# Evaluation of the Impact of Various Functional Fillers on Key Properties of Dental Composites
## 2 Materials and Methods  
To carry out the research experiment, 25 specimens were prepared using a commercial flowable light-cured composite material based on bisphenol A-glycidyl dimethacrylate (Bis-GMA) (Arkona Flow Art, Niemce, Poland) and composite material modified by adding 2 wt% and 5 wt% of hydroxyapatite powder containing fluoride (calcium fluoride) and nanosilver. Hydroxyapatite (HAp) with a grain size of 30 \(\upmu\)m was used for this purpose. Anydrous calcium fluoride (Sigma-Aldrich, Saint Louis, MO, USA) with a purity of 99.99% was incorporated at a concentration of 0.2 wt%. Nanosilver (Sigma-Aldrich, Saint Louis, MO, USA) was added in nanopowder form at a concentration of 1 wt% with a particle size of less than 100 nm. Table 1 contains the designations of the individual specimens. All of the experimental specimens were prepared in accordance with ISO standards and norms [35; 36; 37; 38; 39; 40]. Firstly, the hydroxyapatite filler was synthesized using the so-called wet method. Calcium hydroxide (Ca(OH)\({}_{2}\)) (Sigma-Aldrich, Saint Louis, MO, USA) and orthophosphoric acid (H\({}_{3}\)PO\({}_{4}\)) (Sigma-Aldrich, Saint Louis, MO, USA) were utilized as starting materials for the synthesis of hydroxyapatite. Hydroxyapatite crystals were formed through a precipitation reaction, followed by washing through dec \begin{table}
\begin{tabular}{l l} \hline
**HAp 0\%** & Composite Bis-GMA, Hydroxyapatite-free \\ \hline
**HAp 0\%, F** & Composite Bis-GMA, Hydroxyapatite-free, contains fluoride \\ \hline
**HAp 0\%, Ag** & Composite Bis-GMA, Hydroxyapatite-free, contains nanosilver \\ \hline
**HAp 2\%, F, Ag** & Composite Bis-GMA, contains Hydroxyapatite, fluoride, and nanosilver \\ \hline
**HAp 5\%, F, Ag** & Composite Bis-GMA, contains Hydroxyapatite, fluoride, and nanosilver \\ \hline \end{tabular}
\end{table} 
Table 1: Designations of individual groups of specimens. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Sample** & **Composite** & **Resin Type** & **Filler Content** & **Filler Size** & **Filler Content** & **Filler Size** & **Filler Size** \\
**Symbol** & **Type** & & **HAp [wt\%]** & **HAp [\(\upmu\)m]** & **F [wt\%]** & **Content Ag** & **Ag [nm]** \\ \hline
**HAp 0\%** & light-cured & Bis-GMA & - & - & - & - & - \\
**HAp 0\%, F** & light-cured & Bis-GMA & - & - & 0.2 & - & - \\
**HAp 0\%, Ag** & light-cured & Bis-GMA & - & - & - & 1 & \textless{}100 \\
**HAp 2\%, F, Ag** & light-cured & Bis-GMA & 2 & 30 & 0.2 & 1 & \textless{}100 \\
**HAp 5\%, F, Ag** & light-cured & Bis-GMA & 5 & 30 & 0.2 & 1 & \textless{}100 \\ \hline \end{tabular}
\end{table} 
Table 2: Characteristics of the researched specimens. water. The resulting hydroxyapatiteate was then fractionated with the aid of a LPzE-3e laboratory shaker (MULTIISERW-Morek, Brzeznica, Poland). The grinding and fractionation process was carried out to produce hydroxyapatite grains with a maximum particle size of 30 \(\upmu\)m. The following set of sieves with different-sized openings were used: 0.035 mm, 0.05 mm, and 0.1 mm. The obtained hydroxyapatiteate was subjected to grinding using a planetary ball mill (Retsch PM 100, Retsh GmbH, Haan, Germany). The hydroxyapatite powder was subsequently enriched with additives calcium fluoride and nanosilver. It was integrated into the composite material in a microvial using a Roti-Speed agitator (Carl Roth GmbH + Co., KG, Karlsruhe, Germany) at a speed of 5000 rpm for approx. 5 min. The mixing was performed under standardized conditions of temperature and humidity in a darkened room. The obtained composite was stored in polypropylene syringes with a plunger in order to protect the material surface from oxygen inhibition. The specimens were subsequently subjected to polymerization for 20 s using a diode light-curing lamp (Elipar S10, 3M ESPE, St. Paul, MS, USA). This polymerization lamp delivers a light intensity of 1400 mW/cm\({}^{2}\) within the wavelength range of 450-490 nm. Each polymerized material layer was 1 mm thick.