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I technical paper _ composite and colour

_Colour is an essential ingredient in our environ-ment and is associated with certain feelings, emo-tions and meanings. These associations are definedby the culture we live in as well as our personal ex-periences. Colour communicates emotion, createsmood and affects energy; colour has an emotionalimpact that can delight or distress. It is almost im-possible to separate the seeing of colour from thefeeling of colour because so much of what is seen isbased on what is felt. Not surprisingly these factorsand influences have infiltrated into the oral health-care environment with patients having a high expec-tation of a natural esthetic result, both in the anteriorand posterior dentition.Although colour as an entity should be regarded asonly one of the many building blocks necessary in theachievement of an esthetic result, nevertheless a dis-cordant colour scheme can probably be more devas-tating to the overall effect than many of the otherfactors present. It is for this reason that so much time,research and expense has gone into the colour

matching properties of contemporary estheticrestorative materials.Colour matching and shade talking continues to pro-vide oral health clinicians and technicians with oneof the great and important challenges of their re-spective professions. Yet, despite the importance ofcolour matching, this area still remains largely anduniversally untaught in most teaching institutions(Figure 1). A viable reason for colour matching not tobe part of a healthcare curriculum could well be thefact that of all areas involved in healthcare, it occu-pies the unique position of requiring three equal ele-ments for understanding and implementation. Theseelements could be defined and classified as scientificaspects, objective reasoning and subjective response. Scientific aspects would involve understanding ofthe basic properties and nature of light and colour,and an understanding of the physical and chemicalproperties of natural colour as well as those of the ob-ject being studied. In dental healthcare this would in-volve the understanding of the anatomy and physi-

Smile showing bright, high value healthy teeth.

cosmeticdentistry 1_2005

The natureof colourAuthor_ David Klaff, BDS

The overall impression is esthetically pleasing in spite ofthe chipped incisal edges

UtenzaG4By kind permission of Cosmetic Dentistry International Edition, n. 1, 2005 pag. 20-32

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ology of the various structures that make up the oralenvironment. A knowledge of the anatomy and phys-iology of the eye would be required, as well as a thor-ough understanding of colour and image interpreta-tion by the brain (Figures 2 & 3). Objective reasoning would involve the understand-ing of the effects that various colours have on soci-ety generally and the individual specifically. Therewould be a scientific basis in that such an objectivereasoning forms a part of psychophysics, psychology,philosophy and the morays and ethics of our con-temporary religions. Although these aspects can beculturally and socially diverse, a unified pattern couldnevertheless be established and reasoned, pre-dictable findings applied.Subjective response is probably the least scientific ofthe three elements, yet possibly occupies the mostdominant position. In order to achieve as near perfectcolour matching as possible, the subjective responseneeds to disciplined in a positive and constructivefashion. In the fabrication of a single ceramic crownfor example, three individuals are involved: the clini-cian, ceramist and the patient. Each individual will in-terpret colour differently and success will be deter-mined by achieving a consensus of approval for aparticular shade. Attaining this consensus can oftenbe a difficult and painstaking procedure, with possi-ble remakes of the restoration commonplace. The sci-entific literature describes sexual and age differencesin response to colour stimulation, as well as culturaland ethnic differences. The manufacturers of es-thetic restorative materials have also inadvertentlyadded to the challenge: of accurate colour matching.Although producing wonderful esthetic materials,there still remains a lack of total standardisationwithin the productive process and separate batchesof the same material often display completely differ-ent colour properties. The shade guide remains thetraditional method of recording colour matching,and for the most part this is totally inadequate as theguide is not unique to the chosen material.The objective of this paper is to present an under-standing of the nature of colour and to provide asimple roadmap technique that hopefully eliminates

much of the uncertainty of colour matching (Figures4 & 5).

_The nature of colour

The modern understanding of colour originated inthe discovery of the spectral nature of light by IsaacNewton in the 1600s. Newton considered light to bea stream of particles. His experiments with prismsshowed that white light can be split into individualcolours. We now know that Newtons famous exper-iments demonstrated that. Light consists of energyof different wavelengths. The universe is consideredto be a magnetic field of positive and negativecharges; constantly vibrating and producing electro-magnetic waves. Each of these has a different wave-length and speed of vibration; together they form theelectromagnetic spectrum. We can see about 40% ofthe colours contained in sunlight. So although whitelight appears colourless and intangible, it is made upof distinct colour vibrations, which have not onlywavelengths but also a corpuscular structure.

