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This study evaluated the influence of 120 autoclave sterilization cycles on the color stability of two commercial shade guides (Vita Classical and Vita System 3D-Master). The specimens were evaluated by spectrophotometer before and after the sterilization cycles. The color was described using the three-dimensional CIELab system. The statistical analysis was performed in three chromaticity coordinates, before and after sterilization cycles, using the paired samples t test. All specimens became darker after autoclave sterilization cycles. However, specimens of Vita Classical became redder, while those of the Vita System 3D-Master became more yellow. Repeated cycles of autoclave sterilization caused statistically significant changes in the color coordinates of the two shade guides. However, these differences are considered clinically acceptable.

This article presents the essential aspects for understanding and reproducing the color of natural teeth with the use of direct resin composite. Fluorescence and opalescence are discussed, with special emphasis on counter-opalescence, which is primarily responsible for the appearance of an orange discoloration at the mamelon dentin tips and incisal edges of anteriorteeth. The dynamics of color in natural teeth in relation to age is also discussed, focusing on the age-related changes that occur in enamel, dentin, and pulp. Further, it is demonstrated how to reproduce the esthetic features of natural teeth using latestgeneration direct resin composites.