In silico Fracture Aanalysis of CAD/CAM Composite Crowns

Objectives: Fractographic analysis has been used to investigate fracture behavior of CAD/CAM composite crowns by subjecting them to compression tests. However, it is difficult to investigate detail of fracture including its initiation and propagation by in vitro tests. The aim of this study was to determine the fracture initiation points and the order of fracture of CAD/CAM composite crowns by in silico nonlinear dynamic finite element analysis (FEA).
Methods: The following materials were used; Cerasmart (CS, GC), Katana Avencia Block (KA, Kuraray Noritake Dental), and Shofu Block HC (HC, Shofu) as CAD/CAM crowns, Panavia SA Cement Plus (SA, Kuraray Noritake Dental) as a luting material, and Clearfil DC Core Plus (DC, Kuraray Noritake Dental) as an abutment. Elastic moduli and fracture strains of each material were obtained from the stress-strain curve after in vitro three-point bending tests. Using the data obtained, fracture initiation points and the order of fracture of the materials were determined by in silico nonlinear dynamic FEA. Load-displacement curves were statistically compared with the results of in vitro compression tests (Pearson’s correlation test,α=0.05).
Results: The nonlinear dynamic FEA demonstrated that fracture initiation point was primary observed near lingual side of CAD/CAM crowns and immediately propagated to the central fossa. The models were fractured following in vitro fracture strains, showing the same order for the products tested (CS/KA/HC, SA, and DC). Load-displacement curves with the use of CS, KA, and HC were significantly correlated to those for in vitro compression tests results (CS: r=0.985, p<0.05, KA: r=0.987, p<0.05, and HC: r=0.997, p<0.05).
Conclusions: In silico model established in this study clarified fracture initiation points of CAD/CAM composite crowns and the order of fracture among the products, suggesting that the present approach is useful to analyze the mechanical properties of CAD/CAM composite crowns in detail.