Fracture toughness of 3Y-TZP ceramic measured by the Chevron-Notch Beam method: A round-robin study

Sabine Begand; Sebastian Spintzyk; Jürgen Geis-Gerstorfer; Christoph Bourauel; Ludger Keilig; Ulrich Lohbauer; Christin Worpenberg; Andreas Greuling; Ranko Adjiski; Klaus D Jandt; Nina Lümkemann; Bogna Stawarczyk; André Güllmar; Andreas Kailer; Natalie Oberle; Marc Stephan

doi:10.1016/j.dental.2022.05.001

Fracture toughness of 3Y-TZP ceramic measured by the Chevron-Notch Beam method: A round-robin study

Dent Mater. 2022 Jul;38(7):1128-1139. doi: 10.1016/j.dental.2022.05.001. Epub 2022 May 23.

Authors

Sabine Begand¹, Sebastian Spintzyk², Jürgen Geis-Gerstorfer², Christoph Bourauel³, Ludger Keilig³, Ulrich Lohbauer⁴, Christin Worpenberg⁵, Andreas Greuling⁵, Ranko Adjiski⁶, Klaus D Jandt⁶, Nina Lümkemann⁷, Bogna Stawarczyk⁷, André Güllmar⁸, Andreas Kailer⁹, Natalie Oberle⁹, Marc Stephan¹⁰

Affiliations

¹ Fraunhofer Institute for Ceramics Technologies and Systems IKTS, Michael-Faraday-Str. 1, 07629 Hermsdorf, Germany. Electronic address: sabine.begand@ikts.fraunhofer.de.
² University Hospital Tübingen, Section "Medical Materials Science & Technology", Osianderstr. 2-8, 72076 Tuebingen, Germany.
³ University Hospital Bonn, Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111 Bonn, Germany.
⁴ University of Erlangen-Nuremberg, Dental Clinic 1 - Operative Dentistry and Periodontology, Glueckstrasse 11, 91054 Erlangen, Germany.
⁵ Hannover Medical School, Clinic for Dental Prosthetics, Carl-Neuberg-Straße 1, 30625 Hannover, Germany.
⁶ Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena, Germany.
⁷ Department of Prosthetic Dentistry, University Hospital, Dental School, Ludwig-Maximilians-University Munich, Goethestraße 70, 80336 Munich, Germany.
⁸ University Hospital Jena, Polyclinic for Conservative Dentistry, An der Alten Post, 407743 Jena, Germany.
⁹ Fraunhofer IWM, Freiburg, Wöhlerstraße 11, 79108 Freiburg im Breisgau, Germany.
¹⁰ Materials Competence Center bei Institut Straumann AG, Peter-Merian-Weg 12, CH-4002 Basel, Switzerland.

PMID: 35618552
DOI: 10.1016/j.dental.2022.05.001

Abstract

Objective: This interlaboratory round robin test investigated the robustness of the Chevron-Notch Beam (CNB) test method and the effect of the processing and testing variations on the fracture toughness of a dental 3Y-TZP ceramic.

Methods: The round robin test was performed precisely following the procedures recommended in ISO 24370:2005 and applied on a commercial 3Y-TZP ceramic (product information). A total of 335 test specimens with dimensions 3×4 x 45 mm³ was equally distributed among 10 participating laboratories of varying experience in fracture toughness testing. A standard operating procedure was defined with either narrow processing tolerances or alternative (wider) processing tolerances (as proposed in ISO 24370). Fracture toughness data (series 2) was analyzed using one way ANOVA followed by post hoc Tukey HSD test and 95% Confidence Intervals (CI) were computed (p < 0.05). A further, preceding round-robin (series 1) test was conducted with - more possible variations of test conditions regarding CNB notch processing and storage conditions. Those results are summarized in the supplement and discussed with the actual ISO 24370 test.

Results: Fracture toughness of the 3Y-TZP ceramic material, summarized over all laboratories was measured to K_Ic = 4.48 ± 0.11 MPam^0.5 for the standard processing tolerance and K_Ic = 4.55 ± 0.31 MPam^0.5 for the alternative tolerance. The results revealed a significant influence of cutting offset and notch geometry on K_Ic when using CNB method. The test medium also has a significant influence on K_Ic in terms of reduced fracture toughness under the influence of water. With defined testing conditions the number of valid tests and reduced standard deviation increased. In case of strictly following such standard operation procedures, K_Ic can be determined with high reliability. There is no difference between the involved laboratories, but significant influence of cutting offset on K_IC was observed.

Significance: The CNB method is suitable method for determination of K_Ic on fine-grained ceramics such as 3Y-TZP ceramic. By using tighter tolerances for processing and testing, i.e. closely following the ISO 24370 procedure, a highly-precise evaluation of fracture toughness with low data variation is achievable. The information of the storage medium should always be reported along with the data. CNB fracture toughness testing is an alternative method compared to Single-edge V-notch beam (SEVNB), especially for fine-grained ceramics.

Keywords: 3Y-TZP; Fracture toughness; ISO 6872; Interlaboratory test; Zirconia.

MeSH terms

Ceramics*
Dental Materials
Materials Testing / methods
Reproducibility of Results
Surface Properties
Zirconium*

Substances

Dental Materials
Zirconium