This document discusses the optical properties of dental materials. It begins by introducing the topic and defining key terms like hue, value, and chroma. It then describes how light interacts with objects through reflection, refraction, absorption, and transmission. These interactions determine the color appearance. The document outlines several color models including RGB, CMY, and discusses how color is perceived by the human visual system. It also discusses factors that affect color perception and different shade matching systems used in dentistry.

1. OPTICAL PROPERTIES OF
DENTAL MATERIALS
DR SHUBHAM PARMAR
1ST YEAR MDS
DEPARTMENT OF PROSTHODONTICS
28-07-2022
1

2. CONTENT
• Introduction
• Nature of light and human vision
• Interaction of emitted light with an object
• Optical triad
• Colour
• How is colour perceived
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3. • Colour in dentistry
• Factors affecting colour perception
• Shade matching and shade guide systems
• Material selection
• Layering concepts
• Review articles
• Conclusion
• References
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4. INTRODUCTION
• Dentistry is both an art and science
• Study of colour is an integral part of dentistry
• Success of a treatment is determined on the basis of functional and esthetic
results
• Therefore knowledge of the basic underlying scientific principles of optical
properties is essential
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5. NATURE OF LIGHT AND THE ROLE OF HUMAN VISION
• Light is electromagnetic radiation
• Eye is sensitive to wavelengths from approximately
400 nm - 700 nm
• The reflected light intensity and intensities of the
wavelengths in incident and reflected light determine
the appearance properties of hue, value, and chroma
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Anusavice KJ,Shen C, Rawls RH. Phillips’ Science Of Dental Materials. 12th e. Elsevier 2013 5

6. • The wavelengths that reach the eye are received by the
sensory cells on the retina called the rods and cones
• Rods perceive the brightness of the colour (intensity of the
light rays)
• The cones perceive the hue, ie, the colour.
• Human eye contains three different types of cones,
responsive to wavelengths approximating the colours red,
green, and blue,
• Variations of these wavelengths will stimulate each cone at
different intensities
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There are fewer cone cells
(aqua) in the retina than
there are rod cells (green)

7. INTERACTION OF EMITTED LIGHT WITH AN OBJECT
• Reflection
• Refraction
• Absorption
• Transmission
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These phenomenon determine the opacity, translucency or transparency of
an object

8. REFLECTION
• Return of light waves from a surface
• Reflection occurs when light rays strike a solid object,
and then bounces off of it
• wavelengths that are reflected compose the colour of an
object
• An object that reflects all light would be perceived as
white
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GPT -9, Chu SJ, Devigus A, Mieleszko A. Fundamentals of colour, shade matching and communication in esthetic dentistry. 3rd ed. Chicago:
Quintessence Publications; 2004 8

9. TYPES OF REFLECTION
Specular reflection
• A perfectly smooth surface gives a
mirror like finish
Diffuse reflection
• A flat, uneven surface gives a dull
appearance
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Anusavice KJ,Shen C, Rawls RH. Phillips’ Science Of Dental Materials. 12th e. Elsevier 2013
9

10. REFRACTION
• Deflection of light or energy waves from a straight
path that occurs when passing obliquely from one
medium into another in which its velocity is
different
• For perfect shade matching the refractive index of
the restoration should be same as that of tooth
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GPT - 9 10

11. ABSORPTION
• Uptake of energy by matter with which the radiation
interacts
• Object that absorbs all light would be perceived as
black
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12. TRANSMISSION
• Moving of the electromagnetic
waves through a materials
unobstructed
• A transparent material allows
transmission of light
• A opaque material blocks the
transmission of light
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GPT 9, Chu SJ, Devigus A, Mieleszko A. Fundamentals of colour, shade matching and communication in esthetic dentistry. 3rd ed. Chicago: Quintessence Publications; 2004 12

