Determination of the Perceptual Threshold for Complex Visual Color Matching

OBJECTIVE: The purpose of this study was to determine the perceptual discrimination threshold for complex visual color matching using a spectrophotometer (Olympus, Japan) to measure color difference. METHODS: 116 pairs of heterogeneous stimuli consisting of natural maxillary central incisors and ceramic restorations on the contralateral incisors were used for this study. Three observers evaluated color stimuli for discrimination threshold using numerical index of 1-10 (≥9 not perceptible, ≥8 clinically acceptable difference, ≤7 not acceptable). The color difference between the natural teeth and restorations were obtained in the 4 tooth areas(cervical, body, incisal and incisal edge)using the dental spectrophotometer. Two important values were determined; the DE of the threshold for a clinically perceptible difference and the DE for the threshold of a clinically acceptable difference. Statistical Analyses: Data were collected and stored in a statistical database. Due to the lack of confirmed normality for the predictor and outcome variables, non-parametric (Spearman Rank) correlations were used to evaluate the association between different DE and perception scores. Graphical plots were utilized to evaluate the best fit association between DE and perception scores. After confirmation of linear relationships, linear regression models were computed to provide adjusted R² values for associations. RESULTS: The perception score for the body area was most closely correlated to DE. R-square Perception Scores Predictability DE Average 0.5855, Body 0.699, Cervical 0.542, Incisal 0.592, Inc. edge, 0.509. The threshold values for clinically acceptable crowns (≥8) ranged from 1.99 ± 0.59(body area) to 2.56 ± 0.56 (incisal area). The DE for clinically imperceptible differences (≥9) ranged from 1.66 ± 0.38 (body area) to 2.32 ± 0.47 (incisal area). CONCLUSION: The body area has the most significant impact on color threshold perception with DE 1.66 for imperceptible difference.