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

Objectives: The main purpose of this systematic review was to evaluate outcomes related to the number of implants utilized to support complete-arch fixed prostheses, both for the maxilla and the mandible. Materials and methods: This review followed the reporting guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A focused question using the PICO format was developed, questioning whether "In patients with an implant supported fixed complete dental prosthesis, do implant and prosthetic survival outcomes differ between five or more compared to fewer than five supporting implants?". A comprehensive search of the literature was formulated and performed electronically and by hand search. Two independent reviewers selected the papers and tabulated results. Primary outcomes analyzed were implant and prosthesis survival. Implant distribution, loading, and type of retention were observed as secondary outcomes, as they relate to the number of implants. A meta-analysis was performed to compare results for studies by number of implants. Results: The search strategy identified 1,579 abstracts for initial review. Based on evaluation of the abstracts, 359 articles were identified for full-text evaluation. From these, 93 were selected and included in this review, being nine RCTs, 42 prospective and 42 retrospective. Of the 93 selected studies, 28 reported number of implants for the maxilla, 46 for the mandible, and 19 for both maxilla and mandible. The most reported number of implants for the "fewer than five" group is 4 for the maxilla, and 3 and 4 for the mandible, whereas for the "five or more" implants group, the most reported number of implants was 6 for the maxilla and 5 for the mandible. No significant differences in the primary outcomes analyzed were identified when fewer than five implants per arch were compared with five or more implants per arch (p > 0.05), in a follow-up time ranging from 1 to 15 years (median of 8 years). Conclusions: Evidence from this systematic review and meta-analysis suggests that the use of fewer than five implants per arch, when compared to five or more implants per arch, to support a fixed prosthesis of the completely edentulous maxilla or mandible, present similar survival rates, with no statistical significant difference at a p < 0.05 and a confidence interval of 95%.