Probing force and required time for accurate root surface detection

Objective: Probing the root surfaces morphology and roughness is the most common and gold-standard technique for the diagnosis of periodontal diseases. However, root surfaces with calculus are always atypical and it seems very difficult to identify the exact location of insular calculus within invisible periodontal pockets. We tried to estimate the optimal lateral probing force against the root surfaces for effective detection. Methods: Test metal plates, which were 7mm in width, had two single steps or one double step on the surface, with 0.1 mm or 0.3 mm in same height. These test plates were fixed at right angles to the axis of force sensor. Then, test plates were covered by opaque rubber seats with pin-hole. Ten trained dental hygienists tried to figure out the shape of test plates by probing through the pin-hole with Williams probe or CPI probe, totally 16 trials for each examinee were performed. In same time, the probing forces pushing against the test plates were recorded and analyzed. Results: Four examinees identified the shape of test plates, both two single steps or one double step at least one test plates (Sound group), almost others were identified one double steps but not one double step. The average probing force pushing laterally against the test plates with one double step was significantly gentle in Sound group, with Williams probe (21.8+/117.8S v.s. 47.6+/-40.7S) and with CPI probe (17.8+/-16.1S v.s. 48.0+/-34.6S). Average probing time was significantly longer in Sound group with Williams probe (64.9+/41.3S v.s. 31.7+/-19.5S) and with CPI probe (66.3+/-46.4S v.s. 25.1+/-11.9S). Conclusions: To detect accurate morphology of root surface within periodontal pockets, especially steric form like steps, the optimal lateral probing force was suggested to be around 20 gramF and examinee might need to take time to concentrate sophisticated and delicate sensing.