. blue tinge, studies show long time use of oral contraceptives will cause a decrease in color perception of blues and yellows. |
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enamel rods contribute |
LITTLE to overall color of tooth. dentin is largely opaque and provides most of the color. |
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restorative materials |
porcelain and comp process light differently from each other and than vital tooth structure. the color is typically provided by metallic oxides which act as opacifiers. |
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guidelines for proper shade selection: |
proper distance- operator 10-13 inc from dentition. proper environment- shade should be selected in neutral environment as possible, cover bright clothing, remove lipstick and bright cosmetics. keep colors at low saturation level- munsell chroma 4 or less. walls and cabinets should be glossy enough to maintain brightness levels without causing glare. ideal colors are white and off white. |
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blue fatigue |
diminishes ones ability to distinguish between various shades of blue. thought to enhance ones ability to distinguish shades of yellow (teeth). an operator can enhance this effect by staring at a blue card or patient napkin between shade comparisons. |
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best light source for shade selection? |
d55- daylight in dc in june from noon to 1, with slight overcast sky, which yields a color temp of 5,500K and has color rendering index (CRI) of 90 or higher. do not select shade under pure daylight- varies in temp during the day and with weather conditions. use a color corrected daylight fluorescent light- contains balances amount of spectrum, spectral output 4200k or higher, 150 to 200 foot candles illumination ideal. do not select shade using your operative light.- tungsten bulbs produce a light that is too high in the yellow orange part of the spectrum. except: color corrected LED chair lights are now becoming readily available. however watch that their brightness does not exceed 300 foot candles or you risk washing out the color. |
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rite lite shade matching guide |
uses led to deliver simulated north sky daylight with a standardized color temp of 5500K into office. |
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3 modes of light for shade taking to simulate varying lighting conditions found in indoor and outdoor environments: |
1. color corrected light (daylight) 5500k. 2. incandescent (room light) 3200K. 3. ambient light, a combination of room light and daylight 3900K |
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challenges to proper shade selection? |
metamerism- situation where two color samples appear to match under one condition but not under the other-the match is said to be conditional. two samples that conditionally match are said to be a metameric pair. if two samples have identical reflectance spectra, they cannot be metameric-they are unconditional. |
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factors in determining a proper shade match? |
characterizations. incisal shape. surface texture- if the surface texture of the reference shade guide and the tooth to be matched are different, you should apply water to both to normalize. dessication of tooth- tooth dessicates rapidly with a significant change in value and chroma. they do not fully rehydrate for 24h. take shade before cotton roll iso or RDI and do not dry. |
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most current manual shade systems are? |
empirically derived. the Vitapan Classical Shade Guide-industry standard since 1956. many competitive shade systems. no standardized method used for measuring color. Vitapan- 16 tabs, 4 color groups: hue, a red brown, b red yel, c, gray, d red gray. higher numbers mean higher chroma. shade ordering :a1,2,3,3.5,4 b1-4, c1-4, d2-4. value ordering: b1,a1,b2,d2,a2,c1,c2,d4,a3,d3,b3,a3.5,b4,c3,a4,c4 16 tabs cover 6% human teeth- color space! |
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shade taking: 1? |
1. select value first- arrange using value ordering. incisal edge faces away from tab holder. wet teeth and shade guide. pass shade guide in front of teeth select 3-4 that best match the range of brightness for the reference tooth. |
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shade taking: 2? |
2. select the best hue use 2nd shade guide. cut off necks of shade tabs because they are higher in chroma and lower in value. gingival area of tab facing away from tab holder. match middle 1/3 of shade tab to middle 1/3 of tooth. |
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selecting hue? |
try to concentrate on most dominant hue. CI and LI have same hue but different values. Hue is indicated by ABC or D. |
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shade taking: 3? |
3. select chroma |
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Chromoscop Guide: |
20 shade tabs-additional bleach group. 5 hue groups- 100 white, 200 yellow, 300 light brown, 400 gray, 500 dark brown. higher number= higher chroma. IPS. Trubyte- 24 shade tabs, 4 hue groups-r/b, y,g,red/gray. Style A= color ordered lightest to darkest Style B= color ordered by hue group then lightest to darkest. Porcelain and Plastic denture teeth, acrylic provisional material. |
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Vitapan 3d master shade guide: |
1998 est. 26 tabs, 6 main groups based on value- subdiv into chroma, hue. 1 additional bleach group, M standard hue, L=yellow, R=red hues. Only dentin shading- no cerv, incisal. Many commercial porcelain systems- 3d direct comp. The only shade guide that is designed scientifically and systematically. value is found in 3 group more than 50% hue in M group more than 50%, hue shift to red or yellow not mandatory. |
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gingival shade guides and stump guides |
not a well developed standard |
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shade selection with 3d master guide: |
1. determine value hold shade at arms length, select value group, start selection with darkest to lightest, squint. 2. determine chroma- take out Middle hue (M), fan 3 tabs out in vertical position, select one chroma. 3. determine hue 4. verify final shade |
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selection of correct value: |
removal or all L and R tabs from guide can often assist in selection of right value group. |
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problems with shade guides: |
Porcelains/comp do not always match the shade guides that they are being compared to. Shade variations occur btw different die lots of porcelain from the same manufacturer. Shade guide tabs are 4-5mm thick compared to the thin 1.5mm piece of porcelain used for the restoration. Shade guides are not always made with fluorescent porcelain, which causes inconsistencies in color matching. it is difficult to predict the final shade after the layering of opaque, dentin and enamel. guide tabs lack a metal backing when using porcelain-fused to metal restorations. shade tabs are condensed differently than porcelain used for final restorations. |
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limitations of manual shade systems: |
color gaps- shades are not uniformly positioned throughout tooth color space. not all guides well designed for value ordering. inaccurate interpolation- intervals between shades do not yield a single discernable intermediate shade. not systematic- shades are not schematically organized to reflect all 3 color dimensions. |
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current shade systems in the tooth color space: |
classical, 3d master, chromascop. |
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value based 3d- master color system in tooth color space |
26 shades which accurately cover known tooth colors, uniformly positioned throughout tooth color space. systematically organized for easy, accurate shade taking. addresses need for additional shades with high and low values. |
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shade assist software vs. digital shade color/shade analyzers |
shade assist software: clearmatch, shadewave. digital shade color/ shade analyzers: easy shade, shadepilot and shadestar, spectroshade. |
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clearmatch features: |
software based system for communication and shade analysis. uses any digital camera. patented technology normalizes color images. no need for proprietary hardware. contains all major shade guide systems and allows custom guides to be added. process: acquire pt images, import images, point and click to normalize images, click to map value and shade, click once to send info to lab, build and seat prothesis with fewer remakes resulting from incorrect shade/value |
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digital shade analyzers: |
RGB devices-fair. colorimeters-better. spectrophotometers-best-easy shade compact, shade pilot, spectroshade |
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digital shade matching: |
objective. free from color contrast effects. independent of ambient lighting conditions. reproducible. can be programmed to reference familiar shade guides and popular restorative materials. clinician and lab tech can more accurately communicate and verify accurate shade match. |
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monochrome images focus on > |
the importance of value |
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verify value --if its good then? |
problem is hue, chroma or opacity |
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opacities of comp? |
translucent enamel. semi translucent enamel. opacious dentin. |
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translucency too high-then cant? |
cant properly judge the value, hue, or chroma. |
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two layer technique |
body or dentin shade. enamel shade |
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multilayer technique |
dentin shade. enamel shade. translucent enamel shade microfill/hybrid. |
