"All-on-4" immediate-function concept for completely edentulous maxillae: a clinical report on the medium (3 years) and long-term (5 years) outcomes.

BACKGROUND Immediate implant function has become an accepted treatment modality for fixed restorations in totally edentulous mandibles, whereas experience from immediate function in the edentulous maxilla is limited. PURPOSE The purpose of this study was to report on the medium- and long-term outcomes of a protocol for immediate function of four implants (All-on-4, Nobel Biocare AB, Göteborg, Sweden) supporting a fixed prosthesis in the completely edentulous maxilla. MATERIALS AND METHODS This retrospective clinical study included 242 patients with 968 immediately loaded implants (Brånemark System TiUnite, Nobelspeedy, Nobel Biocare AB) supporting fixed complete-arch maxillary all-acrylic prostheses. A specially designed surgical guide was used to facilitate implant positioning and tilting of the posterior implants to achieve good bone anchorage and large interimplant distance for good prosthetic support. Follow-up examinations were performed at 6 months, 1 year, and thereafter every 6 months. Radiographic assessment of the marginal bone level was performed after 3 and 5 years in function. Survival was estimated at patient level and implant level using the Kaplan-Meier product limit estimation with 95% confidence intervals. RESULTS Nineteen immediately loaded implants were lost in seventeen patients, giving a 5-year survival rate estimation of 93% and 98% at patient and implant level, respectively. The survival rate of the prosthesis was 100%. The marginal bone level was, on average, 1.52 mm (standard deviation [SD] 0.3 mm) and 1.95 mm (SD 0.4 mm) from the implant/abutment junction after 3 and 5 years, respectively. CONCLUSION The high survival rates at patient and implant level indicates that the immediate-function concept for completely edentulous maxillae using the present protocol is viable in the medium- and long-term outcomes.