André L Faria-E-Silva1, Andressa Dos Santos2, Angela Tang3, Emerson M Girotto4, Carmem S Pfeifer5. 1. Department of Dentistry, Federal University of Sergipe, Rua Claudio Batista s/n, Bairro Sanatório, Aracaju, SE, 49060-100, Brazil. Electronic address: fariaesilva.andre@gmail.com. 2. Graduate Program in Chemistry, State University of Maringa, Av. Colombo 5790, Jardim Universitário, Maringá, PR, 87020-900, Brazil. Electronic address: dossantos.andressa@hotmail.com. 3. Phillips Academy, 180 Main St., Andover, MA, USA. Electronic address: angelaatang@gmail.com. 4. Department of Chemistry, State University of Maringa, Av. Colombo 5790, Jardim Universitário, Maringá, PR, 87020-900, Brazil. Electronic address: emgirotto@uem.br. 5. Department of Restorative Dentistry, Division of Biomaterials and Biomechanics, Oregon Health & Science University, 2730 SW Moody Ave, 97201, Portland, OR, USA. Electronic address: pfeiferc@ohsu.edu.
Abstract
OBJECTIVES: This study evaluated the efficacy of a thiourethane(TU)-modified silane agent in improving properties in filled composites. METHODS: The TU-silane agent was synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene and 3-(triethoxysilyl)propyl isocyanate with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiol and alkoxy silane groups. Barium glass fillers (1μm average particle size) were functionalized with 5wt% TU-silane in an acidic ethanol solution. Commercially available 3-(trimethoxysilyl)propyl methacrylate (MA-silane) and (3-mercaptopropyl)trimethoxysilane (SH-silane), as well as no silane treatment (NO-silane), were used as controls. Composites were made with BisGMA-UDMA-TEGDMA (5:3:2), camphorquinone/ethyl-4-dimethylaminobenzoate (0.2/0.8wt%) and di-tert-butyl hydroxytoluene (0.3wt%) and 70wt% silanated inorganic fillers. Polymerization stress (PS) was measured using a cantilever beam apparatus (Bioman). Methacrylate conversion (DC) and rate of polymerization (RP) during photoactivation (800mW/cm2) were followed in real-time with near-IR. Flexural strength/modulus (FS/FM) were evaluated in three-point bending with 2×2×25 mm. STATISTICAL ANALYSIS: 2-way ANOVA/Tukey's test (α=5%). RESULTS: DC, Rpmax and E were similar for all groups tested. FS was similar for the TU- and MA-silane, which were statistically higher than the untreated and SH-silane groups. Stress reductions in relation to the MA-silane were observed for all groups, but statistically more markedly for the TU-silane material. This is likely due to stress relaxation and/or toughening provided at the filler interface by the oligomeric TU structure. SIGNIFICANCE: TU-silane oligomers favorably modified conventional dimethacrylate networks with minimal disruption to existing curing chemistry, in filled composites. For the same conversion values, stress reductions of up to 50% were observed, without compromise to mechanical properties or handling characteristics.
OBJECTIVES: This study evaluated the efficacy of a thiourethane(TU)-modified silane agent in improving properties in filled composites. METHODS: The TU-silane agent was synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene and 3-(triethoxysilyl)propyl isocyanate with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiol and alkoxy silane groups. Barium glass fillers (1μm average particle size) were functionalized with 5wt% TU-silane in an acidic ethanol solution. Commercially available 3-(trimethoxysilyl)propyl methacrylate (MA-silane) and (3-mercaptopropyl)trimethoxysilane (SH-silane), as well as no silane treatment (NO-silane), were used as controls. Composites were made with BisGMA-UDMA-TEGDMA (5:3:2), camphorquinone/ethyl-4-dimethylaminobenzoate (0.2/0.8wt%) and di-tert-butyl hydroxytoluene (0.3wt%) and 70wt% silanated inorganic fillers. Polymerization stress (PS) was measured using a cantilever beam apparatus (Bioman). Methacrylate conversion (DC) and rate of polymerization (RP) during photoactivation (800mW/cm2) were followed in real-time with near-IR. Flexural strength/modulus (FS/FM) were evaluated in three-point bending with 2×2×25 mm. STATISTICAL ANALYSIS: 2-way ANOVA/Tukey's test (α=5%). RESULTS:DC, Rpmax and E were similar for all groups tested. FS was similar for the TU- and MA-silane, which were statistically higher than the untreated and SH-silane groups. Stress reductions in relation to the MA-silane were observed for all groups, but statistically more markedly for the TU-silane material. This is likely due to stress relaxation and/or toughening provided at the filler interface by the oligomeric TU structure. SIGNIFICANCE: TU-silane oligomers favorably modified conventional dimethacrylate networks with minimal disruption to existing curing chemistry, in filled composites. For the same conversion values, stress reductions of up to 50% were observed, without compromise to mechanical properties or handling characteristics.
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