Characterization of methacrylate-based composites containing thio-urethane oligomers

Abstract

ObjectiveTo evaluate the ability of thio-urethane oligomers to improve the properties of restorative composite resins. MethodsOligomers were synthesized by combining 1,6-hexanediol-diissocyante (aliphatic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 0–20wt% to BisGMA-TEGDMA (70–30wt%). Silanated inorganic fillers were added (70wt%). Materials were photoactivated at 800mW/cm2 filtered to 320–500nm. Near-IR was used to follow degree of methacrylate conversion (DC). Mechanical properties were evaluated in three-point bending with 2mm×2mm×25mm bars for flexural strength/modulus and toughness (FS/E, and T) according to ISO 4049, and 2mm×5mm×25mm notched specimens for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Results were analyzed with ANOVA/Tukey's test (α=5%). ResultsSignificant increase in DC was observed in thio-urethane-containing materials especially for the group with 20wt% of aliphatic version. Materials composed by oligomers also promoted higher FS, E, and KIC in comparison to controls irrespective of thio-urethane type. A significant increase in toughness was detected by ANOVA, but not distinguished in the groups. The PS was significantly reduced by the presence of thio-urethane for almost all groups. ConclusionsThe use of thio-urethane oligomer to compose methacrylate-based restorative composite promote increase in DC, FS, E and KIC while significant reduces PS. SignificanceA simple additive was shown to reduce stress while increasing convrersion and mechanical properties, mainly fracture toughness. This has he potential of increasing the service life of dental composites, without changing current operatory procedures.