New urethane oligodimethacrylates with quaternary alkylammonium for formulating dental composites

The aim of this study was to prepare urethane dimethacrylates containing quaternary alkyl (C16, C12) ammonium and polyethylene glycol short sequences (Mn, 400 g/mol) and to investigate their behaviour in some experimental formulations in order to evaluate their potential applicability in the dental composites field. The structure of urethane dimethacrylates has been confirmed by H-1 (C-13) NMR and FTIR spectra, as well as by electrospray ionization tandem mass spectroscopy, and gel permeation chromatography measurements. The effects of the cationic macromers on the properties of the filled/non-filled composites were examined through FTIR, photoDSC, and specific measurements as volumetric polymerization shrinkage, water sorption/solubility, contact angle, mechanical parameters, and morphology. The monomer compositions based on cationic dimethacrylate (6.88-27.52 wt%), BisGMA-analogue (48.18-68.82 wt%) and TEGDMA (23.3 wt%) showed a good photoreactivity in terms of double bond conversion (DC, 50.07-68.81 %) and polymerization rate (R-p, 0.099-0.141 s(-1)) measured by photoDSC compared to a control sample (BisGMA-1/TEGDMA: DC, 45.91 %; R-p, 0.162 s(-1)), while the polymerization shrinkage increased in acceptable limits (5.37-7.74 vol%). The mechanical properties (compressive, flexural and diametral tensile strength) of the composite resin incorporating 70 wt% silanized zirconium silicate micro/nanopowder can be modulated by the initial co-monomer concentrations.