ORAL MUCOSAL WETNESS IN HYPOSALIVATORS AND NORMOSALIVATORS

After a person swallows, a film of residual saliva covers the oral har d- and soft-tissue surfaces. Here, the thickness of this film was meas ured at 11 selected mucosal surfaces on each side of the mouth (22 sit es total) in two groups of dry-mouth and one group of normal individua ls. Each group contained 25 individuals; one of the dry-mouth groups h ad resting flow rates less than or equal to 0.1 ml/min while the other and the normal had flow rates above that. Residual saliva thickness w as determined by placing frying-pan-shaped filter-paper strips (Sialop aper(TM)) against the mucosa at each site for 5 s and measuring the sa liva volume collected with a modified Periotron 6000(R) micro-moisture meter; the thickness was then calculated by dividing the collected sa liva volume by the strip area. The two groups with dry-mouth symptoms had mean resting (unstimulated) saliva flow rates of 0.04 and 0.19 ml/ min and mean mucosal saliva thicknesses of 22.4 and 27.8 mu m, respect ively. The control group had a higher mean saliva flow rate of 0.39 ml /min and mucosal saliva thickness of 41.8 mu m. As was observed in a p revious study on normo salivators, the various sites had a characteris tic pattern of wetness, with the hard palate and lips the least moist regions. In this study, these observations were also true in the two d ry-mouth groups. Lower resting saliva flow rates were associated with lower mucosal thickness of saliva and with dryness symptoms becoming e vident when hyposalivation was below about 0.1-0.2 ml/min. The charact eristic pattern of mucosal wetness was not affected by saliva flow rat e. As saliva readily collects in the floor of the mouth and is then sp read over other mucosal surfaces upon swallowing, it was suggested tha t hyposalivation could also lead to the dryness symptoms because there was not enough saliva to cover the various oral surfaces, especially the palate and the lips. In this regard, a critical level of moisture was proposed as necessary to protect vulnerable mucosal surfaces from becoming dry. Lower resting saliva flow rates and correspondingly lowe r mucosal wetness were also associated with a more acidic salivary pH, which was shown earlier to be associated with lower dental plaque pH. (C) 1998 Elsevier Science Ltd. All rights reserved.