ArticleBMC oral health2026
A methodological framework for fractal analysis in monitoring periapical lesions after endodontic retreatment: a comprehensive parameter optimization study.
Article in BMC oral health, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundThis retrospective study aimed to investigate the efficacy of Fractal Analysis (FA) in the quantitative assessment of periapical bone healing after non-surgical endodontic retreatment, and to standardize the key methodological parameters - region of interest (ROI) selection, image processing filters, and box-counting algorithms - that govern its reliability.
methodsNinety-five patients free of systemic conditions affecting bone metabolism who had undergone endodontic retreatment were divided into two groups: a healed group with PAI < 3 (n = 60) and a non-healed group with PAI ≥ 3 (n = 35). The non-healed group served as a clinical non-healing reference group to verify whether FA parameters remained stable in the absence of biological change. A total of 11,970 Fractal Dimension (FD) measurements were performed on 190 images (7 ROI types × 3 filters × 3 algorithms = 63 combinations). Seven ROI types (ROI-1 through ROI-7), three Gaussian filters (σ = 4, 12, 32 pixels), and three box-counting algorithms (B64, B32, BoneJ Auto [BA]) were tested. Mixed-effects GLM was used as the primary analysis; paired t-tests with Benjamini-Hochberg FDR correction (q < 0.05) served as the confirmatory analysis.
resultsIn the healed group, FD increased significantly over one year of follow-up (p < 0.001, Cohen's d = 1.07, AUC = 0.91 [ROI-1, BA + σ4; 95% CI: 0.85-0.96]). In the non-healed group, no significant FD change was observed for any combination (all p > 0.05, d ≤ 0.07). The highest discriminatory power was achieved with lesion-focused large ROIs, and the BA + σ4 combination yielded the strongest results across all significant regions.
conclusionFA is a powerful quantitative tool complementary to PAI for monitoring endodontic healing. A lesion-focused circular/polygonal ROI (ROI-1/ROI-2), σ = 4 filter, and BoneJ Auto algorithm is recommended as a standardized protocol for 2D FA studies.
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