Multi-scale analysis of the influence of filler shapes on the mechanical performance of resin composites using high resolution nano-CT images.

OBJECTIVE

The aim of this study was to investigate the criteria for predicting the fracture initiation of resin composites (RCs) at the micro-scale and assess the influence of filler shapes on the flexural properties of RCs by combining nano-CT imaging and in silico multi-scale analysis.

METHODS

Experimental RCs composed of irregular-shaped (IS) silica filler (31.2 vol%/50.0 wt%) and Bis-GMA/TEGDMA were prepared. The RC specimens were scanned by a nano-CT with 500-nm resolution, and 10 micro-scale models (100 × 100 × 100 μm) were randomly extracted from a scanned region. In silico micro-scale models containing sphere-shaped (SS) fillers with the same volume content as the experimental RC were designed. Each RC model's elastic modulus and Poisson's ratio at the macro-scale were calculated using homogenization analysis. The flexural strength of the RC models were predicted by finite element analysis using the elastic moduli and Poisson's ratio values.

RESULTS

Significantly greater elastic modulus values were obtained in the X, Y, and Z directions for RC models containing IS fillers than SS fillers. Similarly, smaller Poisson's ratio values were observed in the Y and Z directions for RC model containing IS fillers than SS fillers (p < 0.05). The flexural strength of RC model containing IS fillers was significantly greater than the RC model containing SS fillers (p < 0.05).

SIGNIFICANCE: The in silico multi-scale analysis established in this study demonstrated that RC model containing irregular-shaped fillers had greater flexural strength than RC model loaded with SS fillers, suggesting that the mechanical strength of the RC can be improved by optimizing the shape of the silica fillers.