Combating dry mouth by studying the rheology of saliva

Saliva is essential for chewing and swallowing food and helps protect the surfaces in the mouth. While it is largely taken for granted, some people fail to produce enough saliva, resulting in a symptom called dry mouth.

In a first step toward understanding dry mouth, Mishra et al. studied the rheological characteristics of saliva in healthy adults with normal salivary secretion rate.

“Saliva has a complex structure which is difficult to imitate,” said author Hülya Çevik-Aras. “The products used today for relieving dry mouth are far from the structure of saliva and have a short-term effect. Therefore, people with dry mouth generally prefer to drink water more often. If we know the rheological and compositional changes in the saliva of people with dry mouth, we will be able to develop new, more effective products.”

The researchers collected saliva from 11 adults with normal saliva secretion. The samples were measured for rheological properties like shear time response as well as for their concentrations of proteins, calcium and glycoproteins. The results showed the saliva to be a viscoelastic material that demonstrated shear thinning behavior as well as thixotropy, which is a property that causes a material to break down under shear but recovers at rest.

“The present study helps us to understand how the biochemical composition and rheological properties of saliva are interrelated,” Mishra said. “It also showed that the rheological properties of saliva have a power law correlation with saliva secretion rate.”

Next, the researchers plan to look at the saliva from people with dry mouth to assess any rheological differences in their saliva compared to healthy adults.

Source: “The complex shear time response of saliva in healthy individuals,” by Ases Akas Mishra, Ulrica Almhöjd, Hülya Çevik-Aras, Amela Fisic, Richard Olofsson, Annica Almståhl, Roland Kádár, Physics of Fluids (2025). The article can be accessed at https://doi.org/10.1063/5.0245979 .