Influence of Lighting Variability on the Accuracy and Consistency of Visual Shade Matching: An In Vitro Study

Abstract

Accurate tooth shade selection is essential for achieving optimal esthetic outcomes in restorations, yet visual shade matching is subjective and may be influenced by lighting conditions. This in vitro study evaluated the effect of different lighting conditions on the accuracy and consistency of visual shade selection. Visual shade matching of 16 blinded tooth samples was performed using the VITA Classical Shade Guide under warm (3000 K), neutral (4000 K), and daylight (5500 K) illumination. A repeated-measures design was used, in which the same examiner conducted shade selection twice at a 1-week interval to assess intra-examiner repeatability. Color differences (ΔE) were calculated using the CIELAB color system, and data were analyzed using two-way repeated-measures analysis of variance (ANOVA), Holm-adjusted pairwise comparisons, and Cohen’s kappa. The results demonstrated that lighting condition significantly affected ΔE values (p = 0.012), with the lowest mean ΔE under daylight illumination (0.663), indicating improved shade-matching accuracy. A significant difference was observed between warm and daylight illumination (mean difference = 1.496 ΔE, adjusted p = 0.009), whereas the other pairwise comparisons were not significant. Neither measurement session (p = 0.707) nor the lighting-session interaction (p = 0.913) was significant. Intra-examiner repeatability was highest under daylight (κ = 0.865), followed by neutral (κ = 0.661) and warm illumination (κ = 0.525). Within the limitations of this study, daylight illumination was associated with lower color differences and greater repeatability than warm illumination. Standardized, color-corrected, daylight-like illumination is recommended for visual shade selection to minimize lighting-related variability and improve clinical consistency.