lecture 4

electromagnetic spectrum of light

380- 750 nm

what can we see in the visible spectrum

ultra violet, infrared, x ray radiation

speed equation

speed = frequency x wavelength

natural light sources

sun

earths atmosphere

colour temperature (natural)

winter - 5400k

summer - 5800k

what does the colour of a material depend upon

- the spectral composition

- intensity of light falling on it

- refraction, reflection, absorption

- composition of reflected light

3D characterisation of colour

HUE - colour name

CHROMA - colour density

VALUE - lightness, vitality, brightness

colour space

specific organisation of colours in a systematic way and with certain structure

types of cone cells

(physiological basis of colour perception)

red cones - 600-700nm long wl sensitivity

green cones - 500-600 nm medium wl sensitivity

blue cones - 400-500 nm short wl sensitivity

colour detection

light enters eye

focuses on retina

cones are stimulated by diff wl of light

cones respond by sending electrical signals to brain via optic nerve

trichromatic theory of colour vision

Thomas Young

Hermann Von Helmholtz

eye combines red green and blue to produce a wide range of colours

opponent process theory

Ewald Hering

red-green channels

Blue yellow channels

colour vision occurs due to opposing pairs of colour receptors

metamerism

change in colour combo of two objects under diff light sources

metameric pair

two objects under influence of one light but not others

isomeric pair

colour matched under the influence of all light sources

opal effect

reflect light of shorter wavelengths

transmit light of longer wavelengths

shine

property of surface to appear shiny

Fluoresence

emission of light at wl different from that incident on it

emission ceases when light source is removed

phosphorescence

same as fluorescence but light emission stays after light source is removed

transparency

physical characteristic of material media

measure of permeability to EM waves or other radiation types

translucency

optical behaviour of materials

healthy teeth are not completely opaque - allow certain amount of light to pass thru

ways to determine colour features of tooth structure

1) manually, visually

2) machine, apparatus

colour standards made of ceramic (table)

Vita Classical; Vita Lumin

Vita 3D Master

Vita Linearguide

Vita Bleachguide 3D master

Chromascop

Vintage Halo Shade Guide

Bioform

colour standards made of composite materials

Venus (Heraes Kulzer)

Esthet-X (Dentsply)

Filtek supreme (3M)

shades for soft tissues in maxfax area

Ivocap Plus Gingiva indicator (Ivoclar vivadent)

4 Gummy gingiva- indicator set (Shofu dent)

clinically made shades

Vita classical

- 1939 first shade

-1956 Vita Lumin Vaccum Shade Guide introduced --> attempt to make universal tooth colour standard

vita classical

4 colour groups A to D

A - red brown

B - red yellow

C - grey

D - red grey

no subgroups

total sum of colour is 16

vita classical coupon order

1) B1 (9) A3

2) A1 (10) D4

3) B2 (11) B3

4) D2 (12) A3.5

5) A2 (13) B4

6) C1 (14) C3

7) C2 (15) A4

8) D3 (16) C4

VITA 3D master

26 tabs divided into 5 groups

leading sign - bleaching

saturation - vertical

colour tone - horizontal

what do the letters M R and Y stand for in Vita 3D Master

medium

red

yellow

what do the last digits

1, 1.5, 2, 2.5 and 3 denote

level of saturation

higher the number, the more saturated the colour and the more colourful the tab

Vita 3D Master vs Vita Classic

degrees of value are more varied

the range of colour tone has increased in relation to red spectrum

colour tabs are more evenly spaced

separation into groups is better

vita linearguide

2006 new development with prof R Paravina

colourway is based entirely off 3D master incorporating all 29 tabs

how does it differ in colour matching to 3D Master and Classical

classical is one step but made difficult by multiple selection of all tabs

3D is a three step process

Linearguide is 2 stage

what does Vita Bleachguide 3D master do

determines colour shades and evaluates teeth whitening

has 15 tabs which correspond to 29 shades approved by ADA

chromascop groups

5 groups:

group 100 - white dominant

group 200 - yellow

group 300 - light brown

group 400 - grey

group 500 - dark brown

each group has 4 subgroups

as number increases, the density of the colour increases whilst bleaching decreases

total number of colour standards with Bioform

24

colour space is divided into 4 groups

red-brown

yellow

red-grey

grey

what to do to achieve optimal aesthetic results

ensuring colour matching of hard dental tissues is not sufficient enough in some clinical cases

so an appropriate colour match of the soft tissues to be restored with those present in the oral cavity or skin is also necessary

what has an even wider colour range than natural hard tooth tissues

colour of gingival tissues

can the base of a denture whether removable or fixed be made into a standard or custom made soft tissue shade

yes.