13. OPTICAL TRIAD
• Fluorescence - a process by which a material absorbs
radiant energy and emits it in the form of radiant
energy of a different wavelength band, all or most of
whose wavelengths exceed that of the absorbed energy
• Natural tooth structure absorbs light at wavelengths
between 300 – 400 nm and emits a blue-white colour
primarily in the 400- to 450-nm range
• Achieved in dental porcelains by adding rare earth
oxides as cerium oxide
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14. • Opalescence - Opalescence is the ability of a
translucent material to appear blue in reflected light and
red-orange in transmitted light
• Under direct illumination, the shorter wavelengths of
the visible spectrum (ie, blue wavelengths) are reflected
from the fine particles of natural enamel and dental
porcelain, giving the white tooth colour a bluish
appearance, while the longer wavelengths (ie, red-
orange wavelengths) are absorbed
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Sakaguchi R, Ferracane J, Powers J. Craig’s Restorative dental materials. 14th e: Elsevier 2019
Chu SJ, Devigus A, Mieleszko A. Fundamentals of colour, shade matching and communication in esthetic dentistry. 3rd ed. Chicago: Quintessence Publications; 2004 14

15. • Transluency - Translucency is a property of
substances that permits the passage of light but
disperses the light
• 4th dimension of colour
• Densitometer can be used to check for
translucency of shade tabs
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16. 28-07-2022 16
Transparent Translucent Opaque
Allows
maximum
transmission
of light
without any
distortion
Allows
transmission
of light in a
diffuse/control
led manner
Does not allow
transmission
of light
All of the light
is transmitted
Some amount
of light is
transmitted
No light is
transmitted

17. COLOUR
• A phenomenon of light or visual perception that
enables one to differentiate otherwise identical objects
• The quality of an object or substance with respect to
light reflected or transmitted by it
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GPT- 9 17

18. • In order for colour to exist there needs to be interaction between 3 elements
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Light
Object
Viewer
Colour

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20. HOW IS COLOUR PERCEIVED
• Light is emitted from a light source
• light reaches the eye
• perceived by receptor cells (ie, rods and cones) in the eye
• recognized by the brain as a specific colour
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21. RGB COLOUR MODEL
• Red, Green and blue form the primary colours
• Mixes of these 3 primary colours stimulate cones in
the eye
• RGB wavelengths when combined would give a
white light
• Called as additive primary colours
• Used in electronic media
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• When complementary
colours are added together,
they neutralize each other
and form gray
• complementary colours can
be combined to lower the
value of excessively bright
restorations

23. CMY COLOUR MODEL
• The primary colours in this colour system are those created by the absorption of one of
the RGB wavelengths and the reflection/transmission of the others
• Cyan - red is absorbed and green and blue are reflected/transmitted
• Magenta - green is absorbed and red and blue are reflected/ transmitted
• Yellow - blue is absorbed and red and green are reflected/transmitted
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24. • Referred to as the subtractive primary colour
• colour is created by subtracting certain numbers of RGB wavelength
• Presence of all three colours (CMY) would result in all wavelengths being
absorbed and none reflected/transmitted - colour black
• Subtractive primaries are used in colour printing
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25. COLOUR IN DENTISTRY
• Hue - often referred to as the basic colour or
dominant colour of the object
• It represents the dominant wavelength
• Chroma – degree of saturation of a colour or hue
• Always present with hue
• Value – relative lightness or darkness of a colour
• Most important factor in shade matching
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26. 28-07-2022 26
Measurement of colour
Munsell system CIELab system

27. MUNSELL COLOUR SYSTEM
• Albert H. Munsell noted that each colour has a logical
relationship to all other colours
• brought clarity to colour communication by establishing an
orderly system for accurately identifying every colour
• Made a “colour wheel” which include the dimensions of
hue, value, and chroma
• Translucency is not addressed in Munsell’s system
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28. CIELAB SYSTEM (CIE L* A* B*)
• Represents quantitative relationship of colours on three
axes
• L* value indicates lightness
• Represented on a vertical axis with values from 0
(black) to 100 (white)
• a* value indicates red-green component
• +a* (positive) and –a* (negative) indicate red and
green values respectively
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Chau B et al .Research Techniques Made Simple: Cutaneous colourimetry: A Reliable Technique for Objective Skin colour Measurement. Journal of Investigative Dermatology 2020;140:3-
12 28

