Chojnacki et al., "Independent and combined cytotoxicity and genotoxicity of triethylene glycol dimethacrylate and urethane dimethacrylate," Molecular Biology Reports, vol.
Bis-GMA, bisphenol A diglycidyl methacrylate; HEMA, 2-hydroxyethyl methacrylate; CQ, camphorquinone; UDMA, urethane dimethacrylate; 10-MDP, 10-methacryloyloxydecyl dihydrogen phosphate; GPDM, glycerol phosphate dimethacrylate; GDMA, glycerol dimethacrylate.
The presence of hydrophilic constituents of HEMA or resin molecules that contain hydrophilic moieties and acid-base reaction as part of the photochemical polymerization process explains the high level of water sorption in N100, in addition to that the material may contain air bubbles due to the hand mixing of the two pastes, which may accelerate water sorption.3,21-23 Posterior bulk fill flowable base (SDR) contains the lowest filler load, with ethoxylated bisphenol A dimethacrylate (EBPADMA), modified urethane dimethacrylate
(MUDM), and triethylene glycol dimethacrylate (TEGDMA) resins, and the last two are more hydro-philic than EBPADMA, so higher water sorption is expected from this material compared with other resin-based composite materials.3, 19
The urethane dimethacrylate monomer (UAc-M) was synthesized through the reaction of IPDI (0.01 mol) with 2-hydroxyethyl methacrylate (0.02 mol) in 5 ml anhydrous THF and in the presence of dibutyltin dilaurate under dry nitrogen atmosphere at 40[degrees]C for 4 h.
The FTIR spectra of urethane dimethacrylate oligomers (e.g., FTIR spectrum of UMO-2 is shown in Fig.
Returning to the low-molecular-weight urethane dimethacrylate (UAc-M) used together with bisGMA (1.5:4 weight ratio), the cure profile is characterized by a reducing of the transformation degree in the initial irradiation step (20 s) at ~14% conversion (see Fig.
The polymerization shrinkage results obtained for the formulations S1-S3 (between 5.6 and 7.15%) in the absence of filler may be correlated with the literature data, taking into account the fact that each urethane dimethacrylate is included in the polymeric specimen in a small amount (18 wt%).
5, in the case of UAc-M/bisGMA (1:1) used in formulation, the influence of urethane dimethacrylate structure on the [I.sub.1]/[I.sub.3] ratio as a function of irradiation time suggested an analogous response, the value of [I.sub.1]/[I.sub.3] ranging from 0.4 to 0.5 upon UV exposure (380 s).
Compared with UMO-1, for the polymerization of low-molecular-weight urethane dimethacrylate (74.65% UAc-M), TEGDMA (25.35%), DMAEM/CQ, pyrene derivative, and filler (Aerosil/Sr-Zr glass, 1:1), the total area ([I.sub.1]/[I.sub.4]) of the fluorescence intensity falls abruptly at 22% during the polymerization reaction (see Fig.
Other photocurable dimethacrylate monomers are the ethoxylated bisphenol A-dimetha-crylate (bis-EMA), decane-diol dimethacrylate ([D.sub.3]MA), and urethane dimethacrylates with an aliphatic (UDMA) or partially aromatic (TMX-UDMA) core structure (4-6).
Two urethane dimethacrylates of oligomer type were prepared according to the general synthetic route shown in Scheme 1, via condensation of the poly(ethylene glycol) (PEG) with an aliphatic diisocyanate, such as IPDI, to yield a prepolymer with end isocyanate groups, which finally was converted to a dimethacrylate by the reaction with 2-hydroxyethyl methacrylate.
Composites Organic matrix (40 wt.%) Filler (60 wt.%) Monomers Initiation system Experimental I Bis-GMA (29%) CQ/amine BaAlSi, 0.5 UDMA (31%) (0.4/0.8%) [micro]m (80%) Experimental II Bis-EMA (31%) CQ/PPD/amine Si[O.sub.2], TEGDMA (7%) (0.2/0.2/0.8%) 0.04 [micro]m Experimental II PPD/amine (20%) (0.4/0.8%) Bis-GMA, bisphenol A glycidyl dimethacrylate; BIS-EMA, ethoxylated bisphenol A dimethacrylate; UDMA, urethane dimethacrylate
; TEGDMA, triethyleneglycol dimethacrylate; CQ, camphorquinone; PPD, 1-phenyl-1,2- Table 2--Polymerization shrinkage stress values (MPa) and standard deviation of commercial and experimental composites at three evaluation times (n = 5).