Assessment of right–left differences in trabecular bone structure within the maxillary lateral incisor–canine region using fractal analysis

Abstract Background Maxillary lateral incisor agenesis, peg-shaped lateral incisors, impacted canines, and cleft lip and palate frequently involve the maxillary lateral incisor–canine region and often show side-related distribution patterns. Whether trabecular bone structure within this region differs between sides in clinically healthy individuals remains unclear. This study evaluated right–left differences in maxillary trabecular bone structure using fractal analysis. Methods Panoramic radiographs of 88 adults (43 males, 45 females; 18–40 years) with Class I occlusion and no dental, skeletal, or orofacial anomalies were retrospectively analyzed. Bilateral polygon-shaped ROIs were defined between the maxillary lateral incisor and canine roots. As methodological validation, standardized 20 × 20 pixel square ROIs were additionally analyzed. FD values were calculated using the ImageJ box-counting method. Inter-observer reliability was assessed by two independent oral and maxillofacial radiologists using the intraclass correlation coefficient (ICC) and Dahlberg error. Right–left comparisons were performed using paired-samples t -tests or Wilcoxon signed-rank tests. Associations with age and sex were also evaluated. Results Using anatomically defined freehand ROIs, FD values were significantly higher in the left maxillary region than in the right (0.77 ± 0.23 vs. 0.70 ± 0.25; mean paired difference = 0.07, 95% CI: 0.01–0.13; p = 0.024; Cohen’s d z ​ = 0.24 ). The same direction of the right–left difference was confirmed using standardized square ROIs. No significant right–left differences were found for ROI area ( p = 0.229), mean gray value ( p = 0.618), minimum gray value ( p = 0.682), or maximum gray value ( p = 0.708). The right–left FD difference was not associated with age or sex. Conclusions A small but statistically significant right–left difference in FD values was detected within the maxillary lateral incisor–canine region. Although the effect size was small and the biological significance remains uncertain, consistent findings across two ROI approaches together with excellent inter-observer reproducibility support the methodological consistency of the proposed protocol. The findings should be interpreted as a subtle radiographic observation rather than as definitive evidence of physiological maxillary asymmetry. Clinical trial registration Not applicable.