29. • b* value indicates yellow and blue component
• +b* (positive) and –b* (negative) indicate yellow and blue values
respectively
• Center of the plane is neutral or achromatic
• Distance from the central axis represents the chroma (C*) or
saturation of the colour
• Angle on the chromaticity axes represents the hue (ho)
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Chau B et al .Research Techniques Made Simple: Cutaneous colourimetry: A Reliable Technique for Objective Skin colour Measurement. Journal of Investigative Dermatology 2020;140:3-
12 29

30. FACTORS AFFECTING COLOUR PERCEPTION
• Illumination and clinical lighting conditions
• Contrast effects and optical illusions
• Impact of viewer’s physical and mental state on colour perception
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31. ILLUMINATION
• Colour can be neither accurately perceived nor
correctly evaluated without proper illumination
• Quantity as well as quality of illumination is important
• Intensity of light is the most common regulator of
pupil diameter, which is a crucial factor in accurate
shade matching
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32. • Type of illuminant used can significantly impact the perception
of colour
• International commission on illumination categorized
illuminants based on their effect on colour perception
• Three standard illuminants, A, B, and C
• A - A tungsten light source with a correlated temperature of
about 2,856 K, producing a yellowish-red light
• Generally used to simulate incandescent viewing conditions (eg,
household light bulbs).
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33. • B - A tungsten light source coupled with a liquid filter
to simulate direct sunlight with a correlated temperature
of about 4,874 K
• Rarely used today.
• C - A tungsten light source coupled with a liquid filter
to simulate indirect sunlight with a correlated
temperature of about 6,774 K (Fig 3-7)
• Used in viewing booths because indirect sunlight is
considered a common viewing condition
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34. CLINICAL LIGHTNING CHALLENGES
• Lighting conflicts
• Dental operatory is not free from conflicts
in lighting
• colour-corrected lighting tubes that burn at
about 5,500 K should be installed
• colour temperature meter should be used
periodically to verify that a optimum
colour temperature is achieved in the
shade-matching area
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3rd ed. Chicago: Quintessence Publications; 2004 34
ceramic tooth viewed
under tungsten lighting
approximately 2,856 K
ceramic tooth viewed
under daylight
approximately 5,200 to
5,500 K
ceramic tooth viewed
under fluorescent light
approximately 4,000 K

35. • Metamerism - Phenomenon in which the colour of
an object under one type of light source appears to
change when illuminated by a different light source
• Bezold Brucke Effect - the apparent change in hue
that accompanies a change in luminance
• At low light levels, the rods in the retina of the
human eye are more dominant than the cones, and
colour perception is lost. As the brightness
becomes more intense, colour appears to change
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GPT 9 35

36. CONTRAST EFFECTS
• Visual phenomena that can considerably alter the perception of colour, as well
as the ability to evaluate colour in a clear, concise, and objective way
• These effects create optical illusions that are difficult to decipher
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37. • Simultaneous contrast - occurs when two colours are observed at the same
time. When perceiving more than one colour, the brain will attempt to achieve
a harmonic balance of the colours
• Perception of the colour therefore is affected by three factors:
• the surrounding relative lightness
• the surrounding colour
• the surrounding relative saturation
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38. • Value contrast - if the surrounding background is dark,
an object will appear light.
• However, if the same object is placed against a lighter
background, it is perceived as darker
• Perceived lightness can vary, even though the reflectivity
of the object is constant
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clinical significance - when dealing with excessively
inflamed gingival tissues. The dark value of the
inflamed gingiva will trick the eyes into perceiving the
tooth shade as being lighter than it actually is. As a
result, the fabricated restoration will appear too dark
once the tissues have healed