_The colours in light

One way colours in sunlight are made visible to us isto pass white light through a prism. Because each ofthe colours has a different wavelength, each is bentby a different amount. Rainbows are formed whenwater droplets in the Sky act as natural prisms. As sun-light passes through the droplets, each of the differ-ent rays is bent by a different amount, creating a rain-bow. The rainbow colours form one octave of lightand are known as the true hues: Red is the longestwavelength we can see and it has the slowest fre-quency of vibration. Its magnetic energy is warmingand stimulating. Violet has the shortest wavelengthand the quickest vibration. It is cooling and cleansing(Figure 6).

_Beyond the visible spectrum

At either end of the visible spectrum are many wave-lengths we cannot see. Ultraviolet light is just beyond

Fig. 1 Fig. 2 Figs. 2 & 3_ Direct composite resto-ration on second maxillary bicuspid.

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I technical paper _ composite and colour

violet, and farther beyond this are electromagneticrays with increasing frequencies as the wavelengthsget progressively shorter; these include X-rays andgamma rays. At the opposite end, infrared light is found just be-yond red light. Like red it has warming qualities al-though it gives off more concentrated heat; thesequalities are utilised in infrared lamps. Beyond this areelectromagnetic rays with increasing wavelengthsand decreasing frequencies; these include radiowaves. Human colour recognition depends upon light, ob-jects that reflect light and the viewer's eyes and brain.The colour of a self-luminous object is called self-lu-minous colour and can be natural or artificial. Thecolour of an illuminated object is called object colourand can arise from reflected or scattered light. The en-ergy carried by waves (which are approximately 400 700 nm) stimulates the receptors in the human retina,producing colour stimuli. This gives rise to the threeprimary colours: _ 400-500 nm = b!ue_ 500-600 nm = green_ 600-700 nm = red All colours encountered in nature can be reproducedby combining light of these three wavelengths invarying intensities:_ 100 % = white light _ 0 % = black _ 50 % = grey (Figure 7).

_The colour wheel and complementarycolours

If we arrange all these colours around a circle we havea colour wheel. Looking at the colour wheel we can seethat certain colours fall opposite to each other: Eachcolour has a complementary or opposite hue, so thaton the colour wheel we have three complementarypairs. Just as positive and negative magnets attracteach other, complementary colours also attract. Figure8 graphically shows the relationship between thethree primary colours of red, green and blue and thethree primary lights cyan, magenta and yellow.

_Colour temperature

Colour is intimately related to temperature. Colour T0is expressed in Kelvins. The higher the colour T0, thecloser to blue the colour is and the lower the colour T0,the closer the colour is to red. The sun at noon is 5,000Kelvin (Figures 9 & 10).

_Describing colour

Colour can be described in at least three different ways: _ Spectrophotometry describes the physical char-

acteristics of a colour (e.g. the spectral reflectanceof a surface at different wavelengths).

_ Colorimetry describes what a colour matches with _ TheMunsellsystemdescribeswhatthecolourlooks like.

cosmeticdentistry 1_2005

Fig. 3 Fig. 4

Fig. 5 Fig. 6

Fig. 3 and 4_ Restoration of centralincisor showing precise colour

matching. It is esthetically pleasingdespite misalignment of incisors.

Fig. 5_ Rainbow showing true huesof nature.

Fig. 6_ The visible spectrum. Bluebetween 400500 nm, green be-

tween 500600 nm and red between600700 nm.

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_The Munsell colour system

This system was proposed by the American AH Munsellin 1905 and revised in 1943.The system defines threeattributes of colour: H (hue), C (chroma), and V (value).Colour matching in dentistry is based on this system.Munsell established numerical scales with visually uni-form steps for each of these attributes.

_Hue

Hue is that attribute of a colour by which we distinguishred from green, blue from yellow etc. Munsell called red,yellow, green, blue and purple principal hues and placedthem at equal intervals around a circle. He inserted fiveintermediate hues:_ Yellow-red _ Green-yellow_ Blue-green_ Purple-blue _ Red-purple. This makes ten hues in all.

_Value

Value indicates the lightness of a colour: The scale ofvalue ranges from 0 for pure black to I0 for pure white.Black, white and the greys between them are calledneutral colours. They have no hue. Colours that havea hue are called chromatic colours (Figure 11).

_Chroma

Chroma is the degree of departure of a colour from theneutral colour of the same value. Colours of low chromaare sometimes called weak, while those of high chromaare said to be highly saturated, strong or vivid (Figure 12).

_Munsell colour space

Hue, value and chroma can be varied independentlyand the colours can be arranged in a three-dimen-sional space. The neutral colours are arranged in thevertical line called the neutral axis. Black is at the bot-

tom, white at thetop and all greys arein between. Huesare displayed at var-ious angles aroundthe neutral axis andchroma arrangedperpendicular tothe axis increasingoutward (Figure13).

