Background <p>Maxillary sinus augmentation is widely performed to enable implant placement in the atrophic posterior maxilla, and the radiographic remodelling patterns of different graft materials remain a topic of clinical interest. This retrospective study compared trabecular bone remodelling following lateral window maxillary sinus augmentation with allograft versus xenograft materials using FD analysis of panoramic radiographs over a one-year follow-up.</p> Methods <p>One hundred patients (50 allograft, 50 xenograft) treated between 2015 and 2023 were included. Panoramic radiographs obtained immediately postoperatively and at 3 months, 6 months, and 1 year were analyzed using ImageJ software according to the White and Rudolph box-counting method. Intragroup temporal changes were evaluated with the Friedman test and Bonferroni-corrected Wilcoxon signed-rank tests; intergroup comparisons were performed using the Mann–Whitney U test or independent samples t-test according to data distribution. Interobserver reliability was assessed using the intraclass correlation coefficient (ICC).</p> Results <p>Age and sex distributions were comparable between groups (<i>p</i> = 0.250 and <i>p</i> = 0.288, respectively). FD values changed significantly over time in both the allograft (<i>p</i> = 0.021) and xenograft (<i>p</i> &lt; 0.001) groups. In the allograft group, only the 3-month versus 6-month comparison reached significance (<i>p</i> = 0.001), whereas in the xenograft group all pairwise comparisons except 6 months versus 1 year were significant. Intergroup comparisons revealed significantly higher FD values in the allograft group immediately postoperatively (<i>p</i> = 0.010) and at 3 months (<i>p</i> &lt; 0.001), but no differences were detected at 6 months (<i>p</i> = 0.107) or 1 year (<i>p</i> = 0.751). Interobserver reliability was good across most measurements (ICC 0.794–0.856), with moderate reliability for the 6-month xenograft measurement (ICC = 0.744).</p> Conclusions <p>Allografts produced higher early-phase FD values, while both materials achieved comparable radiographic trabecular complexity by the 6-month and 1-year follow-up periods. These findings suggest convergent radiographic remodelling over time. Further histomorphometric and clinical studies are needed to confirm these FD-derived findings.</p> Trial registration <p>Not applicable.</p>