Micropuncture measurements of interstitial fluid pressure in normal and inflamed gingiva in rats

Interstitial fluid pressure (IFP) in normal and inflamed gingiva of rats was measured by sharpened glass capillaries (diameter 2-4 microns) connected to a servocontrolled counterpressure system ad modum Wiederhielm. Gingival inflammation was induced by a steel ligature placed unilaterally around the first maxillary molar. After 8 weeks, the ligature was removed and measurements of IFP in normal and experimentally inflamed gingiva were made by puncture through the intact oral epithelium. Average IFP on the control side was 3.5 mm Hg in free, and 7.4 mm Hg in attached gingiva. Compared to the control side, IFP on the experimental inflamed side was elevated significantly (p less than 0.05) both in free and attached gingiva. In the ligated inflamed side IFP in free gingiva averaged 6.7 mm Hg, whereas in attached gingiva it showed a mean value of 10.4 mm Hg. Histological examinations showed a dense infiltrate of inflammatory cells in the connective tissue, while the contralateral control side showed normal features of epithelial and connective tissue. The present finding of increased IFP in the inflamed gingiva may in theory contribute to augmented crevicular fluid flow during inflammation.