understanding colour

The science and art of porcelain laminate veneers - Galip Gurel 1

Colour is a human need like fire and water. It is a raw material indispensable to life

- Fernand Leger (artist)


Understanding Colour

Presented by:Apurva Thampi

MDS 1st year


Contents • Introduction• Types of colour• Colour perception• Factors influencing colour perception• Dimensions of colour• Colour measurement• Contrast effect• Impact of materials and material science on colour• Shade selection• Systems for shade selection• Steps in shade selection• Advances in shade selection

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Introduction

• Clinician masters the art and science of colour treatment planning• Clinician has correctly communicated the shade selections to the

laboratory• Correct interpretation by the laboratory technician

For a successful esthetically pleasing anterior restoration

The science and art of porcelain laminate veneers - Galip Gurel


Terminologies • Translucency : It is the amount of incident light transmitted and

scattered by the object• Opacity: It is the opposite of translucency. It is the ability of a material

to block the passage of light

MATERIAL WITH HIGH OPACITY IS THE MATERIAL WITH LOW TRANSLUCENCY


• Opalescence : Optical property of the material in which there is a scattering of the shorter wavelength of the visible

spectrum.

• Iridescence : it is the rainbow like effect of different colours which changes according to the angle from which they are viewed or the incidence angle of the light source


• Fluorescence : Absorption of light by a material and the spontaneous emission of light in a longer wavelength.

• Luminiscence : Any process in which energy is emitted from a material at a different wavelength from that at which it is absorbed


• Phosphorescence: Light emitted by an atom or molecule persists after the excitation source is removed. It is temperature dependent

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Types of colourSpectral colours


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Types of colourPigment colours

Primary colour Secondary colour Complementary colour


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Colour perception• Absorption and reflection of various wavelengths of light• Psychophysical reality of colour


Colour Perception Psychophysiological reality

Physical Wavelength of light

Psychophysical Reception of wavelength of light by the eye

Psychological Interpretation of wavelength of light by the brain


Factors influencing colour perception

Illuminant

Observer Object

• Colour content• Colour rendering effect

• Reflection• Transmission

• Individual differences• Binocular differences• Age• Drugs• Fatigue


Color content:

Intensity of light emitted at each wavelength which varies according to

the type of illuminnat

Colour rendering:

It is the effect that the illuminnt has on the colour appearance under a

reference source

Colour rendering index:

Measue of the degree to which the illluminnat can impart colour of an

object compared with that acheieved by a reference source


Reflection:

A material gains it reflective colour by reflecting the part of the spectrum of light incident

upon it and absorbing the other parts of the spectrum

Transmission:

A translucent material gains its transmitted colour by the

spectrum it transmits. Wavelengths that are not transmitted are absorbed

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• Individual differences in colour

Number of Dentist Number of prosthesis Number of natural teeth total

Same shade selected by 3 dentists

18 teeth (14%) 10 teeth (14.3%) 28 teeth (14%)

Same shade selected by two dentists

72 teeth (59.2%) 30 teeth (42.9%) 102 teeth (51.5%)

Same shade selected by 0 dentists

38 teeth (26.7%) 30 teeth (42.9%) 68 teeth (34.3%)



• Chronological age and colour perception


• Fatigue and colour perception• Adverse visual perception – due to systemic/local/mental fatigue

• Drugs and colour perceptionDrug Effect

Alcohol/Morphine Long wavelength = brighterShort wavelength = darker

Caffeine Long wavelength = darkerShort wavelength - brighter


It is the phenomenon

where an object appears

different in different lighting

Tooth under corrected lighting

Tooth under fluorescent lighting

Tooth under incandescent lighting

METAMERISM


Dimensions of colour

HueValue

ChromaTranslucency


Munsells colour system

CIE colour system


MUNSELL’S colour system

Attribute of colour that

makes it appear blue, yellow or red

Lightness or darkness of

colour

Intensity of colour or

amount of hue saturation(runs from 0-

10)

