An ex vivo salivary lubrication system to mimic xerostomic conditions and to predict the lubricating properties of xerostomia relieving agents

Jeroen Vinke,Prashant K Sharma,Arjan Vissink,Hans J Kaper

doi:10.1038/s41598-018-27380-7

Jeroen Vinke, Prashant K Sharma + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-27380-7

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Abstract

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.

Highlights

Saliva is the collective secretion from parotid, submandibular, sublingual and minor saliva glands and consists of approximately 99% water with some electrolytes, proteins, glycoproteins and enzymes[1,2,3]
Since each experiment started with step 1 (Fig. 2e), i.e., tongueenamel dry sliding, a large data set of 148 experiments was available with an average COFmax and COFmedian of 3.21 ± 1.53 and 1.87 ± 0.75, respectively, which represent COFmStaexp,1average and COFmSteedpi1an,average from equation (1) and (2)
SMSL and UWS resulted in a high Relief, i.e., >8 -fold decrease in COFmax whereas Stimulated human whole saliva (SWS), RWS, parotid saliva (PS), Saliva Orthana (SO) and Dentaid Xeros mouthwash (DX) provide low Relief, i.e., a three- to six-fold decrease in COFmax, which are very similar to the Relief of Demineralized water (DW)

Summary

Introduction

Saliva is the collective secretion from parotid, submandibular, sublingual and minor saliva glands and consists of approximately 99% water with some electrolytes, proteins, glycoproteins and enzymes[1,2,3]. Placebos were found to reveal similar results in relieving symptoms as saliva substitutes which makes it difficult to rate a saliva substitute as truly effective[20,22,23] This indicates a great need of a simple ex vivo test setup where the dry mouth condition can be simulated. A COF of 0.25 ± 0.03 has been reported between a stainless steel ball sliding against a saliva coated porcine tongue[31], which supports the premise of relatively high COF in the oral cavity This strongly suggests the use of biological surfaces in the development of a system to mimic dry mouth conditions instead of artificial PDMS surfaces. The tongue-enamel system was compared to a PDMS-PDMS system for their ability to differentiate between water, stimulated and unstimulated saliva, and saliva from different glandular sources

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