Fractal analysis of bone architecture changes following transcrestal sinus lifting with simultaneous implant placement

Background Evidence regarding the microarchitectural characteristics of newly formed bone after transcrestal sinus lifting remains limited. This retrospective longitudinal study aimed to quantitatively evaluate trabecular microarchitectural changes in peri-implant bone using fractal analysis in patients who underwent transcrestal sinus lifting with simultaneous implant placement. Methods Clinical and radiographic records of 76 patients treated with transcrestal sinus lifting and simultaneous implant placement in the posterior maxilla were retrospectively reviewed. Baseline and approximately 6-month follow-up panoramic radiographs were analyzed. Fractal analysis was performed on predefined regions of interest (ROIs) representing mesial and distal peri-implant trabecular bone, apical trabecular bone, and superior and inferior maxillary tuberosity trabecular bone. The primary outcome was the change in peri-implant fractal dimension (FD) values over time. Secondary outcomes included changes in maxillary tuberosity FD values and inter-regional differences between peri-implant and tuberosity areas. Apical FD values were assessed as exploratory outcomes. Results Peri-implant FD values increased significantly from baseline to 6 months (1.182 ± 0.054 vs. 1.233 ± 0.058; p < 0.001; Cohen’s d = 1.28). In contrast, median FD values in the maxillary tuberosity region remained stable over time (1.252 [1.215–1.286] vs. 1.256 [1.212–1.289]; p = 0.116; r = 0.18). At baseline, peri-implant FD values were significantly lower than those of the maxillary tuberosity region (1.180 [1.154–1.222] vs. 1.252 [1.215–1.286]; p < 0.001; r = 0.83), and although this difference remained significant at 6 months (1.249 [1.193–1.272] vs. 1.256 [1.212–1.289]; p < 0.001), the effect size decreased ( r = 0.62). Exploratory analysis also showed a significant increase in median apical FD values (1.182 [1.145–1.225] vs. 1.253 [1.220–1.289]; p < 0.001; r = 0.84). Conclusions In patients undergoing transcrestal sinus lifting with simultaneous implant placement, peri-implant FD values increased during the 6-month follow-up period, while FD values in the maxillary tuberosity reference region remained stable. These findings suggest that fractal analysis may provide a reproducible adjunctive radiographic method for monitoring trabecular pattern changes after transcrestal sinus lifting. However, FD changes should not be interpreted as direct evidence of histological bone maturation or implant stability without further clinical validation.