TY - JOUR
T1 - Rheological and mechanical properties and interfacial stress development of composite cements modified with thio-urethane oligomers
AU - Bacchi, Ataís
AU - Pfeifer, Carmem S.
N1 - Funding Information:
The authors thank NIH-NIDCR ( 1R15-DE023211-01A1 and 1U01-DE02756-01 ) for financial support. The donation of methacrylate monomers by Esstech is also greatly appreciated.
Publisher Copyright:
© 2016 The Academy of Dental Materials
PY - 2016/8/1
Y1 - 2016/8/1
N2 - Objectives Thio-urethane oligomers have been shown to reduce stress and increase toughness in highly filled composite materials. This study evaluated the influence of thio-urethane backbone structure on rheological and mechanical properties of resin cements modified with a fixed concentration of the oligomers. Methods Thio-urethane oligomers (TU) were synthesized by combining thiols – pentaerythritol tetra-3-mercaptopropionate (PETMP) or trimethylol-tris-3-mercaptopropionate (TMP) – with isocyanates – 1,6-hexanediol-diissocyante (HDDI) (aliphatic) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic) or dicyclohexylmethane 4,4′-diisocyanate (HMDI) (cyclic), at 1:2 isocyanate:thiol, leaving pendant thiols. 20 wt% TU were added to BisGMA-UDMA-TEGDMA (5:3:2). 60 wt% silanated inorganic fillers were added. Near-IR was used to follow methacrylate conversion 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). PS was measured on the Bioman. Viscosity (V) and gel-points (defined as the crossover between storage and loss shear moduli (G′/G″)) were obtained with rheometry. Glass transition temperature (Tg), cross-link density and homogeneity of the network were obtained with dynamic mechanical analysis. Film-thickness was evaluated according to ISO 4049. Results DC and mechanical properties increased and Rpmax and PS decreased with the addition of TUs. Gelation (G′/G″) was delayed and DC at G′/G″ increased in TU groups. Tg and cross-link density dropped in TU groups, while oligomers let to more homogenous networks. An increase in V was observed, with no effect on film-thickness. Significant reductions in PS were achieved at the same time conversion and mechanical properties increased. Significance The addition of thio-urethane oligomers proved successful in improving several key properties of resin cements, without disrupting the procedures dentists use to polymerize the material. This approach has potential to be translated to commercial materials very readily.
AB - Objectives Thio-urethane oligomers have been shown to reduce stress and increase toughness in highly filled composite materials. This study evaluated the influence of thio-urethane backbone structure on rheological and mechanical properties of resin cements modified with a fixed concentration of the oligomers. Methods Thio-urethane oligomers (TU) were synthesized by combining thiols – pentaerythritol tetra-3-mercaptopropionate (PETMP) or trimethylol-tris-3-mercaptopropionate (TMP) – with isocyanates – 1,6-hexanediol-diissocyante (HDDI) (aliphatic) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic) or dicyclohexylmethane 4,4′-diisocyanate (HMDI) (cyclic), at 1:2 isocyanate:thiol, leaving pendant thiols. 20 wt% TU were added to BisGMA-UDMA-TEGDMA (5:3:2). 60 wt% silanated inorganic fillers were added. Near-IR was used to follow methacrylate conversion 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). PS was measured on the Bioman. Viscosity (V) and gel-points (defined as the crossover between storage and loss shear moduli (G′/G″)) were obtained with rheometry. Glass transition temperature (Tg), cross-link density and homogeneity of the network were obtained with dynamic mechanical analysis. Film-thickness was evaluated according to ISO 4049. Results DC and mechanical properties increased and Rpmax and PS decreased with the addition of TUs. Gelation (G′/G″) was delayed and DC at G′/G″ increased in TU groups. Tg and cross-link density dropped in TU groups, while oligomers let to more homogenous networks. An increase in V was observed, with no effect on film-thickness. Significant reductions in PS were achieved at the same time conversion and mechanical properties increased. Significance The addition of thio-urethane oligomers proved successful in improving several key properties of resin cements, without disrupting the procedures dentists use to polymerize the material. This approach has potential to be translated to commercial materials very readily.
KW - Dynamic mechanical analysis
KW - Mechanical strength
KW - Polymerization stress
KW - Resin cements
KW - Rheological properties
KW - Thio-urethane oligomers
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U2 - 10.1016/j.dental.2016.05.003
DO - 10.1016/j.dental.2016.05.003
M3 - Article
C2 - 27257101
AN - SCOPUS:84975311469
SN - 0109-5641
VL - 32
SP - 978
EP - 986
JO - Dental Materials
JF - Dental Materials
IS - 8
ER -