Loading Protocols for Implant-Supported Overdentures in the Edentulous Jaw: A Systematic Review and Meta-Analysis

Purpose: High survival rates have frequently been reported for immediately loaded implants. The aim of this systematic review was to compare immediately loaded with early and conventional loaded implants for overdenture treatment with regard to their 1-year survival rates. Materials and Methods: Systematic database (Medline, Embase, CENTRAL) and hand searches were performed to identify prospective studies reporting on loading protocols for two-piece implants with micro-rough surfaces and diameters > 3 mm. Studies were grouped according to loading protocol, jaw, number of implants per jaw, and splinting. Meta-analyses of comparative reports were performed based on the calculated risk difference (RD). Descriptive analyses included the remainder prospective studies. Two investigators extracted the data independently. Kappa statistics served to evaluate the inter-investigator agreement. Results: Of the 3,142 identified articles, 58 were included for data extraction. They comprised 11 studies comparing loading protocols as well as a further 47 prospective reports. Comparative studies were only available for mandibular overdentures. The meta-analysis revealed a statistical tendency to support conventional over immediate loading (RD: -0.03, 95% confidence interval: -0.06, 0.00). The descriptive analysis of studies with lower evidence demonstrated partially contradictory findings. There, reported survival rates for immediately loaded implants lay between 81.6% and 100%, but depended on the number of implants placed. Most investigators preferred verifying an initial high insertion torque (>= 35 Ncm) or ISQ value (>= 60) before considering an implant for an immediate or early loading protocol. Conclusions: Although all three loading protocols provide high survival rates, early and conventional loading protocols are still better documented than immediate loading and seem to result in fewer implant failures during the first year. Only a few prospective case series are available to document immediate loading of implants supporting an overdenture in the edentulous maxilla.