In silico Three-point Bending Model to Reflect in vitro Tests

Objectives: To investigate fracture of CAD/CAM composite crowns, finite element analysis (FEA) is useful. However, in silico model of compression tests of CAD/CAM composite crowns is not available. The aim of this study was to assess the validity of our in silico approach in reflecting the results of in vitro tests, focusing on three-point bending tests of each component for compression tests of CAD/CAM composite crowns.
Methods: The following materials which have been used for compression tests were included; Katana Avencia Block (KA) and Shofu Block HC (HC) as CAD/CAM crowns, Panavia SA Cement Plus (SA) as a luting material, Clearfil DC Core Plus (DC) as an abutment, and Unifast Lab type F (UL) as a supporting material. Three-point bending tests were performed using each material (4.0 × 1.2 × 14.0 mm specimen for KA and HC, 2.0 × 2.0 × 25.0 mm specimen for other materials) after storage in water for 24 h or 7 days, and flexural moduli and fracture strain were obtained from the stress-strain curve. Micro-CT analysis and weight measurement were conducted to calculate densities. Using the data obtained by those in vitro tests, fracture initiation points and the order of fracture were evaluated by nonlinear dynamic FEA.
Results: The nonlinear dynamic FEA demonstrated that fracture initiation point was primarily observed near the bottom center of the specimen similarly to in vitro tests. The models were fractured following in vitro fracture strains, showing different order of fracture after 24 h (DC, SA, UL and KA or DC, HC, SA and UL) and 7 days (DC, SA, KA and UL or DC, SA, HC and UL).
Conclusions: In silico models established in this study showed fracture properties with reflection of in vitro testing results, suggesting that the present approach can be applied to conduct in silico compression analysis of CAD/CAM composite crowns.