Variation of salivary calcium, phosphate and buffering capacity in adolescents

Calcium, phosphate and buffering capacity were measured in children's (n=43) unstimulated saliva between September 1990 and June 1991 inclusive. Saliva samples were collected in the afternoon, once a month, on 10 consecutive occasions. Buffering capacity was assessed immediately after sample collection using the Dentobuff strip method. The remainder of the saliva sample was then stored at -18 degrees C and, after thawing, total calcium and inorganic phosphate were measured. The intra-individual variation of buffering capacity over time was statistically significant (Friedman two-way ANOVA, p < 0.001). The intra-individual variability of salivary calcium was also statistically significant (repeated-measures ANOVA, p < 0.001). However, no evidence of a statistically significant variation in phosphate was observed. It is concluded that a combination of flow-rate fluctuation over time and the methods used to assess salivary constituents might have contributed to this variability.