In this study, we designed and synthesized a new dental composite including Spiro [fluorene-9,9’-xanthene]-3',6’-diylbis (oxy) bis (2-hydroxypropane-3,1-diyl) bis (2-methylacrylate) (Xanthene-GMA) resin containing xanthene and fluorene parts and natural filler of fish bone powder with low water sorption and solubility and excellent biocompatibility. This dental composite reduces the risks that Bisphenol A derivatives released from composite Bis-GMA may pose to the oral environment. The Xanthene-GMA resin was synthesized from the condensation reaction in the presence of an acid catalyst. The surface of the fish bone powder was also modified by (3-trimethoxysilyl) propyl methacrylate (Silane A174) modifier for creating better bonding with the resin. The structural characterization of the compounds was confirmed by Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (NMR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), and thermogravimetric analysis (TGA) techniques. Then, the dental composite (Xanthene-GMA resin based on modified fish bones powder (XGMFB)) was prepared by heat and light curing. Finally, water sorption, solubility, cytotoxicity and antibacterial activity tests were evaluated.The thermal resistance of the composite was low due to the use of natural filler in fish bone powder. The composite showed low water sorption and solubility. The antibacterial and cytotoxicity activity of the composite was evaluated. S. aureus (MIC 16 μg/mL) and E. coli (MIC 32 μg /mL) were recognized as most susceptible gram-positive and gram-negative bacteria, respectively, after XGMFB treatment. The most inhibitory effect of XGMFB was observed against MCF7 cells (IC50 = 73.5 μM, Maximum Inhibitory effect 78.18%)
