Department of Pediatric Dentistry, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ota-ku, Tokyo, 145-8515, Japan.
Department of Conservative Dentistry, Division of Biomaterials and Engineering, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan; Department of Prosthodontics, The Stomatological Hospital, Tianjin Medical University, No.12 Qixiangtai Road, Heping District, Tianjin, China.
J Mech Behav Biomed Mater. 2021 May;117:104389. doi: 10.1016/j.jmbbm.2021.104389. Epub 2021 Feb 23.
The presence of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) at the adhesive-dentin interface enables ionic binding to calcium salts, which results in rigid nano-layering within the submicron scale resin-dentin interdiffusion zone. MDP has been used with additional co-monomers, such as hydroxyethyl methacrylate (HEMA) and/or 4-methacryloyloxyethyl-trimellitic acid (4-MET), mainly to enhance the chemical bonding properties. However, the use of co-monomers may compromise the rigidity of the adhesive-dentin interface. In this study, we use high-resolution mechanical mapping across the interface to discern the in situ mechanical properties of each target region at the nanoscale. Visualization by modulus mapping demonstrated that HEMA increases the diffusion properties of MDP into dentin structures. However, the rigidity of the adhesive-dentin interface indicated by the storage modulus was markedly lower in MDP containing HEMA than in MDP containing 4-MET. Dynamic indentation testing revealed that the bonding layer was more deformable in the presence of HEMA. Moreover, the presence of MDP in the bonding layer might also increase the deformability because the polymerization linearity allows a large degree of viscoelasticity. These factors also diminish the rigidity of the adhesive-dentin interface. Within the limitations of this study, our findings demonstrated that 4-MET is a better co-monomer than HEMA in MDP-based dental adhesives. Modulus mapping and nanoindentation are introduced as new tests for the adhesive-dentin interface to address queries about the effectiveness of dental adhesives.
在黏附-牙本质界面中存在 10-甲基丙烯酰氧癸基二氢磷酸酯 (MDP)，使其能够与钙盐发生离子键合，从而在亚微米尺度的树脂-牙本质混合层内形成刚性的纳米分层。MDP 已与其他共聚单体（如羟乙基甲基丙烯酸酯 (HEMA) 和/或 4-甲基丙烯酰氧基乙基偏苯三酸酐 (4-MET)）一起使用，主要是为了增强化学结合性能。然而，共聚单体的使用可能会影响黏附-牙本质界面的刚性。在这项研究中，我们使用高分辨率机械映射技术在界面上进行测量，以在纳米尺度上辨别每个目标区域的原位力学性能。通过模量映射进行可视化，结果表明 HEMA 增加了 MDP 向牙本质结构中的扩散性能。然而，含有 HEMA 的 MDP 的黏附-牙本质界面的储能模量表明其刚性明显低于含有 4-MET 的 MDP。动态压痕测试表明，在存在 HEMA 的情况下，结合层的变形能力更强。此外，由于聚合线性度允许较大程度的粘弹性，所以结合层中存在 MDP 也可能增加其变形能力。这些因素也降低了黏附-牙本质界面的刚性。在本研究的限制范围内，我们的研究结果表明，在基于 MDP 的牙科黏附剂中，4-MET 是比 HEMA 更好的共聚单体。模量映射和纳米压痕测试被引入到黏附-牙本质界面中，以解决关于牙科黏附剂有效性的问题。
