Novel Low-Shrinkage-Stress Composite With Antibacterial Dimethylaminododecyl Methacrylate Monomer

Objectives: Dental composites are one of the most used dental materials for tooth cavity restorations. However, recurrent caries are among the most common causes of dental restoration failure due to the lack of bioactivity and marginal leakage resulting from polymerization shrinkage. A previous study found that low-shrinkage-stress resin was able to reduce polymerization shrinkage stress up to 79% compared to BisGMA-TEGDMA. However, there has been no study investigating the incorporation of dimethylaminododecyl methacrylate (DMADDM) as an antibacterial agent with low-shrinkage-stress resin. Therefore, this study aimed to investigate and optimize a novel low-shrinkage-stress dental composites with different concentrations of DMADDM as an antibacterial agent.
Methods: Urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE) were used to develop a low-shrinkage-stress resin. Then, dental composites containing different mass fractions (0%, 1.5%, 3%, and 5%) of DMADDM were formulated. The flexural strength and elastic modulus were tested. The antibacterial response was tested against S. mutans biofilm model via colony-forming units (CFU), metabolic activity, and lactic acid production.
Results: The low-shrinkage-stress composite containing 3% DMADDM demonstrated higher flexural strength (117.7±7.4) MPa than the commercial control (99.0±9.0) MPa (p<0.05). However, the elastic modulus of the low-shrinkage-stress composite containing 3% DMADDM (7.2±0.4) GPa was less than the commercial control (10.6±0.5) GPa (p<0.05).The incorporation of 3% DMADDM showed a 6 log reduction in the CFUs inhibition (p<0.001) compared to the control. Lactic acid production was significantly decreased with incorporation 3% DMADDM (1.4±0.32) mmol/L than control group (9.35±1.22) mmol/L (p<0.05). Biofilm biomass assessment indicated that DMADDM was able to decrease the biomass significantly (p<0.05).
Conclusions: The novel dental composite with low-shrinkage-stress resin and 3% DMADDM demonstrated a potent antibacterial action against S. mutans with good mechanical properties. The designed formulations could be used as a strategy to prevent secondary caries around dental restorations.