## 4 Discussion  
Our results showed that the addition of marine derived HA particles to commercially available GIC materials influenced SR, microhardness and FR, leading to rejection of the null hypothesis. HA particles used for experimental part were micro-sized because it was found that nano-HA-filled materials were rougher [22]. Additionally, micro-particles of HA are easily mixed with resin and nano-HA considerably prolongs the setting time of GICs [23]. SR values for Fuji II were significantly lower in comparison to the values for Fuji IX with no dependence on HA concentration. This is in agreement with the findings of [PERSON] et al. [24] who showed that resin modified glass ionomer cement (RMGIC) exhibited lower surface roughness than did chemically cured, possibly due to its smaller filler size  
Figure 2: Fluoride release after 24 h, 7 days, and 45 days. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mean \(\pm\) Standard Error** & **24 h (mg/L)** & **7 Days (mg/L)** & **45 Days (mg/L)** & \(p\) \\ \hline Fuji IX0 & 77.7 \(\pm\) 1.7 \({}^{\,\mathrm{c}}\) & 17.1 \(\pm\) 0.8 \({}^{\,\mathrm{d}}\) & 2.7 \(\pm\) 0.1 \({}^{\,\mathrm{d}}\) & \textless{}0.001 \\ Fuji IX2 & 138.1 \(\pm\) 1.3 \({}^{\,\mathrm{a}}\) & 24.5 \(\pm\) 0.5 \({}^{\,\mathrm{b}}\) & 3.9 \(\pm\) 0.1 \({}^{\,\mathrm{b}}\) & \textless{}0.001 \\ Fuji IX5 & 138.6 \(\pm\) 2.3 \({}^{\,\mathrm{a}}\) & 30.4 \(\pm\) 0.2 \({}^{\,\mathrm{a}}\) & 4.8 \(\pm\) 0.0 \({}^{\,\mathrm{a}}\) & \textless{}0.001 \\ Fuji IX10 & 83.3 \(\pm\) 2.3 \({}^{\,\mathrm{b}}\) & 20.8 \(\pm\) 0.4 \({}^{\,\mathrm{c}}\) & 3.3 \(\pm\) 0.1 \({}^{\,\mathrm{c}}\) & \textless{}0.001 \\ \hline Fuji II0 & 19.6 \(\pm\) 0.9 \({}^{\,\mathrm{e}}\) & 8.9 \(\pm\) 0.1 \({}^{\,\mathrm{f}}\) & 1.4 \(\pm\) 0.0 \({}^{\,\mathrm{f}}\) & \textless{}0.001 \\ Fuji II2 & 21.1 \(\pm\) 0.5 \({}^{\,\mathrm{e}}\) & 10.4 \(\pm\) 0.1 \({}^{\,\mathrm{e}}\) & 1.6 \(\pm\) 0.0 \({}^{\,\mathrm{e}}\) & \textless{}0.001 \\ Fuji II5 & 15.8 \(\pm\) 1.3 \({}^{\,\mathrm{f}}\) & 8.1 \(\pm\) 0.1 \({}^{\,\mathrm{f}}\) & 1.3 \(\pm\) 0.0 \({}^{\,\mathrm{f}}\) & \textless{}0.001 \\ Fuji III0 & 22.1 \(\pm\) 0.4 \({}^{\,\mathrm{e}}\) & 8.8 \(\pm\) 0.0 \({}^{\,\mathrm{f}}\) & 1.4 \(\pm\) 0.0 \({}^{\,\mathrm{f  
(0.02-0.04 \(\upmu\)m). SR values increased with the rise of HA concentration in both materials tested as a consequence of HA particles formed by hydrothermal conversion having a cauliflower-like morphology, thus increasing the surface roughness and specific surface energy [20]. Additional SEM analysis confirmed predominantly smooth, and featureless surfaces in Fuji II specimens probably due to incorporation of the resin, while the surfaces of Fuji IX appeared relatively rough demonstrating macro defects on the surfaces faster. Our results demonstrate a trend of higher microhardness values for Fuji II than for Fuji IX. The exception is value for 2 wt % HA, where mean for Fuji IX sample is higher than mean for Fuji II sample. [PERSON] et al. examined the microhardness of the GIC and RMGIC with 10% or 30% HA [25]. They reported that the microhardness of GICs decreased as the amount of HA increased, which is in accordance with results of the present study. The explanation for difference in results could be the fact that the microhardness of HA-added Fuji II increased during water storage [12]. In addition, larger particle size and fewer voids and cracks of RMGIC resulted in higher microhardness values. Among all the eight groups, RMGIC (Fuji II) with 10 wt % HA had the highest microhardness value. When compared to an earlier study where the group with 10 wt % HA had the highest flexural strength value [26], it is possible that this exact concentration of HA particles could improve two important physical properties of Fuji II, microhardness, and SR. This result is in agreement with [PERSON]'s survey, which was shown that the physical properties of RMGI improved with the incorporation of 10% nano- and micro-HA [27].