A Comparison of 2 Patient Populations Using Fractal Analysis

This study was undertaken to demonstrate that the fractal dimensions calculated using digitized non‐standardized, clinical radiographs of mandibular alveolar bone from a population of patients diagnosed with periodontitis are statistically different from fractal dimensions calculated from another population diagnosed as having gingivitis or healthy gingiva. The fractal dimension was calculated using a public domain fractal analysis program distributed by the National Institutes of Health (NIH). Fractal dimensions were calculated from digitized clinical radiographs for 29 patients diagnosed with healthy gingiva and/or gingivitis and 32 patients diagnosed with periodontitis and compared. To estimate the reproducibility of the technique, we recalculated the fractal dimension from images of the gingivitis patients 3 months after the original calculations and compared them to the originals. A 2 sample, 2‐tailed Student t test showed the gingivitis data group to be different from the periodontitis data group ( P = 0.0012). The original gingivitis and repeat gingivitis groups fractal dimension calculation were the same and analysis showed the two data sets were not significantly different ( P = 0.99). We found that: 1) fractal dimensions could be used to distinguish between gingivitis and periodontitis patient groups; 2) fractal dimensions could be calculated from non‐standardized clinical radiographs; and 3) fractal dimensions for gingivitis patients were reproducible over a 3‐month period. J Periodontol 1998;69:9–13 .