_CIE XYZ

In 1931 the CIE de-veloped the XYZcolour system, also called the norm colour system.Red components of a colour are tailed along the X-(horizontal) axis and green components along the Y-(vertical) axis. Every colour is assigned a particularpoint and the spectral purity of colours decreases asyou move left along the coordinate plane. What isnot taken into consideration in this model is bright-ness.

_CIE L*A*B *

Three-dimensional model with the colour differencesperceived corresponding to distances when measuredcalorimetrically. The a-axis extends from green (-a) to red(+a); b axis from blue (-b) to yellow (+b). Brightness (I) in-creases from the bottom to top (Figure 14).

_Chromatic and achromatic colours

Achromatic colours are white, black and grey in between.They lack the attributes of hue and saturation. Chromaticcolours are everything that we perceive as having colour;everything other than white, black or grey.

_Colour of the natural tooth

In describing the colour of a natural tooth we findthere are two additional attributes. In addition to hue,

Fig. 7_ The colour wheel showing theprimary hues red, green and blue.Opposite each primary hue is the cor-responding complementary colour,cyan, magenta and yellow.

Figs. 8 and 9_ Colour temperature illustrating high temperature blueand low temperature red.

Fig. 8 Fig. 9

Fig. 7

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chroma and value, we discover the attributes ofopalescence and fluorescence. The definitions of thefirst three attributes are identical to those defined byMunsell, but each can be qualified further: _ Hue: the primary source of colour is dentine and the

hue of a vital, healthy tooth is in the yellow to yel-low-red range

_ Chroma: In natural teeth the chroma is dictated pri-marily by dentine but is influenced by the translu-cency and thickness of enamel. The thinner theenamel, the less the effect on the chroma. Thus inthe cervical area, with its thin enamel, the chromaappears densely saturated. The thicker the enamel,the more the chroma is masked giving rise to a dif-fuse chromatic appearance.

_ Value: In natural teeth this is primarily influencedby the quality and thickness of enamel. The thickerthe enamel, the greater the optical effects resultingin a higher value. Thick, dense opaque dentine hasthe effect of lowering the enamel value (Figures 15,16 & 17).

_ Opalescene: In a natural tooth, this is an effect pro-duced in enamel and is due to different refractory in-dices of the various organic and inorganic compo-

nents of enamel as well asthe ability of hydroxyapatitecrystal to scatter incidentlight. The result is that thelong wavelengths are trans-mitted through the toothwhilst the short wave-lengths are reflected, pro-ducing a bluish gleam. Theeffects vary from blue togrey to white gleaming ar-eas (Figure 18)._ Fluorescence: This effect

occurs when a body ab-sorbs luminous energyand then diffuses it backto the visible spectrum. Innature this is caused byultraviolet light strikingpigments in the dentine

enamel interface resulting in light emission rangingfrom intense white to light blue.

_Translucency & opacity

These are difficult parameters to explain and evenmore difficult to quantify:_ Opacity: most of the light rays are reflected or ab-

sorbed due to the presence of dense particulatematter within the object.

_ Transparency: most of the light rays are transmit-ted due to the object being mainly devoid of partic-ulate matter.

_ Translucency: light rays are both transmitted andreflected due to the presence of discrete minuteparticles in the object.

A translucent material, by definition, must have par-ticulate matter embedded which when struck by lightreflects and scatters the rays. In natural teeth, theseparticles (owing to their minute irregular size andshape) primarily reflect the shorter wavelengths (i.e.,blue wavelength). When struck by light these particleshave the property of imparting a glow or vitality tothe tooth, i.e., opalescence. It would be prudent at this stage to dispel one of thegreat myths of colour matching in the natural tooth.Translucency is currently one of the buzzwords inesthetic restorative dentistry and clinicians, in theirsearch for the invisible restoration, demand more andmore translucency from their ceramists. Understand-ing of the previous paragraph would surely indicatethat the desire is not for more semi-transparency butrather for more glow and vitality effects, i.e., opales-cence. A small point but once grasped, the author sub-mits that use of the term opalescence as opposed totranslucency would convey a greater understand-ing (with significantly less confusion) as to the re-quirements of a particular restoration.

_Physiology of natural tooth colour

The observed colour of a tooth results from the com-bined effects of the interaction of light with dentine& enamel.

