Probing force and the relationship of the probe tip to the periodontal tissues

Abstract. Recently an increasing pocket depth was found to be related to an increasing probing force. The purpose of the present study was to investigate whether or not a plateau value in pocket depth measurements exists and to study, with different probing forces, the location of the tip of the probe in relation to the periodontal fibers and the alveolar bone. Two groups of patients were selected for this study; in one group a number of teeth had to be extracted for periodontal reasons (the extraction group) and in the other a single periodontal surgical procedure was required (the surgery group). All patients received preliminary treatment consisting of plaque control and removal of subgingival deposits. At the time of the investigation the gingival condition was assessed by means of a new index, the Periodontal Pocket Bleeding Index (P.P.B.I.) The criteria were: 0 - no bleeding of the pocket after probing with a force of 0.75N, and 1 - bleeding of the pocket within 30 sec after probing with a force of 0.75N. After local anesthesia in the extraction group, reference marks parallel to the long axis of the experimental teeth were cut with a cylindrical diamond burr. By means of the pressure probe, pocket depth measurements were performed with increasing forces of 0.50, 0.75, 1.00 and 1.25N. After extraction and staining of the remnants of the periodontal fibers, the distance from the most coronal intact connective tissue fibers to the most apical point of the reference marks was measured. In the surgery group using the same pressure probe, interproximal measurements with increasing forces of 0.50, 0.75, 1.00 and 1.25N were made from the apical border of the restorations to the bottom of the pocket. The same measurement, this time to the crest of the alveolar bone, was repeated after a flap had been raised. Results with the P.P.B.I. showed that oral hygiene procedures resulted in a mean index of 0.36 in the surgery group and 0.43 in the extraction group. The results of the present study indicated that 1) using a probe of 0.63 mm diameter, the optimal force level for clinical pocket depth measurements is 0.75N, 2) a force of 0.75N is clinically well tolerated and meets with few objections from patients, 3) when a probing force of 0.75N is used the tip of the probe in both shallow and deep periodontal pockets is located at the most coronal intact connective tissue fibers, 4) a plateau value in pocket depth measurements is found when a probing force of 1.25N is employed, and 5) the mean width of the connective tissue attachment is approximately 1.9 mm.