Instrumental and visual assessment of color changes in 3D‑printed denture tooth resins

OBJECTIVE: To determine the color stability of a 3D‑printed denture tooth resin across four shades (BL, B1, A2, A3) stored under dry or water conditions for 60 days. MATERIALS AND METHODS: Disc‑shaped specimens of each shade were fabricated using a manufacturer‑validated workflow for Premium Teeth Resin (Formlabs). Spectrophotometric color measurements were recorded at baseline and after 24 h, 48 h, 72 h, 7 days, 30 days, and 60 days of storage in dry conditions or water. Color change (ΔE₀₀), yellowness index (YIO), and relative translucency parameter (RTP₀₀) were calculated. Visual shade matching against the VITA Classical guide was performed at baseline and 60 days by four calibrated evaluators. Instrumental data were analyzed using repeated‑measures ANOVA with Tukey's test; visual scores were analyzed with Kruskal-Wallis and Dunn's tests, and inter‑observer agreement assessed with Fleiss' kappa. RESULTS: Shade, storage condition, and time significantly affected ΔE₀₀ and YIO, while RTP₀₀ was affected only by shade. Water storage accelerated color change, with all shades exceeding acceptability thresholds by 30 days. BL showed the greatest ΔE₀₀, while A3 demonstrated the least change. Yellowness decreased over time, particularly in lighter shades stored in water. No clinically relevant changes in RTP₀₀ values were identified. Visual evaluations showed fair agreement (K = 0.311). After 60 days, BL improved in visual match to its reference tab, whereas A3 exhibited poorer matching following water storage. CONCLUSIONS: Color stability of 3D‑printed denture tooth resin is shade dependent and strongly influenced by storage medium and duration. Visual perception depends on both the magnitude and direction of color shift, highlighting the need to combine instrumental and visual methods when assessing esthetic dental materials.