Fig. 10_ Value scale and chart graduated from 0 to 10. A black or

low value Is represented by 0. 10 represents a white or high value

with the mid-tones being grey. Fig. 11_ Chromatic scale, extendingfrom weakly saturated on the left to

densely saturated chroma on theright.

Fig. 12

Fig. 10 Fig. 11

Fig. 12_ Munsell Colour Space. Verti-cal axis represents value extending

from black on the bottom to white ontop, with grey in the middle. The col-our wheel arranged around the axisrepresents the hues and chroma in-

creases outwards and perpendicularto the vertical axis. Thus hue, chromaand value can be observed at various

combinations.

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_Dentine effects

The macro- and micro-anatomical structure of thedentine produces areas of high and low saturation ofopaque colour resulting in dentine being primarilyresponsible for the hue and chroma of the tooth. Thescientific literature describes the predominant hueas being in the yellow-red range, but varies in quan-tification of this as being between 76% to 86%, withthe remaining percentage leaning towards the yel-low range. Using the Vitapan standard this woulddescribe the hue of teeth as being predominantly inthe A range with a small percentage of B shades. Dentinal tubular architecture, exhibiting varying di-ameter; frequency and an S-shaped distributionproduces areas of dense and sparse mineralisation.The various micro-anatomical structures, tubulararchitecture, combined with the overall grossanatomy of dentine result in areas of differing re-fractive indices resulting in a non- homogenous re-flection and scattering of light rays. This results in ar-eas of dense opacity and saturation of colour givingdentine a polychromatic effect. Vanini (1996) stud-ied this effect and defined and applied the termchromatic banding to the polychromatic effects(Figure 19). Traditionally, chromatic banding hasbeen described at the gross level as consisting ofthree broad areas: _ The cervical third_ Middle third_ IncisaI third. The chroma is most saturated in the cervical area,gradually decreasing through the middle third intothe incisal third which exhibits the lowest chroma.Vanini demonstrated that even within the threebroad bands there are areas of dense opacity andsaturated chroma mixed with areas of less satura-tion, giving rise to a true polychromatic appearance.These areas can be organised in a definite pattern re-sembling bands of differing chroma or there mightbe a randomised scattering of differing chromas. Or-ganic pigments present within the microstructure ofdentine are responsible for fluorescent effects giv-ing iridescent areas of white or blue.

_Enamel effect

The inorganic organisedarrangement of theenamel prisms, the vary-ing thickness of enamelover the dentine con-tours and the presence oforganic protein pigmentsallows light to be re-flected, refracted andtransmitted. The translu-cent and opalescentcharacteristics of enamelimpart value as well as ar-eas of intense colourand/or opalescent effectsto the underlying dentins giving the sparkle and vi-tality to the tooth. The thicker the enamel, the morelight is refracted and reflected, thus increasing theluminosity and hence the value giving a whiter ap-pearance.

_Combined effects of enamel and dentine

The observed colour of a tooth is achieved through thecombined optical effects of enamel and dentine.Therefore, it is imperative to understand the influencethat each component makes on the others basicproperties. The opaque dentine, exhibiting the attributes of hueand chroma, has the tendency to decrease the valueof enamel, thus moving the overall colour towards thegrey. If the enamel is very thin and the dentine verysaturated (such as the cervical area) then the hue ofthe dentine dominates the overall perception. As theenamel thickens and the dentine decreases in density(middle third) so does the value of the enamel in-crease, leading to a whiter effect. Careful observationof the tooth will show that the polychromatic natureof dentine will exert similar effects on the value, giv-ing rise to a pattern of variance of vale of enamel thatmatches the polychromatic pattern of dentine (Figure20).

Fig. 14

Fig. 13

Fig. 15 Fig. 16

Fig. 13_ CIE L*A*B scale. Lightnessis calculated on the vertical or L scaleund huelchroma along the ab axis.

Figs. 14, 15 and 16_ Variations invalue in natural teeth. Low value giving a grey appearance, mid-valuegiving a cream appearance and highvalue giving a white appearance.

