Optical behavior of 3D-printed dental restorative resins: Influence of thickness and printing angle

Abstract

Objectives: To evaluate the influence of thickness and printing angle on the optical properties of 3D-printed dental restorative resins.

Methods: Four 3D printing resin systems were evaluated: DFT-Detax Freeprint Temp; FP- Formlabs Permanent Crown; FP- Formlabs Temporary CB; and GCT- GC Temporary-. Samples from each material were printed at 0° and 90°, and polished up to 0.5, 1.0, 1.5 and 2.0 mm thickness. Scattering (S), absorption (K) and albedo (a) coefficients, transmittance (T%), light reflectivity (RI) and infinite optical thickness (X_∞) were calculated using Kubelka-Munk's model. Data were statistically analyzed using Kruskal-Wallis¸ Mann-Whitney tests, and VAF coefficient.

Results: The spectral distribution on S, K, T%, RI,X_∞ were wavelength dependent. Although the spectral behaviors were similar for all the specimens evaluated, the values of S, K, T% andX_∞ presented significant differences between specimen thicknesses for all the materials used and for both printing orientations. Values for S and K increased, and T% and X_∞ decreased. Significant differences between 0° and 90° were found for RI values at 0.5 and 1.0 mm thick samples, for S and K at 2.0 mm, for X_∞ at 0.5 and 1.0 mm for DFT, and at 0.5 mm for FT.

Conclusions: Optical properties of 3D-printed restorative resins vary between thicknesses, and could be affected by the building orientation. Therefore, these factors should be considered in order to improve the biomimetic potential of 3D-printed dental restorative resins.

Clinical significance: Understanding the optical behavior of the 3D-printed restorative resins is essential to optimize their clinical performance.

Keywords: 3D-printed dental resin; Absorption; Kubelka-Munk Theory; Light reflectivity; Printing orientation; Scattering; Thickness; Transmission.