IADR Abstract Archives
Properties and Accuracy of 3D Printed Lithium Disilicate Restorations
Objectives: The aim of the study was to evaluate the feasibility of 3D printing (additive manufacturing) lithium disilicate glass-ceramic crowns using ceramic stereolithography.
Methods: Lithium disilicate glass powder (SiO2-Li2O-P2O5-ZrO2-Al2O3-K2O-CeO2) was dispersed into a photocurable resin, and test specimens were printed and then fired (sintered/crystallized). Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) were used to determine what effect the additives necessary for printing have on thermal and crystallographic properties. Fired material strength was measured in biaxial flexure (n=12). The microstructure was evaluated by SEM. A crown STL file was generated by 3D scanning a prepared model and multiple copies of the crown were printed, fired, and then 3D scanned. Dimensional accuracy of the printed crowns was assessed by comparison to the STL file using Geomagic Qualify™.
Results: DSC evidenced that the additives that enable 3D printing had no effect on glass transition, crystallization, and melt temperatures of the material. XRD of fired samples verified formation of the desired lithium disilicate crystals, which give the material its high strength and fracture toughness. Biaxial flexure strength of the material was 270 (±23) MPa, ~25% lower than commercial material. SEM revealed lower crystallinity compared to commercial material, and some residual porosity, both of which are likely contributors to the reduced strength. Root mean square error (RMSE) of the scanned printed crowns compared to the reference model were in the range 50 - 60 microns.
Conclusions: Initial results of 3D printing lithium disilicate crowns indicate that commercial standards for material properties and contour dimensions can be met with engineering optimization of material formulation and key processing steps. The process offers a number of advantages compared to milling, including the ability to form thinner structure, and to batch process hundreds of parts simultaneously, which could radically change the economics of producing dental restorations.
Methods: Lithium disilicate glass powder (SiO2-Li2O-P2O5-ZrO2-Al2O3-K2O-CeO2) was dispersed into a photocurable resin, and test specimens were printed and then fired (sintered/crystallized). Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) were used to determine what effect the additives necessary for printing have on thermal and crystallographic properties. Fired material strength was measured in biaxial flexure (n=12). The microstructure was evaluated by SEM. A crown STL file was generated by 3D scanning a prepared model and multiple copies of the crown were printed, fired, and then 3D scanned. Dimensional accuracy of the printed crowns was assessed by comparison to the STL file using Geomagic Qualify™.
Results: DSC evidenced that the additives that enable 3D printing had no effect on glass transition, crystallization, and melt temperatures of the material. XRD of fired samples verified formation of the desired lithium disilicate crystals, which give the material its high strength and fracture toughness. Biaxial flexure strength of the material was 270 (±23) MPa, ~25% lower than commercial material. SEM revealed lower crystallinity compared to commercial material, and some residual porosity, both of which are likely contributors to the reduced strength. Root mean square error (RMSE) of the scanned printed crowns compared to the reference model were in the range 50 - 60 microns.
Conclusions: Initial results of 3D printing lithium disilicate crowns indicate that commercial standards for material properties and contour dimensions can be met with engineering optimization of material formulation and key processing steps. The process offers a number of advantages compared to milling, including the ability to form thinner structure, and to batch process hundreds of parts simultaneously, which could radically change the economics of producing dental restorations.