39. • Hue contrast - A colour will be perceived differently
when viewed in conjunction with various background or
adjacent colours with contrasting hues
• Dentists can precondition their eyes when taking shades by
first looking at a complementary colour, then looking at the
tooth shades
• majority of tooth shades fall into the orange hue family
• To view the orange tones with a more critical eye dentists
can precondition their eyes by looking at a light blue shade
immediately prior to the shade selection process
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40. • Chroma contrast - follows the same effect as the
value and the hue contrasts.
• An object will appear more intense against a
background low in chroma, and less intense against a
more chromatic background
• The closer the object is to the hue and chroma of the
surrounding background, the less visible it becomes
• During shade matching; using backgrounds of similar
hue and chroma to the teeth will make it more
difficult to distinguish the shade
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41. • Areal contrast - larger object will appear lighter than a smaller object of
the same colour
• lighter object will appear to be larger than a darker object of the same size
• If teeth or restorations appear too large, consider decreasing the value
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42. • Spatial contrast - An object closer to the observer will appear larger and lighter
• an object more recessed will appear to be smaller in size and darker
• frequently seen with rotated and overlapped teeth
• To compensate for spatial contrast, recessed teeth can be made lighter, and
protruding teeth can be made darker
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43. • Successive contrast - occurs when one colour is viewed following the
observation of another colour
• Visual perception remains after the eye has left the object
• Afterimages are categorized as positive (similar) or negative
(different)
• Positive afterimages have the same colour as the original perception
• Positive afterimages occur following a short visual interaction
• Negative afterimages have the opposite, or complementary, colour to
the original perception.
• Negative afterimages occur after long visual contact with an object
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44. VIEWER-ASSOCIATED EFFECTS
• Colour blindness
• Age
• Fatigue
• Binocular difference
• Nutrition
• Emotions
• Medications
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45. • Colour blindness - A person with colour blindness has
trouble seeing red, green, blue, or mixtures of these
colours
• Caused by a deficiency in or absence of one or more of
the three types of photosensitive pigments able to detect
red, green, and blue
• Ability to discriminate hue, saturation, and lightness is
reduced
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Chu SJ, Devigus A, Mieleszko A. Fundamentals of colour, shade matching and communication in esthetic dentistry. 3rd ed. Chicago: Quintessence Publications; 2004 45

46. • Age - aging is detrimental to colour-matching abilities
• Cornea and lens of the eye become yellowed with age, imparting a yellow-
brown bias
• Differentiation between white and yellow become increasingly difficult
• Begins at age 30, more noticeable after age 50, and has clinical significance
after 60 years of age
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47. • Fatigue - inability to accurately determine hue and chroma is most evident
during times of fatigue
• colour may be perceived as faded or blurry
• Nutrition - individual’s eating habits play an important role in the health of
the eye
• there is an association between macular degeneration and a large intake of
substances high in saturated fat
• eating fresh fruits and dark green, leafy vegetables may delay the severity of
macular degeneration
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48. • Emotions - It is known that emotion can affect pupillary diameter
• initial mood or mental state of the observer can be a critical factor in colour
determination.
• Medications - abuse of drugs, alcohol, and caffeine will affect colour
perception
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49. • Binocular difference - Binocular difference is the
perception difference between the right eye and the
left eye
• Placing shade tabs either above or below the tooth
to be matched will help to eliminate error caused by
binocular difference
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50. SHADE MATCHING & SHADE GUIDE SYSTEMS
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51. SHADE DISTRIBUTION CHART
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• Shade distribution charting is a practical
approach to accurate shade matching
• Tooth is divided into three regions:
cervical, middle, and incisal
• Each region is matched independently

52. SHADE MATCHING PROTOCOL
• Cover the patient with a neutral-coloured bib if the patient is wearing bright
clothing
• Tooth structure on which the restoration will be fabricated is cleaned and
evaluated
• Translucency and opacity of the patient’s natural teeth are determined
• Surface roughness, gloss, and local colour characteristics are noted.
• Shade selection is made at the beginning of the appointment, before the eyes
become too fatigued
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53. • Eyes should be aligned evenly with the patient’s teeth level, at a distance of 25
to 35 cm.
• Important not to view the comparison for more than 5 to 7 seconds at a time to
avoid fatiguing the cones of the retina
• A neutral gray card should be observed between trials
• Shade tabs should be held and aligned so that light reflects off the shade tab
and the natural teeth in a similar manner
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54. • Important to determine the shade when the teeth are most hydrated
• Value is analyzed first, followed by chroma, then hue
• Number of potentially matching tabs should be reduced to a few as quickly as
possible
• Shade selection can be verified using different lights, observation angles, and
distances
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55. VITA CLASSICAL
VITA 55
• Gold standard for shade matching in dentistry since it was introduced in 1956
• The tabs are arranged alphabetically according to hue:
• A = Reddish Brownish
• B = Reddish Yellowish
• C = Grayish
• D = Reddish Grayish
• The chroma and value for each hue are communicated by a system of numbers:
• 1 = Least chromatic, highest value
• 4 = Most chromatic, lowest value

