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.

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.

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.

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).

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.