Ultra-High-Speed Sintering of 3.5Y-TZP Zirconia: Time Reduction Without Compromising Translucency
Tatiana Roman1,2, Hamdi Jmal3, Teissir Ben Ammar4
1Strasbourg University Hospitals, INSERM UMR_S 1121, CNRS EMR 7003, University of Strasbourg, Biomaterials and Bioengineering, CRBS, Strasbourg, France.
Objectives:
To assess, firstly, the impact of three sintering speeds on translucency and grain size of 3.5Y-TZP zirconia (Katana HT) across clinically relevant thicknesses, and secondly, the effect of thermocycling on translucency.
Materials And Methods:
Disc specimens were fabricated at six thicknesses (0.7-2.0 mm) and sintered using SLOW (7 h), FAST (90 min), or UHSS (18 min) protocols. Translucency (TP00, TPab) was calculated after color measurements with a VITA Easyshade V on white and black background before and after thermocycling (n = 15). Grain size and crystalline composition were assessed was analyzed using SEM images (linear intercept). The effects of thickness, sintering, and thermocycling were quantified using a three-way ANOVA with η2a linear mixed-effects model with specimen as a random factor and partial η2.
Results:
Thickness was the primary factor determining translucency (pη2 = 0.97, p < 0.001). In addition, the sintering protocol had a statistically significant, but limited effect (pη2 = 0.360.29). FAST produced higher translucency than UHSS (p = 0.01)Sintering protocols resulted in statistically significative translucency differences, yet within the acceptability thresholds (ΔTP00 < 2.627). The effects of thermocycling were negligible (pη2 < 0.001 = 0.003). Grain size decreased with faster sintering (p < 0.05), with no SEM-detected degradation after thermocycling. Crystalline composition was affected by sintering protocol. The effects of thermocycling were negligible for all outcomes.
Conclusions:
Considering the 3.5Y-TZP zirconia composition and the furnace specificity, translucency was predominantly influenced by thickness, while sintering speed exhibited minimal clinical impact. UHSS enables major time reduction without compromising optical performance.
Clinical Significance:
Within the limitations of this in vitro study and within the tested furnace systems, ultra-high-speed sintering protocolUHSS allowed a substantial reduction in 3.5Y-TZP processing time while maintaining translucency within clinically acceptable thresholds. Ultra-high-speed sintering protocols for 3.5Y-TZP restorations, appear to be a promising solution, reducing processing time while maintaining translucency within clinically acceptable thresholds. Restoration thickness remains the primary design parameter for achieving desired translucency.
