Dentin Bonding Evaluation to Identify Quaternary-Ammonium Concentration for Antibacterial-Adhesive

Objectives: Bacterial colonization of the resin-dentin bonding interface harshly shortens the lifespan of composite restorations. An antibacterial dental adhesive can potentially inhibit biofilm growth in this critical area. The incorporation of antibacterial compounds should not impair the core properties of the intended dental materials. This study has explored the effects of different concentrations of a quaternary ammonium compound, benzyldimethyldodecylammonium chloride (BDMDAC), on the physical and mechanical bonding properties.
Methods: Adhesives were formulated combining 66.66 wt.% of bisphenol A glycerolate dimethacrylate (BisGMA), 33.33 wt.% of 2-hydroxyethyl methacrylate (HEMA), and photoinitiator/co-initiator systems. BDMDAC was added at the following concentrations: 1%, 2%, 3%, 4%, and 5% by weight. An experimental adhesive with no BDMDAC was used as a control. The degree of conversion (DC) and ultimate tensile strength (UTS) were initially evaluated. Besides, dentin surfaces were bonded with the experimental adhesives using a commercial primer and commercial composites for restoration. The specimens were sectioned and subjected to micro-tensile bond strength (μTBS). ANOVA and Tukey tests were used for statistical analyses of the data.
Results: Increased BDMDAC concentration up to 4% has increased the UTS; however, at 5% BDMDAC, the ultimate strength values were similar to control. The DC ranged from (62.8±2.5)% for the control group to (64.8±4.2)% for 5 wt.%. There was no statistically significant difference among groups for DC (p > 0.64). The μTBS values range from (41.7±6.5)% for the control group to (48.2±7.2)% for 5 wt.%. Thus, all adhesives have shown an increasing trend with increasing BDMDAC percentage, but no statistically significant difference.
Conclusions: The adhesive containing BDMDAC up to 4% has exhibited desirable physical/mechanical performance and bonding properties. These findings provide critical information on the superior concentrations to be assessed in further antibiofilm assays. In addition, BDMDAC has demonstrated promising properties for the resin-dentin bonding interface