Dr. Escoe has made some excellent points about the importance of saliva adhesion, cohesion, surface tension and viscosity for the retention of dentures and, one might add, for the integrity of the salivary film.
The differences between saliva and water in the above four properties exist because saliva contains proteins and glycoproteins such as MUC5B and MUC7. Since more than 300 different proteins have been identified in whole saliva, it would be a monumental task to isolate them all and test their contributions to the four properties mentioned above. It also is likely that interactions between individual proteins may occur. The actions of the different salivary macromolecules also could be influenced by the various electrolytes in saliva, such as calcium, and by its ionic strength. The concentrations of both proteins and electrolytes are strongly influenced by the salivary flow rate and by many other factors.1
Saliva is known to be a non-Newtonian fluid,2,3 which means that properties such as viscosity depend on the rate of saliva movement during the measurement. Another complication is that some salivary proteins deposit at air-saliva interfaces, and this can affect the physical properties of the saliva. A thorough discussion of all these matters would need its own supplement, and would require readers to have a strong background in higher mathmatics because of the nature of rheology.
More studies on the four properties identified by Dr. Escoe certainly would be of interest, but, realistically, they require a fairly large research group with expertise in at least salivary physiology, protein biochemistry and biorheology. Clearly, there is still much important research to be done on this complex fluid called saliva.
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