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I technical paper _ composite and colour

_Opalescent, translucent and intensiveeffects

Opalescence in a tooth is caused by minute particlesin the translucent enamel reflecting and refractinglight. This particulate matter is so minute that only theshort wavelengths are reflected, thus creating a bluegleam. In the natural tooth this occurs usually at theedges of the incisal third where the tooth is devoid ofdentine, causing the familiar blue halo. As the dentinethickness increases so more wavelengths are re-flected leading from grey to white opalescent effects(Figure 21). Vanini (ca. 2001/2) in an as-yet unpublished studydemonstrates that there appears to be a definitivepattern to the translucent effects of enamel. This pat-tern can be classified into categories and further di-vided into effect elements. Vaninis work and studystill requires universal acceptance and scientific ver-ification. Nevertheless, its sheer pragmatism andpracticality make it an exquisite diagnostic tool intooth colour matching and provides a wonderfulcommunication tool between clinicians, manufac-turers and laboratory technologists. Vanini postu-lates that the sum total of all opalescent, translucentor enamel effects fall into one of three categories:_ Intensive effects_ Opalescent effects, and/or_ Characterisation Intensive effects present discrete but intensive areasin the enamel surface, usually of a milky/white nature.A typical example of an intensive effect is the stain as-sociated with hypermineralisation (fluorosis) of theenamel structure. The opalescent category attemptsto classify the distribution and appearance of typicalenamel opalescence. The presence of the blue halo inmany teeth, both anterior and posterior is typical ofopalescent effects. This halo can actually be classifiedby describing its physical appearance, such as mam-melon, split mammelon, window or comb. A fifth divi-sion will occur in the elderly patient where loss of theincisal edge has occurred, enamel has thinned and ex-trinsic stain mixes with the opalescent area producingan opalescent stain usually of a white/amber colour:The final category, characterisation, describes the twomost common examples of character effects, the stainand crack as well as the areas of definitive effects thatcan surround the areas of opalescent or intensive ef-fects. As an example, immediately below and above theopalescent halo there is usually an area of solid enameleffect accentuating the halo and thus would be de-fined in the characterisation category as a mammelonor marginal effect. Therefore, by subdividing theopalescent/translucent or enamel effects into threebroad categories, and further dividing each categoryinto four or five elements, a predictable, repeatableand easily describable roadmap for colour matchingcan be recorded and charted (Figure 22).

cosmeticdentistry 1_2005

Fig. 17

Fig. 18

Fig. 19

Fig. 17_ Typical opalescent effectsshowing a blue comb-like halo in the

incisal region and solid white opal-escence in the middle third. Note theband of solid colour at the outer edge

of the halo.

Fig. 18_ Longitudinal section of acentral incisor. The relationship ofthe varying thicknesses of enamel

and dentlne is illustrated. The poly-chromatic effects caused by areas ofdense chroma are clearly evident as

are the opalescent areas of denseparticulate matter in the enamel.

With thanks to Micerium and LorenzoVanlnl for permission to use the side.

Fig. 19_ Typical opalescent effects ofenamel. Notice the blue incisal halosurrounded by a band of opalescent

enamel. An area of intense stain ispresent in the incisal third and the

whole surface is covered with flakywhite opalescence. Notice as well the

obvious polychromatic influence ofdentine, arranged in this instance, In

definite bands of differing chroma.

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_Aging effects in the natural tooth

Young teeth are generally characterised by white,bright opalescence (Figure 23) whereas aged teeth areusually dark opaque and worn (Figure 24). What happens? Young teeth have a thick, dense vas-cular arid opaque dentine surrounded by thickenamel. The thick intact enamel masks and reducesthe opaque effects of the dentine. The young enamelshows marked opalescent effects and in the incisalarea the halo effects are obvious. With aged teeth, thedentine blood supply diminishes and the tubules be-come sclerotic. Although sclerotic dentine is slightlymore translucent, the overall chroma increases andthe dentine becomes darker: The enamel wears andthins with resulting reduced value as well as allowingmore of the opaque dentine to show through. Thethinning enamel shows reduced opalescent effectsparticularly at the incisal edge that shows loss ofenamel due to functional wear: Accumulated stainsalso darken the tooth.

_Colour of composite resin material

The challenge facing clinicians, researchers and man-ufacturers in colour matching a synthetic restorativematerial to a natural living tooth is plainly defined inthis very sentence: matching synthetic to natural. Anatural tooth possesses an intrinsic vitality, and itscolour is a result of the anatomical and biomechani-cal properties of the tooth. A blending of all the com-ponents of a natural tooth give rise to an intrinsictooth colour; and only alteration of these basic struc-tures or the application of stain will cause a colourchange, e.g., aging or pathological destruction. A syn-thetic Material, on the other hand, requires a prede-termined colour to be built in as an intrinsic part of thematerial. Thus it is obvious that in order to accuratelycolour match a wide variety of different hues, chro-mas and values of the same material need to be man-ufactured. Another problem is that colour change dueto aging effects is totally different in natural as op-posed to synthetic materials. The manufacturers tried

