Methods: Disks of resin composites mixed with 1% w/w insoluble cross-linked quaternary ammonium PEI nanoparticles were prepared between two glass slides and light polymerized. Similarly prepared disks without nanoparticles served as controls. Surface analysis of the disks prior to bacterial challenge included: (i) contact angle measurements; (ii) chemical analysis, using X-ray photoelectron spectroscopy (XPS); (iii) and scanning electron microscopy (SEM). Then, S. mutans biofilm was allowed to form in vitro on the composites surfaces for one month. Following biofilm removal surface roughness was measured using atomic force microscopy (AFM)
Results: Contact angle measurements showed increase in surface hydrophobicity and XPS analysis revealed presence of iodide and nitrogen elements. AFM analysis of resin composites incorporating PEI nanoparticles revealed no change in root mean square (RMS) roughness while surface roughness of the controls increased significantly (p<0.0001) following bacteria-surface interaction.
Conclusions: Changing the surface of resin composites by incorporation of antibacterial nanoparticles, may improve their clinical performance by both, inhibiting bacterial growth and by preventing changes in the surface roughness.