Title: 1736 - Round Robin Fracture Toughness of an Indirect Resin Composite
Bjoern Theelke, University of Birmingham
Ulrich Lohbauer, University of Erlangen
Martin Rosentritt, University of Regensburg
Nicoleta Ilie, Ludwig-Maximilians-University
Holger Hauptmann (Presenter)
3M Deutschland GmbH
Objectives: Aim of this study was to investigate comparability and reliability of Fracture Toughness (K1c) measurement of a highly filled experimental indirect resin composite via Single-Edge-V-Notch-Beam (SEVNB) method carried out by four test centers.
Methods: Two test sequences were conducted by four test centers using a thermal cured experimental composite material with a resin/inorganic filler ratio of 20/80 by weight. Within sequence “A” each test center run complete tests following standards as shown in table 1 (3-point-bending-mode, load speed 0.5mm/min). Notch depth and tip radius were determined using a laser scanning microscope (VK-X200, Keyence). For sequence “B” all test-bars (18x4x3mm) were prepared identically by one operator with same material/batch as above followed the specifications of ISO6872:2008 (3-point-testing: 12mm load span, 0.5mm/min load speed). Statistical analysis was conducted within a test sequence and between test centers using Tukey test (0.95 confidence level).
Results: Results of sequence A and B are listed in table1. Fracture toughness values from 0.97 to 1.92 MPa*m^0.5 were measured for sequence A and from 1.27 to 2.15 MPa*m^0.5 for sequence B. Sample preparation in the hand of one operator reduced scattering of notch depth and tip radius significantly. The inter test center deviation was also reduced from 56% to 32%. Within sequence “B” a strong positive linear correlation was found between K1c and fracture force (R2=0.95). No considerable correlations were found between K1c against notch depth and tip radius.
Conclusions: Based on the results above the determination of K1c of composite materials in different test setups has to be critical reviewed. Standardization of test conditions is mandatory for a sound fracture toughness evaluation.
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The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: None