Current State of Evidence for Implant Placement and Loading in Partially Edentulous Patients: A Systematic Review

OBJECTIVES: To systematically review the updated evidence for the clinical outcome of fixed implant prostheses treated with different combinations of implant placement and loading protocols in partially edentulous patients. MATERIALS AND METHODS: An electronic search was performed in Medline, Embase, and Central to identify studies of implants subjected to immediate placement + immediate restoration/loading (Type 1A), immediate placement + early loading (Type 1B), immediate placement + conventional loading (Type 1C), early placement + immediate restoration/loading (Type 2-3A), early placement + early loading (Type 2-3B), early placement + conventional loading (Type 2-3C), late placement + immediate restoration/loading (Type 4A), late placement + early loading (Type 4B), late placement + conventional loading (Type 4C) with implant-supported fixed dental prostheses (IFDPs) in partially edentulous patients. A cumulative survival rate for each type of the implant placement and loading protocols was weighted by the duration of follow-up and number of implants. RESULTS: From 11 427 records, 140 studies (42 RCTs; 98 CCTs/cohort studies) encompassing 10 456 implants met the criteria. Weighted cumulative survival rates for each protocol were: 98.0% (Type 1A), 91.6% (Type 1B), 95.0% (Type 1C), 97.8% (Type 2-3A), 100% (Type 2-3B), 94.0% (Type 2-3C), 97.2% (Type 4A), 97.9% (Type 4B), 97.5% (Type 4C). Protocols 1A, 1C, 2-3C, 4A, 4B, and 4C satisfy scientific and/or clinical validation thresholds, whereas 1B and 2-3B remain insufficiently documented despite high numeric survival. CONCLUSIONS: In immediate placement, Type 1C shows strong survival rates. It is considered scientifically and clinically validated, while Type 1A also meets the criteria for a scientifically and clinically validated protocol with high survival rates. Meanwhile, Type 1B continues to show lower and more variable survival rates-being clinically documented-underscoring the need for careful case selection. Regarding early placement, Type 2-3C is recognized as a scientifically and clinically validated protocol. Type 2-3A, which was previously underreported, now demonstrates similarly validated survival rates that expand the evidence for early implant placement with immediate loading. Although Type 2-3B is clinically documented, it still lacks sufficient evidence. All late implant placement protocols are considered scientifically and clinically validated: Type 4C offers high survival with long-term predictability, while Type 4A and Type 4B maintain stable survival rates backed by well-established evidence.