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GOOD AFTERNOON

The Science of Color and Shade Selection

Presented by

Gaurav TripathiP.G. Student

Dept. of Prosthodontics

The theory or philosophy of taste; the science of the beautiful in nature and art; especially that which treats of the expression and embodiment of beauty by art.[Websters].

Esthetics

EstheticsIt is not absolute but extremely subjective

Earlier it was thought as

Hegel’s Statement

“Beauty is substance of imagination and feeling, cannot be an exact

sign”

Outline• Light and Color

– Description of Light• Quality of light

– Description of Color• Munsell Color System• Hue, Chroma, Value

– Factors influencing perception • The eye (rods and cones)

• Shade selection– Techniques for determining shade / Shade guides– Shade mapping

Visible electromagnetic energy whose wavelength is measured in nanometers (nm)

Without Light Color Does Not ExistWithout Light Color Does Not Exist

We are going to understand the basic relationship of light ,color and visual perception

•The eye is only sensitive to the visible portion of the spectrum (380 – 750nm)•Different wavelengths constitute the different colors we perceive

Main sources of light

The Sun

The Fire

Principle sources of artificial light

Incandescentlight

FlorescentTube

PhotographicFlash

• When passed through a prism we see component colors of white light

• Shorter wavelengths band more than longer wavelengths

Pure White Light

380nm

750nm

Quality of Light / 3 Types

1. Incandescent Light

2. Fluorescent Light

3. Natural Daylight

Most dental offices are outfitted with incandescent and fluorescent lights

1. Incandescent Light• Emits high concentration of yellow waves• Not suitable for shade matching

2. Fluorescent Light• Emits high concentration of blue waves• Not suitable for shade matching

3. Natural Daylight• Northern daylight considered the best • Closest to emitting the full spectrum of

white light• Used as the standard by which to judge

other light sources

Color Rendering Index• CRI = (0-100)

• Shade selection is done with a light having more than 90 CRI

• Northern daylight (hence CRI) affected by– Time of day– Cloud cover– Humidity– Pollution

CRI and Time of DayMorning and evening Mid-day

Color is the subjective impression formed in a specific portion of

brain owing to the specialization of certain cells-rods and cones

distributed in retina of the eye

ColorInfluenced by three main factors

1. Physical properties of the object

2. Assessment of the observer

3. Nature of incident light

Relationship to other colored objects

A surface of an object appears red for an example when it reflects long waves but absorb light or the complementary color blue

“Light that enters the human eye from that object”

Dimensions of Color

• Numerous scientist came with the approach to tell about the part of the color but it was Munsell’s(1961) system which best serves to rank the color coz it view differences between neighboring color at regular interval

• Hue, value, chroma are very well presented in Munsell's’ color scale

• This system was intended for evaluation of opaque surface and therefore not fully applicable for teeth whose surface are translucent

• Therefore 4th dimension that of translucency has to be added in the system

• Hence 4 dimension of color –hue, value, chroma and translucency – should be quantified as clearly and accurately as possible in defining the natural tooth or ceramic color

Translucency • The degree to which light is transmitted

rather than absorbed or reflected • Highest translucency is transparent • While lowest is opacity

Perception of Color

Color Perception• Rods

– Scotopic (gray scale) vision, interpret brightness

• Cones

– Highest concentration on central retina (macula), most color perceptive area of eye

Color Adaptation• Color vision decreases rapidly as object is

observed– Leads to retinal Fatigue

• Viewing a pale blue or gray surface between shade matching will restore color vision

MetamerismTwo colors that appear to be a match under a

given lighting condition but have different spectral reflectance = metamers, the

phenomenon is metamerism.