to solve this with the early composite materials by re-lying heavily on the chameleon effectthe large,loosely packed filler materials allowed sufficient lightto pass through the material so as to obtain colourfrom the surrounding tooth substance. This resultedin a near invisible restoration that was totally devoidof vitality due to low opalescent, fluorescent andvalue effects. These materials, once again due to thelarge particle fillers, exhibited many of the negativeeffects attributed to composite resins, such as exces-sive wear patterns, loss of gloss and unsatisfactorymarginal integrity. In the search for better qualityresins the physical arid chemical properties were al-tered arid the composite resins became denser withsmaller particles, more opaque and less esthetic eventhough their restorative properties improved. This co-incided with the greater public demand for estheticrestorations. In order to combat the poor esthetics,composite resins, like other tooth coloured restora-tives, developed two-tiered systems with separateresins for dentine and enamel. The dentines providedthe strength needed with larger particles and theenamels provided the esthetics with sub-micron par-ticles that were capable of maintaining a high polishwith low wear properties. As composite filler particlesserve grew smaller and more densely packed, so thetwo-tier system becomes more essential. Pigmentswere added to produce opalescence and fluorescenceeffects and the enamels were graded according tovalue with definite high, mid and low value compo-nents. Opalescent effects were produced by providinga large variety of intensive colour components. Man-ufacturers vied with each other to produce compos-ite systems that offered larger varieties of componentcolours. Indeed, one award-gaining quality compos-ite system actually offers 62 different shades of den-tine and enamel components in their total range.

_Problems in colour matchingThe tendency to produce more and more so-callednatural shades of restorative material, whether ce-ramic, composite or acrylic, has led to a plethora ofshade choices that has only served to confuse clini-

Fig. 20_ Another example of thecombined polychromatic effects ofdentine and the opalescent effects ofenamel.Fig. 21_ Vaninis classification ofenamel opalescent effects in graphicand textual form. Vanini divided theeffects into three broad categories:intensive effects, opalescent effectsand characterisation. Each groupwas further divided into more distinc-tive groups as outlined in Table 1:Careful consideration of this classifi-cation will surely convince the readerthat the vast majority of dentine andenamel effects fall within this group-ing. Understanding and application ofthis categorisation will present theclinician with a very simple roadmapto colour matching. Vanlnl has furthersimplified the procedure by studyingthe distribution of the actual colourinvolvement of the various effects.Thus by memorising three categorieswith a total of fourteen subdivisions,the clinician has a definitive route tochart the colour matching processwithout the need for a shade guideand, more importantly, without theneed to possess exceptional artisticability. The procedure is simplifiedeven further by the availability of apurchasable chromatic chart andthe whole process of colour matchingcan be recorded.

Fig. 20 Fig. 21

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I technical paper _ composite and colour

cians in their quest to achieve accurate colour match-ing. Multiple-choices of dentine shades and chromas,non-standardised enamel shades, intensive colours.Pigments, stains and even new bleached shades defysimplicity in colour matching. The situation is aggra-vated even further by the fact that manufacturers, par-ticularly of the quality materials, all provide specificprotocols unique to their particular system to achievethe ideal esthetic restoration. This author, on variouslecture tours over the past decade, has found that themost common complaint regarding compositerestorations is the complexity and confusion concern-

ing colour matching, due primarily to the wide varietyof shades and systems available.

_A predicable roadmap to tooth colourmatching

The basic requirement in producing a standardisedroadmap would be to ignore the influence of the ob-jective and subjective elements and to concentrate onthe influence of the bio-physiological structures of atooth and its interaction with light. Vanini worked onthis interaction and in two keynote papers in 1996 de-scribed the interaction of light with the dental hardtissues compared to the interaction with the dentalhard tissues compared to the interaction with com-posite restorative materials. The interaction of lightand tooth has been discussed in the previous para-graphs and can broadly be described as the polychro-matic effects of dentine and the translucent opales-cent effects of enamel. In order to reproduce these ef-fects in synthetic composite material the followingcriteria would need to be fulfilled: _ A two-tiered composite system consisting of den-

tine and enamel composites _ High opacity/low translucency dentines in the yel-

low-red range having a range of chroma varyingfrom I to 6. The ideal system would present an inte-grated graduated chromatic system. That is to say

that mixing chroma 1 with chroma 2 would repre-sent points in between the two chromas as definedby CIE L*A*B*. Thus mixing equal parts of chroma 1and chroma 2 would produce a true chroma 1.5. Thisis not possible with any of the Vita or Ivoclar shadeguides owing to the chromatic spectral arrange-ment of these guides. The author is aware of onlyone composite system that offers this spectralarrangement of the dentine resins. The New Gener-ation Enamel Plus HFO System (Micerium, Genoa,Italy) with its unique universal single hue dentinecomposites offers a true graduated chromatic sys-tem:

_ The dentine resins should have fluorescent pig-ments intrinsically added

_ The glass connect layer consisting of filled resinmaterial

_ High translucent enamels, graduated into three lev-els of value (i.e. high. mid and low values)

_ Esthetic modifiers containing high opalescent ef-fects and intensive colours

_ A pre-printed form on which data can be recorded _ Chromatic Map (Micerium, Genoa, Italy).

