## 3 Results and Discussion
### Flexural Properties  
Comparative charts related to the flexural properties of the experimental dental nanocomposite resins are represented in Figure 8, while the calculated median values accompanied by their interquartile range (Q3-Q1) are clearly given in Table 3. According to the obtained results, the insertion of silanized nanosilica improved the stiffness of the formed composites. Typical flexural modulus values reported in the literature for analogue composites usually range almost from 1.40 to 4.5 GPa [14,17,19,21,23,25,24], namely, overlapping the data of the present study. Higher values up to 9.5-10.3 GPa mentioned in previous studies [24,28,30,31,66,66] could be associated with the applied shorter water aging time intervals. In particular, the overall trend of the modulus increment followed the scheme: MPS nanocomposite > MPS-ACPS nanocomposite > ACPS nanocomposite > ACPS-OTMS nanocomposite > MPS-OTMS nanocomposite > OTMS nanocomposite > Neat silica. The stiffness almost doubled for composites containing MPS (130.19%), MPS-ACPS (107.55%), and ACPS (93.71%) when compared with the counterpart filled with neat silica. The higher modulus of elasticity values being yielded by the functional silane-treated silica nanocomposites could rather be justified by the relatively better dispersion of the aforementioned particles in the polymer matrix (Figure 3b,d,g). The stiffness trend between ACPS and ACPS-OTMS composite is in contrast to the results reported by [PERSON] et al. wherein ACPS was mixed with the non-functional cross-linking silane BTSE [24]. A possible explanation could be that OTMS can provide three methoxy- groups available for silica silanization, instead of BTSE with six ethoxy- groups, which can result in more efficient coupling with silica and ultimately in more stable matrix-nanofilier interface of the composite. In the present study, the maximum flexural strength of the composites was found 44.30 MPa, i.e., in some cases much lower than that reported by other researchers [14,15,21,32,66]. This observation is reliable, as the longer aging time utilized here intended to simulate an extreme condition as it happens in the oral cavity, where the composite would be even more effectively exposed to the water molecules, as the latter would have the time needed to reach a maximum diffusion into the polymer network and highly affect the mechanical performance. It is noteworthy that a similar to modulus attitude was also detected for the strength values. The silica silanization caused a nearly 3-fold increase in the resistance of dental resin against the exerted flexural stresses, especially for MPS (189.35%), followed by MPS-ACPS (179.75%) and ACPS (162.44%) nanocomposites. The well-dispersed filler particles in the polymer network of those nanocomposites might be responsible for the normal stress distribution at the matrix-filler interface, thus limiting the agglomeration of loadings and finally improving the flexural strength. In terms of the decreasing series MPS-ACPS composite > ACPS-OTMS composite > MPS-OTMS composite, it can be stated that these comparative findings are supported by the results of Wilson