IADR Abstract Archives
Effect of Polymerization on Additive Manufacturing of Zirconia Ceramics
Objectives: Additive manufacturing has exploded in different fields over the past few years. However, 3D-printing of dental zirconia using photopolymer slurry-based techniques, such as stereolithography (SL) and digital light processing (DLP), has revealed technical issues, such as body porosities and reduced mechanical strength. To achieve high density and low porosity, low viscous slurries are highly loaded with zirconia-ceramic powder. Photopolymer polymerization is thought to negatively affect zirconia printing due to shrinkage stress. In this study, we comparatively investigated the effect of polymerization shrinkage on the density of 3D-printed and polymerized green bodies (‘3D-printed_polymerized’) versus poured and unpolymerized bodies (‘poured_unpolymerized’) by measuring biaxial bending strength (BBS), Thermogravimetry/Differential Thermal Analysis (TG/DTA) and SEM.
Methods: 3mol% yttria-stabilized zirconia was mixed in an UV-curable acrylate resin to be used as zirconia photopolymer slurry. Polymerized green bodies were prepared using an SL 3D-printer (SZ2500, SK Fine, Kusatsu, Japan). Unpolymerized bodies were prepared by pouring the same slurry in a resin mold without polymerization. Both green bodies were de-binded and sintered, upon which BBS was measured according to ISO standard 6872 (ANOVA and Tukey's post-hoc tests: α=0.05). Unpolymerized and polymerized resin (without zirconia) was examined by TG/DTA. The microstructure of both sintered zirconia bodies was characterized by SEM.
Results: BBS of the 3D-printed_polymerized bodies was significantly higher than that of the poured_unpolymerized bodies. TG of polymerized resin revealed a slow reduction as compared to that of unpolymerized resin. SEM confirmed the higher density and lower porosities of the 3D-printed_polymerized bodies.
Conclusions: 3D zirconia printing resulted in better mechanical properties and higher density, which should be ascribed in part to polymerization shrinkage upon UV curing. Furthermore, the lower vapor pressure of monomer in the poured specimens produced more porosities and cracks during de-binding. Polymerization shrinkage during 3D-printing is beneficial to achieve high zirconia density.
Methods: 3mol% yttria-stabilized zirconia was mixed in an UV-curable acrylate resin to be used as zirconia photopolymer slurry. Polymerized green bodies were prepared using an SL 3D-printer (SZ2500, SK Fine, Kusatsu, Japan). Unpolymerized bodies were prepared by pouring the same slurry in a resin mold without polymerization. Both green bodies were de-binded and sintered, upon which BBS was measured according to ISO standard 6872 (ANOVA and Tukey's post-hoc tests: α=0.05). Unpolymerized and polymerized resin (without zirconia) was examined by TG/DTA. The microstructure of both sintered zirconia bodies was characterized by SEM.
Results: BBS of the 3D-printed_polymerized bodies was significantly higher than that of the poured_unpolymerized bodies. TG of polymerized resin revealed a slow reduction as compared to that of unpolymerized resin. SEM confirmed the higher density and lower porosities of the 3D-printed_polymerized bodies.
Conclusions: 3D zirconia printing resulted in better mechanical properties and higher density, which should be ascribed in part to polymerization shrinkage upon UV curing. Furthermore, the lower vapor pressure of monomer in the poured specimens produced more porosities and cracks during de-binding. Polymerization shrinkage during 3D-printing is beneficial to achieve high zirconia density.