Sinus Floor Elevation Magnitude and Longitudinal Peri-Implant Marginal Bone Change over a Minimum Five-Year Follow-Up: A Retrospective Cohort Study

Background/Objectives: The magnitude of maxillary sinus floor elevation may reflect site anatomy and surgical complexity, but its association with peri-implant marginal bone change remains unclear. This study evaluated whether elevation magnitude was associated with longitudinal peri-implant marginal bone-level change over a minimum 5-year follow-up, distinguishing immediate postoperative differences from subsequent change. Methods: This retrospective cohort study included 248 patients with 528 posterior maxillary Dentium SuperLine bone-level implants placed concomitantly with sinus floor elevation. Paired cone-beam computed tomography measurements were available for 522 implants from 247 patients. Elevation magnitude was modeled per 1-mm increment. The primary analysis used a longitudinal mixed-effects model with the time × elevation interaction as the main inferential term. Secondary generalized estimating equation models evaluated baseline and minimum 5-year marginal bone levels after covariate adjustment. Results: Greater elevation magnitude was associated with a slightly higher immediate postoperative marginal bone level (B = 0.017 mm per 1-mm increase; 95% CI, 0.005–0.029; p = 0.006). The time × elevation interaction was small and not statistically significant (B = 0.004 mm; 95% CI, 0.000–0.008; p = 0.066). After adjustment for baseline marginal bone level and the available covariates, no association between elevation magnitude and marginal bone level at the minimum 5-year follow-up was detected (B = 0.000 mm; 95% CI, −0.004 to 0.005; p = 0.842). Re-expression on the longitudinal change scale yielded the same estimate, and sensitivity analyses of the secondary models produced similar results. Conclusions: Within this retrospective cohort and the clinical protocol used, sinus floor elevation magnitude between 1 and 6 mm was not statistically associated with differential marginal bone-level change over at least 5 years among surviving implants with paired radiographic assessments. This finding should not be interpreted as evidence of equivalence across elevation magnitudes.