Influence of the sinus floor-to-lower window margin distance on outcomes of bone window repositioning in lateral sinus floor elevation: A retrospective study.

BACKGROUND: Bone window repositioning technique has been introduced as a significant modification to the traditional lateral sinus floor elevation (LSFE). However, the optimal position of the lateral bone window in LSFE with bone window repositioning remains controversial. PURPOSE: The study aimed to evaluate the influence of distance from sinus floor to lower border of the window (DSLW) on outcomes in LSFE using bone window repositioning. STUDY SELECTION: Patients who underwent LSFE with bone window repositioning and simultaneous implant placement between 2019 and 2024 were included. They were divided into DSLW ≥ 3 mm and DSLW < 3 mm groups. Cone-beam computed tomography (CBCT) at baseline (T0), immediately postoperative (T1), and 6 months (T2) was used to assess apical bone height (ABH), endo-sinus bone gain (ESBG), palatal/buccal bone height (PBH/BBH), and augmentation volume (AV). Immediate postoperative CBCT was used to evaluate sinus membrane elevation as a technical parameter. RESULTS: This study included 47 patients and 63 implants. Complete palatal sinus membrane elevation occurred more frequently in the DSLW < 3 mm group (73.2%). After adjustment for residual bone height, sinus width, and implant position, DSLW < 3 mm remained significantly associated with complete palatal membrane elevation (adjusted OR, 3.97; 95% CI, 1.02-15.38; p = .047). No significant differences were observed in ABH, ESBG, PBH, BBH, or AV from T1 to T2 (p > .05). Median AV reduction was 13.56% in the DSLW ≥ 3 mm group and 15.85% in the DSLW < 3 mm group (p = .616). CONCLUSIONS AND RELEVANCE: Within the limitations of this retrospective study, DSLW < 3 mm was associated with a higher rate of complete palatal membrane elevation, without affecting short-term bone augmentation outcomes in LSFE with bone window repositioning.