HUE CHROMAVALUE


CIE COLOUR SYSTEM

• Developed by Commision International de l’Eclairage

• Based on the concept of TRICHROMACY

• Three primaries – tristimulus values

• 1931 – concept of standard observer was introduced


• Terminologies used in CIE colour system

• Imaginary primary colours – [X], [Y], [Z]Primaries

• In 1964 – a 2º viewing angle

• Characterise response of cone receptors denoted as x,y and z

• Perception of colour depends on, light, object, observer

Tristimulus values

• Decribes the other two dimensions of colour

Standard observer

Chromaticity

Color matching function

Chromaticity diagram


In CIE L*a*b

• L represents lightness or value

• ‘a’ is the measurement along red-green axis

• ‘b’ is the measurement along yellow -blue axis

Colour difference ΔE* = [(ΔL*)2 + (Δa*)2 + (Δb*)2]1/2

CIE L*a*b system


Colour measurementsSpectrophotometers

It measures the amount of light reflected at each wavelength

Double beam spectrophotometer

Compares responses with a reference standard

Colorimeters

It measure the amount of light reflected at selected colours are

based on the CIE tristimulus

Disadvantages:EDGE EFFECT


• Photography + spectrophotometry

Clinician holds 3-4 most matching shade guides

Photographed under 35mm camera under balanced light

Sent to dental laboratory

A computer program aids in selecting the closest match


Contrast effects

Optical illusions

Simultaneous contrast

Light/Dark contrast

Hue contrast Successive contrast


Optical illusions


Simultaneous contrast

Light/ Dark contrast Hue contrast


Light/Dark contrast


Hue contrast


Areal contrast

Visual colour perception affected by the size of the object


Spatial contrast

Spatial contrast is equated to brightness and size


Successive contrast• One colour is observed after the perception of another colour


Impact of materials and material science on colour

• McLean from England – innovators in dental ceramics• Improved characteristics – higher density• Increased density – better light transmission• Five categories of materials used in tooth coloured restorations• Sintered Aluminium oxide ceramics (Procera)• Lithium disilicate ceramics (IPS Empress 2 Eris)• Leucite reinforced ceramics (Empress I, Cerpress SL)• Feldspathic ceramics (Creation, Ceramco 3, Finesse)• Synthetic low fusing quartz glass ceramics (HeraCeram)


Sintered aluminium oxide• Full coverage – excellent marginal adaptation• High resistance to fracture (690 Mpa)• High opacity • Low translucency


• Developed in 1998 (IPS Empress 2)• Fracture toughness – 340 Mpa• Excellent marginal adaptation and superior marginal integrity• More opaque than conventional materials• Esthetically beneficial for masking discoloured teeth


Leucite reinforced ceramics

• Developed by Ivoclar in 1990• Fracture toughness – 180MPa• Can be fabricated with varying forms of opacity – high, medium and

translucent


Feldspathic ceramics• Weinstein in 1960 – metal ceramic restorations• Highly versatile• Can be produced using platinum foil or refractory die technique


Synthetic low-fusing quartz glass ceramics• Karino in 1982 – metal ceramic restoration• McLaren in 1998 – fired at 100ºC lower than feldspathic ceramic• Chu in 2001 – completely synthetic glass ceramic for metal ceramic

restorations• Causes less wear to the opposing natural tooth• Low opacity• High translucency


To be continued…

42

Welcome back!!!


Shade matching

Shade matching is a process of

converting shade perception into

shade communication


Importance of shade matching in dentistry

Natural appearance of the teeth

Proper communication with the dental laboratory

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Shade guide systems

Conventional shade guide systems

Technology based shade guide systems


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Conventional shade guide systems

• Used as visual guides• Require a neutral environment• Maintenance of quantity and quality of light• Absence of eye fatigue• Examples : Vitapan Classical, Ivoclar Chromascope, Vitapan ED

Shademaster



Vitapan Classical shade guide

• Based on hue• Categorised into groups

• A – Orange• B – Yellow• C – yellow/gray• D – Orange/gray

(brown)

Chromascope system

• Based on hue• Uses numbers instead of

letters• 100 – white• 200 – yellow• 300 – orange• 400 – gray• 500 - brown

Vitapan 3D shademaster

• Based on value• Different from

conventional systems• L – tendency

towards yellow hue• R – tendency

towards red hue• Developed by Miller and

further by McLaren

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Sequence for shade selection

Basic shade

Basic shade variations

Enamel shade, translucency and location

Special effects


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Armamentarium for shade selectionShade guide

Shade prescription form

Accesory shade guides

Instant photograph or slide

Daylight colour corrected fluorescent lighting

Neutral environment


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• Accessory armamentarium include:• Magnifying loops• Fluid resin stains• Custom shade tabs• Hand mirror


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Basic shade

• Match centre shade of natural tooth with closest appropriate tab• Hue should be assessed correctly• Tabs with same colour may appear similar• Doubts?? - compare two approximate matching tabs under the

natural tooth


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• A shade – young individuals• B shade – rarely encountered in natural dentition• C shade– middle aged / older individuals - subgroup of B ( similar hue

but lower value)• D shade– subgroup of A


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Basic shade variationsORANGE MODIFICATION

• Natural tooth colour - either orange or yellow hue• Porcelain shade guides are yellow hue not orange• Orange tonality – confined to cervical aspect of the tooth• Apply fluid colour resin – helps visualize quality or intensity of tone


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VARIATIONS BASED ON LOCATION

• Most frequent variation observed at the incisal third• Next frequent was uniform – monochromatic appearance• Thirdly, colour deviation from basic hue – cervical third• Cervical variations – cervical part of the shade tabs• Basic hue of the incisal third – mammelon colour• Mammelon – blunt and widen with aging – whitish orange hue


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Laboratory considerations• Basic hue – dentin build-up• Single shade or different hues alternated horizontally• Opal/vintage porcelain system – bright shades of high value –

preserve value through firing cycles• Mix 10% corresponding value plus porcelain with dentin shade



