Journal of Dental Research, Vol 64, 1275-1280, Copyright © 1985 by International & American Associations for Dental Research Online Journals
Micro-analytical determination of pH, calcium, and phosphate in plaque fluid
C. A. Rankine, E. C. Moreno, G. L. Vogel and H. C. Margolis
Micro-analytical techniques for the determination of calcium, phosphate,
and pH in a small volume (less than 0.25 microliter) of plaque fluid are
described and evaluated. The accuracy and the precision of the techniques
were compared with those for standard macrotechniques applied to a large
pooled plaque fluid sample. The results obtained for the micro-analysis of
pooled plaque fluid were in excellent agreement with those obtained by
macromethods. The described techniques were also used to analyze plaque
fluid obtained from single quadrants of the oral cavities of five
individuals. In this fashion, it was determined that, although a
significant variation in plaque fluid composition exists between the
quadrants, a greater variation exists between subjects. Analyses of plaque
fluid obtained from six individuals, following sucrose exposure, were also
conducted. The pH value of the fluid changed with time, following a typical
Stephan curve, with a minimum value occurring between 15 and 30 minutes;
following this, the pH increased to a value near that for resting plaque.
An inverse relationship between pH and calcium and phosphorus
concentrations was observed. It is noted that the described techniques are
sensitive enough to carry out the above analyses both accurately and
precisely using plaque obtained from a single quadrant.
