[Color differences between light-cured composite resin made shade guides and manufactured shade guides]

The purpose of this study was to investigate color differences between shade guides and light-cured composite resins. Resin specimens were made with resins and opaque resins of Silux Plus and Silux (3 M Co.) in a shade-guide metal mold. The resin specimens and the shade guides therefore were identical in shape and size. The sample resin specimens were compared with the shade guides provided with Silux Plus and Silux light-cured composite resins. Color measuring was performed with the Murakami Color Research Laboratory Fast Spectrophotometer C M S -500 and the Flexible Sensor F S -1. Specimens were placed on a plastic disc fixed to the top of the flexible sensor, and identical areas of their incisal, central, and cervical parts were measured. Conclusions. 1) The delta E*ab values between all shade guides and resin specimens showed color differences detectable to the naked eye. 2) Color differences between shade guides and resin specimens were great for the incisal colors (I, X L) and the deep and dark colors (D G, D Y, Y B, D G O, D Y O, Y B O, D D Y O). Color differences were relatively small, however, for the general colors (U, Y, G, U O, Y O, G O). 3) The L* values of shade guides ranged more widely than those of resin specimens. For many colors, L* values of the shade guides were lower than those of the resin specimens. 4) The a* values of shade guides and resin specimens were much more limited. The a* values of all colors showed minus values. The magnitude of a* values of shade guides were lower than those of resin specimens. 5) The b* values of shade guides were higher for some colors and lower for some colors than those of resin specimens.