Xerostomia and the oral microflora

Xerostomia is the feeling of a dry mouth usually caused by hyposalivation. It may occur after radiation therapy of the head and neck, in systemic diseases such as Sjögren’s syndrome, or as a side effect of medication. Hyposalivation changes the oral microbiome with the most dramatic changes after radiation therapy. The number of lactobacilli and Candida albicans increases. Also the number of mutans streptococci increases in hyposalivated subjects, but sugar consumption is a stronger determinant for the level of mutans streptococci. Hyposalivated subjects are more susceptible to oral infections such as caries and mucosal infections. This is both caused by changes in the oral microflora and weakening of salivary protection mechanisms such as cleansing by the salivary flow and buffering capacity.

In the case of ventilated patients at intensive care units, hyposalivation leads to accumulation of dental plaque and a shift in microflora, which may cause lung infections. Oral hygiene in combination with oral antiseptics reduces the risk for lung infections in these patients.

Therapies for xerostomia consist of artificial saliva, gels, or spray. These products may contain polymers that form a microbial substrate. Application of salivary antimicrobial substances like lysozyme, lactoferrin, or lactoperoxidase in these products did not lead to lower microbial counts in vivo.

In conclusion, hyposalivation leads to changes in the oral microflora. In combination with a lower defense, this leads to a higher susceptibility to oral infections such as caries and mucosal infections. There is a need for products normalizing the oral microflora and thereby decreasing the risk of oral diseases in subjects with hyposalivation.