Bacchi Ataís, Pfeifer Carmem S
Department of Restorative Dentistry, Division of Biomaterials and Biomechanics, School of Dentistry, Oregon Health and Science University, 2730 SW Moody Ave, Portland, OR 97201, USA; Department of Prosthodontics and Dental Materials, School of Dentistry, Meridional Faculty, Av. Senador Pinheiro, 304, Passo Fundo, RS 99070-220, Brazil.
Department of Restorative Dentistry, Division of Biomaterials and Biomechanics, School of Dentistry, Oregon Health and Science University, 2730 SW Moody Ave, Portland, OR 97201, USA.
Dent Mater. 2016 Aug;32(8):978-86. doi: 10.1016/j.dental.2016.05.003. Epub 2016 May 30.
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.
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. 20wt% TU were added to BisGMA-UDMA-TEGDMA (5:3:2). 60wt% silanated inorganic fillers were added. Near-IR was used to follow methacrylate conversion and rate of polymerization ( [Formula: see text] ). 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.
DC and mechanical properties increased and [Formula: see text] 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.
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.
硫代聚氨酯低聚物已被证明可降低高填充复合材料的应力并提高其韧性。本研究评估了硫代聚氨酯主链结构对用固定浓度低聚物改性的树脂水门汀流变学和力学性能的影响。
通过将硫醇（季戊四醇四 - 3 - 巯基丙酸酯（PETMP）或三羟甲基 - 三 - 3 - 巯基丙酸酯（TMP））与异氰酸酯（1,6 - 己二醇二异氰酸酯（HDDI）（脂肪族）或1,3 - 双（1 - 异氰酸酯 - 1 - 甲基乙基）苯（BDI）（芳香族）或二环己基甲烷4,4'-二异氰酸酯（HMDI）（环状））按异氰酸酯：硫醇1:2的比例混合，合成硫代聚氨酯低聚物（TU），并保留端基硫醇。将20wt%的TU添加到BisGMA - UDMA - TEGDMA（5:3:2）中。添加60wt%的硅烷化无机填料。使用近红外光谱跟踪甲基丙烯酸酯转化率和聚合速率（[公式：见原文]）。通过三点弯曲试验（ISO 4049）评估弯曲强度/模量（FS/FM）和韧性的力学性能，通过缺口试样（ASTM标准E399 - 90）评估断裂韧性（KIC）。在Bioman上测量聚合收缩率（PS）。通过流变学获得粘度（V）和凝胶点（定义为储能剪切模量和损耗剪切模量（G'/G″）的交叉点）。通过动态力学分析获得玻璃化转变温度（Tg）、交联密度和网络均匀性。根据ISO 4049评估膜厚度。
添加TU后，转化率（DC）和力学性能提高，聚合收缩率（PS）和聚合速率（[公式：见原文]）降低。TU组的凝胶化（G'/G″）延迟，且在G'/G″时的DC增加。TU组的Tg和交联密度下降，而低聚物使网络更均匀。观察到粘度增加，且对膜厚度无影响。在相同的转化率下实现了PS的显著降低，同时力学性能提高。
添加硫代聚氨酯低聚物被证明成功改善了树脂水门汀的几个关键性能，而不会干扰牙医用于聚合材料的操作程序。这种方法很有可能很容易转化为商业材料。
