In vitro study of crevicular fluid sampling methods: Sampling variability and effect of volume and orientation on fluid removed

An in vitro system was designed to evaluate properties of gingival crevicular fluid (GCF) sampling. Four polysiloxane test wells were fabricated with volumes of 2.7. 4.3. 6.2 and 11.0 μl. Wells were sampled for a test solution of 50% fetal call serum in phosphate buffered saline, while in upright and inverted orientations, using capillary micropipettes and filter paper strips. With the pipette method. 6 sample volumes removed from each well were calculated directly. With the paper method, 1μ(Ci/ml of 3H‐lbymidine was added to the test solution, and countsper‐minute (CPM) were determined at 24 hours for 10 test samples in each condition and for 10 standard samples. For both sampling methods, well volume and well orientation had significant effects on amount of fluid removed. Larger volumes/increased CPM were obtained from both deeper and inverted wells. For upright wells only, a quadratic relationship, associated with a ceiling effect, was found between total well volume and volume removed/CPM. Coefficients of variation of measurements involving the paper method were higher than those for the pipette method when wells were inverted but not when they were upright. Pocket depth and tooth arch (analogs of variables tested in vitro) may affect GCF sampling variability in vivo.