56. 28-07-2022 56
Red-brown Red-yellow Grayish Red-Gray

57. VITA 3D-MASTER SHADE GUIDES
• Marked using a number-letter-number combination
representing value, hue, and chroma
• Group 0 = 3 tabs (bleached shades, the lightest)
• Group 1 = 2 tabs
• Group 2 = 7 tabs
• Group 3 = 7 tabs
• Group 4 = 7 tabs
• Group 5 = 3 tabs (the darkest)
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58. • In groups 2, 3, and 4, tabs with differing hues are
divided into 3 columns, which are communicated by
letters
• L (left) = Yellowish
• M (middle) = Middle hue
• R (right) = Reddish
• Within the groups, chroma is communicated by the
numbers (descending vertically) following the letter:
• 1 = Low chroma
• 2 = Medium chroma
• 3 = High chroma 28-07-2022 58

59. • Value determination - select the
value level that is closest to the
value of the tooth to be matched
• take the medium (M) shade sample
from the selected value group.
• Chroma determination - select the
colour sample from the M group
with the chroma level that is closest
to that of the tooth to be matched.
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60. • Hue determination - The clinician
checks whether the natural tooth
displays a more yellowish (L) or more
reddish (R) shade than the colour sample
of the M group selected in the second
step
• Now the best-matching shade sample
can be determined
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61. VITA LINEARGUIDE 3D-MASTER
• Has the same shade tabs as the Toothguide
• Shade matching is reduced to two steps
• Linearguide recommended for a “pick the best
match” approach
• Toothguide is recommended for a “dimension-
by-dimension” approach.
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62. • Value selection - A dark-gray holder,
containing only 6 middle tabs (0M2 to 5M2)
is used
• Chroma and hue selection - A final selection
based on chroma and hue is made from the
initial value group selected
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63. CHROMASCOP
• Developed by Ivoclar Vivadent, is another viable shade guide.
• Like the Vita Classical shade guide, the tabs are initially divided based on hue, and then
further intragroup selections are made.
• Chromascop differs in the use of a three-digit numbering system and the use of five
groups of four tabs
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64. • Group 100 = White
• Group 200 = Yellow
• Group 300 = Orange
• Group 400 = Gray
• Group 500 = Brown
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• Chroma and value are
communicated by a system of
numbers:
• 10 = Least chromatic, highest
value
• 40 = Most chromatic, lowest value

