3D Printed Zirconia Dental Implants with Seamlessly Integrated Directional Surface Pores Combine Mechanical Strength with Favorable Osteoblast Response

Dental implants need to combine mechanical strength with promoted osseointegration. Currently used subtractive manufacturing techniques require a multi-step process to obtain a rough surface topography that stimulates osseointegration. Advantageously, additive manufacturing (AM) enables direct implant shaping with unique geometries and surface topographies. In this study, zirconia implants with integrated lamellar surface topography were additively manufactured by nano-particle ink-jetting. The ISO-14801 fracture load of as-sintered implants (516±39 N) resisted fatigue in 5-55°C water thermo-cycling (631±134 N). Remarkably, simultaneous mechanical fatigue and hydrothermal aging at 90°C significantly increased the implant strength to 909±280 N due to compressive stress generated at the seamless transition of the 30-40 µm thick, rough and porous surface layer to the dense implant core. This unique surface structure induced an elongated osteoblast morphology with uniform cell orientation and allowed for osteoblast proliferation, long-term attachment and matrix mineralization. In conclusion, the developed AM zirconia implants not only provided high long-term mechanical resistance thanks to the dense core along with compressive stress induced at the transition zone, but also generated a favorable osteoblast response owing to the integrated directional surface pores.Funding Information: Fei Zhang thanks the Research Foundation - Flanders (FWO Vlaanderen) for her post-doctoral fellowship (12S8418N, 12S8421N). This work was supported by the Research Fund of KU Leuven under project C24/17/084 and the Fund for Scientific Research Flanders (FWO Vlaanderen) under grants G0B2618N and G095920N. Masanao Inokoshi thanks the JSPS Grant-in-Aid for Scientific Research (C) JP19K10241. We acknowledge the use of the 3D optical non-contact profilometer within FWO project I009220N - Complexurf: Laboratory of complex surfaces and interfaces. The authors thank XJET, Prof. S. Yang and Prof. B. Van Hooreweder for the use of the XJET Carmel 1400. The authors further thank VITA Zahnfabrik for the provision of the VITA Ceramic implants (project number VITA-SAF-2020-01001).Declaration of Interests: The authors declare no competing financial interests. Ethical Approval Statement: The collection and usage of cells for biomaterial testing was approved by the Ethics Committee of the Albert-Ludwigs-University of Freiburg (vote Nr. 411/08_121010) and informed consent was given.