Xerostomia Patients Exhibit Altered Salivary Rheology

Objectives: Assess salivary rheology, mucin concentration, dryness perception & surface hydration in xerostomia patients (with evidence of oral dryness) and healthy age matched control subjects.

Methods: 12 patients and 12 controls were recruited and scored for oral dryness. Unstimulated whole mouth saliva (UWMS) was collected by passive drooling technique. Residual mucosal saliva (RMS) was collected using Sialopaper^TM from four intra-oral locations. Samples and purified mucin standards were analysed by gel electrophoresis and Periodic Acid Schiff staining (validated by immune blotting with mucin antibodies). Mucin concentrations were quantified using image analysis (ImageJ). Rheological analysis was achieved using Pendant-Drop imaging (for surface rheology) and Neva-Meter (for extensional rheology). Statistical significance was assessed using t-test and Pearson's rank correlation.

Results: Xerostomia patients had significantly lower UWMS flow (p<0.05) and scored significantly higher (p<0.005) on the clinical oral dryness scale compared to controls. RMS was reduced on all four locations analysed in patients compared to controls. Interfacial rheology of fresh UWMS showed no significant difference between patients and controls. Extensional rheology showed xerostomia patients have significantly lower spinnbarkeit compared to controls (p<0.005) and this is independent of whole saliva flow rate (p<0.05). UWMS mucin (MUC5b & MUC7) concentrations showed no significant difference between patients and controls. MUC7 concentration positively correlated with spinnbarkeit in controls (p<0.05).

Conclusions: Altered salivary rheology may also contribute towards xerostomia in addition to hyposalivation.

Acknowledgements: Biotechnology and Biological Sciences Research Council, UK and Colgate-Palmolive, USA; in partnership with King’s College London.