Maxillary Rehabilitation With All-On-6 and Bilateral Lateral Window Sinus Elevation: 1-10-Year Outcomes

To evaluate the long-term clinical and radiographic outcomes of fixed full-arch maxillary rehabilitation supported by six implants combined with bilateral lateral-window sinus floor elevation.

This retrospective cohort study included patients with completely edentulous maxillae treated with an All-on-6 protocol and simultaneous bilateral lateral-window sinus floor elevation between 2015 and 2024. The immediate provisional prosthesis was supported by the four anterior implants, whereas the two posterior implants in the augmented sinus regions were left submerged and incorporated into the definitive prosthesis after healing. Only patients with at least 1 year of follow-up after definitive prosthesis delivery were included. The primary outcome was longitudinal marginal bone loss (MBL), assessed across the 0-1-, 1-5-, and 5-10-year follow-up intervals. Radiographic measurements included crestal bone level, cumulative and interval MBL, apical bone height, endo-sinus bone gain, and graft bone volume. Graft bone volume was additionally evaluated as an exploratory outcome in patients with suitable serial CBCT scans. Marginal bone level changes were measured on panoramic radiographs. CBCT was used for assessment of sinus graft-related parameters and, when necessary, for anatomical confirmation. Secondary outcomes included implant and prosthesis survival, mechanical and biological complications, and patient-reported outcomes. Longitudinal MBL was analyzed using linear mixed-effects models, and implant-level mechanical complications were assessed using generalized estimating equation logistic regression.

Thirty-five patients restored with 210 implants and 35 definitive full-arch prostheses were included, with a mean follow-up of 6.06 ± 2.08 years. The overall implant survival rate was 99.1% (210/212), and the post-definitive implant and prosthesis survival rates were 100% (210/210 and 35/35, respectively). Mechanical complications of definitive prostheses were frequent, occurring in 82.9% of patients and 45.7% of implants, with prosthetic screw loosening being the most common event. Augmented posterior sites were associated with prosthetic screw loosening, whereas angulated abutments and greater cantilever/AP distance were associated with abutment screw loosening. Biological complications were less frequent, with peri-implantitis observed in 2.9% of patients and 0.95% of implants. Cumulative MBL increased over time, while annualized cumulative MBL and interval MBL decreased, suggesting early marginal bone remodeling followed by gradual stabilization. Patient-reported outcomes remained high across all assessed domains.

Fixed full-arch maxillary rehabilitation supported by six implants with bilateral sinus augmentation showed high implant and prosthesis survival and stable marginal bone conditions over long-term follow-up. However, screw-related prosthetic complications, particularly prosthetic screw loosening and abutment screw loosening, were common. These findings suggest that this treatment modality may be biologically stable but necessitates structured long-term prosthetic maintenance for patients.