Optical behavior and translucency parameter of additively manufactured 3Y-TZP zirconia: influence of thickness and build orientation.

OBJECTIVES: To evaluate the influence of thickness and build orientation on the optical properties and relative translucency of an additively manufactured 3Y-TZP zirconia system and to compare its optical behavior with that of a subtractively manufactured 3Y-TZP zirconia system. MATERIALS AND METHODS: Zirconia discs were fabricated at five thicknesses (0.25-2.00 mm) and allocated to three groups: additively manufactured at 0º (AM0º), additively manufactured at 90º (AM90º), and subtractively manufactured (SM) (n = 9). Spectral reflectance was measured over white and black backgrounds. Kubelka-Munk scattering (S) and absorption (K), transmittance (T%), light reflectivity (RI), infinite optical thickness (χ∞), and albedo coefficient (a) were calculated. Relative translucency (RTP00) and translucency differences were determined according to translucency perceptibility and acceptability thresholds. RESULTS: Scattering was the dominant optical property governing light extinction in all groups (0.978 < a < 0.999). Scattering and absorption increased, whereas transmittance decreased, with increasing specimen thickness. The SM zirconia system showed lower scattering and higher transmittance than the AM zirconia system. RTP00 values were higher for SM zirconia than for AM 3Y-TZP zirconia at equivalent thicknesses. Translucency differences between SM and AM groups exceeded the translucency acceptability threshold, whereas differences between AM0º and AM90º remained below the perceptibility threshold. CONCLUSIONS: The additively manufactured 3Y-TZP zirconia system exhibited higher scattering and lower translucency than the subtractively manufactured 3Y-TZP zirconia system, whereas differences in translucency between build orientations remained below the perceptibility threshold. CLINICAL RELEVANCE: The additively manufactured 3Y-TZP zirconia system exhibited lower translucency than the subtractively manufactured 3Y-TZP zirconia system at equivalent thicknesses. These findings may be considered when selecting between the evaluated zirconia systems for esthetically demanding restorative situations.