IADR Abstract Archives
Effect of air-Particle Abrasion on Reliability of Additively-Manufactured Zirconia Ceramics
Objectives: Due to its excellent accuracy and capability to produce dense objects, stereolithography (SLA) is the most promising additive manufacturing technology for zirconia ceramics. Still, surface finish can be compromised, which may affect materials' strength. Also, the strength may be altered when adhesion-promoting surface treatments, i.e., air-particle abrasion (APA), are employed, which are even more critical for newer translucent zirconia. The aim was to evaluate and compare the effects of APA on mechanical properties of different zirconia ceramics fabricated with SLA and dry-pressing (DP).
Methods: Disk-shaped specimens (n=90/gp) were fabricated from 3%mol. (3Y) and 5%mol. (5Y) yttria-zirconia by SLA (CeraFab 7500; Lithoz GmbH, Vienna, Austria; lateral resolution of 40 μm and layer thickness of 25 μm) and uniaxially DP (147 MPa, 30 s) that served as control. Top surface of specimens (n=60) was treated by APA with 50 μm Al2O3 at 2 bars. Half of APA specimens were treated with regeneration firing (RF; 1000°C, 15 min). Control specimens (n=30) were left in as-sintered state. Biaxial flexural strength was determined (ball-on-three-balls method; 1 mm/min) coupled with Weibull analysis and fractography (SEM). XRD and FIB-SEM determined crystal phases and depth of transformation zone (TZD), respectively. ANOVA with Tukey's post hoc and t-test was used (p<0.05).
Results: SLA zirconia exhibited lower characteristic strength (σθ) and reliability (m), regardless of zirconia type (3Y, 5Y). The APA increased σθ and m of 3Y and decreased σθ of 5Y material, whereas m was increased, regardless of fabrication method. No differences between SLA and DP zirconia were noted regarding crystal phase structure and TZD. The prevailing critical flaws for SLA and DP were process-related; size of flaws was substantially larger in SLA.
Conclusions: Compared to DP, SLA zirconia presented mechanically inferiorly, still reaching clinically-acceptable strength; whereas APA effects did not differ between SLA and DP zirconia. Main observed defects were process-related.
Methods: Disk-shaped specimens (n=90/gp) were fabricated from 3%mol. (3Y) and 5%mol. (5Y) yttria-zirconia by SLA (CeraFab 7500; Lithoz GmbH, Vienna, Austria; lateral resolution of 40 μm and layer thickness of 25 μm) and uniaxially DP (147 MPa, 30 s) that served as control. Top surface of specimens (n=60) was treated by APA with 50 μm Al2O3 at 2 bars. Half of APA specimens were treated with regeneration firing (RF; 1000°C, 15 min). Control specimens (n=30) were left in as-sintered state. Biaxial flexural strength was determined (ball-on-three-balls method; 1 mm/min) coupled with Weibull analysis and fractography (SEM). XRD and FIB-SEM determined crystal phases and depth of transformation zone (TZD), respectively. ANOVA with Tukey's post hoc and t-test was used (p<0.05).
Results: SLA zirconia exhibited lower characteristic strength (σθ) and reliability (m), regardless of zirconia type (3Y, 5Y). The APA increased σθ and m of 3Y and decreased σθ of 5Y material, whereas m was increased, regardless of fabrication method. No differences between SLA and DP zirconia were noted regarding crystal phase structure and TZD. The prevailing critical flaws for SLA and DP were process-related; size of flaws was substantially larger in SLA.
Conclusions: Compared to DP, SLA zirconia presented mechanically inferiorly, still reaching clinically-acceptable strength; whereas APA effects did not differ between SLA and DP zirconia. Main observed defects were process-related.