Abstract: Objective To explore the feasibility of implant placement during the early healing phase following the lateral window technique for sinus floor elevation (LSFE) by evaluating the osteogenesis effects and implant survival rates. Methods Patients with posterior maxillary edentulism and severe alveolar bone atrophy (VBH≤4 mm) requiring LSFE and delayed implant placement were recruited. LSFE was performed using deproteinized bovine bone mineral (DBBM) as the sole graft material. Patients were divided into four groups based on healing duration: 4~5 months, 6~7 months, 8~9 months, and ≥10 months. Bone biopsies were obtained from implant sites during the second-stage surgery. The primary outcome was the percentage of vital bone (VB%) in bone biopsies, and the secondary outcome was the 1-year implant survival rate. Results From September 2017 to December 2020, 146 patients (160 maxillary sinuses) underwent LSFE and delayed implantation, with 275 implants placed. Ninety-five complete bone biopsies were obtained. Three implants failed in two patients (all in the 4~5 months group), resulting in a cumulative implant survival rate of 98.91% (272/275). The implant survival rate in the 4~5 months group was 95.31% (61/64), which was lower than that of other groups (100%), but the difference was not statistically significant (P=0.18). Histomorphometric analysis showed that the proportion of vital bone increased slowly with longer healing durations, with a statistical difference observed between the ≥10 months group and the 4~5 months group (P=0.02). However, no statistical differences in the percentages of residual DBBM or non-mineralized tissue were found among the groups (P=0.23, P=0.81). Conclusion With prolonged healing time, the proportion of vital bone increased slowly. No significant differences were found in new bone formation between 4 to 9 months after LSFE, while a statistically significant increase was noted at ≥10 months compared to the 4~5 months group. These findings suggest that implant placement at 4~9 months post-LSFE provides comparable bone quality, with implantation at 4 months offering the benefit of a shorter treatment duration.

Key words: Lateral window technique for sinus floor elevation, Early healing phase, Osteogenesis effect, Implant survival