Zirconia fixed dental prostheses fabricated by 3D gel deposition show higher fracture strength than conventionally milled counterparts

• Published in: Journal of the mechanical behavior of biomedical materials 2022-11, Vol.135, p.105456, Article 105456
• Main Authors: Rabel, Kerstin, Nold, Julian, Pehlke, Daniela, Shen, James, Abram, Anže, Kocjan, Andraž, Witkowski, Siegbert, Kohal, Ralf-Joachim
• Format: Article
• Language: English
• Subjects: 3D gel deposition; 3D printers; Additive manufacturing; Additives; Ageing behavior; Artificial mouth; Ceramic materials; chemistry; Computer aided design; dental material; Dental Materials; Dental Porcelain; dental procedure; Dental prostheses; Dental Prosthesis; dental restoration; Dental Restoration Failure; Dental Stress Analysis; Denture; Denture, Partial, Fixed; Deposition; Dynamic loads; Energy dispersive spectroscopy; Fabrication; Filling; Fixed; Fixed dental prosthesis; fixed partial denture; Flexural Strength; Focused ion beam-scanning electron microscopies; Fracture; Fracture behavior; Fracture toughness; In-vitro; Ion beams; Laser scanning microscopy; Layer microstructures; Materials Testing; Microstructure; Partial; Restoration; Scanning electron microscopy; Surface layers; tooth prosthesis; Zirconia; zirconium; Zirconium - chemistry; zirconium oxide
• ISSN: 1751-6161; 1878-0180; 1878-0180
• DOI: 10.1016/j.jmbbm.2022.105456

Zirconia restorations, which are fabricated by additive 3D gel deposition and do not require glazing like conventional restorations, were introduced as "self-glazed" zirconia restorations into dentistry. This in vitro investigation characterized the surface layer, microstructure and the fracture and aging behavior of "self-glazed" zirconia (Y-TZP ) three-unit fixed dental prostheses (FDP) and compared them to conventionally CAD/CAM milled and glazed controls (Y-TZP -FDPs). For this purpose, the FDPs were analyzed by (focused ion beam) scanning electron microscopy, laserscanning microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and a dynamic and static loading test. For the latter, half of the samples of each material group (n = 16) was subjected to 5 million cycles of thermocyclic loading (98N) in an aqueous environment in a chewing simulator. Afterwards, all FDPs were loaded to fracture. Y-TZP -FDPs demonstrated a comparable elemental composition but higher surface microstructural homogeneity and fracture strength compared to Y-TZP -FDPs. Microstructural flaws within the FDPs' surfaces were identified as fracture origins. The high fracture strength of the Y-TZP -FDPs was attributed to a finer-grained microstructure with fewer surface flaws compared to the Y-TZP -FDPs which showed numerous flaws in the glaze overlayer. A decrease in fracture strength after dynamic loading from 5165N to 4507N was observed for the Y-TZP -FDPs, however, fracture strength remained statistically significantly above the one measured for Y-TZP -FDPs (before chewing simulation: 1923N; after: 2041N). Within the limits of this investigation, it can therefore be concluded that Y-TZP appears to be stable for clinical application suggesting further investigations to prove clinical applicability.