Thio-urethane oligomers improve the properties of light-cured resin cements.
Thio-urethanes 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 10-30 phr to BisGMA-UDMA-TEGDMA (5:3:2, BUT). 25 wt% silanated inorganic fillers were added. Commercial cement (Relyx Veneer, 3M-ESPE) was also evaluated with 10-20 phr of aromatic oligomer. Near-IR was used to follow methacrylate conversion (DC) and rate of polymerization (Rpmax). Mechanical properties were evaluated in three-point bending (ISO 4049) for flexural strength/modulus (FS/FM, and toughness), and notched specimens (ASTM Standard E399-90) for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Volumetric shrinkage (VS, %) was measured with the bonded disk technique. Results were analyzed with ANOVA/Tukey's test (α=5%). In general terms, for BUT cements, conversion and mechanical properties in flexure increased for selected groups with the addition of thio-urethane oligomers. The aromatic versions resulted in greater FS/FM than aliphatic. Fracture toughness increased by two-fold in the experimental groups (from 1.17 ± 0.36 MPam(1/2) to around 3.23 ± 0.22 MPam(1/2)). Rpmax decreased with the addition of thio-urethanes, though the vitrification point was not statistically different from the control. VS and PS decreased with both oligomers. For the commercial cement, 20 phr of oligomer increased DC, vitrification, reduced Rpmax and also significantly increased KIC, and reduced PS and FM. Thio-urethane oligomers were shown to favorably modify conventional dimethacrylate networks. Significant reductions in polymerization stress were achieved at the same time conversion and fracture toughness increased.
Piracicaba Dental School, Campinas State University, Prosthodontics and Periodontics, Av. Limeira, 901, Piracicaba, BR 13414-903, Brazil; Meridional Faculty - IMED, School of Dentistry, Prosthodontics and Dental Materials, Av. Senador Pinheiro, 304, Passo Fundo, RS 99070-220, Brazil.
Ataís
A
Bacchi
Piracicaba Dental School, Campinas State University, Prosthodontics and Periodontics, Av. Limeira, 901, Piracicaba, BR 13414-903, Brazil.
Rafael L
RL
Consani
Maringa State University, Department of Chemistry, Av. Colombo 5790, Maringa, PR 87020-900, Brazil.
Gedalias C
GC
Martim
Oregon Health and Science University, Biomaterials and Biomechanics, 611 SW Campus Dr, rm 501, Portland, OR 97239, USA. Electronic address: pfeiferc@ohsu.edu.
Carmem S
CS
Pfeifer
D015097:3-Mercaptopropionic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D055119:Elastic Modulus; D006018:Glycols / Q000737:chemistry; D017953:Isocyanates / Q000737:chemistry; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D011409:Propylene Glycols / Q000737:chemistry; D019279:Resin Cements / Q000138:chemical synthesis / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared; D013499:Surface Properties; D013718:Tensile Strength; D014520:Urethane / Q000737:chemistry*
D006018:Glycols; D017953:Isocyanates; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D011409:Propylene Glycols; D019279:Resin Cements; C000611772:trimethylolpropane tris(3-mercaptopropionate; C015262:1,6-hexamethylene diisocyanate; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D014520:Urethane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D015097:3-Mercaptopropionic Acid; C027765:hexamethylene glycol
Mechanical resistance; Polymerization stress; Resin cements; Thio-urethane oligomers