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The importance of lubrication between oral surfaces provided by the salivary film is most acutely apparent when it is disrupted, a prevalent consequence of salivary gland hypofunction experienced with aging, a symptom of certain diseases, or a side effect of some medical interventions. Sufferers report difficulty with speech and oral food processing and collectively is detrimental to quality of life. Polyethylene glycol (PEG) is widely employed as a successful biocompatible boundary lubricant in engineering and biomedical applications. It is hypothesized that the immobilization of PEG to biological materials such as oral epithelial cells and tissue can mimic the salivary film and provide durable relief from the symptoms of mucosal dryness. To do so, PEG is functionalized with a sugar binding lectin (wheat germ agglutinin) to enhance epithelial adhesion through lectin-sugar interactions. Retention and lubricity are characterized on an ex vivo oral tissue tribology rig. WGA-PEG coats and retains on mucin films, oral epithelial cells, and porcine tongue tissue, and offers sustained reduction in coefficient of friction (COF). WGA-PEG could be developed into a useful topical treatment for reducing oral friction and the perception of dry mouth., (© 2021 Wiley-VCH GmbH.)

Objectives: The aims of this study are to assess different saliva substitutes for their efficacy to lubricate the oral cavity, and to relate this oral lubrication to the ability of saliva substitutes to adsorb on and change the structure of the existing salivary conditioning film (SCF)., Materials and Methods: Quartz crystal microbalance with dissipation was used to study the capability of saliva substitutes to interact with natural SCF and the ability to change the secondary SCF (S-SCF). A tongue-enamel friction system mimicking xerostomic conditions was used to assess the relief and relief period expected from these substitutes under set circumstances., Results: Saliva Orthana spray, Biotène spray and Gum Hydral gel had an immediate effect on a SCF, increasing its structural softness. BioXtra gel, Biotène gel, Gum Hydral gel and Glandosane spray changed the S-SCF by increasing salivary protein adsorption, while others showed no sign of interaction. With respect to relief, only 2 out of the 16 saliva substitutes tested (Saliva Orthana spray and Gum Hydral gel) performed better than water. Overall, relief period correlated positively to structural softness change, whereas a positive correlation was seen between relief and mass adsorption., Conclusions: The majority of saliva substitutes did not adsorb on the SCF, thus did not enhance lubrication. Only saliva substitutes containing carrageenan, carboxymethylcellulose, pig gastric mucin, xanthan gum and carbomer performed better in enhancing oral lubrication., Clinical Relevance: This objective assessment will help clinicians and patients make better choice of saliva substitutes. This study provides a scientific basis for future improvement in saliva substitutes.

Advances in medical research has resulted in successful treatment of many life-threatening infectious diseases as well as autoimmune and lifestyle-related diseases, increasing life-expectancy of both the developed and developing world. As a result of a growing ageing population, the focus has also turned on chronic diseases which seriously affect the quality of older patient life. Xerostomia (dry mouth) is one such condition, which leads to bad oral health and difficulty in consumption of dry foods and speech. Saliva substitutes are used to ease symptoms. However, they often don't work properly and objective comparison of saliva substitutes to mimic natural salivary functions does not exist. The study thus aims to develop an ex vivo friction assay simulating dry mouth conditions and facilitating objective comparison of saliva substitutes. A reciprocating sliding tongue-enamel system was developed and compared to a PDMS (polydimethylsiloxane)-PDMS friction system. The tongue-enamel system, but not the PDMS-PDMS model, showed high mucin-containing saliva (unstimulated and submandibular/sublingual saliva) to give higher Relief than mucin-poor lubricants (water, parotid saliva, Dentaid Xeros) and correlated well (r = 0.97) with in vivo mouth feel. The tongue-enamel friction system mimicked dry mouth conditions and relief and seems suited to test agents meant to lubricate desiccated oral surfaces.