Novel Antibacterial Copolymers Based on Quaternary Ammonium Urethane-Dimethacrylate Analogues and Triethylene Glycol Dimethacrylate.

The growing scale of secondary caries and occurrence of antibiotic-resistant bacterial strains require the development of antibacterial dental composites. It can be achieved by the chemical introduction of quaternary ammonium dimethacrylates into dental composites. In this study, physicochemical and antibacterial properties of six novel copolymers consisting of 60 wt. % quaternary ammonium urethane-dimethacrylate analogues (QAUDMA) and 40 wt. % triethylene glycol dimethacrylate (TEGDMA) were investigated. Uncured compositions had suitable refractive index (RI), density (dm), and glass transition temperature (Tgm). Copolymers had low polymerization shrinkage (S), high degree of conversion (DC) and high glass transition temperature (Tgp). They also showed high antibacterial effectiveness against S. aureus and E. coli bacterial strains. It was manifested by the reduction in cell proliferation, decrease in the number of bacteria adhered on their surfaces, and presence of growth inhibition zones. It can be concluded that the copolymerization of bioactive QAUDMAs with TEGDMA provided copolymers with high antibacterial activity and rewarding physicochemical properties.

Synthesis and Characterization of Novel Quaternary Ammonium Urethane-Dimethacrylate Monomers-A Pilot Study.

Six novel urethane-dimethacrylate analogues (QAUDMAs) were synthesized and characterized. They consisted of the 2,4,4,-trimethylhexamethylene diisocyanate (TMDI) core and two methacrylate-terminated wings containing quaternary ammonium groups substituted with alkyl chains of 8, 10, 12, 14, 16, or 18 carbon atoms. QAUDMAs, due to the presence of quaternary ammonium groups, may have possible antibacterial effects. Since they showed satisfactory physicochemical properties, they will be subjected to further research towards the development of dental composites with a capacity to reduce secondary caries. The synthesis of QAUDMAs included three stages: (i) transesterification of methyl methacrylate (MMA) with N-methyldiethanolamine (MDEA), (ii) N-alkylation of the tertiary amino group with alkyl bromide, and (iii) addition of TMDI to the intermediate achieved in the second stage. The formation of QAUDMAs was confirmed by 1H and 13C NMR. They were characterized for density (dm), viscosity (η), refractive index (RI), glass transition temperature (Tg), polymerization shrinkage (S), and degree of conversion (DC). QAUDMAs were yellow, viscous resins (the η values ranged from 1.28 × 103 to 1.39 × 104 Pa·s, at 50 °C). Their RI ranged from 1.50 to 1.52, Tg from -31 to -15 °C, DC from 53 to 78%, and S from 1.24 to 2.99%, which is appropriate for dental applications.

Physicochemical and Mechanical Properties of Bis-GMA/TEGDMA Dental Composite Resins Enriched with Quaternary Ammonium Polyethylenimine Nanoparticles.

Modification of dental monomer compositions with antimicrobial agents must not cause deterioration of the structure, physicochemical, or mechanical properties of the resulting polymers. In this study, 0.5, 1, and 2 wt.% quaternary ammonium polyethylenimine nanoparticles (QA-PEI-NPs) were obtained and admixed with a Bis-GMA/TEGDMA (60:40) composition. Formulations were then photocured and tested for their degree of conversion (DC), polymerization shrinkage (S), glass transition temperature (Tg), water sorption (WS), solubility (SL), water contact angle (WCA), flexural modulus (E), flexural strength (σ), hardness (HB), and impact resistance (an). We found that the DC, S, Tg, WS, E, and HB were not negatively affected by the addition of QA-PEI-NPs. Changes in these values rarely reached statistical significance. On the other hand, the SL increased upon increasing the QA-PEI-NPs concentration, whereas σ and an decreased. These results were usually statistically significant. The WCA values increased slightly, but they remained within the range corresponding to hydrophilic surfaces. To conclude, the addition of 1 wt.% QA-PEI-NPs is suitable for applications in dental materials, as it ensures sufficient physicochemical and mechanical properties.

Novel Urethane-Dimethacrylate Monomers and Compositions for Use as Matrices in Dental Restorative Materials.

In this study, novel urethane-dimethacrylate monomers were synthesized from 1,3-bis(1-isocyanato-1-methylethyl)benzene (MEBDI) and oligoethylene glycols monomethacrylates, containing one to three oxyethylene groups. They can potentially be utilized as matrices in dental restorative materials. The obtained monomers were used to prepare four new formulations. Two of them were solely composed of the MEBDI-based monomers. In a second pair, a monomer based on triethylene glycol monomethacrylate, used in 20 wt.%, was replaced with triethylene glycol dimethacrylate (TEGDMA), a reactive diluent typically used in dental materials. For comparison purposes, two formulations, using typical dental dimethacrylates (bisphenol A glycerolate dimethacrylate (Bis-GMA), urethane-dimethacrylate (UDMA) and TEGDMA) were prepared. The monomers and mixtures were tested for the viscosity and density. The homopolymers and copolymers, obtained via photopolymerization, were tested for the degree of conversion, polymerization shrinkage, water sorption and solubility, hardness, flexural strength and modulus. The newly developed formulations achieved promising physico-chemical and mechanical characteristics so as to be suitable for applications as dental composite matrices. A combination of the MEBDI-based urethane-dimethacrylates with TEGDMA resulted in copolymers with a high degree of conversion, low polymerization shrinkage, low water sorption and water solubility, and good mechanical properties. These parameters showed an improvement in relation to currently used dental formulations.