# Optimization of Mechanical and Setting Properties in Acrylic Bone Cements Added with Graphene Oxide
## 3 Results and Discussion
### Mechanical Properties
#### 3.2.2 Bending Properties
According to ISO, the bending modulus of all formulations was between 2.4 and 2.7 GPa (Table 7), which means that all formulations studied present bending modulus values above 1800 MPa, which is the minimum required for ABCs 5833-02 [51]. The formulations with 0.3 wt.% of GO, 1 or 5 h of sonication, and 2.5 wt.% of BPO presented the highest values in this property, represented in higher stiffness of the cements. Figure 9: Interaction plot between the effect sonication time vs. GO/liquid ratio and BPO/solid ratio vs. GO/liquid ratio for the Bending variable modulus. In the ABCs formulations, it is necessary to comply with the mechanical and setting properties described in ISO 5833-02 [51] to guarantee the implant's long-term stability [11]. Considering that most of the formulations studied met all the mechanical and set requirements specified in the standard, a selection criterion based on the bending strength was employed since some formulations did not reach the minimum value required. In an ABC, it is desirable low values of \(T_{max}\), moderate \(t_{set}\) to facilitate the application of cement (in applications such as vertebplasties and kyrophplasties, longer setting times are desirable as it allows the surgeon to inject the cement), and high mechanical performance that allows the adequate transfer of loads during the patient's daily activities. Table 8 presents a summary of the formulation's properties with better performance in bending strength. Although all the formulations mentioned in this table accomplish the requirements outlined in ISO 5833-02, those with 0.3 wt.% of GO independent of sonication time and BPO content showed the highest mechanical performance. That allows adequate load transfer during the patient's daily activities [7]. The longest \(t_{set}\) that facilitates cement application and the lowest \(T_{max}\) values decrease the risk of thermal necrosis of the surrounding tissue. The characteristics mentioned in the formulations with 0.3 wt.% of GO make them promising to be applied as ABCs; therefore, complementary studies of properties such as residual monomer content, cell viability, antiviral activity, among others, are suggested to evaluate how these properties are affected by the BPO content and the sonication time of GO nanoparticles, to limit these factors. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Sonication Time**} & \multicolumn{1}{c}{**Mean**} & \multicolumn{3}{c}{**BPO/Solid Ratio**} & \multicolumn{1}{c}{**Mean**} & \multicolumn{1}{c}{**Grouping \({}^{*}\)**} \\ \multicolumn{1}{c}{**‘GO/Liquid Ratio**} & \multicolumn{1}{c}{**(MPa)**} & & \multicolumn{1}{c}{**\({}^{*}\) GO/Liquid Ratio**} & \multicolumn{1}{c}{**(MPa)**} & \multicolumn{1}{c}{**Grouping \({}^{*}\)**} \\ \hline
**1-0.3** & **2690.23** & **A** & & & 2.5-0.3 & 2/06.26 & **A** & \\
**5-0.3** & 2651.86 & **A** & B & & & 2.0-0.3 & 2635.83 & B & \\
1-0.5 & 2595.33 & B & C & & 2.5-0.2 & 2594.27 & B & C & \\
5-0.2 & 2574.34 & C & D & & 2.5-0.5 & 2583.08 & B & C & \\
1-0.2 & 2568.70 & C & D & & 2.0-0.1 & 2558.13 & C & D \\
1-0.1 & 2552.97 & C & D & & 2.0-0.0 & 2556.24 & C & D \\
5-0.1 & 2543.64 & C & D & E & 2.0-0.2 & 2548.78 & C & D \\
1-0.0 & 2534.07 & C & D & E & 2.5-0.1 & 2538.47 & C & D \\
5-0.0 & 2521.01 & & D & E & 2.0-0.5 & 2499.69 & & D \\
5-0.5 & 2487.44 & & & E & 2.5-0.0 & 2498.84 & & D \\ \hline \hline \end{tabular} \({}^{*}\) Means that do not share a letter are significantly different.  
\end{table} 
Table 7: Grouping information for the bending modulus using Tukey’s test and 95% confidence.