what is gummy gingiva

four gingival colours denoted by numbers:

1 - light pink

2 - medium pink

3 - medium dark pink

4 - dark pink

what is Ivocap Plus Gingiva indicator

offers 4 shades

pink

light pink (US-L)

pink with strands (US-P)

preferred (PREF)

what must be considered for shade guides

material of the final restoration

composite

diff types of ceramic masses

(pure or metal)

magnifying loupes with light is what

applying constant unchanging and close to natural light

light source can be on ceiling or fixed on a wall

are a combination of magnifying loupes and light sources which emit light optica for colour determination

tips for colour matching with shade guides (1)

light source requirements:

colour temp = 5500k

CRI index = at least 90

cabinet LI = 18-2800 lux

Lab LI = 2800 lux

tips for colour matching with shade guides (2)

surrounding colours have their influence

- patient clothing

- clothing of staff

- colour of the ceiling should be 9 on munsell value scale

colour of walls must be 7 on munsell scale

tips for colour matching with shade guides (3)

advisable to do shade matching at beginning of patient visit

not mandatory to determine colour in one visit

teeth involved must be cleaned, free of any traces of buildup or staining

preferable to use several diff quality light sources

tips for colour matching with shade guides (4)

register colour between 10am and 2pm

optimal distance for registration is 25cm

dental structures should be at eye level

optimal colour registration time is 15-20s

tips for colour matching with shade guide (5)

desirable to measure by dividing tooth into cervical incisal and middle parts

plates of shade placed under lip and at site of missing tooth is possible

moistened surface of tray is close as possible in texture to natural tooth structures

20-30 min should restore the normal appearance

tips for colour matching with shade guides (6)

position of tooth in the row also influences colour characteristics

if in doubt, leave upper ones lighter and lower more saturated

what can the colour detection devices be divided into

colourimeters

spectrophotometers

digital imaging instruments and systems

hybrid devices

what is a colourimeter

emit a momentary beam of light which is reflected into the surface of the tooth with the help of their light sources

this is reflected into tooth surface and returned thru the same opening

provide stable measurements on transparent and translucent objects

not reliable in multilayered translucent structures

less accurate than spectospheres due to aging of filters

what was the first device designed specifically for colour assessment

chromascan by Sterngold in USA

developed in early 1980s

what is the ShadeEye NCC

1997, one of the oldest devices developed

its old name was ShadeEye EX

3-5 measurements taken and results averaged

which colour shade guides does the ShadeEye NCC use

Vita Classical.

Vita 3D Master

Chromascop

Biodent shades

spectrophotometer

the most accurate useful appliance in daily practise

measures light energy reflected from an object at 1.5-2mm intervals over entire visible spectrum

offer a 33% increase in accuracy and in 93.3% colour matchinf

difference between colorimeters and spectrophotometer

spectrophotometres analyse the scatter of the whole visible spectrum 400-700 micrometers

this makes them slower than colorimeters

Vita EasyShade Compact

has reduced dimensions and fiber optic cable is removed

also has specially developed software that faciliates the processing of colour information

fiber optic tip is about 5mm in diameter and contains 19 optical fibers each 1mm in diameter

light source is a halogen stabilized filament lamp illuminating continuously.

different measurement modes in EasyShade

single tooth mode

tooth area mode (incisal, middle and neck)

comparison mode

checking colour of restoration

advantages + disadvantages of EasyShade

one of few devices that allows access to distal teeth

measurement is comfortable for patient

only works with vita shades

screen size is small

Spectro Shade Micro

instrument combines digital image acquisition with spectrophotometric analysis

combination of digital instrument and LED spectrophotometer is used

spectro shade micro

apparatus has a built in computer that features analytical software

consists of a halogen D65 (6500K) light source

this is directed to the tooth via fiberoptic bundles and lenses to produce uniform field illumination

emitted light falls at a 45 degree angle and the reflected angle is 0 degrees

disadv for Spectro Shade Micro

device is not suitable for measuring distal teeth

colour registration is associated with patient discomfort

high cost

image blurring

transillumination

the examination of a tissue or organ by passing strong light through it

object of observation is located between the light source and the observer

adv of transillumination

visualisation of aproximal caries

best known devices are FOTI (fiberoptic transillumination)and DIFOTI (digital fiberoptic transillumination)