65. TECHNOLOGY-BASED SHADE SYSTEMS
• Technology-based systems have been developed and brought to market to
combat the subjectivity inherent in conventional methods of shade taking
• Several clinical studies have confirmed that computer-assisted shade analysis
is more accurate and more consistent compared with human shade assessment
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66. ADVANTAGES OF COMPUTER-AIDED SHADE DETERMINATION
• No influence of surroundings
• No influence of lighting
• Results are reproducible
• Easy documentation
• Reliable data transmission
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67. • SpectroShade System
• ShadeVision system
• EasyShade compact
• Shade mapping
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68. MATERIAL SELECTION
• colour-related properties of esthetic dental materials and human teeth can be
divided into three categories
• colour compatibility between dental material and teeth and among various
dental materials
• Includes colour compatibility of shade guides.
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69. • colour stability during reproduction or clinical placement and after placement
(aging and staining)
• Includes the effects of tooth whitening on teeth and dental materials.
• colour interactions includes colour shifting of esthetic restorative materials
because of blending (known as the chameleon effect), physical translucency,
and masking potential/layering.
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70. COLOUR COMPATIBILITY
• colour compatibility of dental materials with the same shade designation will
not necessarily be acceptable
• Coverage error (CE) corresponds to the mean colour difference (ΔE*) between
each evaluated natural tooth and the tab that matches best from a particular
shade guide
• smaller the CE, the better the shade guide
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71. • Vitapan Classical and Trubyte Bioform have the largest CEs, while Vitapan
3D-Master has the smallest CE
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72. COLOUR STABILITY
• Dental materials can undergo colour changes during fabrication
• In dental ceramics firing and glazing can provoke these changes
• Polymerization-related colour shifts of composite resins and glass and hybrid
ionomer materials can be very pronounced
• colour stability after placement is related to factors such as aging, staining, and
bleaching.
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73. COLOUR INTERACTIONS
• colour interactions between tooth and dental material or between different
dental materials, especially those related to layering are beneficial
• They make restorations more lifelike and can reduce colour difference between
the material and hard dental tissues
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74. LAYERING CONCEPTS
• Basic
• Classic
• Modern
• Trendy
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75. BASIC LAYERING CONCEPT:
• Includes one or two sets of shaded materials (different
opacities but the same chroma range) for the main
restoration volume, completed by a limited number of
incisal or transparent materials
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76. CLASSIC LAYERING CONCEPT
• Provides one basic set of shaded
materials for dentin replacement
(with approximately the same
opacity and chroma) and two
layers of enamel replacement
materials, including shaded
enamel and incisal materials
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77. MODERN LAYERING CONCEPT
• Uses two shaded materials (with different
opacity levels) for the replacement of dentin
as well as a series of enamel materials
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78. TRENDY LAYERING CONCEPT
• Most recent and the most promising concept
• Application of two basic dentin and enamel materials
that closely replicate the optical properties of natural
tissues
• Allows for effect materials to be placed between them
to create a spatial arrangement - identical to natural
tooth anatomy
• The use of intensive colours or effect materials helps
to replicate specific anatomical peculiarities and
improve final esthetic outcome.
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79. TYPES OF LAYERING MATERIALS
• Powder Opaque
• Paste Opaques
• Opaceous Dentine
• Dentine
• Dentin Modifiers
• Natural Enamels
• Opal Enamels
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• Soft wear Enamels
• Mamelons
• Margin Porcelains
• Final Margin Porcelains
• Add-On Porcelains
• Opaque Correctors
• Porcelain Stains

