Individual variations of pH, buffer capacity, and concentrations of calcium and phosphate in unstimulated whole saliva

In order to evaluate the risk of development of dental caries and/or of for mation of dental calculus, salivary variables have often been used, but not with particular success. A reason for the apparent lack of association cou ld be that the individual temporal variation of a characteristic was so sub stantial relative to the overall variation that it is not possible to chara cterize an individual by a single salivary measurement. The sim here was to examine the individual variation of pH, buffer capacity, and concentration s of calcium and phosphate and to compare it with the overall variation of the characteristics in order to shed light on the above problem. Eight week ly samples of up to 4 ml of unstimulated whole saliva were collected from 1 1 dental students before tooth brushing on their arrival at 8 a.m. in the d ental school. Calcium was determined by atomic absorption spectroscopy, pho sphate colorimetrically, and pH electrometrically. The buffer capacity was assessed by titration of the saliva sample from the pH initially observed t o pH 3. It was found that within each individual the concentration of calci um and of phosphate, pH. the hydroxyapatite ion product and the buffer capa city varied considerably over the 7 weeks. The individual range frequently covered more than a third of the total range. Further, within each of the v ariables, single individuals could be found whose samples covered 60% or mo re of the overall range, whilst others covered less than 10% of the range. It was therefore concluded that, although collected at the same time of the day, pH, buffer capacity and concentrations of calcium and phosphate in un stimulated whole saliva in the single individual vary so much that characte rization of individuals and of their saliva based on a single salivary anal ysis is unreliable and hazardous. (C) 1999 Elsevier Science Ltd. All rights reserved.