Evaluating visual thresholds and color metrics in dental research: An exploratory study.

OBJECTIVES: This study aimed to evaluate perceptibility (PT) and acceptability thresholds (AT) for multiple color measurement devices and assess the performance of three color difference equations (∆E*(ab), ∆E(00), and ∆E(94)) using a visual dataset from expert observers. METHODS: A visual dataset previously published was extended by adding the x-rite MetaVue spectrophotometer and ∆E(94) to the analysis. Visual scaling was performed on 26 sample pairs of teeth using magnitude estimation. Observers answered PT and AT questions to determine thresholds. Threshold estimation was conducted using a model-free method, and device performance was analyzed using the standardized residual sum of squares (STRESS) index and visual instrument agreement scale (VIAS). RESULTS: The PT and AT thresholds varied across devices and color difference equations. For ∆E(00), STRESS values ranged from 23 to 32 (mean 29, sd 2.9), with VIAS scores between 68 % and 77 % (mean 71 %, sd 2.9). ∆E(94) showed higher STRESS values (24-42, mean 34, sd 5.5) and lower VIAS scores (58-76 %, mean 66 %, sd 5.5). ∆E*(ab) demonstrated excellent visual-instrumental agreement with STRESS values from 18 to 36 (mean 24, sd 5.9) and lower VIAS scores (82-64 %, mean 76 %, sd 5.9) outperforming ∆E(94) and ∆E(00). The x-rite MetaVue achieved excellent results under controlled conditions but it is unsuitable for clinical research due to its design. SIGNIFICANCE: This study highlights the variability in PT and AT across devices, suggesting the need for device-specific thresholds. It also demonstrates the effectiveness of ∆E*(ab) in dental colorimetry compared to more complex color difference metrics.