The power of cross-polarization Diagnostic photographs are one of the essential tools used to facilitate communication between the restorative dentist and the lab ceramist by bringing stone models to life on the lab bench. The use of twin point flash dental macro photography creates reflective zones and patterns that are useful to illustrate texture and contours. This gives technicians valuable information about surface morphology. However, these same reflections are a liability when trying to select shade as they essentially mask our ability to see shade three-dimensionally. The elimination of these spectral reflections with management of the polarization of the light removes these artifacts. Specular reflections (or reflection zones) can impede our ability to see underlying idiosyncrasies of the tooth shade. Eliminating these reflective distortions through cross-polarization helps us to visualize the histological stratification of shade (Figs. 1a and 1b). The eye can only interpret the perceived shade with available light that's reflected from the surface. Therefore, we would like to observe our subjects under the fullest spectrum of light at 5,500 degrees Kelvin with a color rendering index (CRI) of 95% or better when selecting shades. Re-creating accurate shades It is important that shade communication images are captured with consistency in angulation, magnification and exposure Figs. 1a and 1b: Images are recorded in RAW format with and without the cross-polarization filters in place to facilitate illustration of the stratification of shades and surface finish/texture. 48 JANUARY 2020 // dentaltown.com in the R AW format. This facilitates the recording of an image without compression, and allows the file to be calibrated with image management software to a known color coordinate. This known color coordinate is the introduction of a white-balance gray reference card into the field of view. Once the image has been color-corrected, the user can then select any other site within that image and determine what the shade is relative to the correct color coordinates. This technique eliminates the use of traditional shade tabs that require interpolation to harmonize a shade. Rarely does the desired shade of the teeth actually match any single traditional shade tab. Once the desired color coordinates have been determined through the use of proprietary software, the corrected formulations of dentin and enamel shades for the ceramics can be selected. This innovative technique was developed by the team at eLab through extensive research and clinical trials (Fig. 2). The newly developed indirect restorations can then be placed on the custom shaded dies with the appropriate try-in paste, which serves as a quality control check of what will be anticipated clinically. The lab technician can then replicate the same series of photographic images on the lab bench that were recorded clinically in a virtual environment. Only then can the restorations be delivered to the dentist with predictable aesthetic outcomes related to micro-aesthetics.http://www.dentaltown.com