## 4 Discussion
However, in this study, fluoride release was found to increase significantly due to ionizing radiation only with Fuji Triage and Fuji IX; the release of fluoride was higher in the experimental group compared to the control group in certain test periods. During the entire test period, Beautiful II released relatively little fluoride compared to the other materials. This result is also consistent with the results of previous studies [35]. The fluoride-releasing capacity of Beautiful II was reportedly not as high as that of materials based on glass ionomers [36]. Beautiful II is a gel substance containing S-PRG filler particles in the resin matrix [37]. The process for the preparation of S-PRG fillers involves theinteraction of the fluoridated glass filler surface with polyacrylic acid in the presence of water, resulting in acid-base reactions. Giomer materials do not have an acid-base reaction; so, they do not have a glass ionomer matrix phase [38]. The amount of fluoride released by giomer materials has been found to be lower than that of GIC-based materials, as they contain only S-PRG particles as the fluoride component [35; 38]. In addition, it has been suggested that the resin in resin-based products may act as a diffusion barrier for water and fluoride [37]. It is well known that fluoride release from GICs is highest on the first day and then decreases sharply before stabilizing after three to four weeks [31; 32; 35; 37]. The rapid elution of fluoride at the surface of glass particles due to an acid-base reaction is known as the \"burst effect\". Giomer Beautiful II did not show a burst effect, which was consistent with [PERSON] et al. 's research, where the conventional and resin-modified SICs developed an initial burst effect, while the compomer and giomer did not [24]. The results are also correlated with the research of [PERSON] et al., where the bulk giomer did not show the mentioned effect [38]. The slower release of fluoride ions from Beautiful II can be attributed to its hydrophobic resinous matrix and relatively small amount of S-PRG. Similar to our study, [PERSON] et al. also reported a higher release of fluoride ions from SIC compared to giomer [36]. According to their research, differences in the release of fluoride ions between the materials could be caused by the higher porosity of SIC, the lack of matrix phase inside the giomer because there is no acid-base reaction, and the incorporated resin components in the giomer. In addition, since PRG was previously reacted with fluoroaluminosilicate glass and with acid, water sorption had no influence in the acid-base reaction. Materials like giomer and compomers contain resins in their composition that form a barrier that reduces the possibility of water diffusion and fluoride ions, depending on the solubility of the individual filler [39]. In our study, giomer showed the lowest cumulative release of fluoride ions, and according to the study of [PERSON] et al., these values can be explained by the characteristics of the material, where giomers include polyacrylic acid from PRG rather than the modified polyalkenoic acid amino acid in PRG [40]. They also discovered that the experimental giomers containing hydrophilic and flexible polymer matrix based on UDMA showed a higher cumulative release of fluoride ions than the commercial giomers based on rigid and hydrophobic dimethacrylates (TEGDMA). The initial fluoride release of Equia Forte HT, Fuji Triage, and Fuji IX showed a burst effect, in agreement with previous studies [28; 29; 30; 31]. Ionizing radiation had no effect on the fluoride release in Equia Forte HT, while in Fuji Triage and Fuji IX, we found a significant difference and higher release in the experimental group. The highest fluoride release values were obtained from Equia Forte HT, Fuji Triage, and Fuji IX in the experimental and control subgroups on the first day, which may be attributed to its chemical composition, as found in previous studies [30; 31; 32].