Investigation of the antibacterial activity, cytotoxicity, and effects on enamel and composite resin of mouthwash formulations prepared with three different Boron compounds

<bold>Objective: </bold>This study investigated the use of oral rinse solutions formulated with boron-containing compounds, known for their antibacterial activity, as an alternative to chlorhexidine (CHX). <bold>Material and method: </bold>Boron nitride (BN), boric acid (BA) and sodium borate (SB) were used in the study. BN was used in nanosuspension (BN-NS) due to its low solubility in water. BA and SB were also prepared and used in solution form (BA-S, SB-S). Antibacterial activity against cariogenic bacteria was evaluated using agar well diffusion and microdilution techniques, and antibiofilm activity was evaluated using the crystal violet method. Cytotoxicity in human gingival cell lines (HGF-1) was evaluated using MTT and LDH assays. Surface hardness was measured with Vicker's Microhardness tester and surface roughness was measured with a profilometer. CHX was used as the control group. <bold>Results: </bold>BN-NS, BA-S, and SB-S showed antibacterial and antibiofilm activity against all cariogenic bacteria. BN-NS and SB-S demonstrated much lower cytotoxicity compared to CHX, while BA-S exhibited similar cytotoxicity. SB-S caused an increase in enamel surface hardness (p = 0.017), whereas no significant changes were observed in surface roughness or hardness in the other groups (p > 0.05). <bold>Conclusion: </bold>BN-NS and SB-S showed antibacterial effects and antibiofilm activity on all tested cariogenic bacteria. BN-NS and SB-S showed lower cytotoxicity than CHX, and their effects on enamel and composite resin surfaces were similar to the control group. Further studies are needed to support the use of BN-NS and SB-S as alternatives to CHX.