Mechanical Performance of Stereolithography-Printed Zirconia

Objectives: To evaluate the mechanical properties of a partially stabilized zirconia suitable for dental applications that is processed by stereolithographic-based AM. Additive manufacturing (AM) of zirconia is becoming of increasing interest for dental crowns and related appliances due to the substantial freedom available in the design and fabrication process. However, due to the novelty of the field and the challenges associated with printing of dense bulk ceramics suitable for dental applications, there are limited examples of AM zirconia with comparable mechanical properties to that of traditionally manufactured zirconia.
Methods: Bulk printed samples were prepared for and evaluated by hardness (n=3), indentation fracture resistance (n=3) and flexural strength (n=30) according to the applicable ASTM standards. The density, elastic modulus, hardness, indentation fracture resistance, flexure strength, and Weibull statistics were assessed for the printed samples as well as a traditionally manufactured zirconia reference material (control). Results from the property measurements were compared using a one-way ANOVA with repeating measures.
Results: According to the hardness, elastic modulus, and flexural strength of the 3D printed zirconia, the mechanical properties were not significantly different from that of traditionally manufactured zirconia (p>0.05). Furthermore, an evaluation of the Weibull statistics for the flexure strength distributions showed that the printed material resulted in strength distribution better than that of the reference material. However, the measures of strength for the AM zirconia were dependent on the direction of applied stress in relation to the layer orientation.
Conclusions: The mechanical properties of printed zirconia can meet or exceed those of traditionally manufactured zirconia. Stereolithography is a strong candidate to replace the traditional manufacturing processes presently used for fabricating dental implant materials.