Influence of Illumination Conditions and Cross-Polarization on DSLR-Based Clinical Tooth Color Assessment: A Comparison With Spectrophotometric Measurements.

Abstract

Aim: To evaluate the influence of different illumination systems and cross-polarization on tooth color determination using DSLR photography, and to assess the agreement between photographic methods and spectrophotometric measurements.

Materials and methods: Thirty-one participants (62 maxillary central incisors) were included. Color measurements were obtained using a spectrophotometer under standardized conditions. Standardized DSLR photographs were taken using three illumination setups: softbox-equipped studio flash, twin flash, and twin flash with cross-polarization filter. The image area corresponding to the 5-mm probe tip was calculated, and mean L*, a*, and b* values were obtained from all pixels within this region. Color differences (ΔE₀₀) and ΔL, Δa, Δb values were calculated. Data were analyzed using repeated measures ANOVA and Friedman tests (α = 0.05).

Results: Significant differences were observed among all measurement systems for L*, a*, and b* parameters (p < 0.001). The highest color difference relative to the spectrophotometer was found in the softbox system (ΔE₀₀ = 5.69), whereas twin flash (ΔE₀₀ = 3.56) and cross-polarized twin flash (ΔE₀₀ = 3.32) showed lower and comparable values. None of the methods produced color differences within the perceptibility threshold (ΔE₀₀ ≤ 0.8). The highest proportion of clinically acceptable values (ΔE₀₀: 0.8-1.8) was observed in the twin flash group (11.3%).

Conclusion: Lighting conditions significantly influence tooth color determination using DSLR photography, leading to variations across all color components (L*, a*, and b*). These findings indicate that different photographic setups may produce inconsistent color outcomes, highlighting the need for standardized imaging protocols in clinical practice.

Clinical significance: Illumination conditions significantly influence photographic tooth color measurements, leading to clinically relevant discrepancies. Standardization of photographic protocols is therefore essential for reliable color matching in clinical practice.