Mapping regional oral dryness: new perspectives on dry mouth and dry mouth interventions

The Regional Oral Dryness Inventory (RODI), a newly developed questionnaire which quantifies the severity of dryness at various locations in the mouth. It was found that there is a significant difference in dry-mouth feeling between different intra-oral locations. The most severe oral dryness was perceived at the posterior palate and the least dry location was experienced at the floor of the mouth. We envisaged that the RODI might help to discriminate among different causes of oral dryness in patients. It was concluded that the RODI questionnaire was indeed able to identify differences in perceived intra-oral dryness of different patient groups. For example, both healthy volunteers as well as Sjögren’s syndrome (SS) patients experienced the posterior palate as most dry. In turn, patients suffering from dry mouth due to medication experienced the anterior tongue as most dry. Besides, it was found that SS patients, including those using ≥4 medications had the highest RODI scores for all intra-oral regions, in contrast to healthy controls and dry-mouth patients using up to 4 medications. These findings suggest that the RODI questionnaire might be a useful diagnostic tool for dry-mouth diagnostics, because it can help distinguish between possible causes of oral dryness in patients. It was postulated that the dimensions of the intra-oral surface area, especially the palatal surface area, affect the distribution of saliva over various mucosal surfaces and thereby could influence the dry mouth feeling at various intra-oral regions. The intra-oral surface areas were quantified using cone-beam computed tomography. Additionally, the potential correlations between intra-oral surface areas and facial anthropomorphic measurements were investigated. This study found a moderate, but statistically significant, correlation between the palatal surface area and the length of the head. Furthermore, a correlation was found between the surface area of the tongue and the depth of the head. In this light, it could be envisaged that individual intra-oral surface areas can be estimated by measuring facial features, which is more convenient for the patient. Inspired by these findings, the relation between the palatal surface area, measured using an intra-oral scanner, and anthropometric measurements was validated in living subjects. This study concluded that only in females the mandibular length and palatal width correlated with the palatal surface area. Next, we aimed to determine the salivary film thickness and MUC5B levels at various intra-oral locations in healthy volunteers. Furthermore, measurements of the palatal surface area were executed to explore the potential relationship between the palatal surface area, the palatal salivary film thickness and MUC5B levels. It was found that the salivary film and MUC5B levels were unequally distributed over the intra-oral surface. The anterior tongue had the thickest salivary film and contained the highest levels of MUC5B, whereas the anterior palate had the thinnest salivary film with the lowest MUC5B levels. There was no association found between the palatal surface area and the salivary film thickness of the palate. Various interventions are available to relieve oral dryness. The factors that could affect the choice and use of these interventions were studied intensively. The use of dry-mouth interventions in subgroups of patients with different causes of oral dryness was investigated. The use of these dry-mouth interventions was significantly associated with the overall dry-mouth feeling as well as with dry-mouth feeling at different intra-oral locations. In medication induced dry-mouth patients, the “use of a mouth gel”, was significantly associated with dryness of the anterior tongue in particular. While in SS patients the “use of a mouth gel’’ had a significant association with dryness at the inside cheeks.