Self-assembled Nano-layering at the Adhesive Interface

According to the 'Adhesion-Decalcification' concept, specific functional monomers within dental adhesives can ionically interact with hydroxyapatite (HAp). Such ionic bonding has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (MDP) to manifest in the form of self-assembled 'nano-layering'. However, it remained to be explored if such nano-layering also occurs on tooth tissue when commercial MDP-containing adhesives (Clearfil SE Bond, Kuraray; Scotchbond Universal, 3M ESPE) were applied following common clinical application protocols. We therefore characterized adhesive-dentin interfaces chemically, using x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), and ultrastructurally, using (scanning) transmission electron microscopy (TEM/STEM). Both adhesives revealed nano-layering at the adhesive interface, not only within the hybrid layer but also, particularly for Clearfil SE Bond (Kuraray), extending into the adhesive layer. Since such self-assembled nano-layering of two 10-MDP molecules, joined by stable MDP-Ca salt formation, must make the adhesive interface more resistant to biodegradation, it may well explain the documented favorable clinical longevity of bonds produced by 10-MDP-based adhesives.

根据“黏附 - 脱钙”概念，牙科黏合剂中的特定功能性单体可与羟基磷灰石（HAp）发生离子相互作用。已证实10 - 甲基丙烯酰氧癸基磷酸二氢酯（MDP）会以自组装“纳米层状结构”的形式发生这种离子键合。然而，当按照常见临床应用方案使用含MDP的市售黏合剂（可乐丽的Clearfil SE Bond；3M ESPE的Scotchbond Universal）时，这种纳米层状结构是否也会在牙齿组织上出现仍有待探究。因此，我们利用X射线衍射（XRD）和能量色散X射线光谱仪（EDS）对黏合剂 - 牙本质界面进行化学表征，并利用（扫描）透射电子显微镜（TEM/STEM）进行超微结构表征。两种黏合剂在黏合界面都显示出纳米层状结构，不仅在混合层内，而且特别是对于可乐丽的Clearfil SE Bond，还延伸到黏合层内。由于两个10 - MDP分子通过稳定的MDP - Ca盐形成而自组装的这种纳米层状结构必然会使黏合界面更能抵抗生物降解，这很可能解释了基于10 - MDP的黏合剂所产生的黏合在临床上具有良好持久性的记录。