The aims are: (a) To develop the first low-shrinkage-stress nanocomposite with antibacterial and remineralization capabilities through the incorporation of dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP); (b) to investigate the effects of the new composite on biofilm inhibition, mechanical properties, shrinkage stress, and calcium (Ca) and phosphate (P) ion releases. The low-shrinkage-stress resin consisted of urethane dimethacrylate and triethylene glycol divinylbenzyl ether. Composite was formulated with 3% DMAHDM and 20% NACP. Mechanical properties, shrinkage stress, and degree of conversion were evaluated. Streptococcus mutans biofilm growth on composites was assessed. Ca and P ion releases were measured. The shrinkage stress of the low-shrinkage-stress composite containing 3% DMAHDM and 20% NACP was 36% lower than that of traditional composite control (p < 0.05), with similar degrees of conversion of 73.9%. The new composite decreased the biofilm colony-forming unit by 4 log orders and substantially reduced biofilm lactic acid production compared to control composite (p < 0.05). Incorporating DMAHDM to the low-shrinkage-stress composite did not adversely affect the Ca and P ion release. A novel bioactive nanocomposite was developed with low shrinkage stress, strong antibiofilm activity, and high levels of ion release for remineralization, without undermining the mechanical properties and degree of conversion.
ObjectivesWhite spot lesions (WSLs) are prevalent and often lead to aesthetic problems and progressive caries. The objectives of this study were to: (1) develop a novel resin infiltrant containing smart monomer dodecylmethylaminoethyl methacrylate (DMAEM) to inhibit WSLs, and (2) investigate the effects of DMAEM incorporation on cytotoxicity, mechanical properties, biofilm-inhibition and protection of enamel hardness for the first time.MethodsDMAEM was synthesized using 1-bromododecane, 2-methylamino ethanol and methylmethacrylate. DMAEM with mass fractions of 0%, 1.25%, 2.5% and 5% were incorporated into a resin infiltant containing BisGMA and TEGDMA. Cytotoxicity, mechanical properties and antibacterial effects were tested. After resin infiltration, bovine enamel was demineralized with saliva biofilm acids, and enamel hardness was measured.ResultDMAEM infiltration did not increase the cytotoxicity or compromise the physical properties when DMAEM mass fraction was below 5% (p > 0.05). Biofilm metabolic activity was reduced by 90%, and biofilm lactic acid production was reduced by 92%, via DMAEM (p < 0.05). Mutans streptococci biofilm CFU was reduced by 3 logs (p < 0.05). When demineralized in acid and then under biofilms, the infiltrant + 5% DMAEM group produced an enamel hardness (mean ± sd; n = 6) of 2.90 ± 0.06 GPa, much higher than 0.85 ± 0.12 GPa of the infiltrant + 0% DMAEM group (p < 0.05).SignificanceA novel resin infiltrant with excellent mechanical properties, biocompability, strong antibacterial activity and anti-demineralization effect was developed using DMAEM for the first time. The DMAEM resin infiltrant is promising for inhibiting WSLs, arresting early caries, and protecting enamel hardness.
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