## 8 Discussion  
This study determined the antibacterial efficacy of various new-generation hybrid/ fluoride-releasing materials used in restorative dentistry by examining the zone of inhibition around the tested specimens in the culture plates and biofilm inhibition of these materials. Since their introduction, antibacterial activity of GICs has attracted the interest of researchers [15; 16; 28; 29; 30]. However, the methodology of these studies showed a large variety that resulted in difficulty to compare. Most studies were carried out by agar diffusion method [16; 28; 29; 30], whereas some used Direct Contact Test (DCT) [31; 32; 33]. There were also differences in the study periods. Short-term studies (24 and/or 48 h) were conducted predominantly, while a few studies were over a longer period of time [15; 31; 32]. Several factors might have an impact on the antibacterial activity of GICs, including chemical composition, fluoride release and low pH throughout the setting reaction [16; 29; 30; 33; 34]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Materials** & **Mean \(\pm\) SD** & **Median** & **Min–Max** & \(p\) \\ \hline G-aenial A’Chord & 0.096 \(\pm\) 0.020 \({}^{\text{ab}}\) & 0.105 & 0.057–0.109 & \\ Equia Forte HT Fil without coating & 0.056 \(\pm\) 0.031 \({}^{\text{a}}\) & 0.070 & 0.011–0.087 & \\ Equia Forte HT Fil with coating & 0.019 \(\pm\) 0.014 \({}^{\text{a}}\) & 0.012 & 0.005–0.042 & \\ Riva Self-Cure without coating & 0.226 \(\pm\) 0.078 \({}^{\text{b}}\) & 0.217 & 0.151–0.352 & \\ Riva Self-Cure with coating & 0.081 \(\pm\) 0.057 \({}^{\text{ab}}\) & 0.081 & 0.019–0.192 & \\ Zirconomer & 0.202 \(\pm\) 0.068 \({}^{\text{b}}\) & 0.202 & 0.070–0.269 & \\ Beautiful II & 0.110 \(\pm\) 0.038 \({}^{\text{ab}}\) & 0.099 & 0.070–0.183 & \\ Riva Silver & 0.127 \(\pm\) 0.082 \({}^{\text{ab}}\) & 0.114 & 0.057–0.295 & \\ \hline \hline \end{tabular} a and b imply significant differences.  
\end{table} 
Table 2: Amount of biofilm (OD\({}_{620\text{nm}}\)) accumulated on the fluoride-releasing restorative materials (n:10). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Materials** & **Mean \(\pm\) SD** & **Median** & **Min–Max** & \(p\) \\ \hline G-aenial A’Chord & 0.163 \(\pm\) 0.123 \({}^{\text{a}}\) & 0.240 & 0.090–0.469 & \\ Equia Forte HT Fil without coating & 0.591 \(\pm\) 0.302 \({}^{\text{b}}\) & 0.490 & 0.206–1.005 & \\ Equia Forte HT Fil with coating & 0.586 \(\pm\) 0.305 \({}^{\text{b}}\) & 0.558 & 0.300–1.201 & \\ Riva Self-Cure without coating & 1.353 \(\pm\) 0.309 \({}^{\text{c}}\) & 1.353 & 0.734–1.662 & \\ Riva Self-Cure with coating & 1.260 \(\pm\) 0.341 \({}^{\text{c}}\) & 1.260 & 0.896–1.918 & \\ Zirconomer & 1.534 \(\pm\) 0.250 \({}^{\text{c}}\) & 1.649 & 1.206–1.801 & \\ Beautiful II & 0.455 \(\pm\) 0.182 \({}^{\text{b}}\) & 0.480 & 0.174–0.653 & \\ Riva Silver & 1.713 \(\pm\) 0.273 \({}^{\text{c}}\) & 1.713 & 1.358–2.130 & \\ \hline \hline \end{tabular} a, b, and c imply significant differences.  
\end{table} 
Table 3: The Mean (\(\pm\)SD), Median, and Min–Max Ra values (\(\upmu\)m) of the fluoride-releasing materials (n:10). It was concluded in the literature that each of the investigated GICs releases fluoride ions; however, the amount of release varies [35,36]. GICs have a low pH during setting reaction, lasting from several minutes to twenty-four hours [29,30,34]. Studies highlighted the importance of their antibacterial activity, resulting largely from the release of fluoride ions [33,36]. The results of the present study showed that none of the restorative materials tested inhibited the growth of either _S. mutans_ or _L. casei_ for 16-18 h after mixing. This might be due to the susceptibility of the tested bacteria species to fluoride ions. Therefore, the first null hypothesis that there would be no difference in the antibacterial activity of fluoride-releasing materials was not rejected. The lack of bacterial growth inhibition by fluoride-releasing restoratives has also been shown in the literature [20,22]. [PERSON] et al. [34] and [PERSON] et al.