Effect of thiourethane filler surface functionalization on stress, conversion and mechanical properties of restorative dental composites. Issue 9 (September 2018)

• Record Type: Journal Article
• Authors: Faria-e-Silva, André L.; dos Santos, Andressa; Tang, Angela; Girotto, Emerson M.; Pfeifer, Carmem S.
• Is Part Of: Dental materials. Volume 34:Issue 9(2018)
• Page Start: 1351
• Page End: 1358
• Publication Date: 2018-09
• Subjects: Pre-polymerized additives -- Resin composite -- Polymerization; Dentistry -- Periodicals; Dental materials -- Periodicals; 617.695
• DOI: 10.1016/j.dental.2018.06.023
• Languages: English
• ISSNs: 0109-5641

Abstract

Highlights: Silanization of fillers with thiourethane silane was demonstrated. Composites filled with inorganic fillers silanized with different silanes. Silane type did not affect the polymerization kinetics. Thiourethane silane reduced stress without affecting the mechanical properties. 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 (1 μm average particle size) were functionalized with 5 wt% 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 (0.2/0.8 wt%) and di- tert -butyl hydroxytoluene (0.3 wt%) and 70 wt% silanated inorganic fillers. Polymerization stress (PS) was measured using a cantilever beam apparatus (Bioman). Methacrylate conversion (DC) and rate of polymerization (RP) during photoactivation (800 mW/cm 2 ) 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.