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cosmetic dentistry_ beauty & science

10 I I special topic _ shade analysis cosmeticdentistry 1_2012 Fig. 16_Image of Camera Raw in Photoshop. The white balance eyedropper is activated by clicking and then the grey card is clicked on. This will neutralise a colour cast. Fig. 17_Image with backgrounds neutralised in Photoshop. It is much easier to evaluate colour. Fig. 18_Image using the Easyshade compact. mismatch for mismatches in hue as long as the hue is within the natural tooth range, but is noteworthy to evaluate whether there is a reddish, orangish or yellowish hue to the teeth. There are three specific hues, a middle hue (orangish), which corresponds to themiddlerangeofnaturalteeth,ayellowerhue,and a redder hue equidistant in colour space from the middle hue. I would first evaluate the M hue of the closestvaluematchrelativetothetooth(Fig.14),and decidewhetheritmatchesorifitisredderoryellower andthenrecordthechosenhue.Thefinaldetermina- tion for the hue will be determined from the photo- graphy and computer analysis described in the next sections. Specific characteristics (such as crack lines ordecalcifications)canberecordedwithhighquality photography. _Digital photography for shade communication Thesecondpartofmyshade-takingtechniqueis to record the value and chroma images previously described using digital photography. Information on camera and flash selection and specific camera settings is covered in detail elsewhere and the reader should review the references.17–19 The most important points are: _use a digital SLR camera that allows interchange- able lenses, _record shade images in RAW file format, _control exposure and white balance ideally with manual exposure at specific flash/subject dis- tances. There are four images necessary for shade com- munication. One image is taken with the two or three value shade tabs closest to the teeth being matched using the 3D-Master or the Linearguide (Fig. 9). With the Classical guide, the four closest valuetabsshouldbeintheimage(Fig.6).Remember the goal is to have a range of values. Ideally, one tab should be slightly higher in value and one slightly lower in value. The second image is with the two closestchromamatchestotheteeth.Again,onetab is slightly higher in chroma and one slightly lower. The third image is an image with what is perceived as the closest value, using a small piece of digital grey card that has been attached to the shade tab (you could do this with the first value image). I attach the digital grey card using white utility wax (Fig. 9). The reason for this is it allows the ability to correct colour bias that is inherent, as all flashes have subtly different colour temperatures and de- pending on the charge state of the flash capacitor can also affect the colour temperature of the flash. Thistechniquewillbediscussedlater.Thefourthim- age (Fig. 15) is an image of the hydrated prepared tooth with a closely matched shade tab. This is for theceramisttoseethepreparationcolourtobeable to modify the build-up or core colour as necessary to compensate for the preparation colour. It is critical that all the images be taken with the shadeguideandtheteethtobematchedinthesame verticalplane,asobjectsclosertothefilmplanewill be perceived as brighter and objects farther away will be perceived as darker. The shade guide and the teethshouldbewetwithaglazeliquidaspreviously mentioned. This photographic information will be used by the ceramist to visualise contrasts between the shade guide and the natural teeth. Photoshoptoisolatetheshadeimages There are many uses of Photoshop (Adobe) for image management and manipulation. The scope ofthisarticledoesnotallowmetogointo the use of Photoshop for these issues. Photoshop or Photoshop elements are used for two specific purposes in shade analysis and communication. To correct a colour balance, open the shade images in Camera Raw and in the image window click on ‘select all’. Then click on the white balance tool (Fig. 16) in theupperleftoftheCameraRawwindow, then click on the grey card that is in the Fig. 16 Fig. 18Fig. 17