_The stratified layering technique

The colour matching procedure should be recordedby using a chromatic map (Optident Ltd., Yorkshire)(Figure 25). The first Step is to establish the hue andchroma distribution. This step is performed prior toany restorative procedure and the colour is estab-lished with both wet and dry techniques. Surround-ing, ambient conditions should match the ideal forshade taking as outlined in the scientific literature. Inestablishing the basic hue, the author submits that incomposite resin restorations a simplistic approachshould be perfected by primarily considering A shadeswith the very occasional required B shade. The C andD shades should be eliminated as these are grey ver-sions of A and B and can be reproduced by using lowvalue enamels. The overriding chroma is established,recorded as well as two higher chromas of the samehue. For example, if A2 is the overriding chroma thenA4 and A3 are added to the recorded map data. Thevalue of the surface enamel is then recorded the suit-able surface enamel composite chosen. Most qualitycomposite manufacturers offer a choice of three sur-face enamels being graded according to value i.e. low(grey), medium (cream) and high (white). The termi-nology differs with the various available compositesbut the principle is common to all and the clinicianjust needs to establish which surface enamel is low,medium or high value. The predominant opalescentpattern is then chosen and recorded, as well as theoverriding colour effect of the particular pattern.Vanini has demonstrated that the predominantopalescent colours are blue, white and amber andhigh quality, esthetic restorations can be predictably

cosmeticdentistry 1_2005

Fig. 22_ Young, bright smile.

Fig. 22

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technical paper _ composits and colour I

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achieved by limiting the opalescent effects to thesethree colours. If grey predominates then it can beachieved by mimicking the pattern with thicker areasof Iow value surface enamel. The intensive pattern isthen chosen and recordedonce again Vanini hasshown that the predominant colour to be an intensewhite and most systems offer a highly saturatedwhite shade that can be used to reproduce the inten-sive patterns. Finally the characterisation patterns areestablished and recorded. Again, the majority of char-acterisation effects can be achieved from the threeopalescent colours, however in the case of stains andcracks the author uses either brown or ochre ceramicstain pigments. Most quality composites have a stainkit that would suitably reproduce characterisationeffects of a tooth. The completed Chromatic Map isthen handed to dental surgery assistant who then di-vides the required colours into small wedge-shapedincrements and lays these in a composite light wellwith a filtered cover to prevent premature polymeri-sation. Understanding of the procedure as describedto this stage, should convey to the reader that on av-erage, 86% of quality esthetic composite restorationscan be achieved with a choice of three out of a possi-ble five increasing chromas of A; the choice of one ofthree surface enamels graduated according to valueand finally the choice of three opalescent colours andperhaps one intensive colour plus a stain kit. Thus, byutilising a choice of 12 colour elements of a compos-ite system colour matching can be achieved on a pre-dictable basis. The remaining 14% of tooth colourscan be achieved by B shades with chroma increasingfrom 15. This offers a far simpler choice than the 62colours offered by our award winning system. The clinical procedures involved will be outlined in de-tail in the next article in this series by a comprehen-sive step-by-step description of the placement ofClass I, Class II and Class IV composite resin restora-tions. Only the basic principle and broad objective willbe described in this article. The broad objective is tocreate a dentine layer exhibiting a polychromatic op-tical effect or chromatic banding. For ease of descrip-tion, an anterior veneer will be illustrated but thetechnique applies to all classes of restoration suitablefor a composite resin. The first increments insertedwill be the highest chroma of the chosen stage. Thislayer extends from the cervical area into the middlethird area. The layer is thickest in the top cervical areagradually thinning into the middle third area. Thelayer is inserted neither uniformly nor smoothly butin an undulating fashion varying in thickness bothmesiodistally and cervico-incisally (Figure 26). Thenext layer involves the middle chroma chosen and ex-tends from about halfway through the cervical thirdinto the middle of the incisal third, covering the un-derlying layer already placed (Figure .27). This layer isalso placed in an undulating fashion creating thickand thin areas of undulating chroma.

