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cosmetic dentistry_ beauty & science

06 I I special topic _ shade analysis Fig. 1_Using two OttLites held at tooth level 24 inches from the patient to control lighting colour temperature. Fig. 2_Using the Trueshade light and magnifier to control light. Fig. 3_Image of two of the same shade guides with different surface texture. Notice the one with a different texture is perceived as a different colour. cosmeticdentistry 1_2012 _With ever increasing emphasis on aesthetics in dentistry, and patient demands to fabricate ceramic restorations that mimic natural teeth that are indistinguishable from adjacent natural teeth, the ability to evaluate tooth shade information correctly and communicate it to the ceramist ef- fectively is now more critical than ever. Correctly evaluating tooth shade is as much an art as a science. Many articles1–7 and even whole books7 have been devoted to this topic, yet in hundreds of in- formal polls of technicians, problems with shade analysisisthesecondreasongivenforremakes,with impression/preparation problems being the first. Manyfactorscontributetothisproblem:lighting variables that contribute to perception errors; mul- tiple shade systems available with a lack of stan- dardisation in colour systems and corresponding porcelain systems; individual human variables in colour perception; lack of understanding of colour science, especially as it relates to tooth shade; and the ability to interpolate shade information into a porcelain layering technique that obtains the de- siredshade.Afullarticlecouldbedevotedtoeachof those topics. There are many references in dental and non-dental literature on the topics of colour, colour as it relates to teeth and human perception of colour. The objective of this paper is not to offer anexhaustivereviewofthesetopicsbuttodistilthe essentialaspectsofevaluatingandcommunicating tooth colour. Also, to offer the reader an efficient and effective method for evaluating and commu- nicating tooth shade. This article will focus on: _understandinghowlighting(illumination)affects colour perception, and more importantly how to control it; _understanding the parameters of colour that are mostcriticalinevaluatingtoothshadeandhowto access them relative to the tooth; _the ideal set-up and use of current shade guides; _the use of digital photography for communica- tion; and _the integration of computerised shade-analysis devices into the technique of taking and commu- nicating tooth colour. _Understanding lighting and the effect on colour perception The perception of colour is affected by three primary factors: Fig. 2 Fig. 3Fig. 1 Shade analysis and communication: 2012 The essential elements of evaluating and communicating tooth colour Author_Prof Edward A. McLaren, USA