1st Light source 2nd Light source 3rd Light source

Shade selection

Shade Selection

• Timing• Lighting• Patient preparation• Shade guides

Conventional

Custom made

Technology based shade guide systems

Principles of Shade Selection

1. Teeth to be matched must be clean2. Remove bright colors from field of view

- makeup / tinted eye glasses- bright gloves- neutral operatory walls

3. View patient at eye level

Principles of Shade Selection ……

4. Evaluate shade under multiple light sources

5. Make shade comparisons at beginning of

appointment

6. Shade comparisons should be made quickly to

avoid eye fatigue

Commercial Shade Guides• Most common method of making shade

selections• Guides consist of shade tabs

– Metal backing– Opaque porcelain– Neck, body, and incisal color

• Select tab with the most natural intraoral appearance

Commercial Shade Guides

• Vita Classic

• Vitapan 3D –Master

• Extended Range Shade Guides

Vita Classic Shade Guide

A B C D

• Very popular shade guide

• A3 = hue of red-yellow, chroma of 3

Red/Yellow Yellow GreyGrey

Red/Yellow

A B C D

Vita Classic – Step 1 (Hue Selection)

Operator should select hue closest to that of natural tooth

The intensity or saturation of a hue

Low Chroma High Chroma

Chroma

Vita Classic – Step 2 (Chroma Selection)

• Hue selection has been made (B)• Chroma is selected from gradations within the B

tabs-B1, B2, B3, B4

Several comparisons should be madeAvoid retinal fatigue

Rest eyes between comparisons (blue-gray)

Value

• The relative darkness or lightness of a color, or brightness of an object

Low Value High Value

Vita Classic – Step 3 (Value Selection)

• Value oriented shade guide– B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4, C4,

Value best determined by squinting with comparisons made at arms length

Decreases light Diminishes cone sensitivity, increases rod sensitivity

- Equal in Chroma / Variation in Value- Variation in Chroma / Equal in Value

Chr

oma

Value

Vita Classic – Step 4 (Final Check / Revision)

• Potential Problem–tabs selected for hue and

chroma may not coincide with shade tab selected for value

VITAPAN 3D-MASTER Shade Guide

1 23 4

5

Vita-3D – Step 1• Determine the lightness level (value)

• Start with darkest group moving right to left

• Select Value group 1, 2, 3, 4, or 5

Vita-3D – Step 2• Select the chroma

• From your selected Value group, remove the middle tab (M) and spread the samples out like a fan

• Select one of the three shade samples to determine chroma

Vita-3D – Step 3• Determine the hue

• Check whether the natural tooth is more yellowish or more reddish than the shade sample selected

Vita-3D – Step 4• For more precise shade, intermediate

levels for hue, value, and chroma can be given– 2.5M2 = value between 2M2 and 3m2– 3M1.5 = chroma between 3M1 and 3M2– 3M2 / 3L2.5 = hue between 3M2 and 3L2.5

Extended Range Shade Guides

• Some porcelain systems extend the typical range

• Bleached shades

• Dentin shades

• Custom shade guides

Vita Easy shade.

Shade Eye

Shade Scan.

Advancements in Shade selection

Spactroshade.

Importance of luting agent • Luting agent shade is also important

consideration for the imparting proper shade

• As it imparts color through the restoration

Range for natural teeth

• Value in natural teeth 4 - 8

• Chroma in natural teeth 0 - 7

• Hue in natural teeth 6 YR - 9.3YR

Limitation of shade guide • Don’t tell about the complete tooth color.

• Shade guide is prepared by different materials and crowns are of different.

• Problem we face for selecting shade for porcelain fused to metal crown.

Shade Mapping• Tooth is divided into

– Three regions– Nine segments

• Each region is matched independently• Further characterizations are sketched on diagram, may include…

– Craze lines– Hypo calcifications– Proximal discolorations– Translucency

Summary• An understanding of the science of color and color perception is

crucial to the success esthetic restorative dentistry.

• Although limitations in materials and techniques may make a perfect color match impossible, a harmonious restoration can almost be achieved.

• Shade selection should be approached in a organized manner.

• This will enable the practitioner to make the best choice and communicate it accurately to the laboratory.

References • Contemporary Fixed Prosthodontics Rosenstiel (3rd

edition)• Esthetics in dentistry Ronald E Goldstein• Esthetics dentistry; a clinical approach to technique and

materials Barry G Dale, Kenneth W Aschheim• Esthetic dentistry and ceramic restoration Martin Dunitz• Tylman’s Theory and practice of FPD• Natural Color Concept: A Systematic Approach to Visual

Shade Selection Bernhard Egger• Shade selection By Christopher CK Ho, BDS Hons

(Syd),

What we say till now is just the tip of ice berg

Greater knowledge is still awaiting to be discovered and practiced about

esthetics

Thank You

Have a nice day