Salivary flow rate, buffer effect, sodium, and amylase in adolescents: a longitudinal study

The study aimed to provide information on salivary secretion rate, buffer effect, sodium, total protein, and amylase in adolescence. Paraffin-wax-stimulated saliva was collected annually in 69 initially 10-yr-olds and in 98 initially 15-yr-olds. During the 5-yr follow-up, the rate of flow increased in both sexes in the younger age group. In the older age group there was only a slight increase in the flow within the 2-yr follow-up. In both age groups, girls tended to have lower secretion than boys. In cross-sectional analyses, the rate of flow correlated positively with buffer effect and sodium, and negatively with proteins. These findings are in line with earlier observations. However, with age, the buffer effect did not parallel the flow. At the base-line examination the buffer effect was lower in the 15-yr-old than in the younger age group. In line with that, a decrease was found at the final examination in the initially 10-yr-olds. This decrease was stronger in girls than in boys. The observed change in the buffer effect was not related to a parallel change in the flow rate or total protein and amylase content of saliva. In girls the change was, however, associated with a small, but statistically significant drop in the salivary sodium level. The variation in the buffer effect increased from the age of 12 to 15, especially in girls. This effect could not be demonstrated for the other flow-rate-associated variables used to monitor the functioning of the salivary glands.