Survival and complications of narrow-diameter implants supporting fixed restorations under immediate versus early or delayed loading: A systematic review and meta-analysis

Abstract

Objectives: To evaluate implant survival and complication rates of narrow-diameter implants (NDIs) supporting fixed restorations under immediate versus early/delayed loading protocols. Data: Randomized controlled trials and non-randomized clinical studies reporting implant survival, marginal bone loss (MBL), biological, or prosthetic complications for immediately and early/delayed loaded NDIs were considered. Sources: Electronic searches of PubMed/MEDLINE, Embase, and Scopus were conducted up to January 2026. The study was conducted according to the PRISMA 2020 statement and registered prospectively in PROSPERO (CRD420250654797). Study selection: Two reviewers independently performed study selection, data extraction, and risk-of-bias assessment. Nine studies met the inclusion criteria for qualitative synthesis, of which seven provided sufficient data for meta-analysis. Random-effects meta-analyses were conducted when methodologically appropriate, and the certainty of evidence was assessed using the GRADE approach. Conclusions: Immediate loading of NDIs supporting fixed restorations may achieve implant survival outcomes comparable to early/delayed loading protocols. Short-term biological, prosthetic, and MBL outcomes appeared similar between loading strategies; however, the certainty of evidence was limited. A higher risk of long-term biological complications with immediate loading was observed, although this finding is based on limited evidence with very low certainty. Clinical significance: Immediate loading of NDIs may represent a viable and time-efficient treatment option for fixed restorations in appropriately selected cases. Given the limited certainty of long-term biological outcomes, careful case selection and long-term monitoring remain essential.