Finally, the last and lowest chroma (which corre-sponds to the chosen hue and chroma) is placedsmoothly over the previous layers. Groves and spacesare created, prior to polymerisation, as per the pat-terns established with the Chromatic Chart (Figure28). The halo is created by forming a thin groove im-mediately above the incisal dentine edge. A thin layerof filled resin is applied over the whole dentinal sur-face to act as a light diffusion layer and polymerised.This layer is critical to avoid the effects of opaque den-tine lowering the valve of the enamel layer. Theenamel effects as recorded on the Chromatic Chart

are then inserted. Blue opalescent enamel compositeis placed in the groove created for the halo, using aminimal quantity of the intense opalescent colour.This layer of blue enamel is then accentuated byadding a margin of dentine along the lower border ofthe halo shape. The mammelon areas are filled withopalescent enamels, white, amber or blue or combi-nations of all three. The intensive patterns are filledwith intensive colours according to the desired resultas obtained from the Chromatic Chart. As an example,horizontal bands are created by inserting very thinrows of intensive white enamel (figure 29).Once the patterns of the chromatic charts have beenobtained the added enamels are polymerised. Greatcare should be exercised with regard to the quantitiesof special effect enamels used. Most of the qualitycomposite systems available offer these special effectenamels and they are always resins of intense colour.Over-exuberant use of these intense enamels can cre-ate disharmonious effects and ruin the restoration.Small wisps of intense colour are all that is requiredand these are carefully and sparingly placed in thespaces created in the superficial dentine. An alterna-tive and simpler technique would be to fill the carvedareas and grooves with surface enamel. By filling theshaped patterns thicker areas of enamel would becreated and these would produce a subtle reproduc-tion of the Chromatic Chart pattern even though the

Fig. 23_ The smile of an elderly person.

Fig. 23

32 I

I technical paper _ composite and colour

Fig. 24_ The Chromatic Chart. Diagnosetic map for color matching

(Micerium, Genoa, Italy; Optident, Ilkley, Yorkshire).

Fig. 25_ First incremental layer ofhigh chroma inserted in a wavy, un-dulating fashion, thickest in the cer-

vical area and extending into themiddle third of the tooth.

Fig. 26_ The second incrementallayer of middle chroma, once again

inserted in an undulating pattern andextending into the lower third of the

tooth.Fig. 27_ The final dentine layer of

lowest chroma. This covers thewhole tooth surface and is placed in a

smooth fashion. Groves and spacesare created (prior to polymerisation)as per the patterns established with

the Chromatic Chart.Fig. 28_ Opalescent and Intensive

colours added to fill previously con-toured grooves and ridges. In this in-

stance opalescent blue is placed inthe halo area, and opalescent white

in the intensive areas.Fig. 29_ Completed veneer showing

polychromatic dentine and opal-escent enamel effects.

cosmeticdentistry 1_2005

Fig. 24 Fig. 25 Fig. 26

colour variation was not present. The restoration isthen covered with surface enamel of the desiredvalue, polymerised, polished and finished (Figure30). This procedure, known as stratified layering,blends harmoniously and invisibly with the incre-mental layering technique described in the first ar-ticle in this series. The next article will describe in de-tail the clinical procedures involved in Class I, ClassII and Class IV restorations, and will illustrate tech-niques for blending the two layering protocolsseamlessly.

_Acknowledgements

The author wishes to acknowledge and thank thefollowing outstanding clinicians for the many hoursof swimming pool, coffee table and beachfront con-versations that have gradually led to a more sys-tematic and predictable approach to colour match-ing: Didier Dietschi, Roberto Spreafico, Waller de Voto,Bernard Touati, Pascal Zyman, Douglas Terry, WillieGellar and Ronnie Goldstein. Above all, and paramount in the authors thanks andacknowledgement is the role played by Dr LorenzoVanini. The ethos and spirit of this paper is based pri-marily upon the work done by Dr Vanini and the au-thor expresses his gratitude for many hours offriendship and tuition and for switching on thecolour tamp.

Finally the author wishes to thank Micerium (Genoa,Italy), Dr Vanini (Como, Italy) and Optident Ltd. (Ilk-ley, Yorkshire) for permission to use original slidesand material. _

A complete list of references is available from thePublisher.

Fig. 27 Fig. 28 Fig. 29

David Klaff

David Klaff BDS is a pastpresident and foundingmember of the BritishAcademy of EstheticDentistry (BAAD). Hecurrently runs a privatepractice, limited to

restorative and prosthodontic dentistry in London haslectured extensively on adhesive dentistry in Europe,Asia, the USA and the United Kingdom.

cosmeticdentistry_Author