Effect of mandibular second premolar hypodontia on trabecular bone structure: a fractal analysis approach

The aim of this study was to evaluate the trabecular structure of the alveolar bone in individuals with mandibular second premolar hypodontia using fractal analysis (FA) and to quantitatively determine the potential effects on local bone microarchitecture by comparing the results with those of healthy individuals. This retrospective cross-sectional study analyzed panoramic radiographs of 112 individuals aged 18 years and older. The case group consisted of 56 individuals with congenitally missing mandibular second premolars and retained primary second molars, while the control group included 56 age and gender-matched healthy individuals. FA was performed using ImageJ software with the box-counting method in three regions of interest: the mandibular angle (ROI1), the area between the apices of the mandibular first and second molars (ROI2), and the mandibular second premolar region defined at the apical level using reference lines parallel to the long axes of the mandibular first premolar and the mesial root of the mandibular first molar (ROI3). Measurements were independently performed by one observer, and intra-observer reliability was assessed using the ICC. The fractal dimension (FD) value in the ROI3 region was significantly lower in the hypodontia group (1.28 ± 0.09) compared to the control group (1.36 ± 0.08) (p = 0.003). No significant differences were found in ROI1 and ROI2 regions (p > 0.05). Age and gender had no statistically significant effects on FD values. Mandibular second premolar hypodontia is a factor that affects the local trabecular organization of the alveolar bone. The decrease in FD values in the region of the missing tooth, despite the presence of the retained primary molar, indicates insufficient micromorphological maturation.