title: Characterization of methacrylate-based composites containing thio-urethane oligomers.
abstract: OBJECTIVE
  To evaluate the ability of thio-urethane oligomers to improve the properties of restorative composite resins.
  
  
  METHODS
  Oligomers 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 0-20 wt% to BisGMA-TEGDMA (70-30 wt%). Silanated inorganic fillers were added (70 wt%). Materials were photoactivated at 800 mW/cm(2) filtered to 320-500 nm. Near-IR was used to follow degree of methacrylate conversion (DC). Mechanical properties were evaluated in three-point bending with 2 mm × 2 mm × 25 mm bars for flexural strength/modulus and toughness (FS/E, and T) according to ISO 4049, and 2 mm × 5 mm × 25 mm notched specimens for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Results were analyzed with ANOVA/Tukey's test (α=5%).
  
  
  RESULTS
  Significant increase in DC was observed in thio-urethane-containing materials especially for the group with 20 wt% 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.
  
  
  CONCLUSIONS
  The use of thio-urethane oligomer to compose methacrylate-based restorative composite promote increase in DC, FS, E and KIC while significant reduces PS.
  
  
  CONCLUSIONS
  A 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.
authors.affiliation: Oregon Health and Science University, Biomaterials and Biomechanics, 2730 SW Moody Ave., Portland, OR 97201, United States; Meridional Faculty - IMED, School of Dentistry, Prosthodontics and Dental Materials, Av. Senador Pinheiro, 304, 99070-220 Passo Fundo, RS, Brazil.
authors.forename: Atais
authors.initials: A
authors.lastname: Bacchi
authors.affiliation: Oregon Health and Science University, Biomaterials and Biomechanics, 2730 SW Moody Ave., Portland, OR 97201, United States.
authors.forename: Morgan
authors.initials: M
authors.lastname: Nelson
authors.affiliation: Oregon Health and Science University, Biomaterials and Biomechanics, 2730 SW Moody Ave., Portland, OR 97201, United States. Electronic address: pfeiferc@ohsu.edu.
authors.forename: Carmem S
authors.initials: CS
authors.lastname: Pfeifer
mesh_terms: D015097:3-Mercaptopropionic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D000814:Aniline Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002084:Butylated Hydroxytoluene / Q000737:chemistry; D003188:Composite Resins / Q000138:chemical synthesis*; D055119:Elastic Modulus; D017953:Isocyanates / Q000737:chemistry; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011409:Propylene Glycols / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D013314:Stress, Mechanical; D014520:Urethane / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D003188:Composite Resins; D017953:Isocyanates; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011409:Propylene Glycols; D012821:Silanes; C501435:pentaerythritol tetra(3-mercaptopropionate); C000611772:trimethylolpropane tris(3-mercaptopropionate; C015262:1,6-hexamethylene diisocyanate; C020946:triethylene glycol dimethacrylate; D002084:Butylated Hydroxytoluene; D014520:Urethane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C050795:N,N-dimethyl-4-anisidine; D015097:3-Mercaptopropionic Acid
keywords: Composite resin; Mechanical properties; Polymerization stress; Thio-urethane oligomers