Shade variability and stability in interim and definitive tooth-colored resin-based restorative materials: Comparing manufacturer-claimed shades to a universal shade guide.

Abstract

Purpose: To evaluate the shade variability and stability of interim and definitive tooth-colored restorative materials by comparing manufacturer-claimed shades to a universal shade guide before and after thermocycling.

Materials and methods: Eight commercially available tooth-colored restorative materials were tested, including conventional, milled, and 3D-printed types. Each material was categorized into three shade subgroups (A1, A2, and A3), with 10 samples per subgroup. The color differences (ΔE₀₀) between the materials' shades and a universal shade guide (VITA classical A1-D4) were measured using a digital spectrophotometer before (ΔE_00-R1) and after (ΔE_00-R2) thermocycling. A higher ΔE₀₀ indicated higher variability between the manufacturer-claimed shade and a corresponding universal shade guide. The ΔE₀₀ was analyzed using the CIEDE2000 formula, and statistical analysis was performed to evaluate the effects of materials, shades, and thermocycling. In addition, the ΔE₀₀ was compared against 50%:50% perceptibility threshold (PT) and 50%:50% acceptability threshold (AT) using one-sample t-tests (α = 0.05).

Results: The observations from descriptive statistics showed that the milled Aidite group exhibited the lowest ΔE₀₀. In addition, shade A1 showed higher ΔE₀₀ than A2 and A3 within each group; however, the ΔE₀₀ between shade types A2 and A3 was similar. The three-way interaction among materials, shades, and thermocycling was significant (p < 0.0001), highlighting their combined effect on ΔE₀₀. No significant interaction between shade and thermocycling was observed (p = 0.6239), suggesting that thermocycling did not significantly affect ΔE₀₀ among shade subgroups. Comparison of ΔE_00-R1 and ΔE_00-R2 against 50%:50% PT (0.8) and 50%:50% AT (1.8) revealed significant color differences beyond both thresholds for most study groups.

Conclusions: Color variability in dental restorative materials is influenced by material, shade, and thermocycling. Most samples showed significant discrepancies from manufacturer-specified shades (A1, A2, and A3) when compared to the VITA classical A1-D4 guide. Clinicians might consider using a custom shade guide that is fabricated from the same material as the prostheses to improve shade matching outcomes.