Novel Nanocomposite with Low Shrinkage Stress, Antibacterial and Remineralization Capabilities

Objectives: Objectives: (1) To develop the first nanocomposite with a combination of low shrinkage stress, antibacterial and remineralization capabilities to combat secondary caries; (2) To investigate the effects of the new composite on Streptococcus mutans (S. mutans) biofilm growth, mechanical properties, polymerization shrinkage stress, and calcium (Ca) and phosphate (P) ion release.
Methods: Methods: The low-shrinkage-stress resin consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE). TEG-DVBE is an ether-based monomer that is stable against hydrolysis and esterase degradation. Composite was formulated with 3% dimethylaminohexadecyl methacrylate (DMAHDM) and 20% amorphous calcium phosphate (NACP). Mechanical properties, polymerization shrinkage stress, and degree of conversion were evaluated. S. mutans biofilms on composites were assessed.
Results: Results: Flexural strength (85±10) MPa and elastic modulus (8.9±1.0) GPa of the low-shrinkage composite containing 3% DMAHDM and 20% NACP were similar to those of a commercial composite control (p>0.05). The polymerization shrinkage stress of the new composite was (2.48±0.03) MPa (p<0.05), almost 40% lower than the (4.05±0.04) of traditional composite control (p<0.05). Both composites had similar degrees of polymerization conversion of 73.9%. Biofilm lactic acid production and biomass were substantially reduced on the new composite. The new composite decreased biofilm CFU by 4 logs, compared to control composite. The biofilm medium pH was 4.8 for commercial composite due to biofilm acid production; in contrast, the biofilm medium pH was 7.0 for the new low-shrinkage-stress DMAHDM+NACP composite. The new low-shrinkage composite had high levels of Ca and P ion releases, and incorporating 3% DMAHDM to the composite did not adversely affect the ion release.
Conclusions: Conclusion: A novel bioactive nanocomposite was developed with low polymerization shrinkage stress, strong antibiofilm activity and high levels of Ca and P ion release for remineralization, without undermining the mechanical properties and degree of conversion.