# Effect of the Silanization of Aerosil OX50 in the Properties of Light-Cured Dental Composites
## 3 Results
### Characterization of the Experimental Composites  
The measurement of the degree of conversion of the unsilanized and silanized experimental composites and the monomeric mixtures was carried out at 0, 1, 2, 3, 4, 5, 10, 15,  
Figure 4: Particle size distribution of aerosil OX50. Figure 3: Characterization of the filler: (**a**) micrograph of unsilanized aerosil OX50; (**b**) micrograph of silanized aerosil OX50. 20, 25, 30, 35, 40, and 80 s of irradiation. Figure 5a shows the FTIR spectrum of the C145 composite at the different irradiation times mentioned above. The curves corresponding to each time are indicated in different colors from blue for time 0 to red for 80 s. The two bands under study in this research can be observed in the spectrum. The band corresponding to the aliphatic C=C bond appears around 1637 cm\({}^{-1}\), while the one associated with the vibrations of the C=C aromatic bond can be seen around 1612 cm\({}^{-1}\). Figure 5b shows the results obtained from the determination of the degree of conversion with time. Generally, only the degree of conversion at the final irradiation time, which in normally 40 s, is reported. In this study, in addition, the results of the degree of conversion at several times up to 80 s are reported and analyzed. The results of the depth of cure and degree of conversion at 40 s for the matrices and composites are shown in Table 2. Composite materials meet the requirements of the ISO 4049:2019 standard [12] for cure depth, showing values greater than 2 mm. The highest values are exhibited by the monomeric matrices M1 and M4, (2.95 \(\pm\) 0.01) mm and (2.94 \(\pm\) 0.01) mm, respectively. In addition, there are no statistically significant differences between the monomeric matrices M1 and M4, nor between the composites prepared with them, so no effect of the silanization process was observed for this property. The experimental composites showed a greater value of curing depth than the commercial TT composite used as a reference. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Samples** & **DC (\%)** & **Depth of Cure (mm)** \\ \hline
**Property Value** & **55–80** & \(\geq\)**2** \\ \hline M1 & 86.3 (0.1) a  & 2.95 (0.01) a  \\ M4 & 85 (2) a  & 2.94 (0.01) a  \\ C145 & 71 (5) c  & 2.93 (0.02) b  \\ C145s & 79 (2) d  & 2.93 (0.01) b  \\ C445 & 80 (3) b  & 2.93 (0.01) a  \\ C445s & 76 (6) c  & 2.93 (0.02) a  \\ TT & 63 (4) e  & 2.67 (0.09) c  \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Degree of conversion at 40 s and depth of cure. Figure 5: (**a**) FTIR spectrum of the C145 composite in the region from 1680–1580 cm\({}^{-1}\) at different irradiation times; (**b**) Degree of conversion vs. irradiation time of the matrices and composites. In the case of the degree of conversion for the matrices and composites at 40 s of irradiation, values higher than 67% and, in several cases, more than 75% (C145s and C445) were obtained. As shown in Table 2, all experimental composites present DC values higher than TT, except for composite C145, which does not have significant differences from it. Furthermore, the highest values of this property correspond to matrices M1 and M4, (86.3 \(\pm\) 0.1)% and (85 \(\pm\) 2)%, respectively. The results of the water sorption and solubility test are shown in Figure 6. The highest values of this property evaluated for the different formulations correspond to the pristine monomeric matrices M1 and M4, which slightly exceed the limit value in the ISO 4049:2019 standard [12]. In the case of absorption, the best values correspond to the C145s, C445 and C445s composites, and no significant differences between them are observed. Furthermore, the commercial TT composite showed the lowest water sorption values and significant differences with respect to the experimental composites. Regarding water solubility, no significant differences were observed between C145 and C145s, nor between C445 and C445s.