The aim of this study was to (1) fabricate polymethyl methacrylate (PMMA) nanocomposites having better mechanical strength, (2) investigate the effects of nanobarium titanate (NBT) loadings (1–9 wt%) on tensile and flexural properties, and (3) evaluate surface roughness and hardness of the PMMA nanocomposites. The NBT was treated using a titanate coupling agent. Density, polymerization shrinkage (PS), surface roughness, and hardness were investigated. Tensile and flexural properties of PMMA nanocomposites were also evaluated. The roughness values of PMMA nanocomposites were significantly lower than those values proposed as a reference for clinical use (<200 nm). Moreover, the flexural modulus of the NBT/PMMA nanocomposites increased with increasing filler loadings. A remarkable increase in the tensile modulus values of filled PMMA was also observed ( p < 0.001). In the case of higher filler content, tensile modulus remains unaffected by filler incorporation. The tensile and flexural strength improved with increasing concentration of NBT up to 5 wt% and then decreased by an additional amount of NBT introduced into the nanocomposite resin. However, the tensile and flexural strength values of NBT/PMMA nanocomposites were higher than the PMMA matrix ( p < 0.001). Such enhancements obtained with titanate-treated NBT could lead to the promotion of the dental composites’ longevity.

In this paper, in order to predict the crack growth trajectory and to evaluate the SIF under mixed modes (I & II), one proposes a new finite element program for crack growth using the source code written in FORTRAN. The fin ite element mesh is generated using an advancing front method, where the generation of the background mesh and the construction of singular elements are also added to this developed programme to facilitate the crack process and the fracture analysis. Displacement Ext rapolation Technique (DET) was employed to evaluate the SIFs under mixed mode loading conditions. Therefore, the accuracy of both SIF`s values and the crack path predictions results are compared and validated with other relevant published research work. Ho wever, the assessment indicated that this developed fin ite element programme is reliable and robust to evaluate the SIFs and predicts the crack trajectories successfully based on the applied loading conditions.