• Additional brightness – mix 20 – 30% of value plus porcelain• Shades with low value – value plus porcelain - separate opaque layer• Modified dentin shades – cervical dentin, mammelon dentin, orange

modified dentine, secondary brown/orange dentine

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Enamel shade and translucency• Quality and location of enamel overlay• Young individual – whiter teeth, middle aged – orange teeth

(translucent or almost transparent enamel)• Evaluation done in 2 ways• Patient holds the tab below the tooth while the clinicians stands back 2 yards• Patients holds the tab below the tooth and stands facing a mirror whielt the

clinicians makes the evaluation from behind

• Natural tooth has higher value – low chroma/high value dentine + opaque reflective dentine is used



Laboratory considerations• Young tooth – bright reflective enamel• Increased translucency – enamel mixed translucent or transparent

powder• Maintain same degree of opacity – overlaid over enamel


Need for improved systems for shade selection

Selection subject to variability

Shade selection protocol has several difficulties

Metamerism

Improved ceramics – changes in light reflection, absorption, refraction and dispersion


Technology based shade guide systems

1998 – Shofu SadeEye – Ex Chroma Meter

1999 – Vita Easy shade

2000 – Shade scan

2000 – ShadeRite Dental Vision system

2001 – SpectroShade System


Shofu ShadeEye – Ex Chroma meter

• First reported by Goldstien• Freestanding hand held probe – 3mm• Placed against tooth – activated• Flash of light through probe• Reflected light transmitted through centre of probe• Evenly distributed through colour filters• Docking unit via infrared signal• Database of porcelain samples

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VitaEasy Shade system• Hand held spectrophotometer• Connected to based by mono-coil fibre optic cable assembly• Contact probe tip – 5mm• 19 - 1mm diameter fibre optic bundles• Tooth illuminated by a halogen bulb• Spectrometers measure the internally scattered light• Spectral reflectance is measured in 25 nm bandwidth• Displays closest vita shade in classical/3D guide system


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ShadeScan system• Hand held probe + LCD screen• Fibre optic cable – halogen light – incident on tooth surface at 45

degrees• Light intensity continuously monitored• Image recorded on a flash card


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ShadeRite Dental Vision system• Hand held + LCD screen• Glare spot for focus and alignment• Focused on junction of gingival and middle thirds• Measurement through series of rotating filters• Shade and translucency mapping possible and downloaded


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SpectroShade system• Most complex• Most flexibility – data• Digital color imaging with spectrophotometric analysis• Large hand piece• 2 step process

• Postioned against green and white background• Light halogen tube on tooth – 45 degrees

• Image is seen on computer screen• Incident light monochromated• Spectral scanning – 10nm bandwidth



Clear match system• Purely software based• Requires a Windows PC and digital camera• Black white standards and shade tabs need to be included in each

photo• Detailed shade mapping is possible


Conventional V/S technology based systems - Advantages

Conventional • Cost effective• Easy to use• Visual tool• transportable

Technology based• More objective• Verification of restoration shade

in the lab• Not influenced by surrounding

environment• Increased producvtivity• Tooth dehydration not an issue


Conventional V/S technology based systems - Disadvantages

Conventional • Subjective• Inconsistency in manufacturing• Easily affected by surrounding

environment

Technology - based• Increased cost• Interpretation of the report is

technician dependent• Not easy transportable


Conclusion Understanding colour requires learning the language of colour. In order to overcome the challenges associated with shade selection in esthetic dentistry, it is essential to learn the art and science of colour. Close co-operation of the clinician and the laboratory technician is also required. Only then can an ultimately esthetic restoration be achieved

“A beautiful smile is no longer considered a luxury but rather as an essential component or current lifestyle”

- Stephen J Chu


Bibliography • Science and art of porcelain laminate veneers – Galip Gurel• Esthetics of anterior fixed prodthodontics – Gerard J. Chiche, Alain

Pinault• Advances in color matching,Jane D. Brewer, DDS, MSa,*, Alvin Wee,

BDS, MSb,c,Robert Seghi, DDS, MSb : Dent Clin N Am 48 (2004) 341–358• Clinical Steps to Predictable Color Management in Aesthetic

Restorative Dentistry Stephen J. Chu, DMD, MSD, CDT : Dent Clin N Am 51 (2007) 473–485


• Colour in relation to dentistry. Fundamentals of colour science S M Burkinshaw : British Dental Journal 196, 33 - 41 (2004) • Color matching in dentistry. Part I The three-dimensional nature of

color : Robert C. Sproull, D.D.S. : JPD vol 29(4) 416• Color matching in dentistry. Part II : Practical applications of the

organization of color : Robert C. Sproull, D.D.S. : JPD vol 29(5) 556• Color matching in dentistry. Part III : colour control : Robert C. Sproull,

D.D.S. : JPD vol 31(2) 146


THANK YOU AND

HAVE A PLEASANT DAY!!!

understanding colour

Health & Medicine