The relationship between radiographic and clinical changes in the periodontium.

Change in clinical attachment level (CAL) and radiographic change in crestal bone height are often used to assess periodontal breakdown and disease progression. These two variables are also used to monitor the effect of treatment. The purpose of the present longitudinal study was to evaluate the correlation between changes in CAL and alveolar bone loss. Following initial screening, 79 subjects with established periodontitis were monitored quarterly for 1 yr, using a pressure-sensitive automated probe. CAL and relative attachment level (RAL) were recorded at 6 sites for each tooth. Radiographs were obtained at baseline and 1 yr. Crestal bone changes were determined using an image enhancement technique. Mean change in attachment level was 0.16 mm. Similarly, mean proximal bone loss measured radiographically was 0.16 mm. In 6.9% of all the sites, and 13.7% of all pooled interproximal sites, AL loss was in excess of the threshold defined as 2 s.d. of repeated measurements (mean 1.54 mm). Similar percentages of sites (12.9%) had radiographic evidence of proximal bone loss exceeding the threshold (0.55-1.08 mm). A site-based analysis of active sites revealed an overall poor correlation between the 2 variables (kappa value = 0.03) which was the result of a very poor sensitivity (0.16) despite a relatively good specificity (0.81). A patient-based comparison of clinical and radiographical changes revealed an overall kappa value of 0.08, with sensitivity and specificity of 0.51 and 0.56, respectively. However, baseline CAL and crestal bone height showed good correlation (r = 0.73; p = 0.0001). It is suggested that changes in CAL and radiographic bone level progress somewhat independently. Over a short-term period of time they might not follow the same course; however, in the long term, these differences seem to level off. For longitudinal monitoring of disease progression and response to therapy both methods may be needed; while for cross-sectional evaluation and long-term prospective studies, either variable may be used alone.