A multi-modal strategy for enhancing titanium–bone interface strength and antimicrobial properties of PMMA bone cements

Infection prevention and retention at the bone-device interface are critical for long-term stability of titanium-based biomedical implants. This study utilized a multifactorial approach to assess bond strength and antibacterial activity of polymethyl methacrylate (PMMA) bone cements modified with polymerizable antimicrobials (quaternary ammonium methacrylate, QAM) for sustained antibiofilm effects. Four commercial dental adhesives (Gen 4, Gen 5, Gen 6, Gen 7) were tested between porcine cortical bone and PMMA bone cements (Jet Acrylic or Biomet Bone Cement R). Shear bond strength (SBS), interface analysis (SEM, FTIR/ATR) and cytotoxicity (MTT) were evaluated and compared to controls without dental adhesive, which is the current standard of care. Top performing materials were subjected to stringent mechanical cycling in a bioreactor, followed by SBS assessment. Finally, bone cements were modified with QAMs and evaluated with or without dental adhesive for physical properties, antibiotic activity and SBS. Refobacin was used as an antibiotic-containing commercial control. Results showed more than a twenty-fold increase in SBS after 24 h and up to a fifteen-fold improvement after mechanical cycling with the Gen 6 adhesive, compared to commercial control cements. Refobacin and the QAM-modified cement significantly reduced S. aureus biofilm biomass, but the QAM cements were significantly better able to maintain antimicrobial activity after water storage. Even though the shear bond strength was reduced with either QAM or Refobacin, the presence of the adhesive mitigated this reduction in comparison with the Refobacin applied without the adhesive. Overall, the results suggest that the application of dental adhesives prior to cementation provides an avenue for improving implant retention and that incorporating QAMs may offer a means of sustained infection control.