All-on-6 with grafted sinuses: implants hold, the prosthesis needs maintenance

The edentulous maxilla with pneumatized sinuses forces a choice: tilt the implants and avoid the sinus, or graft it and place implants where the molars used to be. This study looks at the second road, travelled for up to ten years.

It is a retrospective cohort of patients with completely edentulous maxillae treated between 2015 and 2024 with an All-on-6 protocol and simultaneous bilateral lateral-window sinus floor elevation. The protocol is a hybrid: the immediate provisional prosthesis rested on the four anterior implants, while the two posterior implants in the grafted sinuses were left submerged and only incorporated into the definitive prosthesis after healing. Patients needed at least one year of follow-up after the definitive prosthesis. The primary outcome was marginal bone loss (MBL) across the 0-1, 1-5 and 5-10-year intervals, measured on panoramic radiographs; CBCT assessed endo-sinus bone gain and graft volume. Mechanical and biological complications and patient-reported outcomes were secondary outcomes.

Thirty-five patients, 210 implants and 35 full-arch prostheses were included, with a mean follow-up of 6.1 years. Overall implant survival was 99.1% (210 of 212); after delivery of the definitive prosthesis, implant and prosthesis survival were both 100%. Biology was quiet: peri-implantitis in 2.9% of patients and 0.95% of implants. Cumulative MBL grew over time, but annualized and interval loss decreased, consistent with early remodelling followed by stabilization. Mechanics were not quiet at all. Complications of the definitive prosthesis occurred in 82.9% of patients and 45.7% of implants, with prosthetic screw loosening the most common event. Grafted posterior sites were associated with prosthetic screw loosening; angulated abutments and a longer cantilever relative to the anteroposterior spread were associated with abutment screw loosening. Patient-reported outcomes stayed high throughout.

Clinical relevance. In this single-centre series, grafting both sinuses to support a six-implant full arch produced a biologically stable result over the medium-to-long term. The price is paid in maintenance: four patients out of five experienced at least one screw-related event. The design is retrospective, the cohort small and bone levels were read on panoramic films, so the numbers describe this group rather than a general rule. The practical message is to plan recall and screw checks into the treatment from day one, and to keep cantilevers and abutment angulation under control.