80. • Powder/ Paste Opaque - The Ceramco3 porcelain
system includes a paste opaque and/or a powder
opaque
• Has a uniform thickness of 0.2-0.3mm
• Helps to mask colour of underlying metal
• Helps to establish porcelain-metal bond
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81. • Opaceous Dentin - The Ceramco3 Opaceous Dentin
porcelains are the same hue as the Ceramco3 dentin shades,
but have approximately 10% more opacity
• Dentine Modifiers - The Ceramco3 Dentin Modifiers have
the same hue and opacity as the Ceramco3 dentin porcelain
but are approximately 70% higher in chroma
• Natural Enamels - The Ceramco3 Natural Enamels are non-
opalescent and can be used in thin or thick layers over the
dentin to duplicate the vitality of natural teeth
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82. • SoftWear Enamels - The Ceramco3 SoftWear Enamels
can be used in place of the Natural Enamels, to provide
low wear characteristics against opposing natural
dentition
• Mamelon porcelains - The mamelon porcelains can be
used in full concentration or diluted with the clear
enamel porcelain
• They are normally placed on the dentin porcelain lobes
prior to the enamel porcelain application
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83. • Add-On porcelain - The Ceramco3 Add-On porcelain is available in a
translucent enamel, dentin light, white, medium and dark, and tissue colored
pink, reddish-pink, salmon, and dark
• They fire at slightly lower temperatures than the regular dentin porcelain
• Opaque correctors - If during the contouring procedures the porcelain surface
is removed and the metal surface is exposed, this may be easily repaired by
using the opaque correction material.
• This correction opaque should be used for small minor repairs only.
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84. • Margin porcelain - the porcelain margin helps avoid metal
visibility, tissue discoloration and possible overbuilding at the
gingival
• Final margin porcelain - the final margin is designed to be a
final porcelain margin application that can be used to repair
small margin imperfections
• Porcelain stains - designed to closely approximate the average
range of tooth colors found in natural dentition and
commercially available shade guides.
• Designed to increase chroma in a given range, or subtly
characterize and intensify neck and interproximal areas
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85. REVIEW ARTICLES
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86. CLINICAL EFFECTS OF DEHYDRATION ON
TOOTH COLOUR: HOW MUCH AND HOW LONG?
• Aim - To evaluate effects of dehydration on tooth colour and determine
whether colour returns to baseline after 30 min or 24 h
• Materials and methods: 30 participants with intact maxillary central and
lateral incisors were recruited for the study
• colour measurements were performed with a spectrophotometer (SpectroShade
Micro) at baseline and at 10, 20, and 30 min of dehydration, as well as 30 min
and 24 h of rehydration
• CIEDE2000 colour parameters were used to calculate colour difference
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87. • Results
• After 30 min of dehydration
• all the teeth were above the PT (ΔE00 = 0.8)
• 85% of the teeth were above the AT (ΔE00 = 1.8)
• After 30 min of rehydration
• 78.3% of the tested teeth were above the PT
• 31.6% of the teeth were above the AT
• After 24 h of rehydration
• 99.2% of the teeth were below the AT
• 90% of the values were below the PT
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88. • Conclusion
• 10 min of dehydration can result in a clinically significant colour change of the teeth
• Degree of colour change increases by 30 min
• After 30 min of dehydration, a 30-min rehydration period is not sufficient for precise
colour assessment
• After a 24-h rehydration period, reliable colour assessment can be performed.
• Incisal part of the teeth exhibits more colour change after 30 min of dehydration
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89. THE EFFECT OF RESTORATION THICKNESS AND
RESIN CEMENT SHADE ON THE COLOUR AND
TRANSLUCENCY OF A HIGH-TRANSLUCENT
MONOLITHIC ZIRCONIA
• Aim - The purpose of this in vitro study was to examine the effect of varying
resin cement colours and material thicknesses on the colour and translucency
of a high-translucent monolithic zirconia
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Bayindir F, Koseoglu M. The effect of restoration thickness and resin cement shade on the colour and translucency of a high-translucent monolithic zirconia. J Prosth Dent. 2020; 123(1):149-
154 89

90. • Material and methods
• Katana High Translucent (Kuraray) was used as a monolithic zirconia material
• 80 disk specimens (10 mm in diameter) were made in 4 different thicknesses
of 0.5 mm, 1 mm, 1.5 mm, and 2 mm (n=20) per thickness)
• [CIE] L*, a*, b* values) before cementation was measured using a
spectrophotometer
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154 90

91. • Specimens within each thickness were further divided into 2 groups:
transparent (n=10) and opaque (n=10)
• A transparent or opaque self-etch adhesive resin cement was then applied to
each specimen
• After cementation, the colour was measured again
• The translucency parameter (TP) and ΔE were calculated and evaluated with
the colour measurements
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Bayindir F, Koseoglu M. The effect of restoration thickness and resin cement shade on the colour and translucency of a high-translucent monolithic zirconia. J Prosth Dent. 2020; 123(1):149-
154 91

92. • Results
• Statistically significant (P<.001) changes were found with the increasing thicknesses of
the high-translucency zirconia specimens
• TP, L*, and b* values decreased, whereas the a* values increased
• Statistically significant (P<.001) increase in L*, a*, and b* values and a significant
decrease in TP were found with cementation
• Lowest ΔE value (1.19 for 2 mm) was observed for monolithic zirconia-clear cement
• Highest ΔE value (8.05 for the 0.5 mm) was observed for the monolithic zirconia and
opaque cement combination.
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Bayindir F, Koseoglu M. The effect of restoration thickness and resin cement shade on the colour and translucency of a high-translucent monolithic zirconia. J Prosth Dent. 2020; 123(1):149-
154 92

