Micropuncture measurements of interstitial fluid pressure in the rat periodontal ligament.

The interstitial fluid pressure (IFP) or so-called tissue pressure in the periodontal ligament (PDL) has been suggested to play a role in tooth position and affect periodontal blood flow. However, few investigators have actually measured the tissue pressure in the PDL and measurements in the PDL of rat continuously erupting incisors are lacking. The present study was aimed to develop the micropuncture technique for measurements of IFP in the PDL. The PDL of rat incisors was exposed by partial removal of the crown, the coronal pulp was removed. Viewed through a stereomicroscope, a cavity was drilled until the vessels of the PDL were visible through a thin layer (20 microns) of root cement. The cavity was covered with saline and the PDL punctured with glass micropipettes, diameter 2-6 microns, through tiny cracks of the root cement. The periodontal tissue pressure (IFP) was measured by connecting the micropipette to a servocontrolled counter-pressure pump system (Wiederhielm 1964). Mean IFP in 22 Sprague-Dawley rats was 15.2(SD +/- 3.6) mmHg and simultaneously measured systemic arterial pressure (PA) averaged 125 mmHg. Intravenous administration of an antiflogisticum, indomethacin (15 rats), did not change IFP significantly (mean 14.3, SD +/- 4.2 mmHg). Increased blood volume in the PDL, induced by bilateral clamping of the jugular veins, resulted in an immediate rise in IFP, whereas reduced blood volume due to cardiac arrest arrest resulted in an abrupt fall in IFP, indicating low compliance in the rat PDL. It is concluded that the measurements with the present micropuncture technique are relatively atraumatic and thus it seems to be a reliable method for recordings of IFP in the PDL.