# Effect of the Silanization of Aerosil OX50 in the Properties of Light-Cured Dental Composites
## 2 Materials and Methods
### Characterization of the Filler and Experimental Composites  
To verify the occurrence of filler silanization and to analyze the thermal behavior of dental composites, a thermogravimetric analysis (TGA) of 50 to 800 \({}^{\circ}\)C was performed in a Perkin Elmer TGA-7 (Norwalk, CT, USA), with a heating rate of 10 \({}^{\circ}\)C/min and nitrogen flow of 50 mL/min. For the study, 3 mm diameter and 1 mm thickness samples were prepared after polymerization for 40 s.  
The morphology of silanized and unsilanized aerosil OX50 was observed on a TES-CAN VEGA3 scanning electron microscope, and it was coated using an ion sputter coater SBC-12 (KYKY TECHNOLOGY CO., Beijing, China). The study was carried out at an acceleration voltage of 25 kV with a magnification of 50,000 times. From the micrographs obtained, 100 measurements of aerosil OX50 particles were made using the ImageJ program, version 1.54d. These measurements allowed us to obtain particle size distribution of the filler and thus estimate their average size. Fourier transform infrared spectroscopy (FTIR) was used for the characterization of the filler and determination of the degree of conversion in the composites. The aerosil OX50 was analyzed in a Thermo Nicolet 8700 spectrometer (Madison, WI, USA), with a resolution of 4 cm\({}^{-1}\), 100 scans, and in the spectral interval of 4000-500 cm\({}^{-1}\). The samples were dispersed in KBr and the degree of conversion (DC) determined by recording transmission spectra in the 4000-600 cm\({}^{-1}\) range, with the same resolution and 50 scans. Three replicates of each sample were run at 0, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, and 80 s after irradiation. The DC of every dental resin composite was calculated from the absorbance intensities (\(R\)) of the aliphatic C=C bond (1638 cm\({}^{-1}\)) against the internal standard of the aromatic C=C bond (1608 cm\({}^{-1}\)), determined before and after polymerization. The degree of conversion (%) was calculated according to Equation (1) [20; 21; 22]. \[\text{DC (\%)}=100\times[1-(R_{cured}/R_{not\ cured})] \tag{1}\]  
The depth of cure, water sorption (\(A\)), and solubility (\(S\)) tests were evaluated according to the specifications described in the ISO 4049:2019 standard [12]. For the depth of cure, three cylindrical specimens (6 mm in height and 4 mm in diameter) were irradiated for 40 s on one side. After the polymerization process, the specimen was removed from the mold and any soft material was scraped using a plastic spatula. The height was measured with a micrometer (0-25 mm, 0.01 mm precision), the obtained value was divided by two, and the measured magnitude was reported as the depth of cure of the material. Water sorption and solubility tests were performed using five disc-shaped specimens (1 mm in \begin{table}
\begin{tabular}{c c c} \hline \hline
** Composites** & **Organic Matrix** & **Inorganic Filler** \\ \hline C145 & Bis-GMA/TEEGDMA/MPS (M1) & \\ C445 & Bis-GMA/TEEGDMA (M4) & \\ \hline C145s & Bis-GMA/TEEGDMA/MPS (M1) & \\ C445s & Bis-GMA/TEEGDMA (M4) & \\ \hline TT & Bis-GMA/TEGDMA & Mixtures of oxides and \\  & & copolymers (82\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition of experimental light-cured dental composites. height and 15 mm in diameter). The samples were cured with nine overlapped irradiations on one side (40 s for each irradiation; 360 s in total). Diameter and thickness are measured with a micrometer (0-25 mm) to calculate the volume (\(V\)). The samples are weighed and stored in a desiccator until constant weight, the final mass is taken as \(m_{1}\). Then, they are immersed in distilled water (\(m_{2}\)) for seven days at 37 \({}^{\circ}\)C and placed again in a desiccator until a constant mass (\(m_{3}\)). For the calculations, Equations (2) and (3) were used. \[A=(m_{2}-m_{3})/V \tag{2}\]  
\[S=(m_{1}-m_{3})/V \tag{3}\]  
The Origin8 computer program was used for data processing.