93. • Conclusion
• The final colour and TP values of high-translucent monolithic zirconia specimens
were affected by material thickness and cement shade
• TP values significantly increased with the decrease in monolithic zirconia thickness
from 2.0 mm to 0.5 mm.
• Variation in the shade of the resin-luting cement and material thicknesses resulted in
colour changes that are perceptible and near or above clinical acceptability.
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94. EFFECTS OF DENTIN AND ENAMEL PORCELAIN
LAYER THICKNESS ON THE COLOUR OF VARIOUS
CERAMIC RESTORATIONS
• Aim - To investigate the effects of dentin and enamel porcelain layer thickness
on the colour of various ceramic restorations
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Xu B. Effects of dentin and enamel porcelain layer thickness on the colour of various ceramic restorations. J Esthet Restor Dent. 2021;1-8 94

95. • Materials and methods
• Eighty specimens (shade A2 and A3, n = 10 of casting ceramic (EM); alumina
• Ceramic (AL); zirconia ceramic (ZR); and porcelain-fused-metal (PFM) were
prepared
• colour distributions were measured at 4 places using a spectroradiometer
• Dentin/enamel porcelain (D/E) layer thicknesses of the 4 places were 0.8/0.2
mm, 0.6/0.4 mm, 0.4/0.6 mm, and 0.2/0.8 mm
• colour differences (ΔE00) between the specimens and the corresponding
colour shade tabs were calculated
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Xu B. Effects of dentin and enamel porcelain layer thickness on the colour of various ceramic restorations. J Esthet Restor Dent. 2021;1-8 95

96. • Results
• Minimum ΔE00 values were 1.31 (0.6/0.4 mm for EM), 1.41 (0.8/0.2 mm for
AL), and 1.92 (0.2/0.8 mm for ZR) for shade A2
• 0.93 (0.6/0.4 mm for EM), 0.89 (0.8/0.2 mm for AL), and 1.34 (0.8/0.2 mm for
ZR) for shade A3.
• Most of them were below at value (1.8)
• For AL and ZR (shade A2) and ZR (shade A3) D/E layer thicknesses of 0.8/0.2
mm and 0.6/0.4 mm had lower ΔE00
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Xu B. Effects of dentin and enamel porcelain layer thickness on the colour of various ceramic restorations. J Esthet Restor Dent. 2021;1-8 96

97. • Conclusion
• The dentin/enamel porcelain layer thickness that was most colour-matched to
the shade tab was 0.6/0.4 mm for EM, and 0.8/0.2 mm for shade A2 AL and
shade A3 ZR
• When dentin porcelain was thicker than enamel porcelain the colour of shade
A2 AL and ZR and shade A3 ZR was closer to the shade tab
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Xu B. Effects of dentin and enamel porcelain layer thickness on the colour of various ceramic restorations. J Esthet Restor Dent. 2021;1-8 97

98. CONCLUSION
• The study of colour and optical properties is an integral part of esthetic
dentistry
• Many factors influence our ability to achieve accurate shade-matching results,
including subjectivity, shade-matching tools, materials, methods, and
conditions
• It is necessary to understand these challenges and the basic mechanisms of
optics in order to achieve consistent esthetic results
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99. REFERENCES
• Anusavice KJ,Shen C, Rawls RH. Phillips’ Science Of Dental Materials. 12th
e. Elsevier 2013
• Chu SJ, Devigus A, Mieleszko A. Fundamentals of colour, shade matching and
communication in esthetic dentistry. 3rd ed. Chicago: Quintessence
Publications; 2004
• GPT 9
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100. • Sakaguchi R, Ferracane J, Powers J. Craig’s Restorative dental materials. 14th
e: Elsevier 2019
• Xu B. Effects of dentin and enamel porcelain layer thickness on the colour of
various ceramic restorations. J Esthet Restor Dent. 2021;1-8
• Hatırlı H, Karaarslan ES, Yas B, Kılıç E, Yaylacı A. Clinical effects of
dehydration on tooth colour: How much and how long? J Esthet Restor Dent.
2020; 1–7
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101. • Bayindir F, Koseoglu M. The effect of restoration thickness and resin cement
shade on the colour and translucency of a high-translucent monolithic zirconia.
J Prosth Dent. 2020; 123(1):149-154
• Chau B et al .Research Techniques Made Simple: Cutaneous colourimetry: A
Reliable Technique for Objective Skin colour Measurement. Journal of
Investigative Dermatology 2020;140:3-12
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