Novel Antimicrobial Monomers Increase Shear Bond Strength of Dental Restoration
Objectives: Our goal is to advance polymeric composites with expected long-term antimicrobial functionality for clinical application as Class V restoratives. In this study, we evaluated the shear bond strength (SBS) and biocompatibility of novel methacrylate analogs of antimicrobial quaternary ammonium salts functionalized with carboxylic groups.
Methods: 5-carboxy-N-(2-(methacryloyloxy)ethyl)-N,N-dimethylpentan-1-aminium bromide (AMadh1) and 10-carboxy-N-(2-(methacryloyloxy)ethyl)-N,N-dimethyldecan-1-aminium bromide (AMadh2) were incorporated into 3M Adper Scotchbond Primer (comprised of 2-hydroxyethyl methacrylate, acrylic and itaconic acid), at either 10% or 20% (w/w). Restorations also included application of 3M Adper Scotchbond multipurpose adhesive and TPH Spectra Universal composite. The SBS on extracted human molars was assessed for AMadh1-Primer (n=10) and AMadh2-Primer (n=10) restorations. The primer without modification served as a control (n=20). Cytotoxic potential of AMadh1 (≤10.6 mmol/L) and AMadh2 (≤8.8 mmol/L) monomers was assessed using human gingival fibroblasts (HGF) and mouse connective tissue fibroblast (ATCC®CCL-1TM). Statistical data analyses entailed ANOVA and Student’s t-test.
Results: The SBS of all AMadh1- and AMadh2-Primer formulations increased compared to the control. The AMadh1-Primer with 10% and 20% (w/w) antimicrobial monomer increased the SBS by 24% and 9%, respectively. The SBS of AMadh2-Primer with 20% (w/w) antimicrobial monomer increased by 24% (P≤0.001), while with 10% (w/w) monomer increased by 11%, compared to the control. HGFs and ATCC®CCL-1™ cells exhibited different sensitivities to the AMadhs. The AMadhs did not exert a main effect on HGFs, while reducing the metabolic activity of ATCC®CCL-1™ cells (P≤0.001) in a concentration-dependent manner. The effect of exposure time on cells was contingent on the AM monomer type.
Conclusions: AMadhs increased the SBS of the restoration up to 24% and exhibited satisfactory biocompatibility. Both monomers are deemed as suitable AM candidates for the resin phase of the advanced polymeric composites, as our biocompatibility experiments approximated the maximum possible exposure to leachables.