Investigation of experimental resin composites containing different boron compounds incorporated into mesoporous and nonporous hydroxyapatite nanocarriers

This study aimed to investigate the surface hardness, monomer conversion, surface roughness, boron release, and water sorption-solubility properties of experimental resin composites (RC) containing hydroxyapatite nanocarriers (HAP) loaded with different boron compounds, in comparison to a conventional RC. In this study, boron nitride and 4-borono-l-phenylalanine were loaded into mesoporous and nonporous HAP. 1% boron-nanocarrier complexes were added to a conventional resin-composite content. The study groups were designated based on the boron compound and nanocarrier type: Group 1 (Control): (a conventional RC), Group 2: Experimental RC containing mesoporous HAP loaded with boron nitride (BN@MHAP), Group 3: Experimental RC containing nonporous HAP loaded with boron nitride (BN@HAP), Group 4: Experimental RC containing mesoporous HAP loaded with 4-borono-l-phenylalanine (BPA@MHAP), Group 5: Experimental RC containing nonporous HAP loaded with 4-borono-l-phenylalanine (BPA@HAP). Vickers microhardness, surface roughness, degree of monomer conversion, water sorption-solubility, and boron release analyses were conducted on the RC samples. The nanoparticles were characterized using the Energy Dispersive X-ray Spectroscopy (EDX) for elemental analysis and mapping, X-ray Diffraction (XRD) for examining crystal structure, Fourier-Transform Infrared Spectroscopy (FTIR) for evaluating molecular bond structure, and Scanning Electron Microscopy (SEM) for observing surface morphology of mesoporous and non-porous HAP. No statistically significant difference was found between the experimental RC materials containing boron-nanocarrier complexes and the control group in terms of monomer conversion, surface hardness, surface roughness, water sorption and solubility (p > 0.05). However, all experimental groups demonstrated significantly higher boron release rates over time (p < 0.05), with BN@HAP and BPA@MHAP groups exhibiting the highest release rates at all timepoints (p < 0.05). The addition of 1% BN@HAP/MHAP or BPA@HAP/MHAP to the RC is promising for developing an antibacterial RC capable of releasing boron without compromising the tested physico-chemical properties of the material.