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

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 KIc = 4.48 ± 0.11 MPam0.5 for the standard processing tolerance and KIc = 4.55 ± 0.31 MPam0.5 for the alternative tolerance. The results revealed a significant influence of cutting offset and notch geometry on KIc when using CNB method. The test medium also has a significant influence on KIc 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, KIc can be determined with high reliability. There is no difference between the involved laboratories, but significant influence of cutting offset on KIC was observed. SIGNIFICANCE: The CNB method is suitable method for determination of KIc 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.

Hydrothermal Ageing and Its Effect on Fracture Load of Zirconia Dental Implants.

Due to growing demand for metal-free dental restorations, dental ceramics, especially dental zirconia, represent an increasing share of the dental implants market. They may offer mechanical performances of the same range as titanium ones. However, their use is still restricted by a lack of confidence in their durability and, in particular, in their ability to resist hydrothermal ageing. In the present study, the ageing kinetics of commercial zirconia dental implants are characterized by X-ray diffraction after accelerated ageing in an autoclave at different temperatures, enabling their extrapolation to body temperature. Measurements of the fracture loads show no effect of hydrothermal ageing even after ageing treatments simulated a 90-year implantation.

Assessing the osteogenic potential of zirconia and titanium surfaces with an advanced in vitro model.

OBJECTIVES: In recent years, zirconia dental implants have gained increased attention especially for patients with thin gingival biotypes or patients seeking metal-free restoration. While physical and chemical material surface properties govern the blood-material interaction and subsequent osseointegration processes, the organizational principles underlying the interplay of biochemical and biophysical cues are still not well understood. Therefore, this study investigated how the interaction of a microstructured zirconia surface with blood influences its osseointegration potential compared to microstructured titanium with or without additional nanostructures. METHODS: Microstructured zirconia and micro- (and nano)structured titanium surfaces were fabricated via sandblasting followed by acid etching and their topographical as well as physico-chemical features were thoroughly characterized. Following, an advanced in vitro approach mimicking the initial blood interaction of material surfaces upon implantation was applied. Fibrinogen adsorption, human blood coagulation as well as their influence on cell fate decisions of primary human bone and progenitor cells (HBC) were studied. RESULTS: Obtained surface micro- and nanostructures on titanium surfaces were sharp with rugged peaks whereas zirconia surfaces were less rough with structures being shallower, more round and granular. Compared to titanium surfaces, the zirconia surface showed increased fibrinogen adsorption, higher levels of total accessible fibrinogen γ-chain moieties yielding in increased platelet adhesion and activation and consequently thrombogenicity. Mineralization of HBC on microstructured surfaces was significantly higher on zirconia than on titanium, but was significantly lower compared to titanium surfaces with nanostructures. SIGNIFICANCE: This study provides insights into blood-material interaction and subsequent cellular events that are important for implant surface development.

On the feasibility of the Chevron Notch Beam method to measure fracture toughness of fine-grained zirconia ceramics.

OBJECTIVE: The fracture toughness determination of fine-grained zirconia ceramics using the chevron notched beam method (CNB) was investigated to assess the feasibility of this method for quality assurance and material characterization. METHODS: CNB tests were performed using four different yttria-stabilized zirconia ceramics under various testing modes and conditions, including displacement-controlled and load-rate-controlled four point bending to assess the influence of slow crack growth and identify most suitable test parameters. For comparison, tests using single-edge V-notch beams (SEVNB) were conducted. RESULTS: It was observed that the CNB method yields well-reproducible results. However, slow crack growth effects significantly affect the measured KIC values, especially when slow loading rates are used. To minimize the effect of slow crack growth, the application of high loading rates is recommended. SIGNIFICANCE: Despite a certain effort needed for setting up a sample preparation routine, the CNB method is considered to be very useful for measuring and controlling the fracture toughness of zirconia ceramics.

[German Version of the Social Impact Scale (SIS-D)--Pilot Testing of an Instrument for Measuring Experienced Stigmatization in a Sample of Cancer Patients]. / Die deutsche Version der Social Impact Scale (SIS-D)--Pilottestung eines Instrumentes zur Messung des Stigmatisierungserlebens an einer Stichprobe von Krebspatienten.

PURPOSE: PURPOSE of this study was to investigate the psychometric properties of the newly adapted German Version of the Social Impact Scale (SIS), a multidimensional questionnaire measuring perceived stigmatization. METHODS: The SIS was translated into the German language following state-of-the-art criteria and completed in a sample of 139 outpatients with mixed tumor entities. In addition to the SIS-D, participants answered questions about their experience of discrimination and perceived visibility of their disease as well as about illness beliefs and perceptions of cancer control. RESULTS: Comparably to the original scale, exploratory factor analysis resulted in a 4-factor solution and the following dimensions: "social isolation" (Cronbachs α=0.89), "social rejection" (α=0.81), "internalized shame" (α=0.81) and "financial insecurity" (α=0.81). DISCUSSION: Considering the results of this pilot study, it can be concluded that the German version of the SIS is an instrument measuring perceived stigmatization in cancer patients with very good psychometric properties. However, further validation studies are considered necessary.