Primer containing dimethylaminododecyl methacrylate kills bacteria impregnated in human dentin blocks

Antibacterial dimethylaminododecyl methacrylate (DMADDM) was recently synthesized. The objectives of this study were to: (1) investigate antibacterial activity of DMADDM-containing primer on Streptococcus mutans impregnated into dentin blocks for the first time, and (2) compare the antibacterial efficacy of DMADDM with a previous quaternary ammonium dimethacrylate (QADM). Scotchbond Multi-Purpose (SBMP) bonding agent was used. DMADDM and QADM were mixed into SBMP primer. Six primers were tested: SBMP control primer P, P+2.5% DMADDM, P+5% DMADDM, P+7.5% DMADDM, P+10% DMADDM, and P+10% QADM. S. mutans were impregnated into human dentin blocks, and each primer was applied to dentin to test its ability to kill bacteria in dentinal tubules. Bacteria in dentin were collected via a sonication method, and the colony-forming units (CFU) and inhibition zones were measured. The bacterial inhibition zone of P+10% DMADDM was 10 times that of control primer (P<0.05). CFU in dentin with P+10% DMADDM was reduced by three orders of magnitude, compared with control. DMADDM had a much stronger antibacterial effect than QADM, and antibacterial efficacy increased with increasing DMADDM concentration. Dentin shear bond strengths were similar among all groups (P>0.1). In conclusion, antibacterial DMADDM-containing primer was validated to kill bacteria inside dentin blocks, possessing a much stronger antibacterial potency than the previous QADM. DMADDM-containing bonding agent was effective in eradicating bacteria in dentin, and its efficacy was directly proportional to DMADDM mass fraction. Therefore, DMADDM may be promising for use in bonding agents as well as in other restorative and preventive materials to inhibit bacteria. A novel antibacterial agent shows promise for use in dental bonding agents and other restorative materials. To preserve tooth structure for successful long-term restorations, dentists are now encouraged to remove as little decayed dentin as possible, but this requires new materials and techniques. Hockin HK Xu at the University of Maryland, USA, Xue-Dong Zhou at Sichuan University in China, and co-workers tested dental primers (chemicals that are applied before adhesive to increase bonding strength) made with an antibacterial agent called dimethylaminododecyl methacrylate (DMADDM). After treatment with 10% DMADDM primer, dentin infected with the bacterium Streptococcus mutans, a leading cause of decay, showed a far larger bacterial inhibition zone, and a much lower bacterial count than dentin treated with a control primer. DMADDM also outperformed a primer containing an existing antibacterial agent.