Microscopic evaluation of pocket depth measurements performed with six different probing forces in dogs.

This study investigates the relationship between probing force and probe penetration into the periodontal tissues in pockets with overt gingivitis and in pockets with minimal gingival inflammation. In eight dogs experimental periodontal tissue breakdown was induced during a period of 14 weeks. The dogs were then distributed over two groups of four dogs each. In group the dogs were subjected to meticulous tooth cleaning once every day for a period of 3 weeks. The dogs in the second group did not receive any oral hygiene measures. Next, wooden probes were inserted, mesial and distal to each premolar. In each dog six different probing forces were used. Microscopic examination showed that, in the brushed group, epithelium was always present between the probe tips and the connective tissue. In the nonbrushed group presence of epithelium was found in 21 of 23 specimen. In both groups of dogs it was found that, with increasing probing forces, the location of the tips of the probes changed from a position occlusal to the most coronal connective tissue fibers to a position apical to the most coronal connective tissue fibers. With light probing forces it appeared that in the nonbrushed group the tips of the probes were located more apically. When greater probing forces were used, no differences between the brushed and the nonbrushed group were found. It is suggested that, using a probe of 0.63 mm in diameter, the optimal force level for clinical pocket measurements is about 0.75 N, or in other words, the optimal probing pressure is about 240 N/cm2.