Oral mucosal friction and subjective perception of dry mouth in relation to salivary secretion.

Assessment of oral mucosal friction and subjective perception of dry mouth was performed during treatment with thiazide diuretic bendroflumethiazide (2.5 mg o.d.) or placebo in a randomized, double-blind, cross-over study (2 x 2 wk) in 34 healthy volunteers. Treatment with bendroflumethiazide was associated with a 10% reduction in the stimulated whole saliva secretion rate and a 15% reduction in the salivary sodium concentration, as compared with placebo. Oral mucosal friction was concomitantly measured on the buccal mucosa and on the mucosa of the lower lip by means of a newly developed sliding friction device. In addition, a questionnaire was used to evaluate how the treatment was subjectively perceived with regard to symptoms of dry mouth. Mucosal friction of the lower lip increased significantly during treatment with bendroflumethiazide, as compared with placebo. When the test subjects, regardless of pharmacologic treatment, were divided into groups according to subjective perception of dry mouth, the dry mouth group showed significantly lower resting and stimulated flow rate and higher mucosal friction in comparison to the nondry group. When, in addition, pharmacologic treatment was also considered, the differences between the dry and the nondry group were restricted to resting whole saliva flow rate and mucosal friction during bendroflumethiazide treatment. It is concluded that resting whole saliva flow rate is the best predictive factor for evaluating subjectively perceived dry mouth. However, the sensitivity of the developed sliding friction device is capable of detecting minor changes in salivary secretion rate. In addition, measurements of oral mucosal friction may serve as an easily available method to complement sialometry when evaluating, for example, drug-induced dryness of the mouth.