Impact of Material Aging and Time‐Dependent Factors on the Color Stability of Dental Shade Guides: A Spectrophotometric Assessment

Background/Objectives Dental shade guides are widely used for clinical color determination; however, their chromatic stability under routine clinical use remains uncertain. This study aimed to evaluate whether color changes occur in dental shade guide tabs subjected exclusively to normal clinical use, without accelerated disinfection or sterilization procedures. Materials and Methods Color measurements were performed using a Vita Easyshade V spectrophotometer in Guide Check mode on complete Vita 3D‐Master shade guides, including one unused guide and six guides clinically used for more than 5 years. Each shade tab was measured three times under standardized conditions, and the categorical color parameters (value, hue, and chroma) were recorded according to the manufacturer's shade classification. Identification accuracy was defined as the percentage of exact agreement between the spectrophotometer output and the nominal shade tab designation. Color agreement was evaluated using descriptive analysis and Cohen's κ statistics. Results The spectrophotometer demonstrated an overall identification accuracy of 82.4% (95% CI: 79.2–85.6) based on 546 total measurements. The new guide showed a color match rate of 89.3% ( κ = 0.853), whereas guides used for more than 5 years exhibited a significantly lower match rate of 51.1% ( κ = 0.489). Differences in agreement between new and used guides were statistically significant ( p < 0.001). Conclusions The Vita Easyshade V spectrophotometer showed high reliability for shade identification. However, clinically used Vita 3D‐Master shade guides demonstrated substantial color degradation over time, which may compromise their reliability for clinical shade selection.