# Evaluation of the Impact of Various Functional Fillers on Key Properties of Dental Composites
## 3 Results  
Scanning electron microscopy (SEM) was used to analyze the fracture surfaces of dental composites. To assess the degree of homogeneity of the material, fractures of the prepared composite samples were performed. The fractures of composites containing hydroxyapatite with silver and fluorine are shown in Figure 2.  
Based on the analysis of the presented SEM images, it can be stated that the flow composite has a homogeneous surface. HAp fillings have particles with significant irregular shapes. The surface of these materials is characterized by irregularity and roughness, which is characteristic of composites with filler particle sizes of the order of several \(\mu\)m. Homogeneity (uniformity) is important because it affects the properties of the obtained materials. The surface morphology may be affected to some extent by changing the proportions of additives. The Shore hardness values varied between 53 Shore D in a HAp0%, Ag specimen, and 93 Shore D in a HAp2%, F, Ag specimen (Figure 3). There were statistically significant differences in the Shore D hardness of the tested composite specimens (\(p<0.001\)). HAp0%, Ag specimens obtained lower hardness than HAp2%, F, Ag specimens (\(p<0.001\)) and HAp5%, F, Ag specimens (\(p=0.006\)). Also, the differences were statistically significant between HAp0%, F, and HAp2%, F, Ag (\(p=0.026\)). All of the other comparisons were not statistically significant (\(p>0.05\)). The impact strength values varied between 0.049 J/cm\({}^{2}\), found in a HAp0%, Ag specimen, and 0.138 J/cm\({}^{2}\), found in the HAp0% specimen (Figure 4). There were statistically significant differences in the strength of the specimens (\(p=0.001\)). The specimens of HAp0%, F and HAp0%, Ag groups presented statically significant lower strength values than HAp0% (\(p=0.024\) and \(p<0.001\), respectively). The differences were also statistically significant between HAp0%, Ag and HAp2%, F, Ag (\(p=0.012\)). Nevertheless, differences between the combined fillers (HAp2%, F, Ag, and HAp5%, F, Ag) and the HAp0% were not statistically significant (\(p>0.05\)). Figure 2: Surface morphology of fracture composites with HAp, F, and Ag. (**A**) Fracture of the composite with 2% HAp, F, and Ag. (**B**) Fracture of the composite with 5% HAp, F, and Ag. The compressive strength values varied between 100 MPa, found in a HAp0%, Ag specimen, and 195 MPa, found in the HAp2%, F, Ag specimen (Figure 5). There were statistically significant differences in the compressive strength of the specimens (\(p\) = 0.003). The differences were statistically significant between HAp0%, Ag compared to HAp2%, F, Ag (\(p\) = 0.005) and HAp0% (\(p\) = 0.044), with HAp0%, Ag showing lower strength. All of the other comparisons were not found to be statistically significant, showing that combined fillers HAp2%, F, Ag and HAp5%, F, Ag had similar results to the HAp0% specimens (\(p\) > 0.05). Figure 4: Box plots of impact strength (J/cm\({}^{2}\)) for modified flowable composite resins (\(n\) = 5) (\(\circ\), * symbols represent outliers). Figure 3: Box plots of hardness (Shore D) for modified flowable composite resins (\(n\) = 5) (\(\circ\) symbol represents an outlier). The bending strength values varied between 46 MPa, found in a HAp0%, Ag specimen, and 128 MPa, found in a HAp0% specimen (Figure 6). Although statistically significant differences in the bending strength were found (\(p\) < 0.001), multiple comparisons showed lower values of HAp0%, Ag specimens when compared to HAp0% (\(p\) < 0.001) and HAp2%, F, Ag (\(p\) = 0.013) specimens. Also, HAp 0%, F specimens revealed lower bending strength than the HAp0% specimens (\(p\) = 0.013). All of the other comparisons were not statistically significant, showing that combined fillers HAp2%, F, Ag and HAp5%, F, Ag had similar results to the HAp0% specimens (\(p\) = 0.502 and \(p\) = 0.190, respectively). Figure 5: Box plots of compressive strength (MPa) for modified flowable composite resins (\(n\) = 5) (\(\diamond\), * symbols represent outliers).