On the Unreliability of Gingival Bleeding After Repeat Probing

Objectives: Reliability is defined as proportion of the variance of an observation due to subject-to-subject (experimental units') variability in error-free scores. It can be estimated from results of a replication reliability study. Since periodontal probing is invasive, bleeding on repeat probing cannot be observed independently, and reliability cannot be determined. The aim of the present study was to assess the strength of association of gingival bleeding scores after repeated probing at different time intervals in subjects with plaque-induced gingivitis. Methods: 20 adults with plaque-induced gingivitis participated. Periodontal probing of the sulcus was conducted at 6 sites of every tooth present. Probing pressure was standardized at 1.27 MPa. Probing was repeated in different quadrants immediately after the first probing (T0), after 1 h (T1), 4 h (T4), and 24 h (T24). Results: A total of 3459 sites were probed twice. When periodontal sites were probed the first time, an average of 22.8 ± 8.1% sites bled on probing. The proportions of sites not bleeding after the first but bleeding after the second probing were significantly higher at T0 (difference of proportions of 0.040, p = 0.01) and T1 (difference 0.035, p < 0.05) than the proportion of sites bleeding after the first but not bleeding after the second probing. Two-level binary models adjusted for tooth type, site, age, gender, smoking status, average bleeding index, and sampling schedule revealed odds ratios (95% CI) for BOP at T0-T4 of 5.33 (3.84; 7.39), 3.46 (2.50; 4.80), 3.85 (2.84; 5.22), and 2.87 (2.13; 3.86), respectively. Conclusions: The association between gingival bleeding after repeat probing in subjects with plaque-induced gingivitis is weak. There appears to be a significant effect of probing itself which probably lasts for more than 1 h. Supported in part by KerrHawe, CH, and Kuwait University Research Administration, Grant #DS02/02.