Influence of age and salivary secretion rate on oral sugar clearance

The influence of age and salivary flow on oral sugar clearance was studied. Saliva was sampled with small circular paper discs, absorbing a certain amount of saliva. Glucose concentration was analysed enzymatically. Salivary glucose clearance was estimated in: (i) children of various ages and adults, (ii) hospitalised elderly patients, elderly people living at home and middle-aged adults, and (iii) elderly individuals with various types of prosthodontic reconstructions. Furthermore, an experimental model with pharmacologically reduced salivary flow was used to evaluate the relationship between salivary glucose clearance and salivary flow, also taking into consideration pH changes in dental plaque and the sugar intake concentration. In addition, an attempt to speed up prolonged oral sugar clearance in a group of hospitalised elderly patients was made with an individual programme. The main findings were that 3-year-olds exhibited higher salivary glucose concentration levels and greater variations in glucose clearance between different food products than older children and adults. Elderly people, especially hospitalised patients, cleared sugar from the oral cavity less effectively than young and middle-aged adults. Removable dentures, particularly complete dentures, contributed to higher salivary sugar concentration in elderly people. Higher glucose levels in saliva and more pronounced pH drops in dental plaque were obtained at low than at normal salivary flow. There was a bi-linear relationship between salivary glucose clearance sublingually and salivary secretion rate. Small changes in salivary flow below the border line values--which correspond to the intersection between the two phases--resulted in relatively large differences in clearance. It was possible to speed up prolonged oral sugar clearance in hospitalised elderly patients by using an individual training programme. To conclude, oral sugar clearance was comparatively slow in young children and in hospitalised elderly patients. A low salivary secretion rate was found to affect oral sugar clearance negatively.