Abstract: PURPOSE: To investigate the apical bone condition (bone exposure/bone coverage) of implants and influencing factors following graft-less osteotome sinus floor elevation (OSFE) and provide evidence for clinicians. METHODS: Patients who underwent non-grafted OSFE in Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from January 2011 to December 2022 were enrolled. Based on CBCT evaluations at 6 months post-implantation, the patients were divided into an apical bone coverage group and an apical bone exposure group. Parameters including residual bone height (RBH), sinus cavity width (SW), implant protrusion length (IPL), and bucco-palatal sinus contour were measured. A generalized estimating equation (GEE) with binary logistic regression was established to identify risk factors for apical bone exposure. RESULTS: A total of 88 patients (112 implants) were included. At 6 months postoperatively, totally 80.36% (90/112) of the implants achieved periapical bone coverage, with an endo-sinus bone gain of (2.60±1.09) mm. GEE analysis showed that increased sinus width (OR=1.21, 95%CI: 1.00-1.46, P=0.045), square-shaped sinus cavity (OR=4.46, 95%CI: 1.16-17.24, P=0.030), IPL≥4mm (OR=5.05, 95%CI: 1.64-15.59, P=0.005), and periodontitis (OR=3.46, 95%CI: 1.09-10.92, P=0.035) were independent risk factors for periapical bone exposure. CONCLUSIONS: Periapical bone coverage after graft-less OSFE is affected by implant protrusion length, bucco-palatal contour of the maxillary sinus, and sinus width. Preoperative CBCT evaluation of anatomical conditions should be conducted to formulate appropriate clinical plans.

Key words: Dental implant, Maxillary sinus floor elevation, Osteotome technique, Periapical bone coverage, Risk factors