Basic studies of radiopaque resin monomer (III). Physical properties of trial composite resins.

A series of studies has been conducted on the synthesis of radiopaque monomers and the development of a composite resin having these monomers. Using octachlorocyclotetraphosphazene, P4N4Cl8 (4PNC), three kinds of radiopaque cyclophosphazene monomers, 4PN(Br3Ph)1-3-(EMA)7-5, were synthesized by reacting 1-3 mols of tribromophenol (Br3Ph) and 7-5 mols of 2-hydroxyethyl methacrylate (HEMA). As the monomer for an organic composite filler, 70% (wt) synthesized monomer was used with silica (OX-50) treated with silane mixed at 30% and ground after heat-polymerization and then run through a 325-mesh sieve after polymerization. As a base monomer, 25% urethane monomer (U-2TH) was mixed in 25% synthesized monomer and photosensitizer was added. The composite resin was prepared by mixing 50% organic composite filler with 50% base monomer, and polymerized with a Dentacolor XS (Kulzer) visible light-curing apparatus by irradiation for 90 s on each side, 180 s in total. Mechanical properties did not vary with the increase in the number of tribromophenol replacements. Compressive yield strength was more than 120 MPa in all cases. Transverse strength was 60-75 MPa and hardness was HK 26-30. However, the aluminum equivalent increased with the increase in the number of tribromophenol replacements. In the case of 4PN-(Br3Ph)3, the value was 8.8 mm, whereas in the case of commercial composite resin, it was 0.4-10.4 mm.