## 3 Results  
Figure 1 shows the XRD pattern of the Wave and Freedom pellets light-cured for 40 s. All samples are amorphous, which is demonstrated by a broad diffraction peak centred at 20 = 26\({}^{\circ}\). Both materials do not contain any crystalline add-ons. Figure 2 presents the FTIR spectra of Wave and Freedom materials before and after fluoride ions release. The characteristic bands for the dental resins are clearly visible. The bands with a wavenumber of 1000, 1159, and 1716 cm\({}^{-1}\) come from the vibrations of the C=O double bond, the band at 1296 cm\({}^{-1}\) is related to the vibration of the C-O-C molecule, the band located at 1653 cm\({}^{-1}\) corresponds to the C=C double bond characteristic for dental resins, and intense bands at 2856 and 2920 cm\({}^{-1}\) are related to the vibrations of the C-H bond. In addition, a weak band is visible around 3500 cm\({}^{-1}\) associated with the vibration of the O-H group. Spectra before and after release of fluoride ions are very similar, which shows that there are no structural changes after immersion in different solutions. The Wave material contains an acrylic derivative and also SiO\({}_{2}\). The Si-O-Si groups were observed at 1000-1250 cm\({}^{-1}\) (stretching vibration) and at 700-800 cm\({}^{-1}\) (deformation vibration). The vibration of the Si-O-Si group overlaps with C=O vibrations at about  
Figure 1: XRD diagrams of studied materials. The study was performed for one randomly selected sample of each material: Wave and Freedom. Figure 2: FTIR spectra of Wave (**left**) and Freedom (**right**) materials before and after fluoride release in different media. 1000 cm\({}^{-1}\) on the infrared spectrum [34]. Furthermore, the Freedom material also contains the acrylic derivatives as well as strontium-fluoride glass that is characterized with high transparency in the measured range up to 900 cm\({}^{-1}\) (the bands are not visible). Additionally, on the infrared spectra, the peaks were located at a range from 1025 to 1080 cm\({}^{-1}\) (stretching vibrations) and at 735-775 cm\({}^{-1}\) corresponding to PO4\({}^{3-}\) groups. It is related to the deposition of phosphate salts from an artificial saliva. The similar observations were reported regarding dental cements in the literature [35, 36]. Figures 3 and 4 present SEM micrographs of selected Wave and Freedom samples, respectively. The surface of the control sample is smooth for both materials (Figures 3a and 4a). The most significant changes are visible for samples after fluoride ions release in artificial saliva in pH 4.5. The surface is strongly modified with some fractal-like shapes (Figures 3d and 4d). Additionally deep craters are visible (Figures 3e and 4e). Increase of pH causes lowering of fluoride ions release and therefore smaller changes in surface of samples. The results of in-vitro release of an fluoride ions from composite Wave into nine environments differing in composition of the solution and pH in selected time periods were presented in Table 1 and in Figure 5. ANOVA analysis for dependent samples showed statistically significant differences in F-ions release in certain time periods in tested  
Figure 4: SEM images (magnification 1500\(\times\)) of Freedom samples: (**a**) control, (**b**) H\({}_{2}\)O, (**c**) NaCl, (**d**) AS pH 4.5, (**e**) AS pH 4.5 (magnification 2500\(\times\)), (**f**) AS pH 5.5, (**g**) AS pH 7.0, (**h**) AS pH 7.5. Figure 3: SEM images (magnification 1500\(\times\)) of Wave samples: (**a**) control, (**b**) H\({}_{2}\)O, (**c**) NaCl, (**d**) AS pH 4.5, (**e**) AS pH 4.5, (**f**) AS pH 5.5, (**g**) AS pH 7.0, (**h**) AS pH 7.5.  
incubation conditions (\(p<0.0001\) for all). The significantly highest levels of F-ions release were observed after 1 h and 3 h of incubation for all environments, especially into deionized water and 0.9% NaCl. The cumulated concentration of F-ions was significantly highest during incubation in deionized water and AS pH 5.5 (Table 2 and Figure 6 left).