Berg I Cecilia Hahn, Rutland Mark W, Arnebrant Thomas
Institute for Surface Chemistry, Box 5607, SE-114 86 Stockholm, Sweden.
Biofouling. 2003 Dec;19(6):365-9. doi: 10.1080/08927010310001618571.
The role of saliva in the oral cavity is manifold; an important function is to serve as lubricant between hard (enamel) and soft (mucosal) tissues. Intraoral lubrication is of crucial importance in order to maintain functions such as deglutition, mastication and the faculty of speech. A large number of people suffer from impaired salivary functions, displaying symptoms such as 'dry mouth'. This results in a need for methods to assess the lubricating properties of both native saliva and potential artificial saliva formulations. Here, normal as well as lateral forces, acting between adsorbed salivary films, have been measured for the first time by means of colloidal probe atomic force microscopy (AFM). It was found that the presence of salivary pellicles between hard surfaces reduces the friction coefficient by a factor of 20. This reduction of friction is consistent with the long-range purely repulsive nature of the normal forces acting between the salivary films. The lubricating mechanism is presumably based on a full separation of the sliding surfaces by the salivary films. The friction between salivary films has been investigated at normal loads that cover the clinical jaw closing forces, and it can be concluded that the lubricating properties are maintained within this load interval. The present study indicates the usefulness of colloidal probe AFM, which offers a direct and quantitative measure of lubrication at a molecular level, in the study of biotribological phenomena. In particular, the results obtained here may have implications for the development of saliva substitutes.
唾液在口腔中的作用是多方面的；一个重要功能是作为硬组织（牙釉质）和软组织（黏膜）之间的润滑剂。口腔内的润滑对于维持吞咽、咀嚼和言语功能等至关重要。许多人存在唾液功能受损的情况，表现出诸如“口干”等症状。这就需要评估天然唾液和潜在人工唾液制剂润滑特性的方法。在此，首次借助胶体探针原子力显微镜（AFM）测量了吸附唾液膜之间的法向力以及侧向力。研究发现，硬表面之间存在唾液薄膜可使摩擦系数降低20倍。这种摩擦的降低与唾液膜之间法向力的长程纯排斥性质一致。润滑机制大概基于唾液膜使滑动表面完全分离。已在涵盖临床闭口力的法向载荷下研究了唾液膜之间的摩擦，可以得出结论，在该载荷区间内润滑特性得以保持。本研究表明胶体探针AFM在生物摩擦学现象研究中很有用，它能在分子水平上提供润滑的直接定量测量。特别是，此处获得的结果可能对唾液替代品的开发具有启示意义。
