Number of implants placed for complete-arch fixed prostheses: A systematic review and meta-analysis

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.

A series of 156 consecutive fully edentulous patients were rehabilitated by means of fixed prostheses on either 4 or 6 screw-shaped titanium implants. This retrospective study calculated survival rates for both prostheses and individual implants. Only patients with a 10-year follow-up were considered. The implant lengths were 10 (90%) or 7 mm. They were all inserted after pretapping. In the mandible 13 and 59 prostheses were installed on respectively 4 and 6 implants. In the upper jaw the respective numbers were 14 and 70. Both groups (4 versus 6 implants) were age- and gender-matched. A reduced jaw bone volume was the major reason for limiting the number of implants to 4. Although a tendency existed for an increased failure rate in patients with only 4 implants, the survival rate for both individual implants and prostheses was the same in both groups at the end of the 10-year observation period. The present tendency of some clinicians to install as many implants as possible in full edentulism should be seriously questioned.

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. 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. 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. 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. 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. © 2011 Wiley Periodicals, Inc.